These excellent shrimp are typical when all goes well

This article will depart from the usual format, and relate an interesting project about Shrimp Farming, mainly in S.E.Asia., and the problems which arise of disease which have enormous economic consequences. It was compiled when I was working some years ago, for the very well known firm Monsanto as a consultant. I believe the facts and observations I made at that time, could be of great interest to many Hobbyists.

I therefore propose I hope with your understanding, to take a slightly different approach to the subject of disease in this article, based on the above to try to show the reader how some of the things we observed on this trip, relate to the all important question of disease etc, in the Aquarium industry, which at first sight might appear to very far removed from the area of shrimp culture etc.

One of the reasons, we looked at the shrimp industry in S.E.Asia, was because it is plagued with disease problems that in Thailand account for overall some 40% losses of production (=Wipe outs), of the farmed stock. These losses are in value around $2 billion at today’s prices. In other countries, such as Malaysia, & Indonesia,

Samples from the pond are taken twice daily, to check on growth & to see if any disease is showing

which we also looked at, the percentages are even worse, though as the production is not as large a Thailand, the losses in dollars are not as substantial.

The principal culprits for these losses are viruses, the worst of which is called would you believe ‘white spot’ due to it’s characteristic marking on the shrimp in the early stages before leading to mortality, which happens very

A bowl of Post Larval shrimp at day 15

quickly once it has taken hold. Another important virus is ‘yellowhead’, the name is again descriptive , also there are other bacterial diseases, which are often encountered.

When one examines the typical ponds, in which the shrimp are reared, one is struck, by the lack of information, as to the quality of the water. Although most farms take regular readings of pH , Temperature, DO(dissolved Oxygen, & Salinity) it is rare for other measurements to be taken.

Yet the farmers inform us that they cannot get the shrimp to grow to as large a size as they would like, and after some 150 days at the outside, they must take down the ponds to sell the shrimp, as otherwise they may lose them.

Looking at the ponds one can see vast amounts of Protein floating over the waters, the colour of the ponds, also would lead one to believe that very high levels of Nitrate are there, mostly due one suspects to overfeeding which causes the inevitable processes of nitrification. Those of you who keep Reef Aquariums, will be very familiar with such problems.

Shrimp ponds are fed 5 times daily by hand as shown in this photo

Any Hobbyist who attempts to breed Discus fish or other sensitive fish also find that high levels of Nitrate are very inhibitory to fish, even more so to Invertebrates to which shrimp belong.

It is hardly surprising therefore to hear in so many places that they cannot keep the shrimp for too long, to get the extra size etc, that would bring them a great deal of extra money, (a 40 count shrimp, i.e. 40 per Kilo) which is typical after 150 days rearing from the PL (post Larvae ) stage, can bring the farmer some $9/Kg. However a 30 count shrimp, which would need another 20 or so days to grow, if they could do so, would fetch some $14-15/Kg. As the typical pond when it does not have a wipe out due to disease, can grow some 6 tonnes ( Metric) per Hectare, per crop, the difference to the farmer is a major amount of money, even after one allows for the cost of extra food electricity etc.

Now as a said at the outset of this series of articles stress is probably the most important factor in the creation of conditions that invariably lead to disease, so that in these countries where so

There are nearly 1000 Shrimp hatcheries in Thailand, and they utilize an important part of the world’s supply of Artemia eggs

much money is to be made by the production of good quality shrimp, which is to a large extent a sellers market, it is amazing to find, that so many important measurements are not been taken on a regular basis, and nor are various potential interventions, been tried to see if important improvements can be made. Many of these techniques and interventions, are well known to advanced Hobbyists here in the UK, and elsewhere.

We in the Hobby, when we have expensive Aquariums, with many valued specimens, almost invariably measure on a regular basis such parameters, as Ammonia, Nitrite, Nitrate, Phosphate, and more. We are familiar with the many options for filtration , as well as Protein skimming, UV sterilization, Ozone as a reduction and purification agent, Ammonia towers, and more. For the most part we know the principles as to why we do these things, along with the impact that lack of good water quality can have on the results we expect for our prized Fish etc.

Yet all of this is done, for most of us, as a Hobby. Admittedly in one of the world’s most advanced nations technologically. It is still amazing to me, that where you have an Industry that employ’s

so many thousands of people, makes a most important contribution to the economy of the countries involved, as well as being a most important hard currency earner , yet fundamental measurements and interventions, are not made and recorded.

I mention all of this, so that you the reader may grasp, just how important all these criteria are. When you ask both the farmers, who often were simple rice farmers before taking up shrimp farming, and also when we asked some of the more educated persons working with the farmers, the reasons why the shrimp died, or would not grow etc, very few specific answers were available.

In order to try and solve any problem, one must first have all the relevant information ( sometimes the irrelevant information also). When the considerable number of water quality parameters (some 16 or more), are observed over a large number of ponds for a couple of years, it is virtually certain, that some aspects of the water quality will correlate with the commencement of disease, or the lack of growth. Imagine what would happen to your fish etc, if you never bothered to take any readings of the water quality, nor had any filtration, protein skimming, or any way to kill of pathogens. I am sure you will agree that not too many Aquariums, would have the fine displays that are today becoming the norm throughout Europe, the USA. and many other parts of the world.

Anyway, I hope that this short dissertation will make you be even more aware, of how at a practical level the application of good water management practices can have a really important result to pay of handsomely whether this is for the home Hobbyist or for a shrimp farmer. To finally prove this point, we were with a Thai company, run by Europeans, which has got a couple of farms of it’s own. This company, by applying the kind of modern techniques that I have been mentioning, has had dramatically better results than the average Thai farmer. This fact takes the discussion away from the theoretical to the practical, as they have demonstrated (in dollar terms) that good water quality and management makes a real difference and that this is expressed in large numbers of dollars, in the end result.

I do hope therefore that this article will inspire you all to be aware, that poor water quality does make a difference, that no other factor is as likely to bring about any of the many forms of disease that can strike. Therefore take measurements, intervene to improve the water quality, keep records etc, and the chances are very good, that disease either will not strike or if it does, it can be much more easily brought under control.

At the end of this extensive trip to the shrimp farms of Asia, we finished up in Singapore, where fortuitously I was able to take a few days to visit the now world famous Aquarama show which was taking place at the time we arrived. This show is the only major trade show and exhibition that is devoted ONLY to the tropical and ornamental fish hobby.

Red Snakeskin Guppies from this strain, won first in theGuppy show at Aquarama

Since its inception in 1989, Aquarama has become a major fixture in the industry calendar , and each show has resulted in more exhibitors as well as ever growing numbers of visitors. The show is unique in that all the major shows in the USA and Europe are Pet shows, with a strong representation for Tropical fish, whereas Aquarama is a show specifically for Tropical Fish and Ornamentals including of course Goldfish, Koi, and marines.

An attractive feature of this event, is that each time a really interesting fish competition is held , for most of the interesting species of Fresh water Tropicals. As Singapore is probably the largest producer in the world of so many species, along with the back up from a world class University, the entries would make one’s mouth water. To my mind the categories for most interesting fish displayed were

This variety of Cobalt Discus at Aquarama was a real show stopper.

Guppies, also many of the Discus, also as some of the Arowana’s (now bred by several farms, even though they must all get CITES certificates) , were the most interesting.

All the major European producers were represented in force, such as Eheim, Sicce, Tropica ( plants from Denmark), Aqua Medic, and many many others. Leading American companies such as Instant Ocean, Forty Fathoms, Aquarium Pharmaceuticals, etc had booths, and of course dozens of Singaporean companies, which were principally fish exporters.

In conjunction with the event every second year, they have an excellent series of Scientific lectures by invited speakers, from Universities etc, in many parts of the world. This year was no exception, & among the most interesting lecturers was Dr. Blom form the Netherlands, as well as Dr. Peter Burgess from the UK.

The presentations were divided just as are more august forums, into areas of interest, and this year dealt with

1. The emerging Asian market.
2. Ornamental Fish Production Technology
3. Health & Welfare management.
4. Conservation & sustainable resource management.
5. Demonstration workshops.

We also had time to visit a few farms. Whilst the farms are often quite simple in their layout and methodology, their productivity is enormous, the people that run them, are exceptionally friendly and hospitable. I am posting some photos for readers to get an idea of what is involved.

As is germane to these articles, disease, is always a consideration for these breeders, even more so for the exporters, as overall it is generally agreed that about 20% of the fish that are shipped, either arrive DOA (dead on arrival) or do so within a few days after being received by the importer. This is something that the Singaporean Government, through its arm of the PPD (primary production dept), is now with some more progressive exporters, trying to do something about. They have recently instituted a set of protocols which all members joining the scheme must follow, and as is so typical is this dynamic country, the protocols are being policed, so that no ‘cowboys’ can make claims if they do not follow the scientifically worked out methods to prepare for shipment, which have been proven to reduce loses by an important amount.

One thing becomes very evident in Singapore, and in the writers view at least must play no small part in the reason why Singapore has become so predominant in Ornamental fish culture; even though today the standard of living is higher than in the USA, thus they can no longer rely upon cheap labour to succeed . Therefore the degree to which all the breeders & exporters are ready to cooperate with each other, as well as with the Government agencies, and the National University, makes enormous efficiency a necessity. This very close cooperation , as well as a top rated national airline, plus an airport that is consistently rated for the last 15 or more years, as the finest in the world, gives Singapore products, transport, varieties , and a lot more, that have enabled them to become the force in our industry, that is now world famous.

Many other countries especially Malaysia, Thailand, etc, now seek to supplant them, but it will take a long time, for them to play catch up, as the educational standards in Singapore have been rated year after year in Maths and Science, the highest in the world. This approach to whatever they do, will stand them in good stead to resist the competition that they will face in the years ahead.

Guppies are raised in concrete tanks with net lining as shown in the photo taken at a leading Guppy farm

Anyway, I do hope that this departure from my normal topic, will be of some interest, I will in the next article to revert to dealing with specific problems, which will probably begin with some of the bacterial diseases, as most of the important parasites have now had an airing, although we could continue for a couple of month’s more, with some of the less common ones.

As I get frequent inquiries for advice from readers, could you please try to keep your questions to the point as much as possible, and especially give as many signs (symptoms) as possible so that I can help you. I regret that time does not allow me to get into answering questions on Aquarium filtration as well as many other subjects, so I do hope those of you, will understand this. John Shawn Prescott. john@aquarium-gardening.com

By John Shawn Prescott

In this article as the saying goes in so much advertising “in response to several requests”, I am going to deal with the parasite Amlyodinium or Oodinium. Quite a few readers have written or phoned me about this disease, including one person from Argentina, so I feel now is the time to address this so often fatal infection.

Velvet like dust spots on skin . Oodinium pillularis

Many of you will be aware that although they are variants, there are two forms that attack our fish, one that causes the freshwater infestation ( which also has more than variant), and the other which attacks saltwater fish. I will deal with both starting with the sweet-water form.

Oodinium pillularis . This is the Latin name given to the parasite that causes the disease more popularly known as Velvet , Gold dust or Rust disease. This variant is the most often encountered, but as indicated below there are also a couple at least, of other very similar forms in freshwater which occur from time to time..

The infestation is caused by a parasitic dinoflagellate that is variable in size, as the variants differ somewhat in their measurements. . Other forms that cause very similar signs are Oodinium limneticum and Oodinium vastotor They can measure in some instances more than 100 microns. Though more typical sizes are 50-70 microns.

One of the greatest problems with this parasite in both the freshwater & the saltwater form, is that most typically the Hobbyist will observe the infestation only when he sees a fish, sometimes more than one, gasping for air, and in the last stages before death.

Usually this is when the fish is laying on its side on the bottom of the Aquarium, as it tries desperately to get air by attempting to breathe at the surface.

At this advanced stage of infection it is rare indeed to save the fish, however if prompt action is taken it is possible to save other fish, as without doubt if such remedial measures are not applied then virtually all the fish will succumb, usually within a very short space of time.

The parasite attacks the skin of the fish & inserts “roots” which can easily be seen under microscopic examination (see illustrations). Another favourite site of attack are the gills of the fish,

Oodinium pilluris in the skin mucous x 630

which so typically then cause the most observed sign, that of “panting” for breath as mentioned. These parasites eat into the cells of the epithelial layer, or the sensitive tissue of the gills, destroying them in the process, After the parasite has matured it falls off the fish much in the manner of white spot in both fresh and salt water. Then having fallen off the fish it begins several stages of mitotic division, ending up with some dozens or even more of cells which are flagellated.

In both the free swimming flagellated stage as well as the parasitic stage when attached to the fish, the organism contains a form of chlorophyll. This gives the parasite its typical gold or rust colour, which also enables it to obtain food, as do plants by the process known as photosynthesis. However when in the parasitic form almost all of its nourishment is obtained at the expense of the host, and this causes tremendous damage which leads to death, once the fish is heavily parasitized. On the fish the dinoflagellate form grows in size about 5-6 times, before falling of and replicating itself in the free swimming form.

Oodinium sp. in skin mucous x 400

These flagellated free swimming forms are in fact dinoflagellates, which must within the space of one day find another fish to infect or they will die. Their relatively short life cycle along with massive reproductive capacity ensure that if an outbreak occurs and it is left uncontrolled heavy mortalities will ensue. Thus the Hobbyist should be most careful and always be prepared to treat any sign of this obnoxious pest. Fortunately it is not too common, but has no equal in the speed in which it can cause havoc in any Aquarium unfortunate enough to have an outbreak. Sometimes a few fish will survive an outbreak for reasons that are not entirely clear, these fish often have developed an immunity of some form to the parasite.

Younger fish appear to be much more susceptible to the parasite, perhaps because they have a less well developed immune system. If young fish become exposed the casualties will almost invariably be much higher. However if untreated, even adult fish will succumb

Water .

Without any doubt less than ideal water quality is one sure way, to help in the outbreak of any parasitic infection, & in this respect Oodinium is no exception. However the primary reason for its introduction is usually to be found elsewhere in this instance.

Behaviour .

Gasping for air, with very rapid respiration, most typically on the floor of the Aquarium, but sometimes at the surface, are nearly always observed. In the early stages of an infection, “flashing” or rubbing & scratching are often indications, as the fish tries without success to rub off the irritating organisms.

Fins .

Fins can become clamped and folded.

Body .

The most observed feature of this infestation, is a salt & pepper effect of hundreds of small dots, usually with a pall or colour of gold/yellow or rust , which give the appearance that the fish has been covered with a special form of talcum powder. It is sometimes difficult to see this unless the light is coming from the back, & glances off the fish, when it can easily be seen. This advanced phase of infestation is however almost invariably fatal, & the Hobbyist should try to become aware of the earlier signs if he/she wishes to be able to take meaningful prophylactic action.

Gills

. Excessive mucous will be a sign that the parasite is attacking the gills, & a smear as often described previously should easily confirm this.

Skin .

The skin, becomes “dusted” with hundreds of small raised parasites, giving a colour which according to the variant of the form encountered will be from a yellow gold colour to an almost red shade.

Histo-Pathology .

A scraping of the skin, or gills will invariably show signs of the dinospores , which have a very easily recognized outline. Once the infestation has been confirmed remedial action should take place right away.

Prognosis .

As already stated, if the problem is only discovered when the parasite has made large inroads into many fish, then severe casualties are to be anticipated. Older fish of certain species often will resist the infection, though they will also succumb in many instances if no action is taken. Young fish typically will die like flies, if they are not helped with appropriate action by the Aquarist. However if a suitable remedial regimen is introduced, excellent results can be expected.

Several forms of treatment have given good results. Among them are:-

Heat treatment ( by raising the temperature by some 4-6 degrees C , to about 86F or 30C. ). . At the same time illumination can be employed for the full 24 hour cycle, as this can disrupt the life cycle of the parasite helping to cause it to “burn itself out”.

This often works, but in a mixed tank, however with species such as White Clouds as well as several others which will not tolerate the higher temperatures it is a risky procedure

Use of Quinine hydrochloride at 1 grm to 100 Litres of water as a continuous bath for about 3 days. Reports are variable but mostly good . When the treatment is finished which if possible should be done in a quarantine tank, the water should be either thrown away, or filtered over charcoal.

Use of Copper sulphate at 320 mg of Copper Sulphate in 1 Litre of pure water ( distilled). Use this solution to treat the tank water at 1 ml per 1 gal (US Gal) . This treatment is widely referred to in the literature, but has to be used with extreme care, as many fish are highly susceptible to Copper, and vary species by species in the toleration of it. Furthermore the hardness or otherwise of the water plays a critical role in the effect of the Copper. If it is not hard enough then no benefit will ensue. In addition as Copper tends to fall away, in the treatment of a new tank, that has not been previously exposed to Copper, the Copper level must be monitored frequently if good results are to be expected, and this is often just not practical for the average Hobbyist who has to work during the day.

The treatment of choice is an Acriflavine drug , ( Fish-Vet makes a combination drug Revive, using this in combination with other chemicals that gives excellent results). To make up your own Acriflavine you should obtain the neutral form & use it at 3mg of the Acriflavine in a stock solution of 330 ml. Then use this stock solution at 10 ml to treat a Gal or 4.5 litres. Do not use any charcoal during treatment, note that subdued lighting is recommended.

We have found over many years of experience, that whilst no drug is perfect, Acriflavine or some of its close relatives give an excellent result with minimal effect on the fish. After treatment charcoal should be used in the filter to remove any residual “green/yellow” cast to the water.

Other reported treatments include the use of Permanganate of Potash, sometimes used with rock salt, but these treatments have little back up documentation, so the reader is advised to proceed with caution in any such experiment.

This is the form of the parasite that gives rise to the disease known as Coral Fish Disease.

There are many similarities between this marine variant of the parasite and the fresh water forms.

The salt water Hobbyist should take into the account the differences and not make an error in diagnosis. I will now define some of the special features of the salt water form .

In the fresh water forms O. pillularis & O. limneticum , the organism’s primarily attack the skin, & then spread to the gills. In the saltwater form O. ocellatum the parasite seeks out the gills and may then spread to the skin.

Oodinium ocellatum

Slide shows parasite attached to the gills of a fish, this interferes in oxygen transpiration causing suffocation.

By the time the latter takes place however, the gill damage is almost invariably so severe, that the typical “first alert” I have already mentioned of seeing a fish “gasping” on the bottom of the tank, is unfortunately all too common. They damage to the gills, causing haemorrhaging, swelling, and intense necrosis, which lead to an inability of the fishes gills to pass sufficient oxygen, which leads to suffocation & death.

The reproductive phase of the free swimming dinoflagellate takes place optimally in water of a pH of 8.0- 8.2 with a density of 1.012- 1.021 and with a higher than desirable organic load, especially of Nitrate.

Water.

High organic load, with less than optimum water conditions, can often serve as the precursor for an outbreak. It thrives in Temperatures of 25-30 C , & salinity of 1.012-1.021.

Behaviour.

Gasping for air, with very rapid respiration, most typically on the floor of the Aquarium, but sometimes at the surface, are nearly always observed. In the early stages of an infection, “flashing” or rubbing & scratching are often indications as the fish tries without success to rub off the irritating organism. If the Hobbyist can pick up this “flashing” action at an early enough stage there is a chance he /she can prevent mortality

Gills .

Excessive mucous will be a sign that the parasite is attacking the gills, & a smear as often described previously should easily confirm this. Heavy necrotic damage is easily observed even with a good hand magnifier.

Skin .

The skin will show “gray” patches which if examined closely will manifest a “dust like” appearance, giving the skin a “velvet” look, which has given rise to an alternative name for the disease. Some haemorrhaging may also become evident.

Histo-Pathology

A scraping of the skin, or gills will invariably show signs of the dinospores , which have a very easily recognized outline. Once the infestation has been confirmed remedial action should take place right away.

Prognosis.

The disease as with its freshwater counterpart, usually springs itself upon the awareness of the Hobbyist, with the first fish or more, giving their last gasps as said on the bottom of the tank. At this stage seldom can such fish be saved, so the outlook for them is very poor. If however there are still large numbers of uninfected fish, or some only lightly infested, then if prompt & suitable action is taken, it should be possible to save the others.

The remedy for the saltwater form is rather difficult. Copper has often been indicated as a drug of choice, but has many problems in its use, as well as been dangerous to the fish in even small overdoses, especially if even minor damage has already occurred to the gills of the fish. In Reef tanks it cannot even be considered.

Methylene blue , has been used with some success, as it has the advantage of been an excellent oxygen transporter, which aids the transpiration of oxygen to the fishes gills. Methylene blue however is highly toxic to Nitrifying bacteria, & its use, should be confined to a separate quarantine tank only. If used a 1% stock solution should be made (1 grm in 1 Litre of pure water). Use 1ml of this stock solution for each 4.5 litres of water to be treated.

Acriflavine & related compounds have proven very effective, & this as in salt water has given the writer & his co-workers the best consistent results over the years. (Fish-Vet makes a product called Revive based on this experience, which has an excellent track record.) This product can be used in a fish only and /or a reef tank, and will not impact adversely the Corals etc. Carbon & Protein skimmers should not be used during the treatment period, as they pull out of the water, much of the useful active ingredients, but may be used to clear the tank once treatment is completed. Lighting should be subdued during the treatment period.

In both the fresh-water & saltwater form of the disease, the reproduction and hence the eventual intensity of the infestation is closely related to the temperature. Lower temperatures will slow down the reproduction of the parasite, and thus possibly give the Hobbyist a little more time to take effective remedial action. The Hobbyist must evaluate however the species he/she has in their tank, and the tolerance for a lower temperature that their collection of fish, is likely to withstand.

Some freshwater species such as white clouds will thrive in lower temperatures, others such as Discus, will emphatically not.

The reverse use of temperature may also be employed, by increasing the Temperature by quite a number of degrees as indicated above. This has the effect of speeding up the parasite’s life cycle, combined with the use of a suitable treatment as well as employing a prolonged photoperiod, often causes the parasite to burn itself out. If such a technique is employed then the lowered oxygen level of the water must be compensated for, by increasing the aeration substantially.

Authors note to readers: -

I am very gratified, by the increasing numbers of inquiries coming from readers of these articles. I will continue to answer queries that are sent to my E Mail address (john@aquarium-gardening.com). However as like all of us, I have other work to do, to earn a living, it would help if you could make your inquiries as specific as possible, as sometimes I have to read through a great amount of non relevant material before I am able to discern the question.

John Shawn Prescott john@aquarium-gardening.com

Refs .

Diseases of Fish C.van Duijn Jr. P 52-56. Iliffe Books UK

Handbook of Fish diseases Ed. Dieter Untergasser p. 89-90 TFH Publications.

Papperna I. (1980) Amyloodinium ocellatum (Brown 1931) (Dinoflagellida) infestations in cultured marine fishes in Eilat , Red Sea: epizootiology and pathology J.Fish Dis 3: 363-372

Noga E. (1987) Propagation in cell culture of the dinoflagellate Amyloodinium , an ectoparasite of marine fishes Science 236. 1302-1305.

Cheung P.J., Ruggieri G.D., and Nigrelli R.F. (1978) Effects of temperature & salinity on the developmental cycle of Oodinium ocellatum Brown (Mastigophore: Phytomastogophoresa: Dinoflagellida)(abstract) The Fourth International Congress of Parasitology in Poland.

Negrelli R.F. (1936) The morphology, cytology, and life-history of Oodinium ocellatum, a dinoflagellate parasite on marine fishes. Zool N.Y. 21: 129-164.

John Shawn Prescott

In this article I propose to deal with a very common fresh water parasite viz. Gyrodactylus & a Marine parasite called Brookynella.

Gyrodactylus elegans. Photo shows embryo developing inside the parasite.

Gyrodactylus causes a condition which is termed Gyrodactylidiasis, and this is the name given to the adverse effects that this group of parasites causes to fish when an outbreak occurs.

This very broad group of parasites is widely distributed, & attacks many species of tropical fish kept in Aquaria

Saltwater form of the parasite showing typical hooks which are common to all forms of this species. Photo by courtesy of Dr. Mo. of Central Veterinary Laboratory Oslo Norway.

For some reason Labyrinth fish do not appear to be often affected, some authors claim that darker coloured fish, are attacked less frequently, though this latter is not the writers experience.

The popular name of this family is called “Flukes” and in fact they are skin or gill flukes, which attach themselves to the skin or gills of the fish, and thereby can cause a great deal of damage.

As with almost all the common infestations, less than ideal environmental conditions such as poor water quality, overcrowding, stress by incompatible species etc, will create the conditions that may lead to an explosive & damaging outbreaks. The odd parasite is often present, and appears under good conditions, to remain dormant. Once however stress is caused by any factor an outbreak becomes almost inevitable, so remedial action is imperative.

These worms as in fact they are, obtain nourishment by “eating” skin fragments as well as the sucking the blood of the victim, this contributes to the pale appearance in chronic infestations.

The Hobbyist should suspect the presence of these parasites if he/she observes the natural colours of the fish appear to have faded, this is often concurrent with a clamping of the fins, or a folded appearance . Although in Gyrodactylus the infestation is more typically found on the skin, it often will manifest itself by attacking the gills. The parasite is about .75 mm long, & has at its anterior portion a sucker which has two central large hooks, surrounded by some sixteen smaller hooks for attaching itself to its host.

Gyrodactylus belongs to Phylum Platyhelminthes which are unsegmented flat worms, the Class or sub-division they belong to is Trematoda. This Class is again divided into 2 divisions viz. Monogenea & Digenea. Gyrodactylus belongs to the Monogenea, as it has only the need for one host, unlike the Digenea, which must have an intermediate host to complete the life cycle.

There are several varieties of Gyrodactylus , possibly the most common is G.elegans, others are G. medius, G. gracilis, but there are many more. All however have a similar life cycle, and cause for the most part identical symptoms. It is not therefore necessary for the Aquarist to concern himself with the species identification.

It is worthy of note however that there are salt water forms of this parasite viz. G.salaris as well as others, these can and do cause major problems form time to time in Salmon as well as other culture.

The sizes of the different forms vary just a little, from a low of about .3 mm, to a high of around .8mm. In some cases in early infestation they can be observed with the naked eye on the skin of the fish, but as the outbreak “deepens” the fish puts out massive amounts of slime, in a vain attempt to neutralize the parasite, this covers the organisms so that it is hard to see them individually.

A smear with something like a Q -Tip rubbed gently over the body of the fish, (holding same carefully but gently in a wet net), then applying the smear to a clean microscope slide, should enable the user, or even with a good magnifying glass, in the event that a microscope is not available, to make a certain diagnosis.

Typical signs of infection. Gyrodactylus & related species.

Water Less than optimum water quality, such as a lowering of the pH level, or high Nitrate or Phosphate readings can lead to an outbreak, stress caused by incompatible fish can also cause an outbreak.

G.salaris .Scanning electron photograph, shows parasite attached in typical manner to skin of Atlantic salmon. This method of attachment is similar for all forms.

Photo by courtesy of Dr. Mo. of Central Veterinary Laboratory Oslo Norway

Behaviour Fish will evidence lethargy, and swimming will become intermittent as the fish will tire very easily. Breathing at the surface, or just stationary “hanging” at the surface will be observed, as the fish try’s to obtain sufficient oxygen when the gills are badly infested.

Fins . Fins can become clamped and/or ragged . Often small spots of blood may be observed at the base of the fins.

Body Lesions may become apparent on the body as well as excessive mucous. Colours of the fish become “faded” in appearance.

Gills Gills will usually become protuberant and usually are paler than normal. Excess slime can easily be observed.

Skin . Areas of haemorrhaging can be observed as well as ulcers, which typically have a circular shape . A slime can be observed over the body in advanced cases.

Histo-Patholgy A scraping of the skin, or gills will invariably show signs of the flukes , which will confirm the suspected infection. Be aware that secondary bacterial infection is very usual due to the protective epithelial layers of the skin etc, being adversely impacted.

Life cycle The species multiply by sexual viviparous multiplication, but there is evidence that a form of parthenogenetic reproduction can take place inside the mature parasite, & even within the “daughter” cell. The term given to this rather unusual reproduction method is called “paedogenesis”. Although the parasite only gives “birth” to a single worm at a time, the gestation rate is so high that in a single month, under ideal conditions for the parasite as many as one million young can be produced. In this lies the danger that an outbreak presents, as far less than this number will cause massive mortality in the average Aquarium.

The newly born parasites can creep about on the skin of the host fish, or may search out a new host thus spreading the infestation. They must find a new host rather quickly or they will die, & this gives the Aquarist good opportunities to attack the problem, which if done quickly & correctly can have an excellent outcome.

Prognosis In most cases a cure is almost always possible, so the Aquarist should be aware of what to look for, and assuming that the problem is identified as a Gyrodactylus species that is causing the problem take remedial action as detailed below. If this is done, then losses can be and should be minimal. However if the problem is not discovered, until it has severely progressed, then heavy losses will almost certainly ensue. When the gills of the fish are badly damaged, or heavy necrosis of the skin takes place, the damage is often irreparable . It should be noted, that as in all parasitic infestations that cause necrotic damage, that secondary infection by bacteria and/or fungus may well occur. One author has suggested that the parasites themselves may carry the infectious bacterium from fish to fish.

Treatment . There are several treatments that can be successfully employed.

1) The use of Formalin . Use 2-4 ml of Formalin in 10 Litres of water, preferably in a separate quarantine tank, for 30 minutes. If fish show signs of distress stop the treatment. Alternatively Formalin can be used as an extended treatment in the Aquarium itself at a dosage of 15-20 ppm . Water should be changed after 3 days.

2) Methylene Blue can be used successfully at a dosage taken form a stock solution of 1 gram in 100 ml of water. Use 3-6 drops of this stock solution in a Litre of the water to be treated. Do not use this treatment in your main Aquarium as Methylene Blue, has a very adverse effect on the nitrifying bacteria, & also will cause the silicon bonding in your aquarium to become permanently dyed blue in colour.

3) Acriflavine is also very effective & is used at 1 gram per 100 Litres . ( We at Fish-Vet have a variant of this treatment with 3 active ingredients in our Fish-Vet product called Revive).

Other treatments have been reported as being effective, such as Benzalkonium chloride, Chloramine, as well as Potassium antimonyl tartrate. However there is not much current literature about the use of these, & I would hesitate to recommend them without more recent evidence.

To summarize then, Gyrodactylus in its various manifestations, is quite a common parasite, which if the fish are in good conditions, with clean water & unstressed, should remain at a level which will cause no problems. If for any reason these conditions should change for the worse, then an outbreak will often occur, which if spotted early can be brought easily & quickly under control.

Gyrodactylus is an excellent example, of how prophylactic treatment in a quarantine tank, can be used to preempt the likelihood of any such outbreak.

.

Brooklynella hostilis is found as a parasite in Marine Aquaria far more often than is commonly recognized as it tends to be overshadowed by the more frequent & well known parasites viz. Cryptocaryon irritans and Amyloodinium (Oodinium) ocellatum.

Photo of Brooklynella parasite. Note cilia all along the outer surface. X 400.

It like so many others is a ciliated protozoan which in many respects resembles its counterpart in fresh water Chilodonella ( see my previous article ). When conditions become favourable to its reproduction, very rapid multiplication takes place , reproduction occurs by simple binary fission, and such massive reproduction can and does cause fatalities , which is brought about by severe weakening of the host fishes.

The literature reports many differing species of fish as being susceptible, & the first reports of this parasite were related by accounts from some of the more prominent (at that time) Public Aquariums, such as the New York Aquarium Steinhart, etc.

Typical signs of infection Brooklynella hostilis

Water There is little doubt that fish exposed to lowered water quality , and in particular the stress of elevated Ammonia /Nitrite levels such as are brought about in shipping, can induce an outbreak of this parasite. All the literature seems to confirm this.

Behaviour Fish demonstrate lethargy, will “toy” with their food, appearing to eat & then spitting it out. Respiration becomes difficult as the Gills become heavily parasitized , & can easily be observed.

Brooklynella hostilis infestation on a Damsel fish. Note typical faded body colour, as well as severe erosionof the Dorsal & Caudal fins.

Body A “faded” appearance of small areas becomes apparent , & such areas spread outwardly as the infestation progresses. Sloughing of the epithelium will occur in later stages.

Gills Gills will become massively parasitized and a smear or other examination of the gills should easily determine the cause of the infestation.

Skin As the “sloughing” occurs increasingly large areas of damage can be seen, as the skin becomes broken down by the parasites activities.

Histo-Patholgy Parasite can be confirmed by skin or gill smears from suspected fish. Parasites are mobile and range in size from 60×80 microns to 40×48. In shape they are heart or kidney shaped ( see illustration), and they have typically ventral organ for attachment to their host.

Treatment

The literature has very little on effective treatment, & the authors disagree on the application of Copper as treatment, (Stopskopf’s book recommending its use, whilst Blasiola stating categorically it does not work). In this authors experience I have to agree with Blasiola, I have never found it to be effective against Brooklynella.

The combination of the following treatments & techniques have worked for me, on several occasions with varying degrees of infection, to eliminate the parasite, but I have had to employ at least 2 of the methods, and often all four. With careful attention the parasite can be brought under control( eliminated), but one should be aware there is no ” 24 hour” simple cure. Be very suspicious of anyone telling you that they have such a remedy.

1) Giving a “dip” in freshwater of the same temperature & pH as the Marine tank, for about 15 minutes ( careful observation must be made, during this time, to avoid distress, & the fish removed, if major problem is observed).

2) Giving a bath in Sea water with Formalin added add at a dosage of 1000 ppm for some 15 minutes.

3) Adding an Acriflavine product (such as Fish-Vet’s Revive) to the tank water for a period of 2 weeks after the above treatments.

4) Taking severe steps to ensure that water quality is optimum along with the TOTAL removal of any detrital matter .

I would mention that G.Basleer mentions in his book that Quinicrin gives a good result, regrettably he does not give any figures for dosage, or any contraindications.

If any secondary infections with by bacteria are observed then the use of an antibiotic would be useful. The use of UV to help prevent secondary infection should be employed.

It is useful to point out to the Aquarist who is intending to buy fish, that the judicious way to avoid to problems that this noxious parasite can bring to your Aquarium, is often best managed, by ensuring that your dealer has the fish in his tank for some 2 weeks prior to you taking it home. Most fish that will break out due to the stresses of transport , with this parasite will do so within this time.

To be fair to your dealer, you should show goodwill, by making it a conditional purchase, i.e. offer to pay for the fish, or at least part of it, provided he keeps it, and shows it is alright after the period of time mentioned has elapsed. Brooklynella is not an easy parasite to eliminate, so the effort to avoid it, is worthwhile.

I suspect that some of you as you read what would appear to be a depressing catalogue of parasites just waiting to attack your precious fish, may become disheartened somewhat, especially if you have had the misfortune to suffer one or more attacks in your early days in the Hobby. Therefore at the risk of been repetitive let me again emphasize that fish have an amazing ability to withstand infections, their immune system like most Veterbrates is well developed, & only when the conditions that we prepare for them or that they are exposed to, before we receive them are substandard, can we anticipate outbreaks which will adversely impact their health & our enjoyment of them.

Thus once again, everything you can do, to maximize the conditions in your Aquarium as well as ensure that you buy fish that have been properly collected, ( not with Cyanide for example), held in conditions at all stages of the collecting/shipping processes, can you reasonably expect to have little or no problem.

I can hear some of you saying to yourselves, “how can I know, how the fish are collected /shipped etc”. This is not easy, but careful reading of the literature, observing how your dealer handles his fish ( does he make any effort at quarantine etc), asking about his suppliers, (does he import directly, or buy from a wholesaler, ) does the wholesaler quarantine the fish etc. All of this will give you a far better idea of what to expect with the fish you buy. Furthermore, you should carefully observe how many dead or sick fish are evident in the dealers tanks, good dealers, who buy from good suppliers, will have far less than those that do not. All of this will enable you NOT to eliminate the risk, but greatly reduce it.

John Shawn Prescott. john@aquarium-gardening.com

Ref. 1 Aquaculture for Veterinarians . Pergamon Press. Ed. Lydia Brown 1993. Diseases of Fishes C. Van Dujin Jr. Iliffe Books Fish Medicine Ed. M. Stopskopf. W.B.Saunders Co

Refs.2

Fischkrankenheiten im Meerwasser aquarium G.Basleer Natur Books.

Disease Prevention & Control G. Blasiola F.A.M.A Mar. 1980 pp. 18-19.

Lom.J. Protozoan casing diseases in Marine fishes in A symposium on diseases of fishes and shellfishes. (ed. S.F. Sniezko) pp 101-123. Am. Fisheries Soc.

Lom J. & Negrelli R.F. Brooklynella hostilis . A pathogenic ciliate in marine fishes. Journal of Protozoology 17(2) 224-232.

By John Shawn Prescott

In this article we will deal with a freshwater parasite Trichodonella, ( which has two other closely related types see below. Also for Salt water enthusiasts we will deal with the parasite Unonema marinum. Also a few passing words at the end on Cyanobacteria aka Red Slime Algae.

Trichodina, circle shaped skin Parasite on Gill filament(side view)

Trichodonella

This parasite has 3 different types (aka genera), which are called Trichodina , Tripartiella , & the most common form Trichodonella . All three of these are distinctly circular in shape, with a band of cilia around the circumference of the organism.

Trichodina, the circle shaped Parasite

In size they vary from 40 microns to 60 microns in diameter, & have an easily identifiable movement which is usually a rotating movement. All members of this family have a disc which has many teeth, which they use to “hook” themselves onto a host. Under the microscope they have an appearance that may remind one of a space ship, when observed from above, & if they are seen sideways on, this apparent resemblance to such exotic transport, is heightened as they are bell shaped when observed.

The parasites most frequently attack the gills of the infected fish, which causes in heavy infestations, great difficulty in breathing, so that they come to the surface in a desperate attempt to get sufficient oxygen.

Typical signs of infection. Trichodina & related species.

Water . Less than optimum water quality, such as a lowering of the pH level, or high Nitrate or Phosphate readings can lead to an outbreak.

Behaviour . Fish will evidence lethargy, and scratching of the fish against any suitable object in an attempt to get rid of the organisms. Breathing at the surface, or just stationary “hanging” at the surface will be observed.

Fins . Fins often become clamped or folded.

Body . Typically the body will manifest darker colours than normal.

Gills . Gill examination will show large numbers of the organisms , & an excess of mucus may be produced by the gills in response to the invasion by the parasites.

Skin. (smear). Should show ciliates once an infection has become established. A pale bluish slime is often noticed which covers the skin, this is typically blotchy in nature. Mucus is secreted copiously as a reaction to the parasites. Ulcers may be seen on the skin, where necrosis by the parasite has taken place.

Life cycle . This takes place by simple mitotic division, & can result in uncontrolled situations in a rapidly expanding population which increases exponentially.

Prognosis :- In mild infestations of Trichodoniasis, a cure is almost always possible, & the Hobbyist should if any thing untoward is observed try to make a certain diagnosis following approved methodology, and if the parasite is confirmed then remedial treatment as indicated below should be implemented without delay.

In cases, were severe multiplication of the parasite has already caused heavy invasion of the gills, especially, but also perhaps of the skin, which then invites secondary bacterial & fungal infections to gain a hold, then casualties are to be expected. This however is one disease, that good husbandry & timely action can be expected to overcome without too much in the way of losses.

Treatment . There are several possible cures. As these are quite different in their chemical formulation, one should pay particular attention to the species to be treated, as different fish have totally differing tolerances to the chemicals involved.

I will list some of the most popular methods, along with a few cautions, but as so many Hobbyists have a considerable number of assorted families of fish, in a typical Aquarium, it is vital to pay careful attention, by reading suitable literature, as to the sensitivity of the species you keep to the various potential cures. Failure to do this, ( it happens very frequently), will ensure that some fish will die not so much from the illness as from the cure. This no doubt is one more example of the old adage, that the cure was worse than the disease.

Chemicals that can be used to eliminate Trichodoniasis.

1) Malachite green ( Zinc free ) . Dosage rate is between 0.2-0.25 ppm . Some references give double this figure. Pros . Malachite green whilst very effective as a treatment. Cons . Is badly tolerated by many of the Tetras, and especially so, by scale-less fish such as Elephant noses & Clown loaches.

Ensure that you are aware of this factor before selecting Malachite as a remedy. Heavy aeration should be given whilst treating, a repeat dose may be used after about 3 days, if required. Malachite green breaks down more quickly in tanks with a heavy organic load, than those that are above average in cleanliness, so again pay heed to these factors when choosing it.

2) Salt baths . Fish may be bathed in a 1% solution for about 30 minutes, this repeated for a couple of days. Pros . Effective, inexpensive, generally not harmful to the fish. Easily applied but watch if using it, so no unexpected disasters ensue. Cons. Certain fish, among them members of the Carp family have very limited tolerance to salt, and can succumb to it. Also possibly some varieties of Trichodoniasis, either develop an immunity to the treatment, or possibly the some species are the parasite are Euryhaline ( will tolerate varying salinities), and thus are not affected by the treatment.

3) Formalin (37%-40% commercial formaldehyde). Dosages 250 ppm for about an hour, or 100 ppm for 3 hours. Long term baths may be used at dosages of between 15-20 ppm. Pros . In many cases can be totally effective with only one treatment. Cons . The many diverse species of fish tolerate Formalin in varying degree. It is vital to pay close attention to the literature BEFORE using this method, relate the species in your tank to the body of knowledge which is considerable. If the literature favours the varieties you are keeping, then this could be the drug of choice, but be aware not all families of fish tolerate it so well.

4) Acriflavin Use at 50 ppm as a bath for about 2-4 days. In heavily planted Aquaria, one should treat if possible in a separate treatment tank, to avoid damage to the plants. Pros . An effective treatment that is also effective against other possible infections that may be opportunistically awaiting their chance to become parasitic, also Acriflavin is useful against many of the gram-negative bacteria that are so often the result of an infection. Cons . The treatment dosage with this drug, is greatly influenced by the pH of the water. The higher pH’ s (7.8 & above), have a potentiating effect on the working of the drug, that can impact adversely upon the fish, if this factor is not allowed for. If you choose an Acriflavin type formula, ensure that you check the pH before using, then proceed accordingly.

There are a few other remedies such a Methylene blue, which work also very well, but have the problem in most modern Aquariums of staining the mastick that binds the glass with its colour, there is no way to remove this afterwards. Quinine drugs have also been used, but I prefer to avoid these in almost all cases.

Trichodoniasis , can best be avoided by observing with great care any fish you purchase in an Aquarium store , before handing over your hard earned cash. Most infected fish, will show some of the signs indicated above. Lightly affected ones, will respond to a quick one day treatment as a prophylactic measure, of your choice as indicated above, so if this regimen is adhered to, then you should never be troubled by this parasite.

This parasite is the salt water variant of the fresh water species known as Tetrahymena. It is a free living ciliate species, that is quite often a “visitor” to marine Aquariums that can if unchecked cause quite severe losses. As an interesting aside, a colleague working with Tuna fish culture in Australia, has found this parasite to be her greatest problem, but so far no major report of serious outbreak in the Aquarium marine hobby has been notified, although a few minor cases are recorded.

In Aquaculture as I have just indicated, there have been some major outbreaks, so a Hobbyist should therefore always be aware that such is a possibility.

It affects several varieties of popular Marine Aquarium fish, among them are Tangs, especially the Yellow Tang, Pomacanthid species , Seahorses, as well as some Centropyge s, many species of Butterfly’s, yellow headed Jawfish among others.

Life cycle . This takes place by simple mitotic division, but there seems to be quite a body of evidence that in marine Aquariums at least, that high organic loads appear to favour the reproduction of the ciliate.

Typical signs of infection. Uronema marina .

Water . Less than optimum water quality, especially high loads of organic matter, which may show up in excessive Nitrate and/or Phosphate measurements, as well as an undesirable BOD measurement.

Behaviour . Fish will evidence agitation in the early stages of an infestation. Rubbing and scratching are to be expected as the fish tries to dislodge the irritation. As the disease progresses, extreme lethargy ensues. Eventually the fish will rise to the surface, hanging there, in an attempt to get air, as it gills become more and more parasitized . Heavy breathing may be observed at this stage. The fish may try hiding away from other fish and observers.

Body . In the early stage, a certain fading of the natural colour of the body colour will manifest itself. This will appear as a kind of fading of the colours. As the disease progresses, evident necrotic erosion of the body becomes evident, & haemorrhagic lesions will become apparent.

Eyes . In medium to advanced stages of an outbreak, the eyes typically become clouded, & when very heavy blindness can ensue.

Gills . Gill examination will show large numbers of the organisms .

Skin . (smear). Should show ciliates once an infection has become established. Secondary infection with fungal is commonplace once major invasion of the skin has taken place, adding to the problem. Excessive slime will be noticeable on the skin.

Histo-Pathology . Smears taken form the gills as well as the skin, usually show many hundreds of the ciliates which are about 40 x 20 microns in size. Evidence of infection can also be expected by examination of the ureter, as well as the kidney. As mentioned earlier evidence has now arisen of infestation penetrating the brain as well.

Prognosis: - Outlook is extremely variable. Heavy infestations usually cause such necrotic damage that mortality ensues, probably by secondary infections. The references to treatment in the literature are sparse, so I will relate from my own experience, as well as the excellent short book by Gerald Bassleer (in German), as little else is available. I believe it is possible with scrupulous attention to the details to “defeat” this scourge, which can literally destroy an Aquarists prize specimens rather quickly if not controlled.

Treatment . The preferred treatment which has worked for me, and is also referred to among others by Bassleer, is to use prolonged fresh water baths. These should extend from 15-30 minutes & must be repeated for several days to ensure a good result. The fresh water MUST be the same temperature , pH etc as the water in the Aquarium, to avoid extra unnecessary stress, and under no account should the Hobbyist, try to do any other task during this time. No telephone calls etc. The fish must be closely observed for undue stress (most fish will keel over) but will not be too greatly stressed if the points mentioned are adhered to. However if the fish is in an advanced stage of infection then this method will certainly kill of the fish, not only from the stress, but also because if there is already major necrotic damage, then the change in osmotic pressure that will kill the parasite, can cause the fishes body fluids to “osmose” out to the water of the container, & the result will be its demise. The treatment works well in early cases, especially to prevent fish that have been exposed to the infestation becoming badly infected.

The Aquarium must be “cleaned” of all excessive detrital material as there a correlation between the amount of such and the proliferation of parasite. If possible infected fish should be placed in another Aquarium until recovery appears to be under way. The parasite seems to be unable to tolerate the change in osmotic pressure, and simply stated it bursts, if one is able to keep following through. The problem can be that some species of fish, as well as variation among individual specimens, also occasionally will cause such distress as to harm the fish. This is mostly avoided by keeping a close eye on things.

Bassleer, also recommends using Malachite green or a combination of Malachite and Formalin. Logically this should work, as it does on may other related ciliates. However he states no dosage, so considerable caution should be used, if choosing this regimen, as no other commentator has referred to it. He also mentions the use Methylene blue, and especially mentions a combination of Chloramphenicol with Nifurpirinol. Again for these no dosages are given, but probably he has found they work, as one would expect them to be efficacious against secondary infections, which so often are the ultimate cause of death.

As most of the likely species to be infected in the Hobbyists tank, are among those that are expensive, it is most useful to have some knowledge of what to look for, in this parasite, as I have often saved almost all my fish by discovering it early, when treatment has the greatest potential for success. I have unfortunately witnessed all to many cases, where the outcome was an almost total loss.

Before finishing I want to take up a matter that whilst not strictly a disease, is one that causes many losses in Marine Aquariums. The subject is Cyanobacteria, aka Red Algae.

I get many calls about it as we have asking for a product to get rid of this. However I have for a few years been investigating the underlying reasons for this phenomena so would invite those Hobbyists who have this problem and would care to cooperate in some research to contact me.

There are several references in the literature to the alleged fact that Cyanobacteria are supposed to thrive when the Phosphate levels are excessive. Many times Hobbyists have contacted me to say, that they are plagued by “Red Algae”, but that their Phosphate levels are either zero, or almost so.

I began a few years ago to make some preliminary investigations, as I had a suspicion that perhaps the cause was not PO₄, (inorganic Phosphate), but in fact PO₃ (orthophosphate or organic ). At that time, some Hobbyists were kind enough to send me samples of their water, in every case I tested the water and it showed as they said almost no PO₄, but substantial PO₃ values.

So if any of you out there, have any ideas on how the PO₃ becomes transformed in the biological interactions that take place in an Aquarium, I would like to have your ideas, as well as any references in the literature, as I have been unable to find any. This would be important in trying to find some methods of prevention, rather than cure. As the several Phosphate “sponges” or similar on the market, only remove PO₄, such would be a most

John Shawn Prescott john@aquarium-gardening.com

References Trichodoniasis

Trichodoniasis Dr. Jim Chacko Univ. of Maine in Fish-Vet vers. 2.0 1997 (in press)

Diseases of Fishes C.van Duijn Jnr. London Iliffe Books 1972.

Fish Medicine Paul Cheung Ed. Micheal Stopskopf. W.B. Saunders Co. 1992

Aquaculture for Veterinarians Ed. Lydia Brown. Pergamon Press. 1993

Handbook of Fish Diseases Ed. Dieter Untergasser TFH 1989

Handbook of Drugs for treatment of Fish Disease

Nelson Herwig. C.Thomas Publ. 1979.

Refrences. Uronema marinum

Fish-Vet vers. 1.0 Shawn Precott 1995. Fish Medicine Contributor Paul Cheung Ed. Michael Stopskopf. W.B. Saunders Co. 1992.

Fischkrankheiten im Meerwasser-aquarium Gerald Bassleer. Natur Verlag. 1991. Dr. P.J. Cheung et al. (1980). Studies on the morphology of Uronema marinum Dujardin(Ciliates, Uronematidae) with a descroption of the histopathology