BB Ch20 Other laboratory fishes

Question 1

Fish is a broad encompassing term. What 4 taxonomic classes contain fish?

Answer 1

Myxini, Cephalaspidomorphi, Elasmobranchiomorphi, and Osteishthyes

Question 2

How have fish been used in research?

Answer 2

Toxicology studies (Japanese medaca and common guppy); fish models in study of cancer (zebra fish and swordtails); ecological studies of aquatic environments; and basic physiologic, biochemical, and molecular research

Question 3

How much overhead clearance should a fish tank have?

Answer 3

The minimum overhead clearance for any tank should exceed the depth of the tank to allow the use of nets without impediment and facilitate safe handling of fish.

Question 4

The major safety hazard in aquatic facilities is electrocution. What safety precautions should be employed to avoid disaster?

Answer 4

Use properly wired ground-fault circuit breakers throughout the facility. All electrical outlets should be 3-4 feet above the floor in case of flooding or inappropriate use of water hoses. Use rubber gaskets to seal moisture from outlets. Employees should be trained in safe use electricity near water. Floors should be sloped and drains positioned so there is no standing water. Dip nets should have nonconducting handles and there should be no exposed wiring.

Question 5

How much does water weigh? Why is this a concern?

Answer 5

One liter weighs about 1 kg. One gallon of water weighs 8.3lbs. A 25 gallon tank (100 liters) will weigh over 200 lbs when filled. Support stands and flooring must be strong enough to accommodate the weight.

Question 6

What are 3 types filtration used in aquatic design?

Answer 6

Mechanical, biological, and chemical

Question 7

What is mechanical filtration?

Answer 7

It removes suspended particles from eater by passing it through a medium that obstructs the particles.

Question 8

What is chemical filtration? Provide some examples…

Answer 8

Chemical filtration encompasses a wide range of methods for removing molecular contaminants from water, including ion exchange, foam fractionation (by protein modification and ultraviolet filtration), and activated carbon filters (nonspecific exchange filter).

Question 9

What is biological filtration?

Answer 9

Biological filtration is biological fixation of wastes into less toxic compounds or forms. Bacterial fixation of nitrogen is the most commonly employed form.

Question 10

What is usually the limiting factor in biological filters?

Answer 10

The limiting factor is the surface area for bacterial growth along with the ability to circulate the waste-laden water into contact with the bacteria responsible for nitrogen fixation.

Question 11

What is a flow-through (or open) water system?

Answer 11

It is characterized by the continuous addition of new water with equal volumes being removed.

Question 12

What are some disadvantages of a flow-through system?

Answer 12

Cost is a disadvantage of getting water from a municipal system as well as the expense of removing municipal disinfectants. Wells can fail if using well water. Another disadvantage is tempering and conditioning water and the disposal of effluent water from fish systems.

Question 13

How can the air system for fish tanks transmit pathogens?

Answer 13

The fine bubbles coming to the surface from air stones and airlifts cast millions of small aerosol droplets into the air that can carry bacteria, viruses, and fungal spores.

Question 14

How can fish tanks and water systems be disinfected between experiments?

Answer 14

Most commonly, the water in a system is drained and replaced after cleaning any visible dirt from the tank sides. A second method to decontaminate tanks is to spray 70% ethanol or 2-propanol and allowing the alcohol to evaporate (after cleaning visible debris). This method does not clean the plumbing or filtration systems. The final method is to drain and remove debris and fill the tank with a dilute chlorine or quaternary ammonium solution and circulate for an hour or more. Great care should be taken to ensure all disinfectant is removed from the system before it goes back on line.

Question 15

What are some important considerations when retrofitting an existing animal facility for aquatics?

Answer 15

First evaluate potential water sources for reliability as well as quality. Also evaluate water disposal and cost. Next, look at the electrical supply. Electric resistance-based heaters, pumps, and lighting can double or triple the power requirements of the existing facility. In addition, ground-fault receptacles should be added and placed above splash points. Power-failure alarms and emergency power generators are a necessity for aquatic facilities and should support air supply pumps and generators as a fist priority, along with emergency personnel safety lighting. Also aquatic facilities will load large amounts of moisture in the air which will affect the air handling system.

Question 16

What are important considerations when planning to build a new aquatic facility?

Answer 16

Will the facility hold fresh water species, marine species, or both? How large will holding tanks be to accommodate these fish? What shape will the tanks be (round or rectangle)? What will be the nature of the studies?

Question 17

What is the optimal temperature range for tropical fish?

Answer 17

24-26ºC Temperature of 27ºC is sometimes used when treating protozoal infections.

Question 18

How can fish tanks be heated?

Answer 18

Room air can be heated in the 24-25ºC range. Supplemental heaters should be used to boost temperatures in case of failure of the air-handling system.

Question 19

What is the rule of thumb when predicting wattage of heaters of fish tanks against volume of water?

Answer 19

50-100 watts of heater/40 liters of water

Question 20

How can water be cooled to maintain temperate or cold-water species of fish?

Answer 20

The most common refrigeration systems are heat exchangers driven by a compressible refrigerant. Titanium is the only metal proven suitable for heat-exchangers used in marine systems.

Question 21

What is the ideal choice of tank construction for small water systems?

Answer 21

Glass is the ideal choice because it allows excellent visibility, it is relatively chemically inert, it is hard and less easily scratched.

Question 22

Why should only high-grade or medical-grade silicone be used in glass tank construction or repair?

Answer 22

Low-grade, inexpensive silicone caulks contain heavy metals, cyanide, and organic toxins which can kill fish.

Question 23

What is relatively inexpensive and probably the most commonly used structural plastic in aquarium construction?

Answer 23

Fiberglass (highest tension loading capacity of the plastics) is the most common however there is variability of toxins leaching from the hardening resins which makes it unsuitable for toxicology studies.

Question 24

What plastic is a poor choice in any fish system?

Answer 24

Vinyl is poor choice for fish systems because it is easily damaged and has large residuals of toxic plasticizer and heavy metals trapped in the polymerization process.

Question 25

Concrete is widely used for very large fish systems because of durability, low cost, and formability. How should it be treated before housing fish?

Answer 25

It should be thoroughly washed or leeched with dilute muriatic acid, then several coats of sodium silicate or other sealant should be applied.

Question 26

Can metals be used in aquatic systems?

Answer 26

Stainless steel can be used (American Iron and Steel Type 316) but it will corrode. Titanium is preferred over SS where strength and maximal corrosion resistance are needed. The galvanized coat of iron can contain lethal levels of zinc. Bronze can also be a fatal source of zinc and copper.

Question 27

What are the 3 critical factors which must be monitored continuously in an aquatic system?

Answer 27

Temperature, water level, and power failure

Question 28

Biofilters can te re-seeded after disinfection by placing them into a well-established reserve system. What are 2 ways the biofilters can be fed in the reserve system?

Answer 28

The first is to have resident fish or invertebrates that can provide waste material to feed the bacteria. This can potentially harbor reservoirs of infection. The second is to release ammonia into the system on a periodic or continuous basis.

Question 29

Is “topping off” or the practice of adding water to compensate for evaporative losses equivalent to conducting water changes?

Answer 29

No, toxic compounds do not evaporate at the same rate as water and will accumulate in the water.

Question 30

What is the recommended percentage of water to change out of a tank without harming the fish?

Answer 30

0.75-1.0%/day - small frequent changes reduces the impact of temperature, pH, ionic, or other shocks that may occur 25-50% water change at one time may be used if the water is properly conditioned & may be useful to manage disease

Question 31

Are diets fed to laboratory fish complete for optimal growth?

Answer 31

Probably not. Empirically derived diets are usually relatively unrefined. Trace nutrient balance is rarely considered and quality control, including component selection for diets, is minimal. Relatively little is known about the natural diets of many commonly kept fish or about the effects of trace imbalances on fish physiology.

Question 32

What are some important considerations when housing multiple species of fish in a primary enclosure?

Answer 32

Schooling, size differences, time-in-residence territoriality, gender interactions, and other social complexities

Question 33

What is the best method to ensure fish are disease free before starting research?

Answer 33

On-site screening at the source can reduce the probability of introducing disease into laboratory water systems but these suppliers are rare. Alternatively fish can be quarantined and screened in-house.

Question 34

What is an appropriate quarantine period?

Answer 34

14-21 days for many problems, but 4-6 weeks is recommended for concerns about mycobacterial infections.

Question 35

What is the most common sampling approach of quarantined fish?

Answer 35

Lethal testing is used which allows bacterial cultures of internal organs and histologic examination of all organs.

Question 36

What are 3 stages of suffering that should be recognized in animals?

Answer 36

DISCOMFORT, STRESS, PAIN DISCOMFORT: may be manifested by negative signs such as poor condition, torpor, and diminished appetite. STRESS: condition of tension or anxiety predictable or readily explicable from environmental causes. PAIN: signs such as struggling, screaming, or squealing, convulsions, or severe palpitations are evident.

Question 37

Fish physiologists argue that pain is probably not experienced as a strong sensation by fishes. What are the main sensory cues to which fish respond in an aquatic environment?

Answer 37

Chemical, hydrodynamic, acoustic, thermal, electrical, light, and mechanical; forceful or noxious physical or chemical stimuli may evoke violent reactions in fish

Question 38

Although central reception of pain sensory inputs are unclear in fish, how can pain be assessed?

Answer 38

They demonstrate clinical signs of acute and chronic stress and physiologically stress can be measured by levels of serum cortisol.

Question 39

T/F Anesthesia should be offered to fish for any painful procedure and is required in fish for procedures that do not require it in other species.

Answer 39

True: immobilization, prolonged transport, and minor surgery for topical lesions all require some degree of tranquilization.

Question 40

What are the anesthetic stages and planes of fish?

Answer 40

Stage I, Plane 2: deep sedation; voluntary swimming stops and the respiratory rate (opercular movements) become slower. Stage II, Plane 1: light narcosis; may be preceded by a brief excitement period and an increase in respiratory rate. The fish loses equilibrium but works to right itself in the water. Stage II, Plane 2: deep narcosis; marked by a decrease in respiratory rate back to normal and total loss of equilibrium; suitable for _external sampling_ Stage III, Plane 1: light anesthesia; characterized by a further decrease in respiratory rate and near total loss of muscle tone; suitable for _minor surgeries_ Stage III, Plane 2: surgical anesthesia; characterized by bradycardia, markedly low respiratory rate, and total loss of reactivity to manipulation Stage IV: medullary collapse; characterized by total loss of gill movement followed by cardiac arrest.

Question 41

What are 4 anesthetics that have been used in fish?

Answer 41

Tricaine methane sulfonate (MS-222), metomidate, carbon dioxide, and quinaldine

Question 42

What is the only anesthetic fully licensed for use in fish in the US and is one of the most widely used anesthetic agents for poikilotherms world-wide?

Answer 42

MS-222

Question 43

Why is MS-22 (tricaine) considered by may authors to be an hypoxic agent?

Answer 43

It causes bradycardia, an increase in resistance to blood flow through the gill lamellae, and erythrocyte swelling. Further physiological effects due to hypoxia can include increased concentrations of blood glucose, lactate, potassium, magnesium, hemoglobin, and hematocrit; increased urinary output; and electrolyte loss.

Question 44

What are some side effects of metomidate hydrochloride?

Answer 44

Long recovery time, reduces plasma cortisol and glucose concentrations, and increases fish pigmentation (increases production of melanocyte-stimulating hormone on the same primary protein as adrenocorticotrophic hormone)

Question 45

Although fish are not covered by the US Animal Welfare Act, what are 2 other agencies that define acceptable euthanasia practices?

Answer 45

Guide for the Care and Use of Laboratory Animals and the American Veterinary Medical Association’s euthanasia guidelines

Question 46

What are 2 common bacteria found in fish as well as mammals that could potentially infect humans?

Answer 46

Streptococcus and Staphylococcus

Question 47

Erysipelas rhusiopathiae is present in the external mucus of fish. Is it zoonotic?

Answer 47

Yes, 3 forms of the disease are described 1. Localized skin infections (erysipeloid or “fish rose”) usually on fingers and hands 2. Diffuse cutaneous disease 3. Septicemia.

Question 48

Mycobacterium fortuitum, M. cheloni, and M. marinum are recognized pathogens of fish. Which of these can cause disease in man?

Answer 48

Zoonotic transmisssion of M. marinum and M. fortuitum to fish handlers or persons in close contact with infected fish has been documented.

Question 49

What organisms are often misdiagnosed in fish and humans as mycobacterial disease because of the similarity of clinical signs and positive reaction to acid-fast staining?

Answer 49

Nocardia asteroides and N. kampachi

Question 50

What are 2 syndromes described in humans that contracted Vibrio vulvificus from aquatic organisms?

Answer 50

1. Primary septicemia (associated with ingestion of raw oysters) which produces fever, altered mental status, ecchymotic hemorrages, bulla formation, and pain in lower extremities (mortality 50%). 2. Wound infection characterized by cellulitis, edema, hemorrhages, bulla formation, and extensive tissue necrosis (mortality 25-30%)

Question 51

What are clinical signs seen in fish with mycobacteriosis?

Answer 51

Lethargy, anorexia, fin and scale loss, exophthalmia, emaciation, skin inflammation and ulceration, edema, peritonitis, and nodules in muscles that may deform the fish

Question 52

What fish species are susceptible to mycobacteriosis?

Answer 52

All fish species are susceptible because of world-wide distribution of the organism.

Question 53

How is mycobacteriosis diagnosed?

Answer 53

Clinical signs and the presence of acid-fast bacteria in tissue sections or smears

Question 54

Can mycobacteriosis be treated in fish?

Answer 54

Multiple-drug therapy, such as doxycycline and rifampin, can be used in valuable animals, but because of difficulty of treatment and the risk of spread to other fish and humans, most elect to destroy the infected fish.

Question 55

What holotrichous ciliates infect marine and freshwater fishes?

Answer 55

Fresh water fish - Ichthyophthiruius multifilis Marine fish - Cryptocaryon irritans

Question 56

What are the clinical signs of infection with Ichthyophthirius multifilis?

Answer 56

White Spot Disease - Small white spots widely distributed over the body

Question 57

Describe the life cycle of Ichthyophthirius multifilis.

Answer 57

The white spot on the fish is called the trophont which is the encysted feeding stage. It enlarges, breaks out, and drops to the bottom of the aquarium, attaching to surfaces, and is called a tomont. It then undergoes binary fission which results in hundreds of ciliated theronts released into the water where they search for host fish.

Question 58

What is the treatment for white spot disease and what are the recommended control strategies?

Answer 58

There is no treatment - drugs do not penetrate the encysted trophonts. Prevent reinfection of fish by killing free-swimming trophonts by adding formaldehyde at 25 ppm (1 ml/10 gal) 3 time on alternate days. Also change water (up to 75%) 4-8 hours after treatment. The water temperature can also be elevated several degrees over normal temperature for 5-7 days.

Question 59

What is a small flagellated protozoal parasite that can cause disease in freshwater fish?

Answer 59

Ichthyobodo necatrix

Question 60

What are the clinical signs of Ichthyobodo (protozoa)?

Answer 60

Depressed, anorectic, respiratory distress, a whitish film from excess mucus production

Question 61

How is Ichthyobodo infestation diagnosed?

Answer 61

Microscopic examination of wet mount of skin or gills reveals organisms that are actively motile, small (7-15 microns long), and somewhat comma-shaped. They can be free swimming or attached to cells by their flagellae. They move in a circular fashion.

Question 62

Describe how Ichthyobodo protozoa damages the host.

Answer 62

They feed directly on epithelial cells by penetrating within the fish gullet, thereby destroying gill and skin epithelium.

Question 63

What type of fluke can inhabit the gills in freshwater fish?

Answer 63

Dactylogyrid flukes

Question 64

Describe the pathogenesis of Dactylogryid flukes?

Answer 64

Hyperplasia, destruction of gill epithelium, and clubbing of gill filaments, which can lead to asphyxiation

Question 65

Which of the following are treatment options for Dactylogyrid flukes? 1. metronidazole 2. praziquantel 3. formaldehyde 4. tetracycline

Answer 65

Praziquantel as a bath at 6 ppm or low levels of formaldehyde (25 ppm)

Question 66

Gyrodactylus is a trematode that can infect most freshwater tropical fishes. How do the trematodes feed and what clinical signs are commonly seen?

Answer 66

The parasites feed on blood and epithelium by scraping and sucking. Lesion can include localized hemorrhagic areas, excessive mucus, and localized ulcerations. Infected fish may have a ragged tail from localized hyperplasia, necrosis, and loss of epithelial cells on the fins.

Question 67

Which of the following are treatments for Gyrodactylus? 1. praziquantel 2. formalin 3. formaldehyde 4. salt water baths

Answer 67

Praziquantel at 3ppm in aquarium water. Other treatments include formaldehyde (25 ppm), salt-water baths (2.5-3%), or organophosphate baths.

Question 68

Name some nematodes that can infect teleost fishes.

Answer 68

Larval forms of Eustrongyloides spp and adult forms of Capillaria sp and Camallanus sp

Question 69

What are some of the clinical signs of nematode infections?

Answer 69

Emaciation and failure to thrive to swelling and tumors caused by subcutaneous worms. Infections with Camallanids are usually first noticed when a red worm protrudes from the anus of the fish.

Question 70

What is the most common treatment for nematodes?

Answer 70

Panacur (fenbendazole) in food a 0.25% (250 ppm)

Question 71

Identify members of the microsporidian genera that can be highly pathogenic to teleost fishes.

Answer 71

Glugea, Pleistophora, and Spraguea (synonym Nosema0

Question 72

Where are microsporidian parasites found in the body of the fish?

Answer 72

Intestines, pyloric ceca, bile ducts, liver, mesenteric LN’s, muscles, neural ganglia, subcutaneous tissues, testis, and ovaries. Mechanical distension of intestinal tissue and starvation are thought to be the cause of death.

Question 73

Describe the life cycle of a microsporidian species?

Answer 73

The life cycle is divided into 2 distinct phases: a multiplicative stage (schizogony) and a spore-forming stage (sporogony). The infective germ, the sporoplasm, is extruded to the exterior through a hollow, coiled polar tube that is everted after the spore has been ingested by a specific host. The sporoplasm is injected into the host cell and undergoes multiple binary fission, producing an enormous number of cells.

Question 74

Describe treatment and control strategies for microsporidian parasites in fish.

Answer 74

Remove sick or dying fish before cannibalism by other fish in the tank can occur. No effective chemotherapeutics have been identified at this time.

Question 75

What types of myxospores cause disease in laboratory fish?

Answer 75

All species of Multivalvulida (3 or more valves in spore walls) and a few of Bivalvulida (2 valves in spore walls) are important histozoic parasites that inflict serious injuries to the host.

Question 76

Where do the myxosporidian parasites reside in the host?

Answer 76

They infect the gall bladder and urinary tract (coelozoic) or are intercellular or intracellular parasites of muscle or connective tissue (histozoic). Trophozoites of coelozoic species attach to the transitional epithelium of the gall bladder and urinary bladder during their reproductive cycles, usually with no apparent damage to the host. Infected muscle fibers become enlarged and replaced by cysts filled with mature spores that may be encapsulated by the host’s connective tissue. Muscular liquefaction is due to a proteolytic enzyme released by the parasites after the death of the host.

Question 77

Lymphocystis is a world wide disease occurring in at least 125 species of teleosts. What is the causative agent?

Answer 77

Lymphocystis is an iridovirus

Question 78

What are the clinical signs lymphocystis?

Answer 78

Macroscopic nodules (0.3-2.0 mm or more in diameter) occur primarily on the body surface but can also develop on the internal organs. The nodules appear cream-colored to pink or gray. They take a week to a year or more to develop. The lesions eventually heal.

Question 79

Describe how can the virus that causes lymphocystis can be inactivated in water?

Answer 79

Expose to ether or chloroform, hear (56-600 C), or pH 3.0. The virus is stable to multiple cycles of freezing and thawing.

Question 80

What is the etiologic agent for infectious pancreatic necrosis (IPN)?

Answer 80

An aquatic birnavirus

Question 81

Which fish are particularly susceptible to IPN and what are the clinical signs of IPN?

Answer 81

Acute infection occurs in very young fish of some species and can result in cumulative mortality approaching 100%, particularly in salmonids. Older fish often develop subclinical infection. Affected fry and fingerlings swim by rotating on their long axis, or whirling. They are dark, often with exophthalmia, abdomenal distension, and mucoid fecal pseudocasts. Anemia is a clinical feature of this disease.

Question 82

What are the necropsy lesions observed in fish that have IPN?

Answer 82

The liver and spleen are pale, and the stomach and intestines are empty of food and filled with mucoid fluid. Diffuse petechial hemorrhages throughout the pyloric and pancreatic tissues are characteristic. There is massive necrosis of pancreatic acinar cells and occasionally islet tissue with prominent intracytoplasmic inclusions. The pylorus, pyloric ceca, and anterior intestine show extensive necrosis. Degeneration can also be seen in renal and hepatic tissues.

Question 83

What means can be used to inactivate IPNV?

Answer 83

Chlorine, iodophor, ozone, ultraviolet radiation, prolonged exposure to beta-propiolactone, formalin, drying, heating at 60o C, or pH 2 or 9

Question 84

Which of the following filters would be expected to retain bacteria? 0.45 micron 0.3 micron 0.2 micron

Answer 84

0.2 micron

Question 85

What is the most commonly applied form of chemical filtration?

Answer 85

Activated carbon filters - functions by binding cations and anions