Slide 1

Fish Medicine BIOLOGYAt 31,500 species, fish exhibit greater species diversity than any other class of vertebrates.

Three Classes of FishAgnathan: Jawless fish, *Hagfish, Lamprey

Chondrichthyes: Cartilaginous Fish *Sharks, Rays, Skates

Osteichthyes: Bony Fish * clownfish, Eel, Trout, Marlin

Osteichthyes: Bony Fish

Kingdom: AnimaliaPhylum: ChordateSubphylum: VertebrateClass: Osteichthyes

Fish are aquatic vertebrates that are typically Ectotherms (cold-blooded)Covered with scalesHas a gill cover called an OPERCULUMMinimal Protective Mucus, nonselective defense against bacteria Multiple sets of paired fins and unpaired fins

TaxonomyTeleosts = bony fishsoft rayed teleostsspiney rayed teleosts

External Fish Anatomy

Fish Anatomy

1.2.3.4.5.67.8.Herbivore-Carnivore Comparison

Functions of the GillGill FunctionsWhen water is passed over the gills, oxygen is absorbed and carbon dioxide and ammonium is exhaled. 75% of the ammonia excreted by the fish is through the gills. The gills also help the fish osmoregulate, (equalize body pressures). They are covered by a bony flap known as the operculum. Each gill consists of a bone arch with filaments extending at right angles to the arch. Lamellae are the tiny branches on the filaments. Healthy gills are bright red and do not stick together.

Fish Gill Anatomy

Fish Gill AnatomyFish Gill Anatomy

Gill FilamentsLamellaeFish Anatomy

Finssupported by raystwo types of rayssoftspines

Fin Identificationunpaired finsdorsalcaudalanalpaired finspectoralpelvic

Skinepidermismucous glandsalarm cellscuticledermisscaleshypodermis

ScalesPlacoid scales, also called dermal denticles, are similar to teeth in that they are made of dentin covered by enamel. They are typical of sharks and rays. Ganoid scales are flat, basal-looking scales that cover a fish body with little overlapping. They are typical of gar and bichirs. Cycloid scales are small oval-shaped scales with growth rings. Bowfin and remora have cycloid scales. Ctenoid scales are similar to the cycloid scales, with growth rings. They are distinguished by spines that cover one edge. Halibut have this type of scale.

Placoid scalesGanoid scales Cycloid scales Ctenoid scales Lateral linesensory systema line of pores lead to mechanoreceptorsenvironmental informationpressure, currents, sound

Colorcellschromatophorespigmentsiridophoresreflective substancescontrolendocrine systemnervous system

Respiratory systemlungsgillsbilateraloperculum

Gill structure

gill archesprimary lamellae (filaments)secondary lamellae

Cardiovascular system

2 chamber heartatriumventriclesinus venosusbulbus arteriosus

The heart pumps the blood in a single loop throughout the bodyCirculationvenous blood to hearthepatic portal systemrenal portal systemheart to gillsvia ventral aortagills to bodyvia dorsal aorta

Red blood cellselliptical and nucleatedno bone marrow main sourcehead kidney

White blood cellsSimilar to mammalianno lymph nodeslymphocytes > (granulocyte) neutrophils monocytes thrombocytelymphoid tissuesthymushead kidney spleen

Excretory systemgillskidneysanterior kidneyposterior kidney

Osmoregulation (is the active regulation of the osmotic pressure of an organism's fluids to maintain the homeostasis of the organism's water content)electrolyte balancefreshwater vs saltwater

Osmoregulationfreshwater fishwater diffuses in ions diffuse outdrink littlelots of dilute urineactively reabsorb ionskidneysgillssaltwater fishwater diffuses out ions diffuse indrink a lotconcentrated urineactively excrete ionskidneysgillsgut

Swim bladderTwo typesphysoclisticcapillary networkphysostomatouspneumatic ductfunctionsbuoyancysound, pressure detection

Digestive systemStomachintestinepyloricmiddlerectalspiral colonpyloric cecaeliverpancreas

NutritionSpecies variationfoodfeeding behaviortimelocationobtaining foodgeneral fish nutritionprotein and lipids > carbohydrates

Neuroendocrine systembrainforebrainolfactory bulbsmidbrainoptic lobescerebellumspinal cord

Electrical systemelectric organselectroreceptorsexampleselectric eelelectric catfishelectric ray

Electric eel anatomy: The first detail shows stacks of electrocytes, cells linked in series (to build up voltage) and parallel (to build up current). Second detail shows an individual cell with ion channels and pumps penetratimng the membranceCredit: Daniel Zukowski, Yale University

Bioluminationself -luminousphotophoresLuciferase

Breedingfemales and maleshermaphrodites

Reproductive systemfemaleovariesoviductno uterusmale testes

FertilizationExternal fertilizationopen-spawnerssubstratesInternal fertilization

GestationoviparousovoviviparousviviparousGestation periods vary from 28 to 114 days. Most of the live-bearing species sold for aquariums such as Mollies, Platies, guppies and Swordtails typically gestate for about 28 to 34 days

WATER QUALITYAnd Husbandry

Husbandry PracticesBriefly describe housing, feeding, etc. (refer to specific laboratory standard operating procedures)ExhibitsDisposition of alive and dead animals

Water environmentsfreshwaterbrackish watersaltwater

Freshwater systemspecific gravity: 1.00

Brackish systemspecific gravity 1.01

Saltwater systemspecific gravity: 1.02

Bioload (is the nitrogen processing demand placed upon the material, chemical and biological filters by uneaten food, decomposing inhabitants, accumulated organics and waste produced by livestock, foods and plant matter in the aquarium filtration system)Nonaerated freshwater1 inch fish/ gallonaerated freshwater3 inches fish/ gallonsaltwater0.5 inches fish/ gallonexcluding tail fin

AmmoniaNitrogenous fish waste producttoxic

Nitrification Bacteria Bacteria (Nitrosomas) (Nitrobacter)

ammonia nitrite nitrate Conditioning a new tankseeding bacterialimited populationtime

PHrangesfreshwater: 7.0-7.6brackish: 7.0-7.6saltwater: 8.1-8.3

Decreased PHeffectsinhibits Nitrosomas and Nitrobacterdirect health problems for fishcontrolcheck bioloadremove wastecalcium rich substratesodium bicarbonatetemporaryIncreased PHeffectsammonia is more toxicnonionizeddirect health problems for fishcontrolcheck substrates for calcium rich onespeat mossacetic acidtemporary

Oxygenwater:0.7% dissolved oxygenoxygen solubility decreases as:temperature increasessalinity increaseslow oxygen effects:respiratory distress in fishinhibits Nitrosomas and Nitrobacter

Oxygen replenished by:air:water interfaceaeration systemmonitored as DODissolved Oxygen

Temperaturepreferred ranges variable0 45 C (0-113 F)

temperature changes should be gradual no more than 1 C/ 2 minutes in tankno more than 2 -3 C between tanks

Lightlight cycles12/12at least 8-10/24 hours of darknesslight sourcefluorescent most commonno incandescentno direct sunlight

Chlorine/ Chloraminestoxic/ lethal to fishremovalaeration and timesodium thiosulfatecarbon filter

Heavy metalstoxic/lethal to fishsourcesmetal pipesmetal tank framesmetal decorationsaltwaterextremely corrosive to metals

Filtrationmechanical filtrationchemical filtrationbiological filtration

Mechanical FiltrationPhysically traps suspended particles

sand, gravel, floss, plastic,diatomaceous earth

Chemical Filtrationchemically binds and removes dissolved compounds

charcoal, protein skimmer, UV, ozone

Biological FiltrationNitrificationbacteriasubstrates: plastic, gravel, live rock, decorations

The Importance of Good Water Quality

Causes of Stresswater quality (O2, ammonia, nitrite, pH, other contaminants)transportationnetting & handling temperaturesalinitywater hardness

poor nutritioninappropriate housing conditionsnoiselightingvibrationsstocking density

Stress Response Sympathetic nervous system activation cortisol HR, RR serum osmolality glucose

Immunosuppression( disease resistance) growth rate reproduction ratedelayed capture mortality

Common Pathogens and ParasitesPathogens Aeromonas salmonicida Columnaris Enteric redmouth Fin rot Fish dropsy Flavobacterium Hematopoietic necrosis Heterosigma akashiwo Hole in the head Hypodermal and hematopoietic necrosis Infectious pancreatic necrosis Koi herpes virus Novirhabdovirus Pfiesteria piscicida Photobacterium damselae ssp piscicida Salmon anemia Streptococcus iniae Taura syndrome White spot YellowheadParasites Abergasilus Amoebic gill disease Carp lice Ceratomyxa shasta Dactylogyrus vastator Diphyllobothrium Flukes Glugea Gyrodactylus salaris Henneguya zschokkei Ich (freshwater) Ich (marine) Kudoa thyrsites Myxobolus cerebralis Nanophyetus salmincola Salmon lice Saprolegnia Schistocephalus solidus Sea louse Sphaerothecum destruens Swim bladder disease Tetracapsuloides bryosalmonae

AnesthesiaConsider for painful/stressful procedures and pre-euthanasia

Ice water (transport) - be careful

Chemical - MS-222, Benzocaine

Dose is species specific

MS-222tricaine methanesulfate, ethyl-m-animobenzoate methansulfate, FinquelCNS depressantwater soluble but acidic (add buffer)admin. via bath or recirculating systemfor anesthesia 50-100 mg/L recommended (sedation vs surgical)dose may be species specific - test before experimentMS-222 continduction w/in 3 minutesrecovery w/in 10-15 minutes after removal is residual +/- could affect chemical analysis of tissueno known hazards but wear gloves! Immersion Anesthesia

Levels of Anesthesia

Simple Diagnostics

Skin scrapeFin clipSimple Diagnostics

Gill clipGill sampling

Samples

GillsamplesScale Fin

Clinical Diagnostics

Blood collection for analysisVenipuncture

Radiology

What do you see?

Euthanasia+/- pre-sedation with MS-222decapitationpithingchemical (MS-222)requires experience!!!avoid direct insertion into fixative (alcohol or formalin)

Pithing

Investigate mortality in your systemBasic necropsyKnow your speciesSeek adviceMake appropriate changesEnvironmental Safetyinfectious agentschemical hazards (include MS-222)biohazards

ZOONOSISZoonosis = disease that can be transmitted from animals to humans (or other animals)Anthroponosis = disease that can be transmitted from humans to animalsHigh Risk immunosupressed (AIDs, other debilitating disease)pregnantage Exposure (infected water, fish tissue, fish excrement)dermal contact via skin abrasion, fissureingestionZoonotic Diseases Potential for disease organisms to spread between species (fish human)Bacteria - from handling (mycobacterium, streptococcus, erysipelothrix, vibrio, norcardia, aeromonas, edwardsiella) from ingestion (stahylcoccus, clostridium, vibrio, aeromonas, esherichia, salmonella, edwardsiella)Parasites - primarily from ingestion (nematodes, cestodes, trematodes, protozoa).Toxins - primarily from ingestion (ciguatera, scombroid, dinoflagellates toxins)

Mycobacteria

PREVENTIONFishKnow health of your fishProper husbandry/aquacultureMinimum - wear gloves when handling

All WildlifeKnow the hazards Take all necessary knownprecautionsDO YOUR HOMEWORK!!!

Fish Dissection

Preparation & ExaminationLocate major external anatomical parts:Dorsal FinPosterior DorsalPectoral FinsPelvic FinsAnal FinsCaudal FinGill Covers (operculum)Lateral line - sensory organ of fishRemove several scalesPrepare a dry-mount of a scale.Observe it under a microscopeWhat function do you think scales serve?

DissectionRemove operculum with scissorsObserve gill anatomyRakers - white, comb-like archesFilaments - Red fingerlike projectionsWith a scalpel, remove a section of the lateral lineWhat function does this organ serve?Do you notice a concentration of nerve endings?Begin the main incisionOpen the abdomen (below the gill) carefully with a scalpelCut with a scissors: remove a oval-shaped piece of skin (only skin) running from underneath the gills, to the anus, up to the lateral line, along the lateral line, to the gill, down to where you started the incision. Remove flap of skin (see diagram on next slide)

Main IncisionCut along the blue line... Only cut through scales, muscles, and skin Take special care not to cut too deep!

Anterior View

1. Gills2. Heart3. Liver4. Pyloric caeca5. Small intestine6. Stomach7. Swim bladderDisection

Posterior View

1. Swim bladder2. Gonad3. Large intestine4. Urinary bladder5. Anus Close-up: Body Cavity

MuscleSwim BladderLiverSpleenGastric CecaeEggsStomachOvarySmall IntestineGravid female

Can you identify the parts?

I found him

ReferencesCan Fish Suffer?: perspectives on sentience, pain, fear and stress; K.P. Chandroo et al./Applied Animal Behaviour Science 86 (2004) 225-250Fish Cognition and Behavior; Culum Brown et al.; Blackwell Publishing (2006) ISBN: 9781405134293Fish Medicine; Michael Stoskopf, W.B. Saunders Company; 1st edition (January 15, 1993) ISBN: 0721626297

Pathogeningestion of fish tissue (under cooked or feces cont.)ingestion of infected aquaria waterdermal contact infected

fishdermal contact infected Aquarium/Sea water

BACTERIA

Streptococcus*

Staphylococcus*

Clostridium +

Erysipelothrix+

Mycobacterium*+

Nocardia**

Vibrio++

P. shigelloides++

Aeromonas++

Pseudomonas**

Escherichia+

Salmonella+

Klebsiella+

Edwardsiella++++

Leptospirosis????

PARASITES

Anasakiasis+

Eustrongyloides+

Cestodes+

Trematodes+

Protozoa**

VIRUSES

Calicivirus*

FUNGI

Candida*

TOXINS

Ciguatera Poisoning+

heat and cold stable

Scombroid Poisoning+

cold sensitive

+ reported cases in humans

* no known cases in humans but the potential risk exists

? exposure route of reported human disease unknown