59. Zoo Animals

CHAPTER 59. Zoo Animals

Patricia A. Schenck and J. Jill Heatley




AQUARIUM FISH






I. Unique anatomy




A. Skin is thin, and there is no stratum corneum with minimal subcutaneous (SC) layer


B. Intestinal tracts are shorter in carnivores, longer in herbivores


C. Gills extract oxygen and function in monovalent ion regulation and nitrogenous waste excretion


D. Ultimobranchial bodies are located near the gill slits and produce calcitonin


E. The heart consists of the sinus venosus, atrium, ventricle, and bulbus arteriosus


F. Fish have no bone marrow or lymph nodes


G. Kidneys are segmented into a cranial portion with hematopoietic function and a caudal portion with excretory function


H. The swim bladder controls buoyancy and aids in hearing


I. Electric organs, if present, are used for communication, defense, and stunning prey


II. Water quality and filtration




A. Water-quality problems are the major cause of captive fish illness and death


B. Coldwater fishes require higher dissolved oxygen than do warmwater fishes


C. Low oxygen levels can be caused by power outages that disrupt air pumps, a high fish biomass, and increased oxygen demand because of decay of a high organic load (decaying algae, decaying feed, or decaying fish)


D. Optimal pH varies by species


E. Salinity should be controlled


F. Nitrogenous waste removal is one of the most important factors in fish health. Filtration can be biological (nitrifying bacteria), mechanical, or chemical. Nitrifying bacteria can take several weeks to become fully established


G. Temperature is important; tropical species do not tolerate fluctuations in temperature


III. Nutrition




A. Ensure that all fish are eating and that food is fresh


B. Carotenoid pigments maintain desirable coloration of muscle (salmonids) and skin (goldfishes and koi)


C. Fish are efficient at feed conversion (greater than 50%)


D. Inadequate protein consumption can lead to excessive fat deposition and hepatic lipidosis


E. Carnivorous fishes require a higher protein content in the diet


IV. Restraint




A. Be very careful to not disrupt the scales when handling. Gloves should be worn and free of powder


B. Coarse mesh nets should be avoided


C. Fish can be transported in plastic bags containing one-third water and two-thirds oxygen


V. Anesthesia




A. Withhold feed for one feeding before anesthesia


B. Anesthesia can be administered via water, oral (PO), parenteral, or inhalation routes. Waterborne route is the most common


C. For out-of-water procedures, continuous water flow must be provided to the gills


D. Respiration is the most important method of monitoring anesthetic depth


VI. Diseases




A. Viral




1. Lymphocystis is caused by an iridovirus, and it causes hypertrophied dermal fibroblasts to form a nodule


2. Lip fibromas are caused by retrovirus-like particles


B. Bacterial




1. Bacterial septicemia is common


2. Clinical signs include lethargy, anorexia, reddened fins and oral cavity, exophthalmia, ulceration, distended fin vasculature, and disequilibrium


3. Preferred organs for culture include kidney, and spleen. Skin lesions can also be cultured


4. Antibiotics that are approved for use in food fish include oxytetracycline and sulfadimethoxine-ormetoprim


5. Organisms common in freshwater fishes include Aeromonas hydrophila, Aeromonas sobria, Pseudomonas fluorescens, Flavobacterium spp., Pasteurella piscicida, and other gram-negative rods


6. Organisms common in saltwater fishes include Vibrio spp. and Photobacterium spp. in addition to those seen in freshwater fishes



C. Fungal




1. Integumentary mycosis (water mold) is caused by Saprolegnia, Achyla, Aphanomyces, and Leptolegmia


2. Lesions appear fluffy in the water and slimy out of the water


D. Parasitic infections are common and amenable to treatment




1. Protozoan parasites




a. Ichthyophthirius multifiliis (ich) is the most common. The seawater version is caused by Cryptocaryon irritans. Treatment includes topical application of disinfectants or bath and dip treatments. The environment must also be treated. Increasing the temperature of the aquarium helps with treatment


b. Amyloodinium ocellatum causes “velvet” or “gold dust” disease and requires prolonged treatment


2. Nematode parasites include Capillaria, Contracaecum, Eustrongyloides, and Anisakis spp.


3. Cestode parasites can be prevented by not feeding live intermediate hosts as food


4. Trematode parasites can be prevented by not feeding aquatic-source live food and eliminating snail intermediate hosts


5. Crustacean parasites are usually grossly visible and can be treated by manual removal or other topical treatments


E. Noninfectious


VII. Preventive medicine




A. Quarantine




1. Quarantine for a period of 30 days for most fish


2. Maintain isolated fish in separate tanks and minimize aerosolization and fomite potential


3. Keep tanks small and easy to clean


4. Allow fish to acclimate for a few days before performing diagnostic testing


5. Species compatibility is an important consideration


B. Sanitation




1. Aquariums should be kept free of debris


2. All nets or utensils that are used between tanks should be disinfected before each use


C. Vaccination




1. Vaccines are approved for five diseases: Fibriosis, furunculosis, enteric septicemia of catfishes, columnaris, and enteric redmouth disease


2. Vaccines are administered by injection, immersion, or high-pressure spray; injection is the most effective route


MARINE MAMMALS






I. Marine mammals are defined as any mammal that makes the sea its home for part or all of its life. These animals include the polar bear; the marine mustelids, sea otters and marine otters; the sirenians, dugongs and manatees; the pinnepeds, sea lions, seals, and walruses; and the cetaceans, whales, dolphins, and porpoises


II. The sirenians include the manatees (Family Trichechidae) and the dugongs (Family Dugongidae). These are large, herbivorous shallow water dwelling creatures that prefer warm coastal waters and are endangered largely because of interaction with watercraft and humans




A. Manatees and dugongs are protected by a variety of regulations, including state, regional, and federal laws and international treaties


B. Classification: Kingdom Animalia, Phylum Chordata, Subphylum Vertebrata, Class Mammalia, Order Sirenia




1. Family Trichechidae




a. Trichechus manatus (West Indian manatee), Trichechus manatus latirostris (Florida manatee)


b. Trichechus senegalenses (West African manatee)


c. Trichechus inunguis (Amazonian manatee)


2. Family Dugongidae




a. Dugong dugon (the dugong)


b. Hydrodamalis gigas (Steller sea cow, hunted to extinction in the 1770s, soon after discovery)



D. Captive care




1. Feeding




a. Florida manatees feed on more than 60 species of plants, including turtle grass, manatee grass, water hyacinth, and hydrilla


b. Spend 6 to 8 hours/day grazing; animals in captivity are generally fed multiple times daily to simulate this grazing habit


c. Consume 7% to 15% of their body weight/day; up to 200 lb/day: Sea cow


d. Captive animals fed leafy greens such as hydroponic grass, lettuces, vegetables, high-protein monkey chow, carrots, bananas, and supplementation to balance the calcium phosphorous ration


2. Housing




a. Water depth: 1 to 4 m


b. Temperature: 23° to 30° C


c. Sanitation with ozone treatment


d. Florida manatees can be kept in salt, fresh, or brackish water


e. Second pool for treatments; can be drained


E. Restraint and anesthesia




1. Upon removal from the water, these animals can arc dorsoventrally, swing side to side, or roll


2. Chemical restraint usually unnecessary


3. Objective is to keep chin and tail flat against the surface and in line with body


4. Low metabolic rates dictate lower doses of tranquilizers, sedative, and opioids. Drugs for restraint may include the following:




a. Xylazine, medetomidine, midazolam, butorphanol


b. Reversal should be available


5. Anesthesia




a. Intubation: Nasotracheal with a cuffed foal tube


b. Mechanical ventilation at 6 breaths/min


c. General anesthesia required for limb amputation, wound debridement, deep abscess removal, and dystocia


F. Techniques




1. Intramuscular (IM) injections can be given in the caudal epaxial muscles or at the crease of the fluke


2. Catheter placement is generally in the brachial vascular bundle, an arteriovenous plexus between the radius and ulna, located on the lateral surface of the pectoral flipper


G. Clinical pathology




1. The preferred site for blood collection is the brachial vascular bundle, an arteriovenous plexus between the radius and ulna on the lateral surface of the pectoral flipper. Blood collected here will be a mixed arterial venous sample


2. A ventral midline tail arteriovenous plexus can alternatively be used for blood collection in neonates and anesthetized adults


3. Blood glucose levels should be monitored regularly in neonates


4. Circulating leukocytes are less responsive in manatees than in other marine mammals. 25,000 cell/dL is a severe leukocytosis in a manatee. More important diagnostic information in manatees is gleaned from shift in the leukocyte differential


H. Medicine and disease




1. Medication




a. PO medication administration is usually avoided




(1) Crushing action of molars may result in loss of medication


(2) May result in disruption of normal gut flora


(3) Stomach intubation usually necessary; PO or nasal routes


(4) Recommended for fluid therapy and nutritional supplementation


b. Intravenous (IV) drug administration




(1) Caution is advised with this route because of the possibility of inadvertent injection into an arteriole


(2) Long-term catheterization is difficult to maintain


c. IM drug administration




(1) Preferred method


(2) Caudal epaxial muscles


(3) Shoulder muscles


d. Pharmacokinetics of most drugs in manatees remain unknown. Most drug dosages are based on current knowledge in other species


2. Diseases




a. Infectious disease




(1) Aeromonas spp., Pseudomonas spp., Morganella spp., Staphylococcus spp., Mycobacterium spp. secondary to trauma


(2) Papillomavirus



c. Noninfectious diseases




(1) Cold stress: Cachexia, bacteremia, dehydration




(a) Water temperatures below 68° F cause a complex of clinical signs and disease processes


(b) Adult, full-size manatees tolerate cold better then small juveniles


(c) Acute effects: Lethargy, anorexia, terminal hypothermia


(d) Clinical signs: Shivering, cachexia, anorexia, constipation, absence of gut sounds, and flatulence


(e) Common sequellae: Infectious bronchopneumonia, generalized infectious dermatitis, enterocolitis




i. Various bacteria and fungi isolated


ii. May take months of specific and supportive therapy


(2) Brevetoxicosis-red tide




(a) Red tides are due to dinoflagellates, including Gymnodinium breve, which produce neurotoxins (brevetoxins). Toxins ingested by manatees also include toxin containing ascidians (tunicates). These toxins cause hemotoxic and long-term immune effects in manatees


(b) Clinical signs include seizure, disorientation, incoordination, hyperflexion, muscle fasciculations, flaccid paralysis, and dyspnea. Consumption coagulopathy also occurs


(c) Treatment is symptomatic and includes fluid therapy, anti-inflammatory drugs (corticosteroids and nonsteroidal anti-inflammatories), nutritional supplementation, and devices to prevent drowning


(3) Neoplasms are rare but include benign viral papillomas and disseminated malignant lymphoma


(4) Human-related trauma causes about 30% of manatee death. Similar trauma also occurs in wild cetaceans and pinnepeds. Greater than 75% of manatee deaths are watercraft related; boats cause blunt and crushing injuries and cutting or shearing injuries. These injuries may result in internal hemorrhage, fractures, organ trauma, pneumothorax, and pyothorax. Entanglement in fishing line, crab trap line, and other wastes wrapped around an appendage also commonly occur. Gunshot wounds also occur. Traumatic wounds should be cleansed, debrided, and allowed to heal secondarily unless the body cavity is exposed. Water quality, fluid and nutritional support, systemic antibiotics, and topical wound care should be considered to provide optimal recovery


d. Surgery: Wounds generally heal by second intention, and surgical repair is unnecessary


III. Pinnipeds are aquatic carnivora with flippers for limbs; hence they are literally named fin (pinni) foot (ped). These animals have been present in the fossil record for more than 22 million years and are found throughout the world’s seas and oceans based on water depth, temperature, ocean currents, and nutrient availability. Animals included as pinnepeds consist of three families: The earless or true seals (Phocidae) consist of 18 species; the eared seals (Otaridae) consist of nine species of fur seals and five species of sea lions; and walruses (Odobenidae) has one species




A. Comparative anatomy




1. Specific dental formula varies somewhat by species, but in general pinnepeds have incisors, canines, and precanines but lack molars. Sea lions are the only pinneped with external tusks


2. Ears: Seals and walruses lack external pinnae, whereas sea lions and fur seals have external pinnae


3. Male anatomy: Seals and walruses have testicles located outside the body cavity in ahypodermal layer of skin, whereas sea lions’ testicles are located in an external scrotum. All pinnepeds have a bacula (os penis), are seasonally fertile, and testicle size along with spermatogenesis increases during the breeding season


4. Flippers: Seals have short front flippers, hair on all flippers, and a thick nail on each of the five digits. Sea lions and fur seals have relatively long hairless front and rear flippers. Nails are vestigial and set back from the front flipper edge in the front flipper and are present as three large nails and two smaller nails on the back flipper. Walruses have five nails on each flipper, all set somewhat back from the edge of the flipper; these are larger on the rear flipper


5. Locomotion on land: Seals are unable to rotate their hips and unable to lift weight on their hind flippers; thus, they move in a sluglike fashion on land. Sea lions, fur seals, and walruses can rotate their hips and lift weight onto their hind flipper and can walk on all four flippers, in a standard quadruped motion, on land


6. Locomotion in water: Seals thrust from side to side in a sculling motion of their hindquarters, whereas sea lions and fur seals propel themselves through water with long fore flippers. Walruses propel themselves through the water with a side-to-side motion of the hind flippers



IV. Nutrition




A. Wild diet: Herring, smelt, sardines, mackerel, squid (occasionally), clams (walruses)


B. Captive diet usually consists of frozen fish




1. Frozen, thawed fish is the main diet of captive pinnepeds and cetaceans. Fish should be maintained at specific conditions and carefully handled to avoid multiple nutritional diseases




a. Fish should be kept frozen at −19° F (28° C); avoid deterioration of amino acids and unsaturated fats. Fatty fish should not be stored for longer than 6 months, and few fish can be stored for longer than 1 year


b. Thaw under air refrigeration to decrease bacterial growth and spoilage and to avoid leeching of water-soluble vitamins


2. Appropriate fat content is necessary to maintain weight and cause weight gain in captive animals


3. Nutritional supplementation




a. Thiamine, which quickly diminishes in frozen fish, is supplemented at a rate of 25 to 35 mg/kg of fish fed


b. Sodium chloride is supplemented at a rate of 2 to 3 g/kg fish for animals housed in fresh water


c. Vitamin E is supplemented daily based on body weight




(1) Body weight less than 100 kg: Give 400 international units (IU) daily


(2) Body weight 100 to 400 kg: Give 400-800 IU daily


(3) Body weight greater than 400 kg: Give 1000 to 1200 IU daily


V. Captive housing requirements




A. Pools should minimally measure a depth of 5 times the largest adult length, a surface area of the average adult length, squared, and a horizontal length of 1.5 times the largest adult length. Additionally, dry resting areas should measure the average adult length squared. Two or more males require two visually separated dry resting areas


B. Hyponatremia is a recognized disease syndrome in captive animals, especially those housed in fresh water, and can result in vague neurological problems and even death. Salt tablets given PO are used to prevent this disease; see preceding nutritional supplementation section


VI. Restraint and anesthesia: These species are generally captured and restrained on land. In general, restraint and anesthesia of these species have a narrow margin of safety based on the thick blubber layer, tendency to overheat, and the dive reflex. Animals should be immobilized in cool weather or in an air-conditioned room to ameliorate these concerns. Additionally, animals should be restricted from access to deep water, and an endotracheal tube and appropriate equipment for ventilation should be available before any immobilization event is undertaken




A. Physical restraint




1. A herding board may be used to facilitate capture and restraint


2. Restraint of animals weighing less than 50 kg requires one or two trained personnel. One person wraps a towel around animal’s head for control while straddling the animal and grasping a towel behind the neck. The second person holds flippers against the animal’s body to prevent rolling


3. Restraint of animals 50-100 kg usually requires additional equipment including a bull pole (a long pole with a rope loop on end), net, squeeze cage, or suspension cargo nets. This method should be used only for a short procedure such as for drawing blood or injections


4. Animals may also be trained to allow for routine procedures such as palpation, auscultation, or venipuncture


B. Chemical restraint




1. Diazepam can be given IM for minor nonpainful procedures such as radiography or wound care


2. Medetomidine and ketamine may be administered IM or IV for immobilization. The dose and route vary depending on species


3. Options of inhalational anesthesia include isoflurane for all species as well as sevoflurane for seals, but there is risk of apnea and bradycardia based on the dive reflex



VIII. Infectious disease of captive and wild pinnepeds




A. Bacterial pneumonia is common in young sea lions, fur seals, harbor seals, and elephant seal pups


B. Leptospirosis occurs in northern elephant seals, harbor seals, northern fur seals, and California sea lions. Clinical disease is similar to that seen in dogs with clinical signs of depression, reluctance to move, polydipsia, pyrexia abortion, and neonatal death occurring. Severe diffuse interstitial nephritis is caused by spirochetes in the renal tubules. Animals have had titers to various serovars, and vaccination can be done in endemic areas. Appropriate precautions should be taken with animals with this zoonotic disease. Treatment is based on that in companion mammals


C. Influenza virus can cause disease in harbor seals with the clinical signs of dyspnea, lethargy, blood-stained nasal discharge, SC emphysema, and pneumonia


D. Herpesviruse and the bacteria Mycoplasma have been isolated from juvenile and adult seals with pneumonia. Treatment is supportive, with appropriate antibiotics, such as tetracyclines, for Mycoplasma spp. They have also been found in seals and sea lions with skin disease


E. Distemper viruses cause disease in seals. Pneumonia and death can occur from phocine distemper virus (PDV) and canine distemper virus (CDV). Clinical signs include ocular and nasal discharge, mucous membrane cyanosis, dyspnea, diarrhea, fever, and central nervous system (CNS) signs. Difficulty swimming and diving may occur as a result of SC emphysema of the head and neck from pulmonary damage. Treatment is based on supportive care and controlling secondary bacterial infections. No vaccine for PDV is available, but an attenuated CDV vaccine has been given to stranded seals


F. Seal pox causes skin nodules 0.5 to 1 cm in diameter; these nodules grow and ulcerate and may spread rapidly. Disease is usually self-limiting, regressing in about a month, although lesions may persist for months. This contagious disease is most common in animals that have been recently weaned or brought into captivity and is contagious to susceptible animals. Treatment is usually unnecessary, but nodules may affect an animal’s ability to see or eat, and antibiotics to control secondary bacterial infection may be necessary. Humans can acquire this disease from seals


G. San Miguel sea lion virus is a calicivirus that causes vesicles on the flipper surfaces, around the lips, and on the tongue and hard palate of sea lions. These vesicles erode to ulcers, which may require treatment in case of secondary bacterial infection. This virus is not proven to cause disease in people but is serologically indistinguishable from the causative virus of vesicular exanthema of swine. Opal-eye perch also carry this virus


H. Streptothrichosis (Dermatophilus congolensis) (dolphin pseudopox, cutaneous dermatophilosis): This disease must be distinguished from seal pox, although simultaneous infections occur. Clinically, sharply delineated nodules occur over the entire body, and the patient may progress to death. Demonstration of the organisms on biopsy or culture necessitates systemic treatment with antibiotics of appropriate dose and extended duration


I. Clinically important parasites in pinnepeds




1. Uncinaria spp. (hookworm) infestation commonly causes anemia in wild young otarids. Treatment with anthelmintics and vitamin B is indicated


2. Lungworms include Parafilaroides decorus, P. gymnurus, and Otostrongylus circumlitis. Animals may have pneumonia or may be asymptomatic. Diagnosis is based on finding larvae in the feces or sputum. Treatment consists of ivermectin or fenbendazole as well as corticosteroids to lessen the inflammatory reaction of dead larvae and antibiotics to avoid secondary bacterial infection


3. Heartworms of pinnepeds include Dirofilaria immitis (the companion-animal heartworm) and the parasite specific to phocids, Acanthochelonema spirocaudata. Cardiac insufficiency can occur from either parasite. Preventive treatment with ivermectin is recommended in heartworm-endemic regions, and louse (Echinopthirius horridus) removal from the rehabilitation animal is recommended to avoid vector spread of this disease


4. Lice are commonly observed in wild pinnepeds. Most infections are species specific. Demodicosis also occurs. Treatment is as for companion mammals


5. Infectious disease in captive pinnepeds is rarely seen but includes salmonellosis, clostridial infection, which may cause enteritis and pasteurellosis


6. In captivity, walruses are prone to tusk infections


IX. Noninfectious disease





B. Hyperthermia may occur in these species when the air temperature is greater than 80° F


C. Neoplasias reported in pinnipeds include transitional cell carcinoma, adenocarcinoma, squamous cell carcinoma, and melanoma


D. Foreign body ingestion occurs in pinnepeds. For a more complete discussion of foreign bodies in marine mammals, please refer to the cetacean section. The pinnepeds’ pyloric sphincter is relatively small and prevents passage of foreign objects


E. Thiamine deficiency can occur in any piscivorous species (pinnepeds and cetaceans). Thiamine breaks down rapidly in frozen fish and must be supplemented. Clinical signs include CNS disturbances (ataxia, seizures, coma, and death), anorexia, and regurgitation. IM injection of thiamine results in rapid recovery. PO administration of thiamine is recommended 2 hours before food administration


F. Vitamin E deficiency is also called steatitis or white-fat disease. Improperly stored fish may be low in vitamin E and other antioxidants, necessitating supplementation. Vitamin E deficiency may be linked to hyponatremia in phocids


G. Hyponatremia is most common in phocids maintained in fresh water but can also occur in otarids and other marine mammals. This syndrome appears related to adrenal exhaustion and Addison disease, and animals can develop serum sodium of less than 140 mEq/L. Clinical signs include periodic weakness, anorexia, lethargy, incoordination, tremors, convulsions, collapse, and death. Sodium chloride infusion and corticosteroid administration are indicated in acute cases; mineralocorticoid and salt supplementation, along with serum sodium monitoring, is indicated for chronic case management. Animals maintained in fresh water may be supplemented as above with salt tablets or given access to salt water pools


H. Scombroid toxicity occurs in pinnepeds most commonly but may also occur in other marine mammals. Scombroid fish (mackerel, tuna) and other dark-fleshed fish, herring, anchovies, and pilchard spoil quickly even when frozen. A complex of substances, including histamine, are released by bacterial action. Clinical signs include anorexia, lethargy, vomiting, diarrhea, and postures associated with abdominal pain are seen. A red, inflamed mouth and or throat, urticaria, and pruritis are also evident. With removal of the offending fish, the condition is self-limiting and the animal usually resumes eating within 2 or 3 days. Treatment with antihistamines and corticosteroids may be necessary to lessen signs, especially when respiratory difficulty is evident. Avoid scombroid fish in the diet or carefully control their storage, handling, and quality to avoid this disease


I. Gastric ulcer disease in pinnepeds requires aggressive diagnosis and treatment as they are more prone to ulcerate resulting in peritonitis and death. For a more complete discussion of ulcer disease in marine mammals, please see the cetacean section


J. Trauma may occur in wild pinnepeds; for a more complete discussion, see the sirenian section


K. Ocular lesions




1. Cataracts, corneal edema, glaucoma


2. Wild pinnipeds have a greater incidence of ocular trauma


3. Captive pinnipeds maintained in fresh water have a greater incidence of eye problems than those in salt water


L. Surgery




1. Castration of captive pinnepeds is a similar procedure to other carnivores




a. In phocids younger than 2 years, the testicle should be differentiated from the large inguinal lymph nodes


b. In the phocids and odobenids, removal of the paradominal testes requires two incisions, caudal and lateral to the preputial opening, as well as blunt dissection to exteriorize the testes


2. Cataract surgery is becoming common. Cataracts are removed by incising the cornea and performing an extracapsular removal of the lens


3. In wild pinnepeds, conditions requiring surgery are relatively common and include GI foreign body and obstruction, cesarean section, prolapsed uterus, prolapsed rectum, removal of embedded foreign objects, corneal laceration, removal of infected bones in extremities, laceration repair, laparatomy, and eye enucleation


X. Cetaceans




A. Cetaceans are classified in the Kingdom Animalia, Phylum Chordata, Subphylum Vertebrata, Class Mammalia, Order Cetacea and consist of whales, dolphins, and porpoises




1. Suborder Mysticetes (baleen whales)




a. 13 species


b. None in captivity in the United States


2. Suborder Odontocetes (toothed whales)




a. 70 species


b. Most common species in captivity




(1) Tursiops truncates (Atlantic bottlenose dolphin)


(2) Orcinus orca (killer whale)


(3) Delphinapterus leucas (beluga whale)


B. Anatomy




1. This group of animals has many anatomic adaptations for living in water, which include adaptations for moving in water, thermoregulation, and aids to prey detection




a. Body shape is elongated, streamlined, and fusiform



c. Pectoral fins are the equivalent of forearms in a terrestrial animal. The bones of the pectoral fin are the same as that found in terrestrial animals


d. Flukes are the two horizontally flattened divisions of the tail of a whale. No bones are found in this structure


e. Dorsal fin found in many species. This fin is dense, fibrocartilagenous, and lacks bone. This structure helps in thermoregulation and acts as a dynamic stabilizer


f. Skin: The entire epidermis turns over at a rapid rate in these species to create a smooth interface with the surrounding water


g. The blubber consists of two separate layers of fat, equal to up to 30% of body mass in many species. The skin layer is the insulatory layer, and the more internal SC layer is the first layer to be mobilized for nutrition


h. Periarterial venous rete is a vascular bundle found in the flukes, dorsal fin, and pectoral fins. A single artery is surrounded by several veins. This unique anatomic feature is used for countercurrent heat exchange


i. Multireniculate kidneys in these species consist of many small, independently functioning units called reniculae. The kidney roughly resembles a cluster of grapes. This kidney has more surface area than a comparably sized single-lobed kidney and allows for greater blood volume filtering, greater urine volume, and enhanced diuresis. Each lobe is a complete functional unit, and this kidney can produce urine more concentrated than salt


j. In echolocation, high-frequency signals are produced by nasal diverticulae, which are located behind the melon. The signals bounce off objects and return to the animal, which are channeled to the inner ear and transformed into neurologic signals. Echolocation is used to help find prey and identify objects in the water


k. External nares are positioned on top of the head; lack of turbinates and trachea is adapted into a goose beak, which facilitates breathing through the nares during eating


2. Dental, GI




a. Stomach: Three chambers composed of the fore stomach, the fundic, and the pyloric chamber. The fore stomach is composed of stratified squamous epithelium. The fundic chamber is used for chemical digestion. The pyloric chamber regulates the flow of digesta


b. Salivary glands, cecum, and gallbladder: Absent


3. Reproductive




a. Female reproductive organs




(1) Bicornuate uterus


(2) Pregnancy is in the ipsilateral horn of ovulation, and ovulation usually occurs in the left ovary


(3) Bilateral mammary slits are found on the side of the genital slit


b. Male reproductive organs




(1) Intra-abdominal testes


(2) Fibroelastic penis with a sigmoid flexure


4. Comparative anatomy




a. Mysticetes: Baleen whales




(1) Baleen: Several individual plates that hang from the upper jaw, which filter food from large volumes of seawater. Baleen is composed of keratin


(2) Bilaterally symmetrical blow hole


b. Odontocetes: Toothed whales




(1) Have teeth but do not use them to chew fish


(2) Single external nares


C. Clinical pathology




1. Blood collection sites




a. The caudal vascular bundle, also known as the central fluke vein, is the most common site for venipuncture. Blood obtained from this site is generally a mixed arteriovenous sample


b. Other blood collection sites include peduncle, dorsal fin vein, and pectoral flipper


2. Hageman’s factor: Odontocetes are deficient in factor XII and the Fletcher factor (plasma prekallikrein) of the coagulation cascade. This can make partial prothrombin time long compared with other mammals


3. RBCs of odotocetes are comparatively larger and have higher hemoglobin concentrations than terrestrial mammals


4. White blood cells of odontocetes follow a typical mammalian pattern in most disease processes. Older odontocetes tend to have higher leukocytes counts, and basophils are absent from the odontocete differential


5. The serum enzyme alkaline phosphatase tends to be higher in younger animals (calves) and can be used as a prognostic indicator. Decreased values of serum alkaline phosphatase in a clinically ill animal are associated with a poor prognosis


6. Serum sodium and chloride concentrations are generally 10% higher in odotocetes than in terrestrial mammals, likely because of the high sodium content of their diet and ingestion of seawater


7. BUN concentrations are generally higher than in terrestrial mammals

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Apr 6, 2017 | Posted by in GENERAL | Comments Off on 59. Zoo Animals

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