fowlers zoo and wild animal  medicine current therapy volume 8

Preface

The first two editions of Zoo and Wild Animal Medicine (ZAWAM) covered the world’s animal groups in a comprehensive fashion, as did the 5th edition published in 2003. The 3rd, 4th, 6th, and 7th editions reflected a Current Veterinary Therapy format focusing on specific topics of current interest. This edition returns to the overall taxa format and it is hoped that it will provide an updated reference for zoo and wildlife veterinarians around the world. It has been designed to offer a timely format with guidance to where more detailed information can be found. To ensure a “fresh” approach to this edition, each Senior Author has been changed from the ZAWAM 5. Many of the authors were chosen in their roles as Veterinary Advisors to the taxa that they review as it was felt that this provided a central overview to problems of that animal group. In some cases, authors generously donated their time to research species which are rarely held in captivity or studied in the wild. The problems of zoo animals and wildlife are worldwide, and as before, this edition reflects a diverse, international authorship. Senior authors represent 15 countries: Austria, Australia, Brazil, Canada, Denmark, France, Germany, Mexico, New Zealand, South Africa, 

Switzerland, Taiwan, The Netherlands, The United Kingdom,  and the United States of America

ANATOMY AND PHYSIOLOGY

All adult anurans are without a tail (the “tail” of tailed frogs [Ascaphus

sp.] is, in fact, an extension of the male cloacae, used as a copulatory

organ)

. Highly specialized in the hopping mode of locomotion, their

long hind legs have given rise to their alternative name salientias

(jumpers) 

However, considerable specialization exists in this regard

Some arboreal frogs may move by quadrapedal walking or climbing

Burrowing frogs dig head first with hind legs adapted for excavation

Eyes are voluminous; vision plays a great role in nutritional behavior

Prey movement triggers the feeding response

. A nictitating membrane is present. Posterior to each eye, the circular tympanic membrane represents the ear externally

. A large tongue is attached

anteriorly and is folded back into the oral cavity such that its

distal, bifid end lies posteriorly

. The tongue is extended to catch

insects

. A single row of small teeth lies around the margin of the

upper jaw

The coelomic cavity is not divided. The intestinal tract is relatively short and follows the normal vertebrate plan

. The liver serves

as an important erythropoietic center and plays an important role in

immune function, the synthesis of nitrogenous compounds, antioxidation reactions, and the metabolism of various endogenous and

exogenous substances

. The gall bladder is intimately associated with

the liver, with a bile duct connecting it to the duodenum

. In some

species, it joins the pancreatic duct before it enters the intestinal

tract

. The cloaca is present posteriorly. However, due to the absence

of a tail, it appears to be located somewhat dorsally

Anurans are ectothermic and environmental temperature may

really modulate their life history, influencing body temperature,

evaporative water loss, digestion, and oxygen uptake, as well as

the velocity of muscle contraction, locomotion, and vocalization.

Anurans will compensate daily thermal fluctuation by modifying

their behavior and metabolic changes, for instance, by oriented

aerobic depression of several organs.9

 Therefore, it is important to

keep the animals within the preferred optimal temperature zone

(POTZ). Some species (mostly temperate) hibernate and estivate

Anurans that hibernate in colder climatic conditions accumulate

more energy before winter and even after emerging and before breeding

. Fats are the preferred substrates of aerobic metabolism if oxygen

is not limiting, and are the main source of at least 80% of the energy

used during hibernation.9

 The skin not only has a protective and

sensory capacities but also plays critical roles in thermoregulation,

fluid balance, respiration, transport of essential ions, respiration, and

Sex recognition

The cutaneous gland (in the dermis) secretions may be irritating,

toxic, and even potentially lethal, like the steroid alkaloid toxins of

the poison frogs (Dendrobates and Phyllobates)

. One of the natural

defenses of the skin is production of antimicrobial peptides in granular glands

.14 Discharge of the granular glands is initiated by the

stimulation of sympathetic nerves. Antimicrobial peptides produced

in the skin are an important defense against skin pathogens and may

affect survival of populations

. The skin has low resistance for water

evaporation, and most anurans are vulnerable to rapid water loss. In

terrestrial species, mucous or waxy substances are produced by a

variety of glands to reduce evaporative water loss

. All anurans may

absorb water through the ventral pelvic skin and also reabsorb water

in the kidney and from the urinary bladder

Amphibian lymph consists of all the components of blood, with

the exception of erythrocytes

. In anurans, the lymphatic system is

highly developed and has a major role in fluid exchange and blood

volume regulation. It is composed of pulsatile lymph hearts (that

beat independently of the heart), an elaborate series of lymph vessels,

and subcutaneous lymph sacs. Lymph flow is unidirectional; one-way

valves are present between the sacs. Lymph heart failure should be

in the differentials for subcutaneous and coelomic cavitary accumulations of fluid

In anurans, the primary nitrogenous waste may be ammonia,

urea, or uric acid

. Aquatic species excrete a higher concentration of

ammonia, whereas many terrestrial anurans have evolved metabolic

adaptations to excrete urea and even uric acid

. Dehydrated animals

will decrease their glomerular filtration rate, thereby accumulating

ammonia in body tissues, which may lead to azotemia

. Anurans seem

to be quite resistant to high plasma urea levels

. Urea is less toxic

than ammonia and may be stored in body tissues until water may