An understanding of species' morphological and physiological parameters is crucial to developing conservation strategies for wild animals kept in human care. Detailed information is lacking for crab-eating fox (Cerdocyon thous) eyes and adnexa. Therefore, the aim of this study was to describe anatomical, histological and computed tomography (CT) features of the eye and adnexa in crab-eating fox, compared to domestic dogs. CT of the eye and adnexa of one live animal and a frozen specimen was performed for anatomical identification. In addition, the heads of five animals of each species were fixed in 10% buffered formalin for gross anatomical description of the eye and adnexa using topographic dissection and exenteration techniques. All steps were photographed and features such as location, shape, and distances and relationships between structures were described. For histological evaluation, two eyes of each species were fixed in 10% buffered formalin, processed by routine paraffin inclusion technique and stained with hematoxylin and eosin. The CT scan was difficult to evaluate, mainly that of the frozen head, which did not provide good definition of the soft tissues; nevertheless, it demonstrated the potential for structure visualization and description. The gross anatomical and histological evaluations showed the presence of eyelashes on the upper eyelid and of upper and lower lacrimal points, an incomplete orbit with supraorbital ligament, slightly exposed sclera with discretely pigmented limbus and pigmentation throughout the conjunctiva, and a slit-shaped pupil. Hematoxylin and eosin staining demonstrated structural similarities between the crab-eating fox and domestic dog. Thus, the possibility of using the domestic dog as a study model for the preventive and therapeutic management of wild dogs kept in human care is demonstrated.

SIGNIFICANCE The tear film promotes ocular surface health and protection through its various constituents' functions. The application of methods for ocular surface examination is essential in the research of diseases that affect the tear film. Rabbits have been used as a model to study some human ocular diseases and to test ophthalmic products. PURPOSE The aim of the present study was to determine the biochemical profile, osmolarity, and tear ferning patterns of rabbit tears. METHODS Ten rabbits (Oryctolagus cuniculus) were evaluated for tear osmolarity, tear ferning types and grades (using Rolando and Masmali scales), and biochemical analysis of total protein, urea, and electrolytes (chloride, phosphorus, iron, sodium, potassium, and calcium). RESULTS Median ± semi-interquartile range for tear osmolarity was 283.5 ± 7.5 mOsm/L. Tear ferning test grades were type 1.0 ± 0.5 on the Rolando scale and 1.0 ± 0.5 on the Masmali scale. Type I and grade 1 were the most commonly observed ferning classifications (60 and 50%, respectively) for the rabbits' tears. Results for electrolytes and other biochemical compounds were as follows: total protein 4.40 g/dL, urea 130.60 mg/dL, chloride 196.51 mEq/L, phosphate 7.35 mg/dL, iron 95.76 μg/dL, sodium 202.04 mmol/L, potassium 12.74 mmol/L, and calcium 11.53 mg/dL. CONCLUSIONS The results of the various tests described herein may serve as a basis for research using rabbits as an ophthalmic disease model and in the development of diagnostic and therapeutic agents used for ocular health.

The crab-eating fox (Cerdocyon thous) is a canid widely distributed in South America and is considered the only representative of the genus Cerdocyon. These are nocturnal animals, measuring about 65 cm of body length, with light grey coat and yellowish base, a black dorsal band that extends from the nape to the tip of the tail, darker legs and feet and relatively short hair (Ramos Júnior et al., 2003). This species is often seen in the wild animal surgical clinic, as they are constant victims of trampling or chase, accused of preying domestic animals (Gonçalves et al., 2016). Due to its phylogenetic proximity with domestic dog, the last is used as model for medical approaches in the Cerdocyon thous, once there is a lack of morphophysiological knowledge of these individuals (Ferrigno et al., 2014;Gomes, 2007).The phrenic nerve is the main motor supply of the diaphragm, and it is composed, in most domestic species, by ventral branches of the fifth, sixth and seventh cervical spinal nerves (Ghoshal, 1986).However, diaphragm can also be innervated by intercostal nerves, as