Reptilian Skin and Its Special Histological Structures

Reptilian skin is covered with scales forming armor that makes it watertight and enables reptiles to live on land in contrast to amphibians. An important part of the skin is the horny epidermis, with thick stratum corneum in which waxes are arranged in membrane-like layers. In lizards and snakes, the whole skin is covered in overlapping epidermal scales and in turtles and crocodiles in dermal scutes. The cornified part of the epidermis is strengthened by β-keratin and sometimes α-keratin. In crocodiles and many turtles, the outer scale surface consists of β-keratin and the hinge region containing α-keratin. In lizards and snakes, both keratins form continuous layers with the α-keratin below the β-keratin. Some reptiles have developed a sensitive mechanosensory system in the skin. The colors of reptile skin are produced by melanocytes and three types of chromatophores: melanophores, xanthophores, and iridophores. The color patterns may be fixed or the chromatophores may provide rapid color change. Skin from different species of reptiles, turtles (red-eared slider (Trachemys scripta elegans)), snakes (Emerald tree boa (Corallus caninus) and Burmese python (Python bivittatus)), Cuvier’s dwarf caiman (Paleosuchus palpebrosus), lizards (Leopard Gecko (Eublepharis macularius)), and Green iguana (Iguana iguana), were examined with histology techniques and compared

Morphological evidence for the physiological nature of follicular atresia in veiled chameleons (Chamaeleo calyptratus)

Follicular atresia (FA) has been assumed to serve different functions in reptiles, e.g. helping to develop hierarchies, limiting clutch size, and regression of ovarian structures. Reproductive output is dependent on a balance between ovulations and FA. Excessive rates of FA may not only be detrimental for the survival of a population, but have also been associated with pathological conditions. In order to gain insights into the physiological and potentially pathological processes of FA, we performed a decriptive study on the morphological features of the ovaries in sexually mature female veiled chameleons (Chamaeleo calyptratus, VC). Of 60 clinically healthy female VC with continuous ovarian cycling and at least one confirmed cycle with FA over at least 1.5 years, 30 were selected for macroscopic evaluation of ovarian appearance and 7 were subjected to histology and immunohistology. While FA of previtellogenic follicles happened at a low rate, expected for a species with two germinal beds per ovary and polyautochronic reproductive pattern, atresia in the late vitellogenic stage affected entire generations of follicles, consequential to ovulatory failure. Histologically, no pathological processes were identified in any of the animals. Rather, three stages of FA (early, middle, late) were defined and vitellogenic follicles showed two distinct morphological types of FA: yolky and cystic. Yolky FA was found in 21/30 (70%) animals, while cystic FA co-occurred in 9/30 (30%) of the animals

Treatment options, complications and long‐term outcomes for limb fractures in pet rabbits

Background Limb fractures represent the most common orthopaedic disease in pet rabbits. However, only a few studies have evaluated therapeutic details of limb fractures. There are no data available for long‐term outcomes of limb fracture treatment. Methods The medical records of six institutions were reviewed retrospectively to identify cases of traumatic limb bone fractures in pet rabbits between 1999 and 2020. The medical records (n = 387) were analysed for details of fracture prevalence, aetiology, therapy protocols, treatment complications, outcome and long‐term effects. In addition to the retrospective data evaluation, 13 rabbits were re‐evaluated in person in recent clinical analyses, including orthopaedic examination, radiography and computed‐tomographic imaging. Details of long‐term effects of fracture treatment were requested over the telephone for a further 232 animals using a standardised questionnaire. Results Long bone fractures accounted for the majority of all fractures (296/387; 76.5%). Hindlimb fractures (301/387; 77.7%) were more common than forelimb fractures (86/387; 22.2%), and tibial fractures and combined fractures of the tibia and fibula (119/387; 30.8%) were observed most frequently. Most fracture treatments were based on osteosynthesis procedures (243/328; 74.1%). Treatment complications occurred in 130 out of 328 (39.6%) cases. A high bodyweight (p = 0.047) and an older age (p = 0.01) were found to be significant risk factors for the emergence of therapy complications. Overall, 75.4% of animals (175/232) had a satisfactory long‐term outcome. Limb posture anomalies were evaluated in 61 cases (26.3%). Limitations The multi‐centre approach led to the inclusion of various institutions, veterinarians, treatment protocols and rabbit populations that might have influenced the results. The medical records were reviewed retrospectively, so there were some data that were lacking or could not be collected in a standardised manner. Furthermore, rabbit owners' evaluation of long‐term outcomes might be prone to error, despite the use of a standardised interview questionnaire. Conclusion Limb fractures are a common orthopaedic issue in pet rabbits. The patient's bodyweight and age are significant risk factors for the emergence of complications during the fracture treatment process. Long‐term orthopaedic effects, such as abnormal limb posture and permanent lameness of the affected limb, were observed regularly

VIVIPARITY IN SNAKES – HISTOLOGICAL STUDY OF THE RELATIONSHIP BETWEEN FETUS, FETAL MEMBRANES AND OVIDUCT IN EMERALD TREE BOA (Corallus caninus)

Viviparity is an important reproductive mode in reptiles from an evolutionary perspective. Viviparous reproduction is associated with certain physiological changes, probably in response to inadequate environmental conditions for egg development. Unlike in oviparous species, embryos remain and develop in the oviduct until birth. In order for the developing embryo to exchange respiratory gasses, water, and food, a placenta is required, which consists of fetal membranes that interact with the maternal oviduct. About 20% of squamates (snakes and lizards) are viviparous, but the morphology of the snake placenta has been studied only in the subfamilies Thamnophiinae and Hydrophiinae. Our objective was to study the structure of the placental layers and fetus in situ in the maternal oviduct of a 6-year-old Emerald tree boa (Corallus caninus). Five fertilized and three unfertilized slugs were found in the uterus during post mortem examination. The average mass of the slug with the fetus (48 mm length x 26 width) was 55–65 g and that of the unfertilized slug was 15–35 g. The fetal membranes and two fetuses were examined by light microscopy. Multiple projections of the tissue samples were made and cut into 5 μm thick paraffin tissue sections, which were stained with Haematoxylin-eosin, Toluidine blue, Goldner’s Trichrome and assessed immunohistochemically with monoclonal antibodies for cytokeratin. The morphology of the fetal membranes was described and found to have an anatomy similar to that of most squamates: a type I allantoplacenta. The structure of the oviduct and of the fertilized and unfertilized slug was described. This case report provides a better understanding of placental morphology in boids and expands the spectrum of viviparous squamate species described

Ultrasonographic and computed tomographic characteristics of the reproductive cycle in female veiled chameleons (Chamaeleo calyptratus)

Female veiled chameleons, Chamaeleo calyptratus, have a high fecundity and fast maturation, which makes them a suitable model species for squamate reproduction. The authors investigated the morphological follicular development of a group of 20 healthy adult animals over a 12-mon period using ultrasonography (US) and CT. Four stages of follicular development could be distinguished by imaging diagnostics and were confirmed by histology: previtellogenesis, vitellogenesis, gravidity, and atresia. Using a linear ultrasound transducer (18 MHz), previtellogenic follicles could be visualized as small, round, hypoechoic structures. Identification of this stage was unreliable on CT. On US, vitellogenic follicles remained round and showed increasing echogenicity from the hypoechoic center outwards, displaying vinyl-like hyperechoic banding in later stages. On CT, early vitellogenic follicles were round, hyperdense structures, which reduced in density as they grew. A hyperdense inner ring with a hypodense central point characterized late vitellogenesis. Following ovulation, eggs became distinctly oval on both CT and US, with formation of a hyperdense or hyperechoic outer ring, respectively. Atresia followed in cases where no ovulation occurred, and was divided into yolky and cystic atresia. Sonographically, early yolky atretic follicles became unevenly shaped, packed against one another, and developed heterogenous content. Late atretic follicles were homogenous and reduced in size. Reduction of density and uneven shape were also observed on CT. Cystic atretic follicles developed an anechoic cavity with a dense peripheral accumulation of content. In many animals 2–3 generations of atretic follicles were observed without indication of impairment to the development of the newest batch of follicles. Thus, follicular atresia need not necessarily lead to a pathological condition in veiled chameleons, at least not within a few consecutive cycles

Metastasizing squamous cell carcinoma in a 50-year-old Eastern Hermann's tortoise (Testudo hermannii boettgeri).

A 50-year-old female Hermann's tortoise (Testudo hermannii boettgeri) was presented with anorexia and lethargy. Clinical examination revealed multiple, visually inconspicuous but indentable areas in the shell corresponding to osteolysis radiographically. Soft tissue nodules and osteolytic lesions were also noted in the limbs. Laboratory results revealed elevated aspartate aminotransferase activity and uric acid concentrations, hypoglycemia, and hyperphosphatemia. Klebsiella oxytoca was isolated from a biopsied scutal area, and the biopsy suggested neoplasia. After a short period of clinical improvement, the animal's condition deteriorated, and it died. Post mortem computed tomography revealed polyostotic lytic lesions of multiple bones and the shell with associated soft tissue nodules protruding into the coelom, and nodular lung lesions. Necropsy, histopathology, and immunohistochemistry secured a diagnosis of a poorly differentiated, pan-cytokeratin-positive squamous cell carcinoma with widespread soft tissue and bone metastases, osteolysis and desmoplasia