Sex Determination in Reptiles: A Review

Reptile biodiversity is rapidly declining, with over 11,733 recognized species across 1226 genera being documented, many of which are endangered. Captive breeding programs play a crucial role in conservation; however, effective management requires accurate sex determination, especially due to the fact that many reptile species exhibit minimal or no sexual dimorphism. When present, sexual dimorphism manifests as differences such as size, coloration, and morphological features influenced by evolutionary pressures and hormones. Various sex determination techniques are employed due to the lack of external sexual characteristics in many species. These methods include probing, hydrostatic eversion, popping, ultrasound, CT, radiography, contrast radiography, endoscopy, and genotypic sex determination. Accurate sex determination is crucial for the success of captive breeding programs and the conservation of reptile species. Advanced imaging and molecular methods offer promising non-invasive alternatives but may not be universally accessible or effective. An understanding of the unique reproductive anatomy and the use of appropriate sexing techniques are fundamental to establishing breeding groups, preventing aggressive behaviours among groups, and ensuring the long-term survival of endangered reptile populations.

Reproductive Management of Reptiles

Research in reproductive management of reptiles has focused on developing and investigating feasible methods that can be used in clinical practice and laboratory settings, including sexing in monomorphic species and methods of artificial insemination in endangered reptile species. In captive pet reptile species, research is focused on hormonal regulation of reproductive activity. Gonadotropin-releasing hormone (GnRH) agonist implants may temporarily suppress reproductive endocrine system (eg, circulating concentrations of estrogens and progesterone) in female green iguanas but did not influence male iguana behavior and plasma testosterone levels. Additionally, it did not suppress reproductive activity of females of other lizard species (eg, leopard geckos).

Endoscopic techniques for early diagnosis of cloacal pathologies and sex determination in blue spotted tree monitor (Varanus macraei) and Cuming's water monitor (Varanus cumingi)

This article attempts to present, for the first time, the usefulness and feasibility of using endoscopic techniques in the cloacal region of Varanus cumingi and Varanus macraei. This method can serve both diagnostic and therapeutic purposes, as well as offering an early approach to sex determination through the observation of the urodeum which in males ends in a blind end while in females it consists of two ostia which represent the outlets of the oviducts. In this context, commonly employed sex determination techniques, such as post-cloacal spur detection, have shown unreliability. The study involved the examination of ten specimens, approximately one year old, from a private breeding farm, following a complete clinical evaluation to confirm their general state of health. All subjects underwent sedation, which allowed the evaluation of anatomical structures, the health status of the cloaca and the determination of sex. This study and its findings may provide a critical basis for addressing population declines of these species, particularly for V. macraei, which has already been classified as 'endangered' by the IUCN.

Endoscopy and rectal enema for fecal collection in wild sea turtles (Chelonia mydas, Eretmochelys imbricata) in a field setting

Forty-seven free-ranging sea turtles (46- Chelonia mydas, 1- Eretmochelys imbricata) were examined via novel use of an endoscopy combined with a rectal enema to obtain large fecal sample volumes. The cloaca was insufflated using an endoscope, after which the bladder and rectum separated, allowing access to the colon. Environmental conditions and location influenced the performance of the procedure initially, but after several attempts the procedure was successfully initiated. In all cases, fecal samples were obtained, and the animals were released to their respective locations. Fecal sample collection using this approach enhances the ability to obtain diagnostic information and perform other scientific analyses of sea turtles.

Diagnostic Imaging of the Reptile Urinary System

Reptiles can develop various diseases of the urinary tract, including, but not exclusively, urolithiasis, gout, acute and chronic kidney injury, and secondary renal hyperparathyroidism. Diagnostic imaging is instrumental in differentiating and diagnosing these ailments. This article describes the current diagnostic imaging approaches used in reptile medicine for evaluation of urinary tract disease. The use of radiographs, ultrasonography, computed tomography, MRI, and endoscopy is discussed and compared for the evaluation of urinary tract disease in reptiles.