How can the sex of a sand mouse be determined? - briefly
Sex is identified by inspecting the external genitalia: males possess a visible penile organ and scrotal testes, while females show only a cloacal opening. When morphology is unclear, PCR amplification of sex‑specific genes from a tissue sample yields a definitive result.
How can the sex of a sand mouse be determined? - in detail
Determining the sex of a sand mouse (Psammomys spp.) relies on morphological, anatomical, and molecular methods. External examination provides the quickest assessment. In mature individuals, the anogenital distance (AGD) is greater in males; the distance can be measured with calipers to the nearest 0.1 mm. Male specimens exhibit a visible scrotal sac or a prominent penile papilla, while females lack these structures and display a more rounded ventral surface. In juvenile or subadult mice, external cues may be ambiguous, requiring additional techniques.
Dissection of the reproductive tract yields definitive identification. Male sand mice possess paired testes within the abdominal cavity, connected to the epididymis and vas deferens. Female specimens contain paired ovaries attached to the uterine horns and a single uterine body. Careful removal and inspection of these organs under magnification confirms sex with certainty.
When live handling is required, non‑invasive imaging can be employed. High‑frequency ultrasound detects testicular tissue and ovarian follicles, allowing sex determination without sacrifice. Ultrasonographic images should be captured in longitudinal and transverse planes to visualize the gonads clearly.
Molecular analysis offers a reliable alternative, especially for early developmental stages. Polymerase chain reaction (PCR) targeting sex‑specific markers such as the Sry gene (male) and the Amelogenin X/Y loci distinguishes males from females. DNA extraction from a small ear clip or tail tip provides sufficient template; amplification protocols typically run for 30–35 cycles, followed by gel electrophoresis to visualize band patterns.
For field studies where rapid sorting is essential, a combination of AGD measurement and visual inspection of the perineal area provides an efficient preliminary classification. Ambiguous cases should be confirmed by dissection or molecular testing to avoid misidentification.