Diagnostic assessment of reproductive status in white-spotted bamboo sharks (Chiloscyllium plagiosum)

Abstract

Relatively little is known about elasmobranch reproductive physiology compared to other species. An increased understanding of elasmobranch reproduction would improve the success of captive breeding and may aid in situ conservation efforts by reducing demand for wild-caught individuals. The reproductive status of seven adult female white-spotted bamboo sharks (Chiloscyllium plagiosum) (WSB) was monitored via coelomic ultrasonography and analysis of plasma biochemistry and steroid hormones over 6 months. Based on ultrasonic findings, females were categorized at each blood collection time point as: no follicular activity (INACTIVE), follicles but no eggs present (ACTIVE-OVARY), and eggs present within the oviduct (ACTIVE-OVIDUCT). Triglyceride concentrations were greater for those with the ACTIVE-OVARY (75.98 mg/dL; CI 61.81-90.15 mg/dL) and ACTIVE-OVIDUCT (87.0 mg/dL; CI 70.20 to 103.81 mg/dL) categories than INACTIVE (51.81 mg/dL; CI 37.07-66.54 mg/dL) category. No significant differences were observed for PCV, total solids, calcium, phosphorus, iron or progesterone. Estradiol concentrations were less for the INACTIVE (0.15 ng/ml; CI 0.08 to 0.25 ng/ml) than ACTIVE-OVARY (0.63 ng/ml; CI 0.42 to 0.88 ng/ml) and ACTIVE-OVIDUCT (0.92 ng/ml; CI 0.64-1.26 ng/ml) category. Testosterone concentrations differed among reproductive states, being greater with the INACTIVE (0.22 ng/ml; CI 0.13 to 0.37 ng/ml) and peaking in the ACTIVE-OVIDUCT (2.12 ng/ml; CI 1.25-3.60 ng/ml) state. The ultrasonic technique was performed in a standardized manner, and the anatomy was validated via opportunistic post-mortem examinations and MRI. Using the described diagnostic techniques, reproductive status in WSB can be routinely monitored, and findings have implications for improving the success of captive breeding efforts in other elasmobranch species.

Keywords: Elasmobranch; Plasma biochemistry; Steroid hormones; Ultrasonography.