Abstract
The Grey Nurse (or Sand Tiger) Shark (Carcharius taurus) is critically endangered on the east coast of Australia, as well as being an iconic aquarium species. We initiated a program to improve the breeding of Grey Nurse sharks in captivity by a better understanding of their reproductive cycles and initiating use of artificial reproductive techniques (ART) in this and other species. The ART team was established in May 2003 and a PhD student appointed.1
Initial studies focused on the broadnose Sevengill shark (Notorynchus cepedianus) based on their abundance in the collection and their reproductive strategy involving production of live young. We initiated regular ultrasounds of our females and established careful observation for signs of stress during the procedure. We can monitor and score follicle development via ultrasound in female Sevengill sharks.2
The first shark artificial insemination took place in June 2005 between two Sevengill sharks. No conception resulted from this procedure. We have developed a safe and effective catchout technique to facilitate handling. We have been able to collect semen from a variety of elasmobranchs using different techniques. Manual massage of the ampulla of the vas deferens is mostly effective and less traumatic than catheterization. Elasmobranch semen will retain good motility with chilling at 4°C for up to 1 week. There is an annual cycle of semen production in several elasmobranch species, with variations in quantity, quality and motility.
Grey nurse sharks present some specific difficulties. Males are more difficult to collect semen from due to the urogenital papilla containing four openings. Females have small ovarian follicles that only get up to 1.0 cm and thus it is difficult to follow maturation with ultrasound.
At this stage, there are no pregnancies from ART in elasmobranchs. Studies to date show we can get live semen post-thaw but these samples have poor motility and do not last longer than 15 minutes. Determination of optimal insemination time remains to be completed. Hormone assays may be a clue. The ability of females to store semen clouds the whole AI issue. Blood samples from the last three years have been stored for future examination and correlation with the ovarian status based upon the ultrasound examination. At present we are organizing more studies with smaller elasmobranchs with separate male and female populations.
References
1. Daly J. 2008. Development of assisted reproduction techniques in captive fish (Doctor of Philosophy).
2. Daly J, Gunn I, Kirby N, Jones R, Galloway D 2007. Ultrasound examination and behavior scoring of captive broadnose Sevengill sharks, Notorynchus cepedianus (Peron, 1807). Zoo Biology 26:1-13.