Plasma steroid hormone profiles and reproductive biology of the epaulette shark, Hemiscyllium ocellatum.

Examination of the reproductive biology of the oviparous epaulette shark, Hemiscyllium ocellatum, was conducted on a wild population. Male sharks were found to reach maturity at between 55-60 cm total length (TL) and female sharks mature around 55 cm TL. Blood samples collected from mature male and female sharks were analyzed for sex steroid hormones to examine seasonal hormone patterns. Plasma samples were analyzed via radioimmunoassay techniques with female samples measured for estradiol, progesterone, and androgen concentrations, and male samples measured for androgen concentrations. Male androgen concentrations showed a single broad peak from July to October with maximum hormone concentrations (60 ng/ml) occurring in August. Male androgen concentrations were lowest in December-February (<20 ng/ml), and appeared to correlate with reproductive activity and water temperature. Female androgen concentrations were an order of magnitude lower than those for males and showed peaks in June (6 ng/ml) and December (8 ng/ml). Estradiol concentrations in females peaked during the months of September-November (0.5 ng/ml) coinciding with the egg laying period. Progesterone concentrations ranged up to 0.5 ng/ml prior to the mating season. Observations of ova size and egg production showed eggs develop in pairs and ova are ovulated at a size of 25-27 mm. Females lay eggs from August to January. Males were observed with swollen claspers from July through December, with the highest amount of sperm storage in the epididymis occurring between August through November. Our observations indicate that epaulette sharks in the waters near Heron Island mate from July through December. J. Exp. Zool. 284:586-594, 1999. Copyright 1999 Wiley-Liss, Inc.