Mr. Heupel et al., Plasma steroid hormone profiles and reproductive biology of the epaulette shark, Hemiscyllium ocellatum, J EXP ZOOL, 284(5), 1999, pp. 586-594
Examination of the reproductive biology of the oviparous epaulette shark, H
emiscyllium ocellatum, was conducted on a wild population. Male sharks were
found to reach maturity at between 55-60 cm total length (TL) and female s
harks mature around 55 cm TL. Blood samples collected from mature male and
female sharks were analyzed for sex steroid hormones to examine seasonal ho
rmone patter ns. Plasma samples were analyzed via radioimmunoassay techniqu
es with female samples measured for estradiol, progesterone, and androgen c
oncentrations, and male samples measured for androgen concentrations. Male
androgen concentrations showed a single broad peak from July to October wit
h maximum hormone concentrations (60 ng/ml) occurring in August. Male andro
gen concentrations were lowest in December-February (<20 ng/ml), and appear
ed to correlate with reproductive activity and water temperature. Female an
drogen 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 conce
ntrations in females peaked during the months of September-November (0.5 ng
/ml) coinciding with the egg laying period. Progesterone concentrations ran
ged up to 0.5 ng/ml prior to the mating season. Observations of ova size an
d egg production showed eggs develop in pairs and ova are ovulated at a siz
e 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 Novembe
r. Our observations indicate that epaulette sharks in the waters near Heron
Island mate from July through December. (C) 1999 Wiley-Liss, Inc.