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

Abstract

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. © 1999 Wiley‐Liss, Inc.

Reproductive cycle of the blacknose shark Carcharhinus acronotus in the Gulf of Mexico

“…Males with calcified claspers ≥120 mm long with a testes mass of ≥1·5 g and testes width of ≥7 mm were considered reproductively capable of fertilizing an ovulated follicle. These criteria are consistent with previous studies that reported similar characteristics for other mature elasmobranch species (Koob et al , 1986; Heupel et al , 1999; Conrath & Musick, 2002; Sulikowski et al , 2004) and for those used by Driggers et al (2004 a ) for blacknose sharks in the western North Atlantic Ocean.…”

Non-lethal assessment of reproductive characteristics for management and conservation of sharks

“…Although the draughtboard shark was not found to have a defined seasonal reproductive pattern, variations in hormone levels followed similar trends in reproductive activity obtained from macroscopic examination of the gonads (Awruch 2007). In seasonally reproducing species such as the epaulette shark Hemiscyllium ocellatum (Heupel et al 1999), clearnose skate Raja eglanteria (Rasmussen et al 1999) and Atlantic stingray Dasyatis sabina (Tricas et al 2000), strong correlations between plasma steroid hormone levels and season have been reported. Thus, the application of this technique to seasonally reproducing species may also provide the ability to determine the timing of reproductive events such as follicle development, ovulation and gestation period.…”

Endocrine Control of Embryonic Diapause in the Australian Sharpnose Shark Rhizoprionodon taylori

“…While an association between abiotic factors and hormone levels has been demonstrated in at least three elasmobranchs ( Hemiscyllium ocellatum : [63]; Urobatis halleri : [64], [65]; Scyliorhinus canicula : [61], controlled experiments demonstrating such dependence has only been shown in male U. halleri [64], in which temperature has a role in elevating T levels.…”