Patterns of egg deposition and egg development in the catsharks Poroderma pantherinum and Haploblepharus pictus
Patterns of egg deposition and rates of egg development were examined for two endemic South African scyliorhinid shark species: Poroderma pantherinum, the leopard catshark, and Haploblepharus pictus, the dark shy shark. P. pantherinum laid their eggs at an average depth of 18.95 m (min: 7.4 m; max: : 26.8 m) preferentially attaching their eggs singly onto sea fans Leptogorgia palma, Eunicella papillosa and Eunicella tricoronata. H. pictus laid their eggs at an average depth 3m(min: 1m; max: 30.7 m) and attached their eggs, predominantly in pairs, to the seaweed Bifurcariopis capensis. The average temperature at which eggs were found were similar (15°C) and eggs were laid year-round. Embryo development was observed in the laboratory under constant controlled environmental conditions of 14 and 17°C. Embryo length–age relationships were linear for both species and there were significant differences in growth rate at the two temperatures. For P. pantherinum average growth rate was 0.37 mm/day at 14°C and 0.79 mm/day at 17°C. The average incubation period was 266 days at 14°C and 125 days at 17°C. Embryos thus grew two times faster and development time was 53% shorter when the temperature was raised by only 3°C. For H. pictus, the average growth rate was 0.49 mm/day at 14°C and 0.78 mm/day at 17°C. The incubation period was 242 days at 14°C and 190 days at 17°C. The embryos thus grew 1.6 times faster and incubation time was 21.5% shorter when temperature was raised by only 3°C.
Key words: elasmobranchs, reproduction, egg laying, egg development, South Africa.