Biology And Biometry Of A Beautiful And Forageable Freshwater Crustacean Streptocephalus dichotomus (Baird)

Abstract

Crustaceans are the highly preferred delicacy for many organisms including man. The preference was reflected from the quantum of selective feed in take from the wild predatory organisms, which was evaluated by the gut content analysis. But the gut mainly contain partially digested or fragments of prey after digestion. Such a forage uptake could also used as a tool to quantify the actual consumption by the predators, in this regard the present work on length related parameter evaluation is mandatory. Hence, the relationship between length and other measurable body features (such as total length, total weight, head length, thorax length, abdomen length, cercopod length, male second antennal length and brood pouch length) were established here by measuring 118 males, 143 females and 54 juveniles of Streptocephalus dichotomus collected from the seasonal ponds at Bharathidasan University, Tamilnadu. The maximum size recorded was 42mm ♂ and 37 mm♀ indicating that males grow larger than females. The sexually dimorphic characters such as budding of the brood pouch in females and the predominantly larger second antenna occurred during 4th day from hatching at a size of 5mm length ♂. The first spawning was noted at the 11th day with a size of 9mm length. The body mean ‘Kn\' values coincide with the maturity stages and clutch periods. The results of the length related body measurements forms the basis in assessing its biomass from the gut content remnants of the predatory organism besides predicting the expected maturity size and quantum of cysts produced. The mean ‘Kn\' value in relation to weight was also calculated as a measure of its body condition during its growth phase. Further, Streptocephalus are able to complete their life cycle even in very small water bodies and in shorter duration of a fortnight.

Keywords: Streptocephalus dichotomus, Length-weight relationship, Biometry, Fairy shrimp

Tropical Freshwater Biology Vol. 16 (2) 2007: pp. 35-43