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Studies on the reproductive biology of two species of brine shrimps under different eco-physiological conditions (TH 101)

By N Soniraj


There are asexual Artemia parthenogenetica (Barigozzi 1974) and sexual Artemia franciscana (Kellog 1906) species available at the saltpans of Tuticorin and the chances of dominance of either of these species can not be ruled out. Sexual species is believed to have entered the saltpans because of contamination from the local hatcheries where the imported cysts are being used. Here an attempt was made to study the effect of ecophysiological conditions such as salinity, temperature, starvation , different feeds and feeding levels, photoperiodism etc. on the biology of these two species of Artemia. Sexual species has the advantage of dominating the indigenous asexual species as they had performed better in most of the conditions studied. At fixed temperature the asexual species had a better brood size than the sexual species but at ambient temperature the sexual had larger brood size. The pre reproductive period of asexual species at higher salinities was less than the sexual species, while at lower salinities the sexual had shorter pre reproductive period. The brood sizes of asexual species were also large than the sexual species at higher salinities while at lower salinities sexual species had larger broods. Therefore rather than a complete dominance of either of these species the sexual species may dominate in the winter/rainy season and the asexual one in the summer season . The oviparous mode of reproduction by the asexual species at lower temperature also supports this view as the sexual species could produce nauplii offspring even at this temperature. In laboratory rearing of Artemia algal feeds like /sochrisis sp. or ricebran were found good for biomass production as the fecundity was high with these feeds. Low temperature could induce cyst production in both sexual as well as asexual species, while the asexual responded more positively to low temperature of 25°C as they never turned back to ovoviviparous mode of reproduction. Algal feeds favoured the encystment rate, while ricebran fed animals could never produce cysted offspring. Temperature and feed were found to be the major factors, which influence the encystment while salinity increase and photoperiodism can only enhance the cyst production rate

Topics: Theses, Fish biology, Prawn and Prawn fisheries
Year: 2002
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