A quaculture, 34 (1 9 8 3 ) 2 8 7-30 1 T he Indian pearl oyster Pinctada fucata w as spawned in the laboratory and the larvae w ere successfully reared to spat setting under tropical con dition s. T h e larve grow s through the straight-hinge, u m bo, eye sp ot and pediveliger stages in the pelagic phase b efore m etam orphosing to plantigrade and setting on a substratum as spat, and these stages are described. Large differences were n oticed in larval grow th w ithin and betw een fou r rearing experim ents. Isochrysis galbana was used as standard fo o d th roughou t larval rearing at a cell concentration range 8 0 -350/jul. Spatfall occu rred on day 24-32 o n a variety o f substrata. The highest density o f 4 .7 1 /cm * was observed on fibreglass tank b o tto m . G row th o f P. fucata larvae appears to be a step fu n ction , and that o f spat u p to 13 weeks describes a curvilinear form . IN TR O D U C TIO NFollow ing the developm ent o f techniques fo r farming o f pearl oyster Pinctada fucata and production o f cultured pearls in India (Alagarswami, 19 7 4 ), it became im portant to breed the species artificially as the popula tions in the natural beds display drastic fluctuations (Alagarswami and Qasim, 1973). Spat collection in inshore areas and bays yields only small quantities which com prise several species o f pearl oysters with a low per centage o f P. fucata (Alagarswami, 19 7 7 ). M ethods fo r controlled spawn ing o f pearl oyster were developed earlier (Alagarswami et al., 1980a) and larval rearing cou ld be carried o u t only up to the straight-hinge stage (Ala garswami et al., 1980b). Subsequently success has been achieved in produc tion o f pearl oyster spat in the experiments described in this paper.The few works on breeding o f the Japanese pearl oyster (Kobayashi, 0 0 4 4 -8 4 8 6 /8 3 /$ 0 3 .0 0
Spawning, larval and juvenile rearing of the tropical abalone Haliotis varia L. were studied. Brood stock abalone were induced to spawn by exposure to air for 2 h at 27 jC. Female abalone spawned a mean of 76,530 eggs. Fertilised eggs measured 180 Am in diameter. Seventy percent survival was obtained during larval rearing. Larvae passed trochophore, veliger, gliding and creeping stages and were induced to settle on a mat of diatoms containing Nitszchia sp. and Navicula sp. The larval rearing period of H. varia ranged from 4 to 6 days at 27 jC. The settled spat vigorously fed on the diatom mat until the 50th day of postfertilisation and coralline red algal film, until the 70th day of postfertilisation. First respiratory pore was formed on the 27th day of postfertilisation. Juvenile abalones were reared on three algal diets such as coralline red algae, green filamentous algae and Ulva lactuca from the 71st to 200th day of postfertilisation. Those fed with coralline algae showed best and consistent growth. Shell colour of juveniles was affected by diet. The present study on the production of juveniles in the hatchery is a baseline information to initiate abalone aquaculture in India and to help augment the natural population. D
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