. California fish and game. Fisheries -- California; Game and game-birds -- California; Fishes -- California; Animal Population Groups; Pêches; Gibier; Poissons. DEVELOPMENT OF THE AMERICAN PEARL OYSTER 189 environmental conditions were recorded (Table 1). The early straight-hinge larvae developed after about 24 hours. The height of the shell was on an average ± )im. They had a smooth, transparent prodisoconch I and swam near the water surface. After 24 hours microalgae were added to each breeding aquarium, as described above. These planktotrophic larvae developed to prodisoconch stag
. California fish and game. Fisheries -- California; Game and game-birds -- California; Fishes -- California; Animal Population Groups; Pêches; Gibier; Poissons. DEVELOPMENT OF THE AMERICAN PEARL OYSTER 189 environmental conditions were recorded (Table 1). The early straight-hinge larvae developed after about 24 hours. The height of the shell was on an average ± )im. They had a smooth, transparent prodisoconch I and swam near the water surface. After 24 hours microalgae were added to each breeding aquarium, as described above. These planktotrophic larvae developed to prodisoconch stage II. Their shells were less transparent and had concentric striae. After 8 to 9 days from larval hatching the height of the shell had grown on an average to ± |im. At day 17 the larvae in aquaria 1 and 2 had grown more than in aquarium 3 and 4. Such differences in growth rate persisted until the study terminated (Table 2). Most of the larvae in aquaria 1 and 2 developed to the umbo stage at day 28 (Fig. 3a). The study ended on day 32 because of high mortality. Despite the lengthy period over which the larvae were bred, they remained in the umbo stage, in aquaria 1 and 2. The larvae in aquaria 3 and 4 not only grew less, they never reached more than prodisoconch stage II. Several of these individuals developed abnormalities such as a long antero-posterior axis (the axis parallel with the hinge) in relation to the dorso- ventral axis (Fig. 3b). For other individuals the velum was small. These larvae did not live more than a few days. DISCUSSION Pteria sterna proved to be tolerant to variations in both temperature and salinity within the ranges used in this study. The oysters cannot however, be transported under dry conditions as can other bivalves (, Mytilus and Modiolus) which are intertidal species and normally exposed to desiccation at low tide. This was tested a) b). Please note that these images are extracted from scanned page images that may have been digit
Size: 1585px × 1576px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorcaliforniadeptoffishandgame, bookauthorcaliforniafish
