Histology and teratology of pink salmon larvae near the time of emergence from gravel substrate in the laboratory
During salmonid larval development, emergence from gravel substrate is a major event marked by final yolk absorption and transition to exogenous feeding. The gross and histological changes associated with this fundamental biological process were investigated in pink salmon (Oncorhynchus gorbuscha) 4...
Published in: | Canadian Journal of Zoology |
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Main Authors: | , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
Canadian Science Publishing
1997
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Subjects: | |
Online Access: | http://dx.doi.org/10.1139/z97-119 http://www.nrcresearchpress.com/doi/pdf/10.1139/z97-119 |
Summary: | During salmonid larval development, emergence from gravel substrate is a major event marked by final yolk absorption and transition to exogenous feeding. The gross and histological changes associated with this fundamental biological process were investigated in pink salmon (Oncorhynchus gorbuscha) 4 weeks before emergence (alevins), at emergence (swim-up fry), and 2 weeks after emergence with or without exogenous feeding. Larvae were derived from artificially spawned eggs reared in gravel-filled incubators in the laboratory. Less than 1% of emergent larvae had gross lesions. These included opercular hypoplasia or dysplasia (semioperculum), spinal anomalies (lordosis and kyphosis), conjoined twins, and ophthalmic dysplasia. Apoptosis, or programmed cell death, was a common cellular change, and several cell types were involved: (i) intragonadal supporting cells, (ii) gastric submucosal gland epithelial cells, and (iii) midventral skin cells. Semiquantitative scores for apoptosis were usually highest in pre-emergent larvae and lowest in postemergent larvae. Larvae that were not fed during the first 2 weeks after emergence had slightly higher scores for apoptosis and hepatocellular megalocytosis than did fed controls. |
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