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Title: Reproductive biology of the bass, Dicentrarchus labrax L.
Author: Mayer, I.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1987
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The bass, Dicentrarchus labrax L. exhibits a distinct seasonal reproductive cycle. The spawning period lasts for 4-5 weeks and occurs between April and mid-May for Gower bass. There is a close relationship between the timing of spawning and seawater temperature, spawning only occurring when the seawater attains a temperature of 9oC. From macroscopic and histological observations seven maturity stages can be delineated for developing ovaries of mature females. The reproductive strategy of the bass is characterised by: group-synchronous oocyte development, recruitment of successive clutches occurring from a large heterogeneous population of small oocytes at various stages of secondary growth; fractional spawning, 3-4 clutches being spawned in quick succession (within 10-12 days). All oocytes recruited into the secondary growth phase (viz. vitellogenesis) are either spawned that season or become atretic. Further the bass has a high fecundity (2-25 x 105), the small (1.20-1.25mm) pelagic eggs having a relatively short incubation period (4-5 days). Bass eggs exhibit a high degree of tolerance to both temperature and salinity, good survival occurring in the ranges 6-17oC and 20-39o/oo. Histological, histochemical and ultrastuctural observations indicate that two types of yolk inclusions are formed. Lipid yolk accumulates first as discrete droplets, followed by membrane-bound protein yolk granules. Protein yolk granules maintain their structural integrity through to maturation, forming a densely packed zone in the mid and outer cortex. Lipid yolk droplets coalesce and migrate centripetally forming a prominent zone of large lipid yolk droplets in the inner and mid cortex. Cortical alveoli ('carbohydrate yolk') are formed in the peripheral cytoplasm of secondary oocytes, and it is suggested that the golgi bodies are actively involved in their formation. Ultrastructural and biochemical evidence suggests that the protein yolk is exogeneous in origin, the lipid yolk is endogenous in origin.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available