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Title: Studies of the life history biology of deep-sea gastropod molluscs
Author: Colman, J. G.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1987
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The gametogenic biology, larval development and population structure of a number of deep-sea gastropod species from the Rockall Trough, northeast Atlantic has been examined. The reproductive biology of the neogastropod Colus jeffreysianus is described. This species has a non-planktotrophic mode of development (egg size 170 μm diameter), producing a capsule containing c. 4000-5000 eggs from which only 1 juvenile hatches out, the remainder being utilised as nurse eggs. The capsule wall is a complex structure comprised of 5 layers. Histological examination of gonads of mature individuals from a time series of samples taken at a 2000m permanent station indicates a pattern of continuous production of gametes with no apparent seasonality. Gametogenesis in the archaeogastropod Calliotropis ottoi and in the cephalaspid opisthobranchs Scaphander punctostriatus and Philine quadrata is described, and appears also to be a continuous process. Determination of mode of larval development of 38 species of prosobranch and opisthobranch was made on the basis of protoconch morphology using scanning electron microscopy. Thirteen species have planktotrophic development and 25 have non-planktotrophic development. Descriptions are given of the shells of two previously undescribed archaeogastropod species and of a number of deep-sea prosobranch egg capsules. Shell size-frequency distributions of P. quadrata, S. punctostriatus and Benthonella tenella, the 3 most numerically abundant species from the Rockall Trough, show a trend of decreasing mean size from spring to summer and a peak of newly-settled post-larvae in August, suggesting an annual recruitment of juveniles to the adult population. All 3 species have planktotrophic development. These results are discussed in the light of the hypothesis that the seasonally varying flux of surface-derived organic matter to the deep sea is the selective pressure for reproductive periodicity.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available