Dietary constraints on reproductive periodicity in two sympatric deep-sea astropectinid seastars |
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Authors: | P A Tyler J D Gage G J L Paterson A L Rice |
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Institution: | (1) Department of Oceanography, The University, SO9 5NH Southampton, England;(2) Scottish Marine Biological Association, Argyll, P.O. Box 3, PA34 4AD Oban, Scotland;(3) The Natural History Museum, Cromwell Road, SW7 5BD London, England;(4) Institute of Oceanographic Sciences Deacon Laboratory, Wormley, GU8 5UB Godalming, Surrey, England |
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Abstract: | Examination of the diet of two sympatric species of seastar, Bathybiaster vexillifer and Plutonaster bifrons from 2200 m depth in the Rockall Trough, NE Atlantic Ocean (57°18'N; 10°28'W), suggested that diet may determine the different reproductive patterns found between these two species. In the non-seasonally breeding B. vexillifier, the diet showed a high Shannon-Wiener prey diversity index, the dominant prey being the irregular echinoid Hemiaster expergitus together with a variety of prosobranch gastropods and protobranch bivalves. By contrast, the prey diversity in the seasonally breeding P. bifrons was significantly lower than that of B. vexillifer. In addition, organic carbon content in the sediment residue in the stomachs of P. bifrons displayed a seasonal cycle, while no such seasonality was detected in B. vexillifer. The stomachs of P. bifrons also contained a higher proportion of scavenged material, including the seasonally available remains of mesopelagic blue whiting. These data, together with Bathysnap (time-lapse camera) observations of feeding behaviour in both species, suggest that B. vexillifer is a predator feeding deep in the sediment, whereas P. bifrons feeds close to the sediment surface where it is affected by the seasonal availability of phytodetritus and fish carcasses. |
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