ABSTRACT: Laboratory feeding experiments were conducted to study the importance of suspension-feeding in the protobranch bivalve Yoldia hyperborea at different suspended particle concentrations in order to evaluate the importance of this feeding strategy when compared with its known strategy of deposit feeding. Standard feeding variables (absorption efficiency, AE; gut passage time, GPT; ingestion rate, IR) were estimated by quantifying ⁶⁸Ge/¹⁴C in dual-labelled Thalassiosira nordenskioldii fed to Y. hyperborea. For the first time, results were also used to estimate scope for growth (SFG) in a protobranch bivalve. Absorption efficiency was higher when Y. hyperborea was deposit feeding (87.7 to 94.8%) than it was during suspension feeding (50.1 to 71.7%), whereas GPT was similar in most cases and ranged between 8.15 and 20.11 h. However, IRs for suspended particulate matter (SPM, dry weight) were mostly negligible (<0.01 to 5.77 µgPM h^-1) when compared with deposit feeding (2067.4 to 6872.3 µgPM h^-1), although in one case suspension-feeding individuals ingested 93.7 µgPM h^-1. Scope for growth was always positive in deposit feeders (113.8 to 372.4 J d^-1), whereas under suspension-feeding conditions it was mostly negative and could not meet metabolic requirements. In addition, mortality of Y. hyperborea increased at suspended particle concentrations above 0.085 mg ml^-1. Although deposit feeding is the principal feeding strategy followed by Yoldia hyperborea, suspension feeding is invoked at low suspended particle loads and may serve as a strategy for capturing highly nutritional particles suspended at the sediment-water interface.

KEY WORDS: Yoldia · Protobranchia · Deposit-feeding · Suspension-feeding · Absorption efficiency · Ingestion rate · Gut passage time · Scope for growth

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Published in MEPS Vol. 252 (2003) on April 30
Print ISSN: 0171-8630; Online ISSN: 1616-1599. Copyright © Inter-Research, Oldendorf/Luhe, 2003