Attraction to and selection of prey by immature lobsters (Homarus americanus)

Carter, John Andrew (1979) Attraction to and selection of prey by immature lobsters (Homarus americanus). Masters thesis, Memorial University of Newfoundland.

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Abstract

Little is known of the diet of immature lobsters (Homarus americanus). Attraction to and selection of prey by immature lobsters in Newfoundland were the subject of the present study. -- The relative attractiveness of extracts of Asterias vulgaris, Cancer irroratus, Mytilus edulis, and Strongylocentrotus droebachiensis were determined by observing behaviour of immature lobsters. All extracts, except that of Asterias, were attractive to immature lobsters. Cancer was preferred over Mytilus and the two echinoderm species. Immature lobsters were subjected to metabolites of prey. Most lobsters showed alert phase behaviour, regardless of the quality of the stimulus. Cancer effluent was significantly more effective than controls in eliciting food-searching behaviour. Mytilus and Strongylocentrotus effluents were less effective stimulants. -- The percentage responses of immature lobsters presented with ninhydrin-positive compound (NPC) targets were determined. Proline, ammonia, arginine, and lysine were the most attractive NPCs. The NPC compositions of effluents and extracts of various prey were determined. Extracts of Nereis sp. and Cancer irroratus had the highest total concentrations of NPCs (excluding urea, unknowns, polyamines, and trace amounts). Cancer had significantly higher concentrations of glutamine, proline, and taurine compared to Asterias and Strongylocentrotus. Effluents of Nereis and Cancer had higher levels of ammonia than those of three echinoderm and two mollusc species. -- Selection of intact prey by immature lobsters given a choice was determined. Brittlestars and polychaetes were the most frequently attacked, followed by Cancer, Asterias, Mytilus, and Strongylocentrotus. Consumption of polychaetes by immature lobsters was generally complete. Substantially greater proportions of the other prey species were left unconsumed. Size, morphology, and behaviour of prey appeared to influence the attack rates. -- The natural diet of immature lobsters was determined by gut content analysis. Sea urchins, mussels, and crabs were frequently consumed. Cancer was the dominant item in terms of volume of gut contents. Seasonal differences in feeding behaviour of immature lobsters were observed. Electivity indices indicated a high selection of crabs and mussels by immature lobsters.

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