Abstract
Food detection and acquisition behavior and associated chemosensory structures were studied in shallow- and deep-water species of scavenging amphipods belonging to the superfamily Lysianassoidea. The morphology and distribution of chemoreceptors were examined in 12 amphipod species with light and scanning and transmission electron microscopy. Behavioral observations were made on two species from the genus Orchomene, one shallow- and one deepwater form. Chemoreceptors were classified as olfactory or gustatory on the basis of functional and morphological criteria. The largest concentrations of olfactory receptors occurred in callynophores, patches of aesthetasc setae on the first articles of the antennular flagella, while gustatory receptors were widely distributed on the thoracic appendages, particularly on the gnathopods. As in other crustacean groups, these two groups of chemoreceptors appeared to be employed in different ways, with olfactory receptors operating in the detection of water-borne stimuli and gustatory receptors functioning in the sampling of substrate-bound chemicals. Olfactory setae were typically more abundant than gustatory setae, although this was not true in all cases. Based on behavioral observations of Orchomene abyssorum and 0. limodes, the food detection and acquisition process was separated into 4 stages, each with a characteristic suite of behaviors and each employing a specific set of sensilla. The first two stages, detection and localization, primarily involved olfactory setae, while the third, chemical characterization of the food item, was gustatory in nature. The fourth stage, ingestion, appeared to be largely mechanical, although a chemosensory component may also have been involved.
Published Version
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