Contrasting chemotactic escape responses of the common Antarctic gastropod Margarella antarctica to four species of sympatric sea stars

Escape responses of marine gastropods from sea star predators have long been established in laboratory studies. The degree of the response, which may include shell elevation and rotation and/or rapid flight, can vary with sea star taxa, providing insights into the degree to which a particular sea star species represents an in situ predatory threat. Little is known of such predator-prey interactions among benthic macroinvertebrates along the western Antarctic Peninsula. The present laboratory study employed video analysis to measure chemotactic escape responses (mean speed of flight following contact with the tip of a sea star's arm) in the common Antarctic top shell snail Margarella antarctica to the sea stars Neosmilaster georgianus, Remaster sp., Granaster nutrex, and Odontaster validus. Identical assays in response to contact with the thalli of the macroalga Gigartina skottsbergii provided a control. Significant flight responses to contact with two of the four sea star taxa were detected [N. georgianus (6.2 cm min−1), Remaster spp. (4.4 cm min−1)]. There was no significant difference between gastropod speed in response to contact with the control macroalga (1.9 cm min−1) and to the sea stars G. nutrex (3.1 cm min−1) and O. validus (1.1 cm min−1). Measured patterns of sea star-induced gastropod flight responses are discussed in the context of natural diets and feeding modes of the sea stars.