Defensive responses and payability of specialist herbivores: predation on NE Pacific ascoglossan gastropods

CD Trowbridge
1994 Marine Ecology Progress Series  
Four common species of temperate NE Pacific ascoglossan (= sacoglossan) sea slugs were examined in 1990 and 1991 to determine the nature and effectiveness of their defensive responses and the potential ecological importance of predation. The 3 small, cryptic species (Placida dendritica, StiLiger fuscovittatus, Alderia modesta) responded to mechanical stimulation by waving and autotomizing cerata (finger-like projections on dorsal surfaces), secreting viscous white fluid, and reducing body
more » ... reducing body surface pH. These responses, however, were ineffective deterrents against common intertidal predatory fishes and crabs: the predators readily consumed the cryptic herbivores in short-term laboratory experiments. Furthermore, predators s~gnificantly reduced densities of A. modesta on algal mats of Vauchena sp. in a 12 d field experiment conducted in Yaquina Bay, Oregon, USA. Thus, small, cryptic ascoglossans were subject to intense predation pressure In contrast, the large, conspicuous Aplysiopsis enterornolphae had more intense defensive responses (e.g. ejection of viscous fluid, acidic secretions), and few predators consumed the ascoglossan.
doi:10.3354/meps105061 fatcat:wybwkr4yh5c7votrf7ffl62wym