Lack of Chemical Defense in Two Species of Stalked Crinoids: Support for the Predation Hypothesis for Mesozoic Bathymetric Restriction
Chemical defense; Fish predation; Mesozoic marine revolution; Stalked crinoid
Journal of Experimental Marine Biology and Ecology
Methanol/dichloromethane extracts of (1) the arms and pinnules, and (2) the stalk and cirri of the deep water stalked crinoids Endoxocrinus parrae (Gervais) and Neocrinus decorus (Carpenter) were imbedded at ecologically relevant volumetric concentrations in alginate food pellets containing 2% krill as a feeding stimulant and presented in situ to an assemblage of shallow-water reef fish. Experimental pellets were highly palatable to reef fish; no significant differences in pellet consumption occurred between experimental pellets containing extracts from either species of stalked crinoid or control pellets. Small pieces of cirri, stalks, calyx, arms and pinnules of both species were also tested in in situ feeding assays. While immediate consumption by fish was not apparent, Blue Headed Wrasse (Thalassoma bifasciatum (Block)) and Dusky Damselfish (Stegastes fuscus (Cuvier)) bit at pieces of each body component. Similar fish biting behaviors were also observed when two living Endoxocrinus parrae were deployed on the shallow reef. Observations indicate that neither species of stalked crinoid is chemically defended from predation by a natural assemblage of reef fish. This supports the predation hypothesis that restriction of stalked crinoids in deep-water habitats may have resulted from the Mesozoic radiation of durophagous fishes in shallow seas, resulting in a reduction of stalked crinoids from shallow water.
McClintock, James B., Bill J. Baker, Tomasz K. Baumiller, and Charles G. Messing. "Lack of chemical defense in two species of stalked crinoids: support for the predation hypothesis for Mesozoic bathymetric restriction." Journal of Experimental Marine Biology and Ecology 232, no. 1 (1999): 1-7.