The blue bat star Patiria pectinifera adjusts its handling behavior according to its prey

Abstract

Predator–prey interactions can be divided into pre- and post-capture phases, with the latter involving the processing of prey exhibiting secondary defenses such as chemical toxins, adhesive secretions, or rigid shells. Generalist predators often adjust their handling strategies according to these defenses. Among starfish that perform external digestion, prey-handling behavior has been well documented for bivalve predation. However, little is known about their responses to prey with other defensive traits. The blue bat star, Patiria pectinifera, everts its stomach to digest prey externally, but no study has yet compared its handling behavior among different prey types. Here, we investigated how P. pectinifera handles three prey items with distinct secondary defenses: the limpet Lottia peitaihoensis, the bivalve Mytilisepta virgata, and the crab Hemigrapsus sanguineus. Field surveys revealed frequent predation on shelled invertebrates, and laboratory observations showed that repeated stomach eversion occurred at different frequencies among prey species. The starfish opened bivalves, inverted limpets after detachment, and immobilized crabs through strong adhesion to the substratum. In addition, crabs were observed stealing conspecific carcasses from feeding starfish, indicating kleptoparasitism during digestion. Patiria pectinifera exhibited prey-specific, flexible handling behavior and repeated digestion, suggesting an adaptive mechanism for efficient external digestion. These findings highlight behavioral plasticity in starfish and expand our understanding of predator–prey relationships in marine benthos.