The ecology of Engina armillata (Gastropoda: Buccinidae) in the Cape d'Aguilar Marine Reserve, Hong Kong, with particular reference to its preferred prey (Polychaeta: Serpulidae)

Abstract

The egg capsules and larvae of Engina armillata (Reeve) (Gastropoda: Buccinidae) are described for the first time. Its general ecology in the Cape d'Aguilar Marine Reserve, Hong Kong, is also described, the species occurring under stable boulders with a community of encrusting species, notably sedentary tubicolous polychaetes. The diet of E. armillata at Cape d'Aguilar consists of serpulid and spirobid polychaetes. Of the four commonest such species, Hydroides elegans was preferred to Pomatoleios kraussi, Simplicaria pseudomilitaris and Spirorbis foraminosus. Consumption rates by E. armillata varied considerably amongst individuals, but generally ranged between 1.2 and 6.5% of predator dry weight day^-1 during conditions wherein prey quantity was maintained. Such a figure is low when compared to other boring naticid and muricid predatory gastropods which spend much time and energy accessing their prey. The ready availability of easily accessible prey may account for the low consumption rate of E. armillata (as also seen in other non-boring predatory gastropods) and explain its apparent specialist feeding habits.