Adelomelon ancilla: a predator neogastropod in Patagonian benthic communities

Abstract

Adelomelon ancilla, a volutid commonly found in shallow waters of northern Patagonia, is a top predator in the benthic communities of this region. This species presents an anemone epibiosis (Antholoba achates) that may be protecting it from predators. A. ancilla captures prey by tightly engulfing it with the foot, and ingests them, generally alive, after narcotizing their muscles. A narcotizing substance is produced by the accessory salivary glands and released through the predator’s proboscis onto the prey that is tightly enveloped within the foot, allowing for prey narcotization. In this space, water is not abundant, and therefore, the salivary secretion reaches a high concentration, with a pH of around 10. Analysis of prey obtained in situ indicated that A. ancilla consumes mainly bivalves (88.9%), gastropods (9.5%) and, rarely, sea urchins (1.6%). Ingestion of the prey usually occurs while the predator is buried in the substrate, and lasts for several hours. The anatomy of the alimentary system and pH of various organs involved in prey capture and digestion is presented as its comparison with feeding mechanisms among other species of Volutidae.