First evidence of drilling predation by Conuber sordidus (Swainson, 1821) (Gastropoda: Naticidae) on soldier crabs (Crustacea: Mictyridae)

Moonsnails (Naticidae) are major predators in marine soft substrates worldwide and are thought to prey almost exclusively on shelled molluscs by drilling predation. However, reports on single individuals of various naticid species showing unusual feeding behaviour indicate that naticids possibly also feed on other prey which have an external skeleton. The present study provides the first evidence for size selective feeding of an Australian moonsnail (Conuber sordidus) on crustaceans. C. sordidus preys on soldier crabs (Mictyris longicarpus and Mictyris platycheles) on intertidal sand/muddy tidal flats, representing the first well-documented example of a naticid preying on large non-molluscan invertebrates in addition to shelled molluscs. This indicates that prey choice in C. sordidus is less stereotyped than predicted for naticid species, although the feeding mode documented here is similar to that used to capture their main diet of shelled molluscs. The results strongly support some contested earlier studies that have also indicated that naticids will eat non-molluscan prey with an external skeleton, highlighting a need to re-examine generally accepted models concerning naticid feeding ecology.