PREDATOR-PREY INTERACTIONS BETWEEN LEPSIELLA (BEDEVA) PAIVAE (GASTROPODA: MURICIDAE) AND KATELYSIA SCALARINA (BIVALVIA: VENERIDAE) IN PRINCESS ROYAL HARBOUR, WESTERN AUSTRALIA

On a sandy beach at Shoal Bay in Princess Royal Harbour, Albany,southwestern Western Australia, lives a small muricid gastropodthat feeds virtually monotonically on the overwhelmingly dominantresident bivalve Katelysia scalarina. Lepsiella paivae livesburied in the sand and attacks its prey within it. Because ofits small size (<13 mm shell height), bivalve prey isalso small and this study demonstrates a preference for K. scalarinaof 5 mm shell length, i.e. juveniles. Laboratory experimentsalso suggested a possible preference for attack of the rightvalve. Lepsiella paivae can and does, however, attack largerprey (up to 15 mm shell length), but cannot consume themcompletely. A second visit to Princess Royal Harbour in theAustral winter, when there was no juvenile K. scalarina present,showed L. paivae to be attacking at the sand surface, also bydrilling, the small (<4 mm) gastropod Hydrococcus brazieri(Hydrococcidae). SEM studies of experimentally determined drillholes of L. paivae show them to be of variable form, some straightsided, others bevelled (like a naticid) and <500 µmin diameter. On this sheltered Southern Ocean beach, therefore,L. paivae has specialized to attack juvenile bivalves by burrowingafter them. It can, however, attack other species opportunisticallyon the sand surface when seasonally favoured juvenile bivalveprey are not present. (Received 8 January 2005; accepted 16 March 2005)