The biology of Hipponix australis (Gastropoda : Hipponicidae) on Nassariuspauperatus (Nassariidae) in Princess Royal Harbour, Western Australia

Hipponix australis is identified as having a clear preference for the small , up to similar to 18 mm, intertidal nassariid Nassarius pauperatus in Prin cess Royal Harbour, Western Australia, occurring on a mean of 14% of the po pulation. A few other sand-dwelling nassariids and buccinids (Cominella spp .) are secondary hosts. On N. pauperatus, moreover, H. australis is specifi c in terms of its location, i.e. on the outer lip of the shell, where it oc curs as either solitary females or small undifferentiated individuals, or i n clusters comprising a large female with between 2-4 smaller males and und ifferentiated individuals. H. australis is a protandrous consecutive hermap hrodite, the change in sex occurring at a shell length of similar to6 mm. The degree of specificity in relation to Nassarius pauperatus suggests that this is the main host in Princess Royal Harbour, but that other species ar e colonised opportunistically. This is also seen in other hipponicids and, indeed, host specificity may vary from place to place for the same species.