Parasitic copepods from pelagic sharks in Western Australia

This first attempt to elucidate elasmobranch-copepod associations from West ern Australian waters revealed 17 species of commensal copepod from four sp ecies of pelagic shark (Galeocerdo cuvier, Caucharhinus obscurus, Carcharhi nus plumbeus, and Carcharhinus amblyrhynchos). The copepods represented the families Pandaridae, Euphoridae, Eudactylinidae, Kroyeridae and Caligidae. Praniza stage gnathiids were also common and other symbionts comprised spe cies of Hirudinea, an ostracod and a sphaeromatid isopod. A predominance of tiger sharks (G. cuvier) were caught throughout the study area, which exte nded from the Montebello Islands to Shark Bay. There was a bias toward fema le tiger and sandbar (C. plumbeus) sharks caught, and a difference in the i nfection of tiger sharks in the north and southern regions of the study are a. Several hypotheses are suggested: population differentiation of the tige r sharks, population differentiation of the copepods or ecophysiological di fferences in the two regions. Two major patterns were identified in the dis tribution of the copepods on hosts: those which occur generally on the body surface of their hosts and had a geographical distribution throughout the entire study area, and those which have a specific body location and a more restricted geographic distribution. Nemesis robusta is the one exception t o this rule, as it has a wide geographic distribution, yet is restricted in site of attachment.