Welsh Journals

A WHALE-LOUSE (ISOCYAMUS DELPHINI) ON A COMMON PORPOISE (PHOCOENA PHOCOENA) FROM CARDIGAN BAY. PHILIP M. MILES Although amphipods are allied to isopods, to which the familiar woodlice and Sea Slater (Ligia oceanica) belong, they may be distin- guished in a majority of cases by virtue of their bodies being flattened from side to side, instead of broad and flattened below. Perhaps the best known amphipod of the upper shore is the Sand Hopper (Talitrus locusta) and in inland waters the Freshwater Shrimp (Gammarus pulex) belonging to the sub-order Gammaridea. This sub-order is divided into tribes, one of them being the Caprellina of which two principal families are the Caprellidae or skeleton shrimps and the Cyamidae or whale-lice. Whale-lice live parasitically upon cetaceans and may be recognised by their having a roughly conical head which is joined to the first thoracic segment which consists of seven free, flattened segments. There is a pair of gills situated on segments three and four. In Isocyamus delphini there is an outwardly directed pointed process at the base of each gill. Adult female Cyamidae are identified by the presence of a marsupium or brood pouch on segments three and four and a pair of genital valves on segment five. The second, fifth, sixth and seventh segments are provided with short limbs, terminating in a sharp pointed pleon. By means of chelate appendages the animals fasten themselves to the skin of cetaceans, the claws penetrating the epidermis so that they adhere sufficiently firmly to prevent themselves being washed off by wave action and rate of water flow set up by the host. Cetaceans also carry as well as whale-lice, acorn barnacles (Coronula) and on the acorn barnacle may be a stalked barnacle (Conchoderma). Stalked barnacles are not found directly on the skin of the whale. All these organisms have been recorded together on the slower moving species of whales, especially Humpback ( Megaptera boops Fabricius), suggesting the rate of water flow may be a factor influencing host selection. While barnacles do not do much damage to their host, another parasitic crustacean, a copepod Penella does in fact derive its nourishment from the blubber and which after reproducing dies and the wound heals with scar tissue of lighter colour than the surrounding skin. Right Whales (Balaena glacialis Bonnaterre) are recorded as always having a large number of whale-lice attached to roughened skin forming an excrescence on the snout and similar excrescencies along the lower jaw. Rorqual (Balaenoptera physalis (Linnaeus)) are usually free from Cyamids and rarely carry more than a few. Lamphreys are commonly found attached to whales which