White, 1847
Description
Members of the amphipod Family Cyamidae (whale lice) are dorso-ventrally flattened. The head is partially or completely fused with the first pereion segment. The first antenna is longer than the second. The mouthparts are reduced. The pereion has seven separate segments. The first pereiopod (gnathopod 1) is smaller than or subequal to the second pereiopod (gnathopod 2); second pereiopod subchelate. Pereiopods 3 and 4 are absent, pereiopods 5-7 directed backwards and some or all are prehensile. Pleon reduced, three segments.
Because of their overall flattened appearance, cyamids could erraneously be taken for an isopod, or even for a sea spider (arthropod Class Pycnogonida). However, the Cyamidae have five pairs of reduced pereiopods ("body legs") of different shape which are provided with strong curved hooks (dactylus) to facilitate the attachment on and in the skin of the host (see for an example of a cyamid Cyamus catodontis). In contrast, the Isopoda generally have seven pairs of legs which are more or less similar in shape. The Pycnogonida have four to six pairs of rather uniform legs, all composed of nine segments.
Note that the parasitic isopods of the Family Gnathiidae also have five pairs of legs, as a reduction of the typically seven pairs.
Ecology
Cyamidae are epiparasitic on the skin of whales.
Distribution in the North Sea
The following species of Cyamidae possibly occur in the area (host between hooks):
¥ Isoscyamus delphinii (Guérin-Méneville, 1837) [Phocaena phocaena, Globicephala melaena, Globicephala melas, Mesoplodon grayi, Pseudorca crassidens ]
¥ Platyscyamus thompsoni (Gosse, 1855) [Hyperoodon ampullatus, Mesoplodon grayi ]
¥ Cyamus boopis Lütken, 1873 [Megaptera nouvaeangliae ]
¥ Cyamus catadontis Margolis, 1954 [Physeter catodon ] Cyamus catodontis
¥ Cyamus erraticus Roussel de Vauzème, 1834 [Eubalaena glacialis ]
¥ Cyamus gracilis (Roussel de Vauzème, 1834) [Eubalaena glacialis ]
¥ Cyamus ovalis Roussel de Vauzème, 1834 [Eubalaena glacialis, Physeter catodon ]
¥ Scutoscyamus parvus Lincoln and Hurley, 1974 [Lagenorhynchus albirostris ]