Arrama, new genus (Siphonostomatoida : Caligidae), with two new species, copepods parasitic on Australian fishes

Abstract

ABSTRACT A new genus, Arrama, and two new species, A. tandani and A, cordata, belonging to the copepod family Caligidae (Siphonostomatoida), are described from the gill filaments of two species of plotosid catfishes, Cnidoglanis macrocephalus (Valenciennes) and an undescribed species of Paraplotosus, respectively, from Australia. The new genus can be distinguished from confamilial genera by a combination of characters that include (1) the reduced apical armature of the leg 1 exopod, (2) the 2-segmented rami of leg 2, (3) the absence of the ventral apron of leg 3, and (4) the reduction of legs 3 and 4 to setiferous lobes. The two new species are distinguished from each other by the shape of the genital complex, the setae of the caudal ramus, the arrangement of spinules of the canna of the second maxilla, the apical armature of the leg 1 exopod, and the terminal armature of the leg 2 exopod. The morphology of the suckerlike cephalothorax of the members of the Caligidae appears to be an adaptation for attachment to smooth flat surfaces, i.e., external body surfaces, buccal cavity walls, and branchial chamber walls of the hosts. Two genera, Abasia and Hermilius, have become specialized for living on gill filaments of their hosts by modifications of their cephalothoraces. Although the ventral apron, a structure formed by the expansion of the intercoxal plate and sympod of leg 3, remains intact in these two genera, it may no longer be functional. Members of the new genus, Arrama, which also live on gill filaments, lack the ventral apron.