A NEW FAMILY OF COPEPODS ASSOCIATED WITH ASCIDIACEANS IN THE WHITE-SEA, AND AN ANALYSIS OF ANTENNULARY SEGMENTATION AND SETATION PATTERNS IN THE ORDER POECILOSTOMATOIDA

A new genus and species, Intramolgus arcticus, of parasitic copepod is described from ascidiacean hosts in the White Sea. The new genus repr esents a new family of the order Poecilostomatoida. This family is cha racterised particularly by the sexual dimorphism of the antennules, by the plesiomorphic mandible and by the apomorphic fifth legs. The numb ers and distribution patterns of aesthetascs on male antennules in key poecilostomatoid genera and families are compared in detail. This ana lysis reveals that a total of 10 aesthetascs is expressed within the o rder although nine is the maximum found in any known genus. A modified system of antennulary segmental homologies is proposed for the Poecil ostomatoida, based on a 9-segmented antennule.