External morphology of Arcticotantulus pertzovi (Tantulocarida, Basipodellidae), a microscopic crustacean parasite from the White Sea

摘要

The material on Arcticotantulus pertzovi, a parasite of the harpacticoids Bradya typica and Pseudobradya acuta, was collected in the White Sea (the White Sea Biological Station, Moscow State University) in 2004-2006. The morphology of the tantulus larva, the parthenogenetic female, and the male was studied using SEM. The data obtained add significant details to the previous description of the species. For instance, the tantulus has at least 11 cephalic pores (A I -A IV , D I -D IV , L I -L III ), while the endopod of thoracopod II has a pair of setae. A freeswimming male of A. pertzovi was reared for the first time for Tantulocarida. It has a cephalothorax incorporating the cephalic and two thoracic segments, 6 thoracomeres (including those of the cephalothorax) with natatory thoracopods, the 7th trunk segment with a short penis, and an unsegmented abdomen bearing furcal rami with three setae. There are four pairs of aestetascs representing antennular rudiments. The head shield of cephalothorax is covered with cuticular ridges and bears 7 pairs of pores with setae. Both the cephalon of tantulus and cephalotorax of male lack the lattice organs, which represent the synapomorphy of the class Thecostraca. According to its morphological characteristics, A. pertzovi may belong to the families Deoterthridae or Basipodellidae; the former family is most probably an artificial taxon.