DAO prepress abstract   -  DOI: https://doi.org/10.3354/dao03815

ABSTRACT: Nectonema nematomorphs utilize marine crustacean hosts in their life cycle; 16 decapod and one isopod genera have been reported to date as host genera. This study reports the first case of Nectonema parasitic in the Tanner crab (Chionoecetes bairdi), adding another known host genus. A single nematomorph juvenile was recovered from the body cavity of each of two ovigerous female crabs. A nucleotide sequence for the 18S rRNA gene (1854 bp) was determined from one Nectonema individual. The 18S sequence showed K2P distances of 10.0%, 2.0%, and 1.7% from 18S sequences from Nectonema sp. from an isopod host, N. agile, and N. munidae, respectively. In an 18S-based tree, the unknown species was the sister taxon to a clade comprising N. agile and N. munidae, both of which also utilize decapod hosts. The phylogenetic relationships among the three Nectonema species parasitic in decapods were not congruent with the phylogeny of the hosts, not supporting a hypothesis of nematomorph–host co-evolution.