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A new species of Ectinosomatidae Sars (Copepoda, Harpacticoida) associated with Pseudoikedella achaeta (Zenkevitch, 1958) (Echiura, Bonelliida)

George, Kai Horst, Schwabe, Enrico
Progress in oceanography 2019 v.173 pp. 1-8
Echiura, Harpacticoida, adults, appendages, eyes, females, host specificity, legs, nauplii, new genus, new species, swimming, Pacific Ocean
Adult stages of both sexes of a new Echiuran infesting copepod, Parahalectinosoma maiorovae gen. et sp. nov., are described from the abyss of the north-western Pacific Ocean. The new species, obtained from the coelom of Pseudoikedella achaeta Zenkevitch, 1958, shows derived characters of its appendages compared to other representatives of the Ectinosomatidae in which it is placed by general similar body shape and swimming legs P1–P4 and by reflecting the three following ectinosomatid autapomorphies: an absent naupliar eye, a longitudinally divided telson and the presence of a pseudoperculum. Morphological peculiarities mainly of the appendages of the new species do not fit a current generic concept within the Ectinosomatidae, thus the new genus Parahalectinosoma is established. Parahalectinosoma maiorovae gen. et sp. nov. appears to be a common host-specific species in the studied area. Species’ density within the individual host can be high, but its intensity shows strong variation. Due to the absence of ovigerous females and nauplii an infecting event at a copepodid stage is assumed.