Description of Xanthocalanus quasiprofundus sp. n. from the Arctic and redescription of X. obtusus and X. kurilensis from the North Pacific (Copepoda: Calanoida: Phaennidae)

Abstract

The Arctic Xanthocalanus quasiprofundus sp. n. differs from X. profundus Sars, 1907 in the larger size (7.6 vs. 6.2 mm), presence of 10 teeth on masticatory edge of Md gnathobase and of spinules near bases of central teeth, 1 very enlarged brush-like seta of distal endopodal complex of Mx2, presence of 3 sensory setae on syncoxa of Mxp and of transverse row of spinules on Re1 of P4, and some details of P5 structure. Females of X. obtusus and X. kurilensis have 1 worm-like and 7 slender brush-like sensory setae differing in lenth on distal endopodal complex of Mx2. Male of 5th copepodid stage of X. kurilensis has an additional rudimentary seta, i.e. 9 elements, on distal endopodal complex of Mx2 (number primitive for Bradfordian families). Adult male of X. kurilensis has here 1 enlarged brush-like seta, 4 very slender brush-like setae and 1 rudimentary seta. The presence of 1 and 2 worm-like sensory setae on Li3 and Mx2 is noted in all 3 examined species.