Mesopsyllus Por, 1960

Mu, Fang-hong & Huys, Rony, 2017, New Mesopsyllus species from the Bohai Sea, China, re-evaluation of the validity of Vibriopsyllus Kornev & Chertoprud, 2008 and proposal of Sympodella gen. n. (Copepoda, Harpacticoida, Canthocamptidae), ZooKeys 718, pp. 1-33 : 2

Genus Mesopsyllus Por, 1960

Diagnosis.

Rostrum not defined at base; triangular. Antennule 6-segmented in ♀, with aesthetasc on segments 4 and 6; 8-segmented, haplocer with geniculation between segments 6 and 7 in ♂; with enlarged modified spines on segments 2-3 and 6 in ♀, and segments 2-4 in ♂. Antenna with one abexopodal seta on allobasis; exopod 1-segmented, with 2-3 setae. Mandibular palp with short basis (with one seta), 1-segmented endopod (with four setae) and vestigial unisetose exopod. Maxillule with rami incorporated into basis. Maxilla with two endites on syncoxa; endopod discrete. Maxilliped with well developed seta on syncoxa. Swimming legs of ♀ with 3-segmented exopods and 3- (typical condition in P1) or 2-segmented endopods (P2-P4, unusual condition in P1). Setal formulae of P1-P4 as follows:

Inner seta of P1 enp-1 short, not recurved backwardly and dorsally; outer spine of P1 exp-1 not enlarged; outer exopodal spines of P1-P4 sparsely bipinnate, in P2-P4 without elongate pinnules in proximal half. P2 endopod occasionally with sexual dimorphism (inner seta of enp-1 distinctly shorter in ♀; enp-2 with additional inner seta in ♀). P3 endopod 3-segmented in ♂; enp-2 with inner seta and slender terminal apophysis; enp-3 with two apical setae. P4 enp-1 and sometimes enp-2 and exp-3 with slight sexual dimorphism (setal lengths). P4 exp-3 occasionally sexually dimorphic (length of proximal inner seta). P5 with discrete exopod and baseoendopod; exopod small, with 3-5 and 4-5 elements in ♀ and ♂, respectively; endopodal lobe with four and two elements in ♀ and ♂, respectively. Sixth pair of legs asymmetrical in ♂, unarmed. Caudal ramus short, with six setae.

Type species.

Mesopsyllus atargatis Por, 1960 (by monotypy).

Other species.

Mesopsyllus secundus (Wells, 1965), M. curvisetus (Kornev & Chertoprud, 2008), comb. n., M. dimorphus sp. n., M. spiniferus sp. n.