Evansula, T. SCOTT, 1906

Huys, Rony & Conroy-Dalton, Sophie, 2006, Revision of the genus Evansula T. Scott, 1906 (Copepoda, Harpacticoida, Cylindropsyllidae) with a description of three new species, Zoological Journal of the Linnean Society 147 (4), pp. 419-472 : 421-422

GENUS EVANSULA T. SCOTT (1906B)

Synonyms: Tetragoniceps Brady, 1880 [partim]; Evansia T. Scott, 1906 a nec Pickard-Cambridge (1900).

Diagnosis: Cylindropsyllidae . Body slender, cylindrical. Rostrum elongate, defined at base. Genital doublesomite female without chitinous traces marking original segmentation. Copulatory pore large, semicircular, positioned slightly posterior to gonopores. Copulatory duct and paired anterior extensions very well chitinized. Caudal ramus of moderate length, conical; with seven setae; seta I vestigial; seta V with defined flexure zone between proximal styliform and distal flagellate parts, fused to seta IV; seta VI vestigial.

Sexual dimorphism in antennule, P2–P3 (exopod and endopod), P5, P6, ventral ornamentation of anal somite, and in genital segmentation. Occasionally, also in P2 basis (slight), P4 endopod and caudal rami.

Antennule with segment 1 approximately as long as segment 2; segment 2 with nine setae; segment 6 with three setae in female; seven-segmented and with aesthetasc on segments 4 and 7 in female; indistinctly nine-segmented, haplocer and with aesthetasc on segments 5 and 9 in male; apical segment in both sexes with terminal acrothek consisting of two long setae fused basally to slender aesthetasc. Antenna with incompletely fused allobasis and bisetose, onesegmented exopod. Mandible with two-segmented, uniramous palp consisting of unisetose basis and endopod bearing one lateral and four distal setae. Maxillule with one claw and one seta on coxa, five setae plus one claw on basis; endopod and exopod represented by a small, trisetose segment and two setae, respectively. Maxillary endopod discrete, one-segmented, with four setae; proximal endite of syncoxa with three setae/spines. Maxillipeds well developed, subchelate, syncoxa with zero to one seta, endopod represented by strong claw.

P1–P4 with three-segmented exopods and one- (P2–P4) or two-segmented (P1) endopods. P1 with outer and inner seta on basis; exopod with outer spine on middle segment and two geniculate setae plus two spines on distal segment; endopod prehensile, proximal segment longer than exopod, with inner seta being plumose proximally and pinnate distally (except E. arenicola ), distal segment with two geniculate setae (or spines) and one setule. P2–P4 bases with outer seta. P3 endopod of female with two distal spines. Inner distal spine of P3–P4 exp-3 distinctly shorter than outer distal one. Inner setae of P4 exp-3 and endopod serrate. Armature formula of swimming legs:

Exopod Endopod

P1 0.0.112 1.111

P2 0.0.022 110

P3 0.0.022 020

P4 0.0.122 211

P 2 male with inner seta of exp-3 transformed into claw; endopod with slight setal modifications. P3 exopod male usually without or with reduced hyaline frill on exp-1; exp-3 with secretory pore and elongate outer distal seta. P3 endopod male two- or three-segmented; enp-1 minute or incorporated in middle segment; enp- 2 (enp-1 if ramus two-segmented) with large apophysis and pinnate seta; enp-3 (enp-2 if two-segmented) with one short seta.

P5 baseoendopod and exopod completely fused, forming elongate plate in both sexes; with eight setae/ spines in female; drawn out into spinous pinnate process and with six setae/spines in male. P6 asymmetrical in male, with three setae each; represented by small operculum with three setules in female.

Type species: Tetragoniceps incertus T. Scott, 1892 = Evansula incerta ( Scott, 1892) [by original designation: Scott (1906a)].

Other species: E. pygmaea (T. Scott, 1903a) ; E. arenicola Nicholls, 1939 ; E. cumbraensis sp. nov.; E. spinosa sp. nov.; E. polaris sp. nov.

Species incertae: Evansula (?) spec. sensu Noodt (1955c).