Eucyclops speratus (Lilljeborg, 1901)

Figs 19, 20, 21

Cyclops varius var. speratus Lilljeborg 1901: 88, tab. V: figs 12–15.

Leptocyclops speratus: Sars 1914: 72, pl. XLIV.

Cyclops agilis speratus: Gurney 1933: 104, figs 1395–1405.

Eucyclops speratus: Monchenko 1974: 91, fig. 40; Dumont and Decraemer 1977: 262, figs 3 C, 4; Ishida and Hiruta 1999 (part): 88, fig. 2 f – j; Alekseev et al. 2006: 136, fig. 14.

Eucyclops (Speratocyclops) speratus: Alekseev 2019: 511, fig. 13.

Material examined.

Russia • 1 ♀ dissected on two slides; Saint Petersburg, Orlov Pond; 59.84890 ° N, 30.04384 ° E; 20 June 2023; E. Chertoprud leg; EMKSU VH 2000 / 21–22 (N ° 86) ; • 2 ♀ dissected on two slides; Saint Petersburg, Orlov Pond; 59.84890 ° N, 30.04384 ° E; 20 June 2023; E. Chertoprud leg; in collection of A. Novikov (N ° 98, 111) ; • 1 ♀ dissected on one slide; Saint Petersburg, Olginsky Pond; 60.01293 ° N, 30.35514 ° E; 20 June 2023; E. Chertoprud leg; in collection of A. Novikov (N ° 97) ; • 3 ♀ dissected on three slides; Tatarstan republic, Naberezhnie Morkvashi village, puddle on stream; 55.76324 ° N, 48.85700 ° E; 28 June 2020; A. Novikov and D. Sharafutdinova leg; in collection of A. Novikov (N ° 75, 103, 104) ; • 6 ♀ dissected on six slides; Udmurtia republic, Chistostem village, pond; 56.86162 ° N, 52.21630 ° E; 16 June 2018; A. Novikov leg; in collection of A. Novikov (N ° 30, 59, 60, 93, 95, 96)

Description.

Female. Body elongated (Fig. 19 A – C). Total body length from anterior margin of rostrum to posterior margin of caudal rami: mean 1310 µm (n = 1). Cephalothorax pitted (Fig. 19 E), wider than first and second free somites, largest width 395 µm (n = 1), surface with 253 pores and sensilla, with all groups (Fig. 8 A – D). Naupliar eye not observed. Posterior margin of cephalothorax and all pedigerous somites smooth. Pedigerous and abdominal somites pitted, with “ sutures ” (Figs 19 D, 20 A, B).

Abdomen and P 6 similar to that in E. sibiricus sp. nov. (Fig. 20 A).

Caudal rami similar to that in E. sibiricus sp. nov. (Fig. 20 A, B). Length / width ratio 5.4–6.3 (median 6.04, n = 13). Serra extending from base of seta II to anterior 20 % of ramus (10 % – 36 %, median 20 %, n = 13). Ratio of length of seta VI to seta III 1.07–1.28 (median 1.18, n = 13).

Antennules, antennae, mouthparts, labrum, and paragnaths similar to that in E. sibiricus sp. nov.

Antenna (Fig. 20 C – E). Coxobasis with groups of spinules 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16. Number of spinules of group 7: 3–10 (median 5, n = 13). Number of spinules of group 8: 0–10 (median 4, n = 13).

P 1 – P 4 similar to that in E. sibiricus sp. nov., but with shorter segments (Fig. 21 A – C). Number of inner setules of P 4 Exp 1 (Fig. 21 B): 1–6 (median 1, n = 13). Number of inner setules of P 4 Exp 2: 1–3 (median 0, n = 13).

P 5 (Fig. 20 F) similar to that in E. sibiricus sp. nov., but without outer row of spinules.

Male. Not studied.