Eucyclops sibiricus Novikov, Sharafutdinova, Abramova, Mayor & Chertoprud, 2025, sp. nov.

Eucyclops sibiricus sp. nov. Figs 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 Eucyclops speratus: Ishida and Hiruta 1999 (part): 88, figs 1, 2 a – e; Lee et al. 2005: 146, fig. 5; Chertoprud et al. 2022: 6, table A 1. Eucyclops sp. nov.: Chertoprud et al. 2024: 1014, supplemental material 1: table S 1. Etymology. The species was first discovered and has its main range in Siberia. The word sibiricus is an adjective in the masculine gender. Type material. Holotype: Russia • ♀ dissected on two slides; North Yakutia, Lena River Delta, Floodplain puddle; 72.38755 ° N, 126.48205 ° E; 8 Sep. 2020; E. Abramova leg; EMKSU VH 2000 / 1, VH 2000 / 2 (N ° 45). Paratypes: Russia • ♂ dissected on one slide; North Yakutia, Lena River Delta, Floodplain puddle; 72.36874 ° N, 126.47595 ° E; 20 Aug. 2019; A. Novikov leg; EMKSU VH 2000 / 3. • ♀ dissected on one slide; collection data as for holotype; EMKSU VH 2000 / 4 (N ° 47); • ♀ dissected on one slide; collection data as for holotype; EMKSU VH 2000 / 5 (N ° 48); • ♀ dissected on one slide; collection data as for holotype; EMKSU VH 2000 / 6 (N ° 49); • 3 ♀ and 2 ♂ preserved in 4 % formalin; North Yakutia, Lena River Delta, Floodplain puddle; 72.36874 ° N, 126.47595 ° E; 20 Aug. 2019; A. Novikov leg; EMKSU VH 2000 / 13; • 2 ♀ dissected on one slides; collection data as for preceding; EMKSU VH 2000 / 7; • 1 ♂ dissected on one slide; collection data as for preceding; EMKSU VH 2000 / 8; • ♀ dissected on one slide; collection data as for preceding; EMKSU VH 2000 / 9 (N ° 27); • ♀ dissected on one slides; collection data as for preceding; EMKSU VH 2000 / 10 (N ° 88); • ♀ preserved in 96 % ethanol; North Yakutia, Lena River Delta, Floodplain puddle; 72.38755 ° N, 126.48205 ° E; 18 July 2021; A. Novikov leg; GenBank: OR 917926, OR 941791, OR 918477; EMKSU VH 2000 / 14 (N ° ch 5); • ♀ preserved in 96 % ethanol; collection data as for preceding; GenBank: OR 917925; EMKSU VH 2000 / 15 (N ° ch 6); • ♀ preserved in 96 % ethanol; collection data as for preceding; GenBank: OR 917928; EMKSU VH 2000 / 16 (N ° ch 7); • ♀ preserved in 96 % ethanol; collection data as for preceding; GenBank: OR 917929; EMKSU VH 2000 / 17 (N ° ch 8); • ♀ dissected on one slides; North Yakutia, Lena River Delta, Floodplain puddle; 72.38755 ° N, 126.48205 ° E; 18 July 2021; A. Novikov leg; EMKSU VH 2000 / 11 (N ° 17); • ♀ dissected on two slides; collection data as for preceding; EMKSU VH 2000 / 12 (N ° 19); Additional material. Russia • ♀ dissected on one slides; North Yakutia, Lena River Delta, small river; 72.11877 ° N, 126.98782 ° E; 22 July 2021; A. Novikov leg; in collection of A. Novikov (N ° 21); • 3 ♀ dissected on three slides; North Yakutia, lake; 69.97000 ° N, 125.60158 ° E; 28 June 2019; A. Novikov leg; in collection of A. Novikov (N ° 89, 90, 91); • 2 ♀ dissected on two slides; Central Yakutia, temporary puddles; 64.94187 ° N, 124.84179 ° E; 22 June 2019; A. Novikov leg; in collection of A. Novikov (N ° 69, 73); • ♀ dissected on one slides; Anabar Plateau, small lake; 70.64073 ° N, 105.90506 ° E; 25 July 2023; A. Novikov and E. Chertoprud leg; in collection of A. Novikov (N ° 79); • ♀ dissected on one slides; Putorana Plateau, swampy lake; 68.60415 ° N, 94.05641 ° E; 7 Aug. 2021; E. Chertoprud leg; in collection of A. Novikov (N ° 32); • ♀ preserved in 96 % ethanol; Putorana Plateau, swampy lake; 68.60415 ° N, 94.05641 ° E; 7 Aug. 2021; E. Chertoprud leg; GenBank: OR 917930; EMKSU VH 2000 / 18–20 (N ° ch 1); • ♀ preserved in 96 % ethanol; collection data as for preceding; GenBank: OR 917924, OR 941789; EMKSU VH 2000 / 18–20 (N ° ch 2); • ♀ preserved in 96 % ethanol; collection data as for preceding; GenBank: OR 917927, OR 941790, OR 918478; EMKSU VH 2000 / 18–20 (N ° ch 3); • ♀ dissected on one slides; Putorana Plateau, swampy lake; 68.60344 ° N, 94.05875 ° E; 7 Aug. 2021; E. Chertoprud leg; in collection of A. Novikov (N ° 33); • ♀ dissected on one slides; Putorana Plateau, swampy lake; 68.60029 ° N, 94.05300 ° E; 7 Aug. 2021; E. Chertoprud leg; in collection of A. Novikov (N ° 34); • ♀ dissected on one 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 ° 92); • ♀ on the electron microscope stage no. 90134; Irkutsk region, Tulun district, Aleksandrovka village, river; 55.3905 ° N, 100.8231 ° E; 25 July 2021; T. Mayor leg; LI SB RAS T 13); • ♀ preserved in 96 % ethanol; Irkutsk region, Kuitun District, pond; 54.34722 ° N, 101.52861 ° E; June 2021; G. Dzyba leg; GenBank: OR 941793, OR 918476; in collection of T. Mayor (N ° K 1-4) Diagnosis. Proctodeum with rows of setules. Caudal ramus with serra and dorsal pore. Length / width ratio of caudal rami 5.2–7.0. Ratio of lengths of caudal seta VI to seta III 1.07–1.47. Antennule 12 - segmented, with hyaline membrane on three distal segments. Hyaline membrane finely serrated. Antennal coxobasis with groups of spinules 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16. Maxillular basis with group of spinules. P 1 – P 4 Exp 1 without spinules / setules on outer side. P 1 – P 4 Exp 2 with setules on outer side. P 4 Exp 1 with 8–17 inner setules. P 4 Exp 2 with 6–10 inner setules. Description. Female. Body elongated (Fig. 9 A – C). Total body length from anterior margin of rostrum to posterior margin of caudal rami: mean 1279 µm (n = 3). Cephalothorax wider than first and second free somites, largest width 408 µm (n = 1), surface with 251 pores and sensilla, with all groups, except group 36 (Fig. 8 A – D). Naupliar eye present, color red or orange (Fig. 9 D). Rostrum fused with cephalothorax. Posterior margin of cephalothorax and all pedigerous somites smooth. Body color yellowish, except second pedigerous somite, this somite white (Fig. 9 D). Abdomen (Figs 10 A – C, 11 A) consisting of genital double-somite, two free abdominal somites, and anal somite with caudal rami. Genital, second, and third abdominal somites on posterior margin serrated. Genital double-somite consists of last thoracic somite and first abdominal somite; longer than wide; anterior part with two dorsal pairs of sensilla, dorsal unpaired pore, lateral and ventral pairs of pores; posterior part with three pairs of sensilla, two pairs of pores and dorsal unpaired pore. P 6 (Fig. 10 A, B) lateral, formed plate, partially fused with somite; with one long plumose seta, one short spine and small spiniform process. Genital field (Fig. 10 C) wide, bean-shaped. Copulatory pore medial, located on notable suture cord. Copulatory duct short, chitinised. Anterior and posterior chambers of seminal receptacle equal in wide, narrow. Two egg sacks attached to gonopore area. Second abdominal somite (Fig. 10 A – C) with three pairs of sensilla, two pairs of pores, and dorsal unpaired pore. Third abdominal somite (Fig. 10 A – C) with dorsal unpaired pore, pairs of lateral and ventral pores. Anal somite with one dorsal pair of sensilla: one dorsal, one anterolateral, one lateral, and one ventral pairs of pores; with or without small posterior spinules near sides of proctodeum; with ventro-lateral posterior rows of spinules; proctodeum with rows of setules. Anal operculum slightly protruding. Caudal rami (Figs 10 A – C, 11 A). Length / width ratio 6, 5 in holotype (5.2–7.0, median 5.91, n = 19). Ramus with one ventral and two dorsal pores; with longitudinal row of small spinules (serra); with spinules at base of seta III. Serra extending from base of seta II to anterior 8 % of ramus in holotype (8 % – 30 %, median 16 %, n = 19). Seta I absent. Seta II dorsolateral, small. Seta III spiniform, with spinules on outer side and long setules on inner side. Apical setae IV and V (Fig. 10 D) long; bipinnate; with fracture planes; proximal part bare, medial part with rare long spinules, distal part with dense long spinules; length ratios 1 and 1.63, respectively. Seta VI with several inner setules and with or without outer setules; longer than seta III (ratio of lengths of seta VI to seta III 1.07–1.47, median 1.26, n = 19). Seta VII biarticulate. Antennule (Fig. 11 B, C) 12 - segmented; extending to second pedigerous somite. Armature formula as follows: 1 - [8], 2 - [4], 3 - [2], 4 - [6], 5 - [4], 6 - [2], 7 - [2], 8 - [3], 9 - [2 + ae], 10 - [2], 11 - [2 + ae], 12 - [7 + ae]. Segment 1 with four rows of spinules. Segment 4 with one pore. Three distal segments with finely serrate hyaline membrane (Fig. 11 C); proximal part of membrane of distal segment with 90 small denticles. Aesthetascs located on segments 9, 11, and 12. One seta on segment 6 spiniform. One apical seta on segment 12 fused basally to aesthetasc. Antenna (Fig. 12 A – D) four-segmented include coxobasis and three-segmented endopod. Coxobasis rectangular; with three setae, one of these exopodal long pinnate seta; with groups of spinules 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16. Number of spinules of group 7: 1–6 (median 3, n = 19). Number of spinules of group 8: 0–5 (median 1, n = 19). First endopodal segment with one naked seta; one postero-lateral and postero-medial rows of spinules. Second endopodal segment with nine naked setae on inner margin, these setae longer from proximal to distal; with row of spinules along outer margin. Third endopodal segment cylindrical, same length as second segment; with seven naked apical setae with claw-like tips; with two spinular rows on outer margin. Labrum (Fig. 11 D) trapezoidal. Anterior surface with two groups of long spinules. Distal margin with lateral outgrowths with small denticles and 11 medial teeth. Mandible (Fig. 12 E) composed of coxa and small palp. Coxal gnathobase with 14 distal elements: one serrate seta; eight strong teeth; five slender teeth, three of these fused in base; gnathobase distally with row of long spinules. Palp with three apical setae: two long and plumose and one short and naked. Paragnaths (Fig. 11 E) with paired lateral lobes. Distal parts of lobes with folded outg