Cyclops sibiricus Lindberg, 1949

Connolly, Joseph K., Marshall, Christopher C., Hudson, Patrick L., Watkins, James M., Scofield, Anne E. & Rudstam, Lars G., 2022, Reevaluation of the genus Cyclops Müller, 1776 (Cyclopoida: Cyclopidae) in the Laurentian Great Lakes basin: first report of the Palearctic species Cyclops divergens Lindberg, 1936 from Lake Erie and documentation of Cyclops sibiricus Lindberg, 1949 in the St. Marys River, Zootaxa 5182 (2), pp. 183-195 : 185-186

Cyclops sibiricus Lindberg, 1949

Synonymy:

Cyclops strenuus sibiricus Lindberg (1949) : 87 −90, fig. 1.

Cyclops canadensis Einsle (1988) : 2146 −2149, fig. 1.

Material examined: 1 female dissected and slide mounted, 1 female, collected from the St. Marys River , Sault Ste. Marie, Michigan, USA (46.49853N,- 84.32590W)on May 15,1972,initially reported as C.strenuus in Selgeby (1975) . 4 females dissected and slide mounted, 7 females, collected from the St. Marys River , Neebish Island, Michigan, USA (46.33691 N, - 84.20122 W) on May 3 and May 24, 1995, initially reported as C. strenuus in Hudson et al. (1998) .

Females: Body large, robust and cyclopiform. Prosome longer than urosome ( Table 1 ), cephalothorax longer then wide. Rostrum fairly pronounced. Antennule (A1) consisting of 17 segments ( Fig. 1a ), not extending beyond the cephalothorax. A small convex row of spinules present on the proximal margin of the A1 first segment. Pitting on surface of A1 first segment apparently absent ( Fig. 1b ). Setation present on A1 segments 1−9, 11−12, 14−17. Aesthetascs present on A1 segments 12, 16, and 17. Aesthetasc on A1 segment 12 extending to the middle of segment 14 ( Fig. 1c ). A1 segments 15−17 with finely textured hyaline membrane ( Fig. 1d ). Antenna (A2) 4-segmented with 3 setae on the basipodite including exopodite seta and 1,9, 7 setae on the successive (endopodal)segments.A2 exopodite seta reaching beyond the distal margin of the endopod and lightly ornamented with plumose setules which decrease in length distally. Caudal surface of A2 basipodite ( Fig. 2a ) ornamented with 4−6 broad based spinules descending in height from the lateral to distal margin, a single oblique row of 5−6 short thin spinules at position B ( Hołyńska et al. 2003), 7−9 long thin spinules longitudinally at position A, and flanked laterally by a field of tiny spinules numbering approximately 12 at position C. Labrum (La) and Mandible (Md) not observed in detail. Maxillular (Mxl) palp proximalmost seta ( Fig. 2b ) ornamented only with tiny spinules distally, setae of the lateral lobe ornamented likewise. Surface of Mxl palp either ornamented with exceedingly tiny spinules or apparently bare ( Fig. 2b ). Maxilla (Mx) not observed in detail. Maxilliped (Mxp) syncoxopodite armed with 3 plumose setae, basipodite with 2 plumose setae, endopodite 1 with 1 plumose seta, endopodite 2 with 1 plumose and 2 bare setae. Mxp syncoxopodite frontal surface ornamented with a long membranous element ( Hołyńska & Dahms 2004) with somewhat club shaped distal terminus ( Fig. 2c ) and a transverse row of approximately 10 small spinules. Ornamentation present on the frontal surface of successive mxp segments in the form of thin hair-like spinules with the exception of endopodite 2.

Spine formula of swimming legs 1−4 (P1−P4) third exopodite 3, 4, 3, 3. Full spine and setal formula of P1−P4 shown in Table 2 following Sewell (1949). Ornamentation of swimming legs is as follows. P1 intercoxal sclerite (coupler) and coxopodite unornamented. P1 coxopodite setae densely ornamented with long setules. P1 basipodite armed with a row of long spinules on the frontal surface between insertion of exopodite and endopodite ( Fig. 2d ). P1 medial margin of basipodite haired and medial spine of basipodite with proximal margin bare and distal margin sparely armed with setules ( Fig. 2d ). P2 coupler unornamented, coxopodite seta armed as in P1, coxopodite ornamented with spinules at position B and hairs at position F ( Einsle, 1996a). P2 medial margin of basipodite haired. P3 ornamented as in P2 except coupler caudal surface ornamented with horizontal row of long hairs. P4 coupler ornamented as in P3, coxopodite ornamented with spinules at positions, A, B, C, D, and E ( Fig. 2e ). P4 coxopodite setae short, not extending beyond medial margin of basipodite and sparsely ornamented with setules ( Fig. 2f ; Table 1 ). P4 medial margin of basipodite unhaired. P4 endopodite 3 longer then wide with outer terminal spine relatively short ( Table 1 ). P5 basal segment with spinules present near insertion of lateral seta. P5 distal segment with long apical seta ( Table 1 ) and stout subapical spine. Spinules present lateral to the insertion of the apical seta and at the insertion of the subapical spine. Genital double-somite wider then long at widest point ( Table 1 ), surface pitting discrete if present. Posterior margins of proceeding 2 urosomites crenulate. Posterior margin of anal somite ornamented with fine spinules. Anal operculum unornamented. Caudal rami more than five times longer than wide ( Table 1 ) with inner margins weakly haired.Tiny spinules ornament the insertions of lateral and terminal external ( Einsle 1996a)caudal seta (S4) ( Hołyńska et al. 2003). Terminal median internal caudal setae (S2) relatively long, nearly equal in length to the urosome and more than twice as long as caudal rami ( Table 1 ). Additional morphometry of caudal setae included in Table 1 .

Figures

FIGURE 1: St. Marys River C. sibiricus female (a) A1 17-segmented (b) A1 first segment without surface pits (c) A1 segment 12 with medium length aesthetasc arrowed (d) A1 segments 15−17 with hyaline membrane arrowed.

FIGURE 2: St. Marys River C. sibiricus female (a) A2 basipodite caudal surface ornamentation at position A, B, C (b) Mxl palp proximalmost seta without long setules and surface bear (c) Mxp syncoxopodite with long distally clubbed membranous element arrowed (d) P1 basipodite ornamented with row of spinules arrowed and medial spine with bare proximal margin arrowed (e) P4 coxopodite ornamented with spinules at positions A, B, C, D, and E (f) P4 coxopodite setae arrowed, not extending beyond medial margin of basipodite.