Microcyclops dubitabilis Kiefer, 1934

Gutierrez-Aguirre, Martha Angelica & Cervantes-Martinez, Adrian, 2016, Taxonomic evaluation of eleven species of Microcyclops Claus, 1893 (Copepoda, Cyclopoida) and description of Microcyclopsinarmatus sp. n. from America, ZooKeys 603, pp. 33-69 : 37-40

Taxon classification Animalia Cyclopoida Cyclopidae

Microcyclops dubitabilis Kiefer, 1934 Figures 6, 7, 8

Description of female.

Antennule 11, or 12-segmented (intra- and interpopulation variation); 3-segmented endopod of antenna bearing 1, 9, and 7 setae, respectively (Fig. 6A, B). Antennal basis with three long rows of spinules on caudal surface (Fig. 6B): two basal rows, and one median row; frontal surface of antennal basis with two rows of tiny spinules (Fig. 6C). Labrum with 6−7 teeth between two curved lateral teeth, and 3−4 strong spinules on each round projections of the plate (Fig. 6D). Eight teeth on mandibular gnathobase (Fig. 6E). Maxillule as in Fig. 6F, maxillular palp with one armed seta plus two smooth setae apically, three smooth setae on lateral lobe, and one proximal nude seta (Fig. 6G, H). Maxilla with armed setae on distal coxal endite: proximal seta with one long spine-like setule at its base and bifurcated apically, distal seta with one row of tiny spines along inner margin (Fig. 6 I–K, M). Basipodite with claw-like projection bearing 6−8 thin spinules on concave margin and one long seta on its base; this seta armed with two rows of spinules (long spinules on inner margin, and short spinules on outer margin) (Fig. 6 I–L). Maxilla with two-segmented Enp bearing 2 and 3 setae respectively (Fig. 6 I–L). Maxilliped with syncoxa (3 setae), basis (2 setae), and two-segmented Enp bearing 1 and 3 setae, respectively. Basis of the maxilliped nude, two spinules present on frontal surface of Enp1 (Fig. 6N).

Dorsal margin of prosomal somites smooth (Fig. 7A). Basis of P1 medially hairy. One short spine present on inner margin, spine biserially armed with spinule-like setules (homonomous ornamentation) and reaching slightly beyond distal margin of the Enp1P1. Intercoxal sclerite of P1 naked (Fig. 7 B–D). Pore on lateral margin of Enp2P1 sometimes present (interpopulation variation). Inner margin of basis of P2 and P3 hairy, and intercoxal sclerites of these swimming legs naked (unfigured). Inner margin of P4 basis with short hairs; intercoxal sclerite naked, rectangular (Fig. 7 E–H), Enp2P4 1.9 ± 0.1 times as long as wide; medial spine 1.8 ± 0.3 times as long as lateral spine, and 0.8 ± 0.1 times as long as segment. Apical spines of Enp2P4 are subequal only in female USNM-251322 (Fig. 7E).

Fifth pediger nude; P5 free segment cylindrical, 3.6 ± 0.8 times as long as wide, without inner spine. Free segment 0.4 ± 0.1 times the length of the distal seta (Figs 7 I–K; 8C). Length to width ratio of caudal ramus 2.4 ± 0.2, inner margin naked. With or without spines at base of seta II (intrapopulation variation), spinules always present at base of setae III. Distal margin of anal somite bearing spinules: medial spinules are longer than lateral ones on ventral surface; spinule row can extend laterally or dorsally (Fig. 8 A–C). Seta II inserted at 71 ± 5.7% of caudal ramus.

Seta VII 1.02 ± 0.3 times as long as caudal ramus, and seta VI 1.4 ± 0.2 times longer than caudal ramus. Relative lengths of terminal caudal seta from outermost caudal seta to innermost caudal seta are 1.0: 4.9: 7.1: 1.6 (Fig. 8A, C). Seta IV and seta V with heteronomous setulation: proximally with spine-like setules and distally with long and fine setules (Fig. 8 A–C). Sixth leg with two medial spines and one lateral seta (Fig. 8D).