Microcyclops inarmatus, Gutierrez-Aguirre, Martha Angelica & Cervantes-Martinez, Adrian, 2016

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 : 35-37

Taxon classification Animalia Cyclopoida Cyclopidae

Microcyclops inarmatus sp. n. Figures 2, 3, 4, 5

Microcyclops varicans Reid, 1992; Trans. Am. Microsc. Soc. 111(3), p: 249-250, figs 8d, 9c.

Holotype.

One adult female dissected on two slides: A1, A2 (slide 1, ECOCH-Z-09337); mandible, maxillule, maxilla, maxilliped, P1-P4, and urosome (slide 2, ECOCH-Z-09337). Collected 13.I.1998.

Paratypes.

10 adult females preserved in 90% ethanol with a drop of glycerine. ECOCH-Z-09338. Collected 13.I.1998.

Type locality.

A pond in km 51 lado 1, Villahermosa-Frontera highway 18°23'16"N; 92°47'00"W.

Etymology.

the name of the species means un-armed in Latin; it refers to the absence of ornamentation on the intercoxal sclerites, the lack of spinules at base of caudal furcal setae, the reduced number of setae on second antennal endopod, and the reduced ornamentation on antennal basis.

Additional material.

One adult female collected 1.02.1935 from Laguna Rincon, Haiti (slide SMNK-2391; labelled as Microcyclops dubitabilis with A1, maxilla, P1-P4). One adult female collected from Laguna Rincon, Haiti (slide SMNK-2392; labelled as Microcyclops dubitabilis with urosome).

One adult female collected 05.1986 from Shark river slough, Everglades National Park, Florida, USA (slide 2 of 7, USNM-251321; labelled as Microcyclops varicans with A1, A2, P1-P4, and urosome).

Diagnosis.

Adult female: Dorsal margin of prosomal somites smooth; body length 565 to 615 µm in paratypes. Antennule 12-segmented, not reaching the distal margin of the first prosomal segment (Fig. 2A). Fifth pediger nude; cylindrical free segment of P5 more than 3 times as long as wide, with tiny inner spine; genital double somite expanded proximally. Anal somite with strong spines on ventral distal margin; length to width ratio of caudal ramus less than 3; no spinules at base of lateral and outermost terminal caudal setae (Fig. 2B). Outer median terminal and inner median terminal caudal setae with heteronomous setulation (Fig. 2B). Endopodites and exopodites of P1-P4 bisegmented with setation formula as in Table 1, inner basis of P1 with long spine (long arrow in Fig. 2C), Enp2P1 with one pore on lateral margin (short arrow in Fig. 2C). Intercoxal sclererites of P1-P4 unarmed, long setules on inner margin of basipodites of P1-P4, medial spine of Enp2P4 almost as long as the segment and twice the length of the lateral spine (Fig. 2D).

Adult male: unknown.

Description of female.

Antennule 12-segmented; antenna with 3-segmented Enp armed with 1, 6, and 7 setae respectively (Fig. 3A, B–position of missing setae in specimens is arrowed). Antennal basis with one group of spinules on the basal-outer margin in caudal view (Fig. 3A, B); frontal surface of the antennal basis with two rows of tiny spinules (Fig. 3C). Nine teeth on mandibular gnathobase (Fig. 3D). Maxillule (Fig. 3E) with unarmed palp; apical region of maxillular palp with two armed setae plus one smooth seta, three setae (one armed) on lateral lobe, proximal seta smooth (Fig. 3F). Distal coxal endite of the maxilla with two long setae: the proximal seta with two tiny spines at its base and bifurcated, distal seta with one row of tiny spines along one margin (Fig. 3G, H). Basipodite with one claw-like projection bearing 5-7 strong spines on the concave margin and one long, armed seta on its base; two-segmented Enp bearing 2 and 3 setae respectively (Fig. 3G). Because of the condition of the microscope slide preparatum we could not verify one basal seta on maxillar Enp1 (arrowed in Fig. 3H). Maxilliped with syncoxa (3 setae), basis (2 setae), and two-segmented Enp bearing 1 and 3 setae. Basis of maxilliped with a row of spinules on frontal and caudal surfaces (Fig. 3I).

Basipodites of P1−P3 with long hair-like setules on the inner margins; one row of tiny spinules along the lateral margins of coxa; intercoxal sclerites naked (Fig. 4 A–D). Basis of P1 with one long spine on inner margin; spine reaching distal middle of Enp2P1 and armed with heteronomous setulation: hair-like setules on its base, tiny spinules distally (Figs 2C; 4A, B). One pore on the lateral margin of Enp2P1 (Fig. 4A, B). Basipodite of P4 with long hair-like setules on inner margin; P4 intercoxal sclerite quadrangular (Figs 2D; 4E, F), Enp2P4 2.14 ± 0.2 times as long as wide; and medial spine 1.97 ± 0.25 as long as lateral spine and 0.91 ± 0.04 as long as the segment (Figs 2D; 4E, F).

Fifth pediger nude; P5 with one cylindrical free segment, 3.23 ± 0.4 times as long as wide, bearing one tiny medial spinule. Free segment 0.27 ± 0.01 times as long as distal seta (Figs 2B; 4G, H). Hyaline fringes of urosomites serrated (Fig. 2B), petaloid or rounded (Fig. 5 A, C–F). Length to width ratio of caudal ramus 2.54 ± 0.44, inner margin naked; no spinules at base of lateral caudal (II) and outermost terminal caudal setae (III) (Fig. 2B). Only 5-8 strong spinules present ventrally on the distal margin of anal somite, no spinules dorsally (Fig. 5 A, C–E). Lateral caudal seta (II) inserted at 58.6 ± 3.9% of caudal ramus.

Dorsal caudal seta (VII) 0.9 ± 0.1 times as long as caudal ramus, and innermost terminal caudal seta (VI) 1.4 ± 0.04 times as long as caudal rami (Fig. 2B). Relative lengths of terminal caudal seta from outermost caudal seta to innermost caudal seta is 1.0: 4.9: 7.3: 1.6 (Figs 2B; 5B, C). Outer median terminal caudal seta (IV) and inner median terminal caudal seta (V) with heteronomous setulation: proximally with spinule-like setules and distally with long and fine setules (Figs 2B; 5B, C).