Microcyclops finitimus Dussart, 1984

Gutierrez-Aguirre, Martha Angelica & Cervantes-Martinez, Adrian, 2023, Redescription of two species of Microcyclops (Copepoda, Cyclopoida) and use of ordination models to classify American species, ZooKeys 1173, pp. 111-130 : 111

Microcyclops finitimus Dussart, 1984

Figs 1 , 2

Microcyclops finitimus Dussart, 1984: 57, 58, fig. 19A; Dussart 1983: 325, fig. 2B; da Rocha and Por 1998: 2138; da Rocha 1998: 426-431, figs 6, 7, 12, 18; Gutiérrez-Aguirre and Cervantes-Martínez 2016: 54, fig. 14A-E.

Material examined.

Holotype. One dissected adult female on a slide labelled as Microcyclops finitimus female nov. sp. ‘Lagoon’ with Trapa between Coporito and Barrancas, Venezuela 24.X.1981, 8h40. Collector Bernard Dussart, and det. B. Dussart (MNHN Cp-678).

Other material.

One dissected, adult female on a slide labelled as Microcyclops finitimus female. Rorota, prés Guyane 21.X.1985. GUYANE. Collector Bernard Dussart, and det. B. Dussart (MNHN Cp-7294) .

Redescription based on the holotype.

Female: body length excluding furcal setae = 0.89 mm (as described by Dussart 1984). Labral plate distally toothed: eight central teeth are flanked by lateral, basally widened teeth, which are followed by two low teeth on each side; medial labral plate with two groups of long, wide setulae; lateral lobes rounded (Fig. 1A ).

Antennule 12-segmented: each segment was armed with setae (s), spines (sp) or aesthetascs (ae) in the following order: (1) 8 s; (2) 4 s; (3) 2 s; (4) 6 s; (5) 3 s; (6) 1 s + 1 sp; (7) 2 s; (8) 3 s; (9) 2 s + 1ae; (10) 2 s; (11) 2 s + 1 ae; (12) 7 s + 1 ae.

Antenna with two groups of spinules on the basal margin of the basis in caudal view. In the frontal view antennal basis with two groups of spinules: one next to the exopodal seta, on the distal region (arrowed in Fig. 1B ) and one is along the lateral margin.

Maxillule (Fig. 1C ): praecoxal arthrite with seven setae. Apical region of maxillary palp with two setae armed with tiny spinules, plus a third seta with long setules. Lateral lobe lost (area arrowed in Fig. 1C ). One smooth proximal seta.

Maxillary syncoxal surface smooth (Fig. 1D ). Distal coxal endite with two setae: proximal seta distally bifurcated, with long spinules; distal seta with an elongated row of spine-like setules. Basipodite with a bump bearing robust, engrossed spines on the concave margin and one long, bare seta on its base. Enp1 and Enp2 bearing two and three naked and long setae, respectively.

Maxilliped with syncoxa (3 setae, one broken off), basis (2 setae), and two-segmented Enp bearing one and three setae, respectively. Syncoxa, basis, and Enp1 with rows of spinae: basis on frontal and caudal surfaces; syncoxa and Enp1 only on the frontal surface (Fig. 1E ).

Medial margin of basipodites of P1-P4 with long hair-like setae. There is no medial spine on the margin of BspP1 (Fig. 1F ). Intercoxal sclerite of P1, and P2 quadrangular, naked (Figs 1F , 2A ). Intercoxal sclerite of P3 rectangular with long and robust spinules arranged laterally along the distal margin of the plate (Fig. 2B ). Proximal region of the intercoxal sclerite of P3 not observable (indicated by? in Fig. 2B ).

P4 as illustrated and described by Dussart (1984: 57, 58, fig. 19A): intercoxal sclerite rectangular, with two rows of spinules; distal row with elongated spinules, proximal row with short spinules (Fig. 2C ). Ratio between the lengths to width of Enp2P4 is 2.2-2.5; the medial spine of Enp2P4 is 1.3 × as long as lateral spine and 0.7 × as long as the segment.

Fifth pediger bare, with dorsal hyaline membrane serrated posteriorly (Fig. 2D ); length to width ratio of genital double somite 0.78. Free segment of P5 3.0 × as long as wide, bearing one tiny medial spinule, and 0.4 × as long as distal seta. Hyaline fringes of prosomal somites smooth, except the fourth which is serrated; urosomal somites with hyaline fringes slightly serrated. As described by Dussart (1984), length to width ratio of the caudal ramus is 4.1, the inner margin naked; no spinules at the base of the lateral caudal (II) but spines at the base of the outermost terminal (III) caudal setae (spines verified in MHN-Cp7294). Spinae along dorsal and ventral margins of anal somite. Lateral caudal seta (II) inserted 73.0-75.5% of the caudal ramus.

Dorsal caudal seta (VII) 0.5-0.7 × as long as caudal ramus, innermost terminal caudal seta (VI) 1.05 × as long as caudal ramus. Length ratio between outer median (IV) and outermost terminal seta (III) is 6.0; and between medial median (V) and outermost terminal seta (III) is 8.9 (Fig. 2D ).

Figures

Figure 1. Microcyclops finitimus. Adult female (MNHN-Cp 678) A labrum B antenna, note that the distal group of spines is arrowed in this caudal-frontal view C maxillule, note that the lateral lobe of maxillular palp is missing (area arrowed) D maxilla E maxilliped, note that the insertion of broken off seta is suggested (indicated by?) F first leg, medial area: intercoxal sclerite, Bsp, and Enp 1. Scale bars: 50 µm.

Figure 2. Microcyclops finitimus. Adult female (MNHN-Cp 678) A second leg, medial area: intercoxal sclerite, Bsp, and Enp 1 B third leg, medial area: intercoxal sclerite, and Bsp: the basal area of intercoxal sclerite was not verified (indicated by?) C fourth leg, medial area: intercoxal sclerite, and Bsp D urosome, note the separate terminal caudal seta. Scale bars: 50 µm.