Squatinella curviseta, Luo & Segers, 2020

Luo, Yongting & Segers, Hendrik, 2020, Eight new Lepadellidae (Rotifera, Monogononta) from the Congo bring to level endemism in Africa’s rotifers, Zootaxa 4731 (3), pp. 371-387 : 380-382

Squatinella curviseta n. sp.

Figures 1 a–b, I-3

Type locality. Lohulu River near Bomane, DR Congo 24 May 2010 ( KM49 ) .

Material examined. Holotype: One female specimen in permanent slide, deposited in RBINS ( RIR.332) ; Paratypes: five permanent slides containing one female specimen each, deposited in RBINS ( RIR.333 to RIR.338); one permanent slide containing seven female specimens, deposited in CSB-UK .

Differential diagnosis. This new species is close to S. variegata , as it shares with it a foot made up of two basal foot pseudosegments and a third element consisting of the fused third foot pseudosegment and the toes. The two differ by the rather rigid dorsal spine, which is variable in length but always straight in S. variegata , and relatively short and weakly but clearly and consistently S-shaped in S. curviseta n. sp. This peculiar spine shape may be adaptive: in swimming specimens the spine is bent posteriad, along the longitudinal axis of the body; in S. curviseta n. sp. this S-shaped spine will fit snugly over the body and foot, possibly resulting in reduced drag when the animal glides over a surface.

Differential diagnosis. Parthenogenetic female (male unknown): body elongate, separated in a head, trunk, and foot region, lorica relatively soft but body shape rather constant. Head dorso-ventrally flattened, with a semi-circular head shield covering the homogeneous corona; lateral projections of the posterior corona region present. Head and trunk separated by a weakly constricted neck. Trunk rather plump, ventrally bulbous, dorsally with a middorsal, rigid, weakly S-shaped and terminally blunt spine; this spine movable from erect to dorsally, parallel to the body axis overlaying the foot. Terminal part of the trunk bulging. Foot with two separated foot pseudosegments, the second about twice as long as the first, third foot element more than twice as long as the second foot pseudosegment, bearing a sensory groove dorsally near its basis. Terminal foot element almost parallel-sided in the basal two thirds, then tapering to a point, distally with a short median fissure.

Measurements (n=10). Total length (including foot): 219–257 (238), height: 94–117 (104), second foot pseudosegment: 19–27 (22), fused third segment and toes: 30–46 (37), dorsal spine: 146–190 (161), ratio spine:body length: 0.66–0.92 (0.83).

Etymology. The specific name is an adjective, and refers to the species’ unique curved dorsal spine.

Figures

FIGURES 1–4. Lepadellidae, line drawings. Figure 1a–b: Squatinella curviseta n. sp., a: habitus, lateral (scale bar: 100µm); b: detail of foot, lateral (scale bar: 50µm). Figure 2a–c: Squatinella longipila n. sp., habitus. a: detail, body (scale bar: 50µm); b–c: complete specimens (scale bar: 50µm). Figure 3a–c: Colurella asymmetrica n. sp. a: caudal region and foot, left; b: habitus, right; c: habitus, ventral view. Figure 4: Colurella uncinata bicuspidata: habitus, right (3, 4: scale bar: 50µm).