Colurella asymmetrica, 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 : 374

Colurella asymmetrica n. sp.

Figures 3 a–c, I-1

Type locality. Most specimens are from a pond in Yangambi primary forest, DR Congo, 11 June 2012 (Sample Number: Y27) ; a single specimen from Lohulu River near Bomane, DR Congo, 24 May 2010 ( KM49 ) .

Material examined. Holotype: one female specimen in permanent slide, deposited in RBINS ( RIR.287) ; Paratypes: four permanent slides containing one female specimen each, deposited in RBINS ( RIR. 288 to RIR.291), four permanent slides containing one female specimen each, deposited in CSB-UK .

Differential diagnosis. The taxon belongs to Colurella uncinata— group on account of its relatively short and high lorica, and short toes, and appears closest to C. uncinata bicuspidata (Ehrenberg, 1830) ( Figure 4 ). The animal is, however, readily distinguished by the asymmetrical posterior lorica and by the shape of the single caudal spine, which is not merely an extension of the ventral lorica margin, but is reinforced by a short ridge. By having an asymmetrical caudal spine the animal reminds of C. sinistra Carlin, 1939 and C. ovalis Wei et al., 2019 , but the latter species are larger, and are easily distinguished by their differently shaped lorica and caudal spine shape. The shape of the caudal spine in C. asymmetrica n. sp. is somewhat similar to that of C. collaris Wulfert, 1965 , but this species has a pronouncedly projecting and stippled head aperture margin.

Differential diagnosis. Parthenogenetic female (male unknown): Lorica relatively high (length: height <1.7) and broad (height: width ca. 1.7). Anterior head aperture margins coincident, smoothly and evenly curved, ventrally a deep V-shaped, dorsally a shallower U-shaped sinus. Dorsal margin almost evenly curved, ventral margin straight, sulcus shallow. Foot aperture an inverted U-shape in ventral view, lateral margins protruded into asymmetrical projections: right projection relatively large, broad-based triangular with a terminal spinulet and reinforced by a longitudinal ridge of ca. one fourth of lorica length; left short, broad-based, triangular with a short longitudinal reinforcement ridge. Apertures to the lateral antennas situated relatively high and distally on the lorica. Foot with three short pseudosegments; terminal pseudosegment slightly longer than first and second, with a dorsal sensory groove basally. Toes short, straight, evenly narrowing from basis to pointed tip.

Measurements (n=6). Lorica length: 75–80 (77); lorica width: 47–50 (49), lorica height: 48–50 (49); right caudal spine: 7–9 (7); left caudal spine: 2–4 (3); head aperture width: 4–11 (7); depth dorsally: 5–10 (7); depth ventrally: 26–30 (29); Foot aperture width: 11–13 (12); length: 21–26 (24); toe length: 12–18 (16).

Etymology. The specific name is an adjective, referring to the species’ most remarkable diagnostic feature, the asymmetrical caudal spines of the lorica.

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).