Testudinella pseudobscura, Wei, Nan, De, Willem H. & Xu, Runlin, 2011

Wei, Nan, De, Willem H. & Xu, Runlin, 2011, Two new brackish-water species of Testudinella (Rotifera: Testudinellidae) from Qi’ao Island in the Pearl River estuary, China, with a key to marine and brackish-water Testudinella, Zootaxa 3051, pp. 41-56 : 43-48

publication ID	https://doi.org/ 10.5281/zenodo.207785
DOI	https://doi.org/10.5281/zenodo.6192342
persistent identifier	https://treatment.plazi.org/id/03E887F5-FFB1-0751-27E8-00F39C22FB30
treatment provided by	Plazi
scientific name	Testudinella pseudobscura
status	sp. nov.

Treatment

Testudinella pseudobscura sp. nov.

( Figs 2–5 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 , 6 View FIGURE 6 A)

Diagnosis. Testudinella pseudobscura sp. nov. is characterized by: vase-shaped lorica; dorsal anterior margin with a slightly convex median projection and almost straight or slightly convex lateral parts; ventral anterior margin with a wide V-shaped median sinus and weakly convex lateral edges; longitudinal ventral lorica furrows discontinuous; lateral lorica edges broadly rounded in cross-sectional view; foot opening sub-terminal, inverted U-shaped slit; distal foot pseudosegment moderately long, penultimate one shorter; unci plates with 9–11/10–11 teeth.

Type locality. A tidal river of Qi’ao–Dan’gan Provincial Mangrove Nature Reserve on Qi’ao Island (22° 26' N, 113° 38' E), Zhuhai, Guangdong province, China: depth about 50 cm, distance from shore about 2 m, low tide water, 24 December 2009.

Holotype. A female in a permanent, glycerine glass slide mount deposited in the Biology Museum of Sun Yatsen University, Guangdong, China (ROT00007).

Paratypes. 4 females from type locality. Two females in Biology Museum of Sun Yat-sen University (ROT00008, ROT00009); one female in the Academy of Natural Sciences of Philadelphia ( ANSP 2079); one female in the Royal Belgian Institute of Natural Sciences ( RBINS), Brussels, Belgium (No. IG. 312901, RIR 204).

Etymology. The species name pseudobscura refers to the shape of the lorica which is similar to that of T. obscura Althaus, 1957 .

Description of female. The smooth or occasionally very weakly striated lorica ( Fig. 2 View FIGURE 2 A–D) is vase-shaped, truncate anteriorly. The ratio length/width is on average 1.45 (1.38–1.56). The dorsal anterior margin shows a slightly convex median projection with almost straight ( Fig. 2 View FIGURE 2 B) or slightly convex lateral parts. The ventral anterior margin shows a shallow wide V-shaped median sinus with two weakly convex lateral edges. The dorsal anterior margin is not or slightly projecting beyond the ventral margin. The posterior margin is smoothly rounded ( Fig. 2 View FIGURE 2 A) or shows an inconspicuous rounded projection ( Fig. 2 View FIGURE 2 B). In cross-section the lorica is slightly arched dorsally; the lateral edges are broadly rounded; apparently discontinuous longitudinal ventral furrows delimit a protruding, more or less flat ( Fig. 2 View FIGURE 2 E) or convex ( Fig. 2 View FIGURE 2 F) median part. The foot is composed of a long wrinkled proximal part, a short penultimate pseudosegment, and a longer distal pseudosegment ending in a ciliated cup ( Fig. 2 View FIGURE 2 G). The ratio lorica length/position of antennae relative to dorsal anterior margin averages 2.89 (2.70–3.23) for the dorsal antenna and 2.25 (2.15–2.41) for the lateral antennae. Two red eyespots.

Trophi malleoramate ( Figs 3 View FIGURE 3 , 4 View FIGURE 4 ). The rami are elongate-triangular with rounded latero-ventral margins. Basal and subbasal chambers forming a single large chamber, open latero-ventrally by a large common fenestra ( Fig. 3 View FIGURE 3 B: rf). Weakly developed, more or less spiniform, caudally recurved alulae ( Fig. 3 View FIGURE 3 B: al) situated at the latero-ventral margins of the frontal parts of rami. Asymmetrical median rami apophyses ( Fig. 3 View FIGURE 3 B: ra) weakly developed. The inner margins of the distal rami sections caudally show 17–22/15–19 arched and webbed rami scleropili ( Fig. 3 View FIGURE 3 B: as). Frontally, the inner margins of the rami bear several rows of rami scleropili with acute tip ( Fig. 5 View FIGURE 5 : fs). The basal apophyses ( Fig. 4 View FIGURE 4 : ba) are moderately developed ridges, composed of a series of basally fused scleropili. The fulcrum is short and plank-shaped, more or less trapezoid in lateral view. It is composed of a double layer of longitudinally oriented and appressed sclerite bodies, the caudal series of which is involved in the formation of the junction with the rami, and an anterior series which border a distinct opening proximally ( Fig. 4 View FIGURE 4 : fo). The unci plates consist of 9–11/10–11 weakly curved and strongly webbed teeth. Each uncus has 3, occasionally 4, major teeth with moderately offset lanceolate heads of almost similar dimension, the head of the middle teeth is only slightly smaller than the others ( Fig. 4 View FIGURE 4 ). The minor teeth have a weakly offset lanceolate head bearing two minute lateral knobs at their base; the webbing almost extends up to the base of the heads. The crescent shaped manubria are composed of the superimposed dorsal, median, ventral chamber and weakly developed sub-ventral chamber ( Fig. 3 View FIGURE 3 B).

Male and eggs unknown.

Measurements. Lorica length 130–145 µm (mean=140 µm, N=10), lorica width 93–100 µm (mean=96 µm, N=10), anterior aperture width 64–68 µm (mean = 66 µm, N = 10), penultimate foot pseudosegment 4–6 µm (mean=5 µm, N=10), distal foot pseudosegment 13–15 µm (mean=14, N=10); trophi (N = 5): length × width 19.1– 21.3 × 23.6–26.1 µm, ramus 11.8–13.6 µm, fulcrum 6.3–8.1 µm, largest major tooth 11.0–12.0 µm, manubrium 10.6–12.5 µm.

Distribution and ecology. The species was collected in the intertidal zone of the brackish-water river on Qi’ao Island of the Pearl River estuary, at depths of about 50 cm, and about 2 m from the shore as tide ebbed. Its occurrence was restricted to 6 and 24 December 2009; water temperature 18.6 and 18.5 °C, salinity 13 and 12 ‰, transparency 29.5 and 16.5 cm.

Comments. The new species can easily be confused with the closely related and morphologically very similar T. obscura Althaus, 1957 and T. zhujiangensis . The discrimination between T. pseudobscura sp. nov. and T. zhujiangensis indeed, became clear only after studying a large number of specimens by light microscopy and trophi investigation by SEM. In the original description of T. zhujiangensis (Wei et al. 2010) , data on the trophi from both T. pseudobscura sp. nov. and T. zhujiangensis are mixed up, and the SEM photographs of the trophi (l.c., Figs 3 View FIGURE 3 , 4 View FIGURE 4 ) actually concern T. pseudobscura sp. nov.. Features discriminating both species are as follows: T. pseudobscura sp. nov. is distinguished by its more robust lorica with relatively wider head aperture ( Fig. 6 View FIGURE 6 A, B): the ratio lorica length/lorica width averages 1.45 (1.38–1.56, N=10) for T. pseudobscura sp. nov. and 1.58 (1.49–1.67, N=32) for T. zhujiangensis ; the ratio lorica width/head aperture width averages 1.46 (1.37–1.52, N=10) for T. pseudobscura sp. nov. and 1.56 (1.41–1.69, N=32) for T. zhujiangensis . In cross-section the body of T. pseudobscura sp. nov. is arched dorsally, rounded laterally, and ventrally it shows a flat or more or less convex median part, whereas T. zhujiangensis shows 4 rounded shallow lobes. Furthermore, the slit-shaped foot opening of T. pseudobscura sp. nov. is apparently narrower, deeper and placed less distally. Additionally, T. pseudobscura sp. nov. has a larger body size (130–145 µm, mean 140 µm, N=10) than T. zhujiangensis (115–128 µm, mean 123 µm, N=32) ( Fig. 7 View FIGURE 7 ). The ratios lorica length/postion of antennae relative to the antero-dorsal margin appear similar for both species: for the dorsal antenna the ratio averages 2.89 (2.70–3.23, N=10) in T. pseudobscura sp. nov. and 3.02 (2.80–3.24, N=22) in T. zhujiangensis , for the lateral antennae these ratios are 2.25 (2.15–2.41, N=10) and 2.26 (2.12– 2.33 N=22) respectively. Differences in trophi structure of both species are very little. The alulae ( Fig. 3 View FIGURE 3 B: al) are short, more or less spiniform and inconspicuous in the new species, whereas large, quadratic and robust in T. zhujiangensis ( Figs 12 View FIGURE 12 A, B, 14: al). The number of unci teeth tends to be smaller in T. pseudobscura sp. nov. (9–11/10–11, mostly 10–11/ 10–11, N=15) than in T. zhujiangensis (11–13/11–12, mostly 12/12, N=9). Additionally, trophi size tends to be larger in T. pseudobscura sp. nov. than in T. zhujiangensis ( Fig. 8 View FIGURE 8 ).

In comparison with the more or less elliptical T. obscura , the new species has a distinct vase-shaped appearance. In cross-sectional view, the lateral lorica edges are broadly rounded in T. pseudobscura sp. nov., whereas in T. obscura they converge to a rather sharp angle. Small differences also appear in the ratio lorica length/postion of antennae relative to the antero-dorsal margin: for the dorsal antenna the ratio averages 2.89 (2.70–3.23) in T. pseudobscura sp. nov. and 2.60 (2.40–2.88) in T. obscura , for the lateral antennae these ratios are 2.25 (2.15–2.41) and 2.07 (1.97–2.23) respectively. Main differences in trophi structure concern the number of unci teeth and shape of the head of the teeth. The teeth formula is 9–11/ 10–11 in T. pseudobscura sp. nov. and 10–12/ 11–12 in T. obscura . The heads of the major teeth are weakly offset and lanceolate in the new species, whereas distinctly offset and more or less strongly club-shaped in T. obscura . The heads of the minor teeth of T. pseudobscura sp. nov. are lanceolate as well, whereas cylindrical to elongate-lanceolate, with the webbing not as far extending up to the base as in the latter forming a rake-like structure in T. obscura . Additionally, the new species shows less developed subventral manubrium chambers.

Testudinella pseudobscura sp. nov. resembles T. bicorniculata De Smet, 2009 View in CoL and T. quadrilobata sp. nov. superficially. The new species is easily differentiated from T. bicorniculata View in CoL by the absence of acute antero-lateral projections and the shape of the anterior margins which are undulate with shallow median sinus in the latter. It is readily distinguished from T. quadrilobata sp. nov. which shows medially indented anterior margins and a larger number of unci teeth (9–11/10–11 versus 14–15/14–15).