Testudinella quadrilobata, 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 : 48-51

Testudinella quadrilobata sp. nov.

( Figs 6 C, 9–11)

Diagnosis. Testudinella quadrilobata sp. nov. is characterized by: vase-shaped lorica; dorsal anterior margin almost straight to weakly undulate with minute median indentation; ventral anterior margin strongly undulate with wide V-shaped median sinus; longitudinal ventral furrows of lorica nearly parallel; foot opening sub-terminal, shallow inverted U-shaped slit; distal foot pseudosegment moderately long; proximal fulcrum opening obvious; unci plates with 14–15/14–15 teeth.

Type locality. A mangrove swamp in Qi’ao–Dan’gan Provincial Mangrove Nature Reserve on Qi’ao Island (22° 26' N, 113° 38' E), Zhuhai, Guangdong province, China: depth about 20 cm, distance from shore about 2 m, 17 January 2009.

Holotype. A female in a permanent, glycerine glass slide mount deposited in the Biology Museum of Sun Yatsen University, Guangdong, China (ROT00010).

Paratypes. 4 females from type locality. Two females in Biology Museum of Sun Yat-sen University (ROT00011, ROT00012); one female in the Academy of Natural Sciences of Philadelphia ( ANSP 2080); one female in the Royal Belgian Institute of Natural Sciences ( RBINS), Brussels, Belgium (No. IG. 312901, RIR 205).

Etymology. The name of the species is composed of the prefix quadri derived from the Latin quattuor, meaning in four parts, and the Latin adjective lobata, meaning lobed, and refers to the four-lobed anterior margins of the lorica.

Description of female. The smooth lorica ( Figs 6 C, D; 9A, B) is vase-shaped, truncate anteriorly. The ratio length/width is on average 1.40 (1.35–1.46). The dorsal anterior margin has two slightly convex ( Fig. 9 A) or almost straight ( Fig. 9 B) parts separated by a small median indentation. The ventral margin shows a broader, shallow V-shaped median sinus with two distinct convex lateral parts. The dorsal anterior margin is not or only slightly projecting beyond the ventral margin ( Fig. 6 C, D). The posterior margin is smoothly rounded ( Fig. 9 B) or shows an inconspicuous rounded projection ( Fig. 9 A). Ventrally two almost parallel longitudinal furrows delimit a protruding median part. In cross-sectional view ( Fig. 9 C, D) the lorica is slightly arched dorsally; the lateral margins are broadly rounded, separated by a shallow sulcus from a weakly protruding median part ventrally; the ventral median part is almost flat ( Fig. 9 C) or with very shallow sulci laterally from foot channel ( Fig. 9 D). The foot opening is a shallow inverted U-shaped slit widening distally, situated sub-terminally on the ventral side; an oblique fold may run laterally from the distal edges of the foot opening. 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. 9 E). The ratio lorica length/position of antennae relative to dorsal anterior margin averages 2.68 (2.50–2.82) for the dorsal antenna and 2.51 (2.34–2.72) for the lateral antennae. Two red eyespots.

Trophi malleoramate ( Figs 10 , 11 ). The rami are elongate-triangular with rounded latero-ventral margins, and short blunt alulae ( Fig. 10 B: al) pointing caudally. Basal and subbasal chambers form a single large chamber, opening latero-ventrally by a large common fenestra ( Fig. 10 B: rf). Asymmetrical and interlocking median rami apophyses ( Fig. 10 B: ra) are apparent in caudal view. The inner margins of the distal rami sections bear 33–34/32–33 arched rami scleropili ( Fig. 10 B: as). The basal apophyses ( Fig. 11 : ba) are moderately developed ridges, composed of a series of fused scleropili. The fulcrum is short and plank-shaped, more or less trapezoid in lateral view, and composed of a double layer of longitudinally oriented and appressed sclerite bodies. A distinct frontal proximal opening is present ( Fig. 11 : fo). The unci plates consist of 14–15/14–15 almost straight and webbed teeth with interlocking heads. There are three almost straight major teeth with weakly offset lanceolate head in each uncus; the head of the middle-most teeth is only slightly smaller than the others ( Fig. 11 ). The minor teeth have a sharp, very weakly offset head bearing two minute lateral knobs at their base. The crescent shaped manubria consist of the superimposed dorsal, median and ventral chamber, and very weakly developed sub-ventral chamber ( Fig. 10 B).

Male and eggs unknown.

Measurements. Lorica length 139–165 µm (mean=156 µm, N=10), lorica width 100–119 µm (mean=111 µm, N=10), anterior aperture width 66–75 µm (mean = 70 µm, N = 10), penultimate foot pseudosegment 4–7 µm (mean = 5 µm, N = 10), distal foot pseudosegment 15–19 µm (mean = 16, N = 10); trophi (N = 5): length × width 23.1– 24.9 × 28.2–29.4 µm, ramus 13.7–14.9 µm, fulcrum 6.7–7.3 µm, largest major tooth 11.7–12.5 µm, manubrium 13.7–14.8 µm.

Comments. Testudinella quadrilobata sp. nov. can hardly be confused with any congener. It bears a superficial resemblance with T. dentata Myers, 1934 , from which it differs by the ventral anterior margin consisting of two convex lobes separated by a broad median sinus, instead of the two more or less straight to concave lobes separated by a rounded median sinus delimited by two acute projections in the latter. The dorsal anterior margin with median sinus appears less convex in T. quadrilobata sp. nov. than in T. dentata . In cross-sectional view, T. quadrilobata sp.

nov. is fairly high, asymmetrical dorsally and ventrally, with distinctly arched dorsal margin and flatter ventral margin, whereas T. dentata appears strongly compressed with weakly inflated median part, and symmetrical both dorsally and ventrally. Other Testudinella species with a vase-shaped lorica and undulate dorsal and ventral anterior margin showing a median sinus are T. bicorniculata and T. truncata (Gosse, 1886) which are easily distinguished by the acute antero-lateral lorica projections or angular antero-lateral lorica corners, absent in the new species. As concerns the trophi, T. quadrilobata sp. nov. shows a higher number of unci teeth (14–15/14–15) and arched rami scleropili (33–34/32–33) than T. bicorniculata (10–11/10–11; 11–14/11–16) and T. truncata (12/12; 22/25) ( De Smet 2005, 2009).

Testudinella quadrilobata sp. nov. belongs to the group of brackish water/marine Testudinella -species displaying a slit-like foot opening and proximal fulcrum opening, i.e., T. bicorniculata , T. clypeata (Müller, 1786) , T. elongata De Smet, 2009 , T. obscura , T. pseudobscura sp. nov. and T. zhujiangensis (information on the trophi of the other thalassic species with slit-like foot opening, T. crassa (Levander, 1894) sp. inq. and T. dentata , are unavailable). Of these species, T. clypeata and T. quadrilobata sp. nov. are the only ones sharing a high number of arched rami scleropili and unci teeth: 28–30/25–26 and 14–16/14–16 versus 33–34/32–33 and 14–15/14–15 respectively (overall range of number of arched rami scleropili and unci teeth from 10–21 and 9–13 respectively in the other thalassic species).

Distribution and ecology. The species was to date only collected in small numbers from a shallow mangrove swamp with varying water depth of 5–30 cm depending of the tide, and distances from the shore of about 2 m, in Qi’ao–Dan’gan Provincial Mangrove Nature Reserve on Qi’ao Island in the Pearl River estuary, on 17 January 2009, 28 February 2009, 27 March 2010, and 26 April 2010. Water temperatures varied from 18–23 °C. Salinity varied from 8–14 ‰. It occasionally co-occurred with T. zhujiangensis .

Figures

FIGURE 6. Light microscope photograph of three Testudinella species recorded from Qi’ao Island, China. A. Testudinella pesudobscura sp. nov. ventral view; B. Testudinella zhujiangensis ventral view; C. Testudinella quadrilobata sp. nov. dorsal view; D. Testudinella quadrilobata sp. nov. varying shape of anterior aperture. Scale bar: 50 μm.

FIGURE 9. Testudinella quadrilobata sp. nov. A, B. Lorica, ventral view. C, D. Lorica, cross-section view. E. Foot pseudosegment. Scale bars: A – D: 50 µm, E: 10 µm.

FIGURE 10. Testudinella quadrilobata sp. nov., scanning electron microscope photographs of trophi. A. Complete set, frontal view. B. Complete set (fulcrum lost), caudal view. al: alula, as: arched rami scleropili, dc: dorsal chamber, f: fulcrum, m: manubrium, mc: median chamber, r: ramus, ra: ramus apophysis, rf: ramus fenestra, svc: sub-ventral chamber, u: uncus, vc: ventral chamber.

FIGURE 11. Testudinella quadrilobata sp. nov., scanning electron microscope photograph of trophi. Detail of major teeth and proximal part of fulcrum, frontal view. ba: basal apophysis, fo: fulcrum opening.