Potamocypris narayanani, George, Sunny & Martens, Koen, 2002

George, Sunny & Martens, Koen, 2002, On a new species of Potamocypris (Crustacea, Ostracoda) from Chalakkudy River, Kerala (India), with a checklist of the Potamocypris­ species of the world, Zootaxa 66, pp. 1-15 : 3-8

Potamocypris narayanani n.sp.

( Figs. 1­3 )

Type locality

Chalakkudy River, at Vettukadavu, Meloor, Kerala, India.

Type material

All type specimens were raised from resting eggs which had been collected from approximately 9 cm deep in the river sand. The sediment was collected with a PVC tube on 24.07.1999 and the core was divided in slices of 2 cm. Specimens were raised from the sand by adding filtered well water.

Holotype: a female, with soft parts dissected in glycerine in a sealed slide and with valves stored dry in a micropalaeontological slide (OC.2442). Most illustrations in the present paper are made from this specimen.

Paratypes: two females dissected and stored as the holotype (OC. 2443­2444); four females stored in micropalaeontological slides after use for SEM (OC. 2445­2448); c 20 females in 70% ethanol (OC. 2451).

Deposition: all types specimens are presently curated in the Ostracod Collection of the Royal Belgian Institute of Natural Sciences (Brussels, Belgium).

Derivation of name

The new species is named in honour of Prof. Dr. K. Narayanan Nair, Programme Coordinator of Kerala Research Programme on Local Level Development, Centre for Development Studies, Thiruvananthapuram, Kerala in acknowledgement of his constant encouragement towards one of us (S.G.) and also in great appreciation of his keen interest in the conservation of Chalakkudy river system from where this new species has been collected.

Diagnosis

A medium­sized species, with wide anterior and posterior flanges on the LV (‘ Cyprilla ’), long natatory setae on the A2 and 5 claw­like setae on the distal Mx1­palp segment. LV furthermore relatively elongated, with posteriorly sloping dorsal margin; RV widely overlapping LV on dorsal side. Valve surface pitted and set with stout setae.

Description of female

Valves medium­sized (Le= c 650 µm), and very asymmetrical. LV ( Fig. 3 A, C, D) elongated, overlapping RV with wide anterior and posterior flanges ( Figs. 3 H, I); RV ( Fig. 3 B) triangular, overlapping LV with large dorsal hump ( Figs. 3 F, G) as well as ventrally ( Fig. 3 K). LV with dorsal margin straight over c 2/3 of the length, sloping towards the posterior side; postero­ventral corner pointed, calcified inner margin narrow, postero­ventral one with inner list near or on inner margin, anterior one narrow and rounded. RV with submarginal ventral and caudal selvage. Valve surface ( Fig. 3 G, N) pitted and set with large, stout setae. In dorsal view ( Fig. 3 J), RV showing asymmetrically curved dorsal hump, and curved overlap of RV by posterior flange of LV.

A1 ( Fig. 1 A) with basal segment carrying 1 short dorsal and 2 medium­sized ventral setae. 2nd and 3rd segments both with 1 short dorsal seta. 4th segment with 2 dorsal, natatory setae and one minute ventral seta. 5th and 6th segment with 2 dorsal, natatory setae and one medium­sized ventral seta; terminal segment with a long aesthetasc Ya, 2 long natatory setae and a short seta.

A2 ( Fig. 1 B) with expodite consisting of a small plate, one long, one intermediate and one tiny setae. Aesthetasc Y short and stout. Natatory setae extending beyond the tips of the claws with about 1/3 of their length. Penultimate segment with 3 medium­sized z­setae (z1>z2>z3) and 3 large, serrated end claws. Terminal segment with claw Gm attaining more than 2/3 of the length of GM. Md with coxa ( Fig. 1 F) elongate, slender. Palp ( Fig. 1 D) with alpha­seta slender and short, beta­seta thick, robust and hirsute, and accompanied by 3 setulate setae, gamma­seta long and slender; terminal segment with 2 long claws, one short claw and 2 short setae.

Mx1 ( Fig. 1 E) with second palp segment spatulate, as typical of the genus, set with stout, 5 claw­like setae; penultimate segment of palp with 4+1 lateral setae. Third endite apically with 2 claws and 2 setae and 1 short lateral seta. Respiratory plate ( Fig. 2 D) elongated, set with nearly 30 rays.

T1 ( Fig. 1 C) with elongated palp, set with 3 unequal setae, the middle one being the longest.

T2 ( Fig. 2 B) robust, seta d1 absent, seta d2 short, penultimate segment divided, end claw long and stout. Setae on penultimate and terminal segments claw­like.

T3 ( Fig. 2 A) a cleaning leg, with terminal part of penultimate segment forming a pincer­shaped organ including the terminal segment.

Caudal ramus ( Fig. 2 C) reduced, with short, conical base, carrying a short seta and a long, tapering flagellum­like seta.

Male unknown.

Measurements (in µm)

LV= Le= 644, H= 339; RV: Le= 598, H= 403 (n=1) Cp: Le= 637­688 (n=4); H= 325­374 (n=3); W= 229 (n=1) Relationships

Potamocypris narayanani n.sp. can be distinguished from all species in the genus by at least two unique features, namely the very large dorsal hump on the RV, overlapping the LV, and the large, stiff and stout setae on the valve surface. The new species has long natatory setae on the A2 and 5 claws on the second Mx1­palp segment, and furthermore belongs to the species­group within the genus with wide anterior and posterior flanges, often referred to as Cyprilla . However, also within this group, none of the other species has the large dorsal hump and the typical setae on the external valve surface ( Sars, 1924).

Three other species, belonging to Potamocypris , have thus far been reported from India. These are: P. angularis Victor & Michael, 1975 ; P. producta ( Sars, 1924) and P. minuta patriciae Bhatia, 1968 , the latter cited from fossil deposits of Kashmir only. Potamocypris producta is a very common species in Africa and also occurs in Europe. It is the most widely distributed species with Cyprilla­ like flanges; its presence in India is therefore not surprising. Potamocypris angularis is (very rudimentary) described from Madurai ( Victor & Michael, 1975); the shape of valves and especially of caudal ramus (with cylindrical trunk) indicate that this species rather belongs to Plesiocypridopsis than to Potamocypris (shape of distal Mx1­palp segment is not mentioned). Apart from differences in valves and caudal ramus, P. angularis also lacks the pitted valve surface characteristic of P. narayanani .

Ecology

Species of Potamocypris have been described from a variety of habitats, including lakes, ponds, springs and several types of subterranean habitats. Some species, mostly those with short natatory setae, have been collected from slow flowing streams and rivers. As for Newnhamia dumonti (George & Martens, in press­a), P. narayanani n.sp. was raised from dried river sand, collected with a coring tube. Thus, the expectation that river sand can act as a reservoir of resting eggs is again strengthened. However, whereas N. dumonti was raised from sand one meter below the sediment surface, the present species was recovered from more superficial layers (<10 cm) in the shallow parts of the river itself, where also populations of two different species of Indiacypris occurred (George & Martens, in press­b). It is possible that the shallow, slow­flowing parts of the river indeed constitute the natural habitat of P. narayanani n.sp. However, as this species has long natatory setae on the A2, it is unlikely that it is exclusively rheophylic. The co­occurrence of specimens of the conchostracan genus Cyclestheria in the cultures seems to indicate that this part of the river might be temporary.

Figures

FIGURE 1. Potamocypris narayanani n. sp. (holotype female, no. OC. 2442). A. A 1. B. A 2. C. T 1, palp. D. Md­palp. E. Mx 1, palp and 3 rd endite, chaetotaxy of first two endites not shown. F. Mdcoxa. Scale: 53 µm for A­F.

FIGURE 2. Potamocypris narayanani n. sp. (holotype female, no. OC. 2442). A. T 3. B. T 2. C. caudal ramus. D. Mx 1, respiratory plate. Scale: 53 µm for A­F.

FIGURE 3. Potamocypris narayanani n. sp. (all females). A. LV, internal view (holotype OC. 2442). B. RV, internal view (idem). C. LV, internal view, detail of posterior flange (idem). D. LV, internal view, detail of anterior flange (idem). E. Cp, left lateral view, slightly tilted (OC. 2446). F. Cp, left lateral view (OC. 2447). G. Cp, right lateral view (OC. 2445). H. Idem, detail posterior. I. Idem, detail anterior. J. Cp, dorsal view (OC. 2446). K. Cp, ventral view (OC. 2445). L. Cp, dorsal view, detail anterior (OC. 2446). M. Idem, detail posterior. N. Idem, detail of valve surface. Scale = 96 µm for N; 227 µm for C, D, H, I, L, M; 455 µm for A, B, E­G, J, K.