Pseudostrandesia phetchabunensis, Savatenalinton & Martens, 2010

Savatenalinton, Sukonthip & Martens, Koen, 2010, On the subfamily Cypricercinae McKenzie, 1971 (Crustacea, Ostracoda) from Thailand, with the description of six new species 2379, Zootaxa 2379, pp. 1-77 : 49-54

Pseudostrandesia calapanensis ( Tressler, 1937) ( Figs 32–34)

1937 Strandesia calapanensis Tressler : 197, Figs 33–35.

1981 Strandesia uenoi Klie — Victor & Fernando: 474.

2009 Pseudostrandesia calapanensis — Savatenalinton & Martens: 19.

Material examined. Many females from several samples (see Table 2).

Diagnosis. Carapace in lateral view elongated, greatest height situated at c. 1/3 of length, anterior margin broadly rounded, posterior margin bluntly pointed; valve surface smooth, set with dispersed small setae; carapace in dorsal view subelliptical, greatest width situated at 2/3 of its length, anterior extremity pointed, posterior extremity rounded, LV overlapping RV; LV with internal groove along valve margin; inner lamella with one inner list; RV with large marginal selvage; A1 with long Wouters organ and long Rome organ, aesthetasc ya short; aesthetasc Y on A2 long; two large bristles on third endite of Mx1 serrated; T1 without d-seta; length of distal claw of caudal ramus c. 3/8 of that of ramus, distal seta as long as proximal claw; caudal ramus attachment with Triebel’s loop situated at middle of distal part of main branch, dorsal and ventral branches well-developed.

Differential diagnosis. Pseudostrandesia calapanensis ( Tressler, 1937) superficially resembles P. phetchabunensis sp. nov. It can be distinguished from it by the shape of the carapace in lateral and dorsal view, the presence of a large selvage on the anterior margin of the RV, the length of the shorter apical seta on the terminal segment of the A1, the morphology of the A2-exopodite and by the pair of apical setae on the penultimate segment of the T2.

Measurements (in µ m). LV (n=2), L=820–822, H=393–396; RV (n=2), L=806–813, H=383–389; Carapace (n=2), L=795–830, W=410–412.

Ecology. While no information on the ecology of this species was given by Tressler (1937), Victor & Fernando (1981b) reported it from ricefields, ponds and roadside ditches. We found several specimens in eight localities ranging over lakes, man-made reservoirs, swamps, and ricefields. This species was found in a pH range of 6.79–7.20 and a temperature range of 23.4–30.8° C.

Abbreviated redescription. Carapace in lateral view ( Fig. 32A) elongated (length c. 2.15 times height), dorsal margin almost straight, greatest height situated at 1/3 of length, ventral margin slightly sinuous in front of mid-length, anterior margin broadly rounded, posterior margin bluntly pointed. Valve surface smooth when seen under low magnification, but set with small tubercles when viewed under very high magnification ( Fig 32B), set with dispersed small setae ( Fig. 32A).

Carapace in dorsal view ( Fig. 32C) subelliptical, greatest width situated at 2/3 of its length, anterior extremity pointed, posterior extremity rounded, LV overlapping RV along anterior, ventral and posterior margins.

LV in interior view ( Fig. 32E) elongated, with groove along valve margin; calcified inner lamella anteriorly wide, with one inner list, posterior calcified inner lamella narrow.

RV in interior view ( Fig. 32F) with large marginal selvage, inner lamella without inner list, ventral margin sinuous slightly in front of mid-length.

A1 ( Fig. 33A): first segment with long, tube-like, proximal Wouters organ, long dorso-subapical seta and two long ventro-apical setae; second segment with long Rome organ and short dorso-apical seta; aesthetasc ya on terminal segment short (length c. 2/7 of that of short apical seta).

A2 ( Fig. 33B–C): longest seta of exopodite short (length c. 2/3 of that of first endopodal segment); first endopodal segment with large, long aesthetasc Y, natatory seta long, length of shortest one slightly less than half of that of penultimate segment, apical seta long (reaching beyond tip of terminal segment); distal claws on penultimate segment long (length c. 1.25 times that of penultimate segment).

Md-palp as in Fig. 33D–F, Md-coxa as in Fig. 33G.

Mx1 ( Fig. 34A): basal segment of palp with latero-subapical seta long (reaching beyond tip of terminal segment), two large bristles on third endite serrated, sideways directed setae on first endite unequal, length of short seta c. 2/3 of that of long one.

T1 ( Fig. 34B) without d-seta.

T2 ( Fig. 34C) with seta d1 c. twice as long as d2.

T3 as in Fig. 34D–E.

Caudal ramus ( Fig. 34G) stout, ventral margin serrated, length of distal claw c. 3/8 of that of ramus, proximal claw slightly shorter than distal claw, distal seta as long as proximal claw. Caudal ramus attachment ( Fig. 34F) stout, with Triebel’s loop situated at middle of distal part of main branch, dorsal and ventral branches well-developed.

Remarks. The original description of S. calapanensis , based on material from the Philippines, was brief and provided only an illustration of the carapace in lateral view, of the Mx1 and of the T2. A redescription, including more illustrations of both valves and soft parts, of this species was given by Victor & Fernando (1981b), based on new material collected from the Philippines. We found that the morphology of valves and limbs of the Thai specimens is congruent with that of the specimens from the Philippines, except for the valves surface, which is pitted in the material from the Philippines, and smooth in the Thai specimens, and for the Ύ seta on the Md-palp (illustrated as smooth in the specimens from the Philippines, hirsute in the Thai specimens).

This species is thus far recorded from the Philippines ( Tressler 1937; Victor & Fernando 1981b), Taiwan

( Klie 1938, under the name Strandesia uenoi ), Nigeria ( Imoobe 2008) and Thailand (present study). The occurrence of this species in Nigeria is questionable as the morphology of both valves and soft parts shows difference in several aspects:

1) The dorsal margin of the valves is arched in the Nigerian specimens, but straight in specimens from the Philippines and Thailand.

2) In the Nigerian specimens, the valve surface as examined under light microscope was ornamented with polygonal reticulation and punctuate with tubercles. These features are not found in the specimens from the Philippines and Thailand.

3) The proportion between distal claw and ramus in the caudal ramus is also different. It is 1:2.8-1: 3.3 in Southeast Asian specimens, but 1:2.0 in African specimens.