Strandesia lineata, Smith, Robin J., Janz, Horst & Okubo, Ichiro, 2011

Smith, Robin J., Janz, Horst & Okubo, Ichiro, 2011, Recent Cyprididae and Ilyocyprididae (Crustacea: Ostracoda) from Lake Biwa, Japan, including a summary of the lake’s ostracod fauna, Zootaxa 2874, pp. 1-37 : 4-8

Bradleytriebella lineata (Victor & Fernando, 1981)

( Figs 2A–E , 3 and 4 )

1981c Strandesia lineata n. sp. —Victor & Fernando: 487–489, figs 91–109.

1984 Paracypretta amati sp. n. —Martens: 154–159, figs 54–61, 90–110.

nomen nudum 2004 Strandesia biwaensis sp. nov. —Okubo: 36, figs 18c, d, & j. Synonymy herein.

? 2005 Zonocypris sp.—Yu et al.: 147, plate II, fig. 16. Synonymy herein.

nomen nudum 2008 Strandesia biwaensis Okubo, 2004 nomen nudum —Smith & Matzke-Karasz: table 1, plate 2, figs 1

& 2.

nomen nudum 2009b Strandesia biwaensis Okubo, 2004 —Savatenalinton & Martens: 37.

nov. comb 2009b Bradleystrandesia lineata (Victor & Fernando, 1981) —Savatenalinton & Martens: 1, 36.

syn. 2009b Strandesia amati ( Martens, 1984) —Savatenalinton & Martens: 36.

nov. comb 2009a Bradleytriebella lineata (Victor & Fernando, 1981) —Savatenalinton & Martens: 13, 33, 46.

2010 Bradleytriebella lineata (Victor & Fernando, 1981) —Savatenalinton & Martens: 70–73, fig. 46.

Description of Japanese specimens. Carapace length 596–646 µm, height 363–373 µm. Carapace ( Fig. 3 A & B) rounded, lateral view with maximum height at anterior third marked by dorsal hump. Posterior of hump, dorsal margin steeply slopes down to tightly curved posterior margin, apex of which below mid-height. Anterior margin more or less evenly rounded, much more inflated than posterior margin. Ventral margin straight to slightly concave. Left valve overlaps right along all margins, but posterior overlap very slight, and anterior overlap very prominent. Dorsal view ovoid with maximum width at mid-length. Surface of valves covered with numerous short, wavy striations that follow lateral outline of carapace, with weak reticulation in places. Inner calcified lamella wide. Left valve with well-developed groove running along free margin, and a partial inner list, step-shaped in cross-section, present on the anterior calcified inner lamella. Adductor muscle scars indistinct. Colour translucent pale whitishyellow, each valve with six purple patches ( Fig. 3 C): one each near both posterior and anterior margins, two smaller patches either side of adductor muscle scars, one small patch below adductor muscles near ventral margin, and one thin, short streak running near to hinge (the latter of which seen in dorsal view). Patches somewhat variable in shape and size.

An1 ( Fig. 3 D) with eight segments, first two of which fused together forming large base. Slender Wouters organ with bulbous end on dorsal-apical corner of first segment. Second segment with one short seta on dorsal margin and two long setae on ventral-apical margin. Third segment wider than long, with slender Rome organ with bulbous end, and short seta on dorsal-apical edge. Fourth segment elongate, with two apical setae. Fifth segment with two long and one short apical setae. Sixth segment with four long apical setae. Seventh segment with four long and one short apical setae. Final segment with one long, one medium-length, and one short setae, plus aesthetasc ya.

An2 ( Fig. 3 E & F) with three segmented Y aesthetasc and natatory setae reaching just beyond end of terminal claws. Claw G2 long, almost as long as claw G1. Claw Gm approximately 65% length of GM.

Md ( Fig. 3 G & H) palp with slender alpha seta, wide hirsute beta seta, and relatively short gamma seta with setulous distal end. Coxa with well-developed teeth.

Mx ( Fig. 3 I) palp with longer than wide second segment. Zahnborsten of third endite each with two small spines towards distal end.

L5 ( Fig. 3 J) endite terminating with approximately 13 setae. Basis with two a setae and b seta, but c seta missing. Endite with no d seta. Branchial plate with six rays. Endopodite with one long and two shorter apical, hirsute setae.

L6 ( Fig. 4 A) with seta d1 slightly longer than d2. Seta e and f both long, longer than next segment respectively. Seta h1 longer than h3, claw h2 relatively short and robust.

L7 ( Fig. 4 B) with d1, d2 and dp approximately similar lengths. Seta e of second segment long, f of third segment short. Terminal pincer well-developed.

CR ( Fig. 4 C) long and slender, ramus very slightly sinuous. Claw Gp approximately 75% length of Ga, seta Sa long, approximately 50% length of Ga. CR attachment ( Fig. 4 D) with well-developed Triebel loop on dorsal branch.

Remarks. There are a number of differences between the original description of B. lineata and the Lake Biwa specimens, in particular the following: 1. B. lineata specimens are brownish, while the Japanese specimens have six distinctive purple patches on each pale yellow valve. 2. The second endopodal segment of the antenna is reportedly weakly divided (by a ‘suture’) in B. lineata , while the Japanese specimens lack this division. 3. B. lineata apparently lacks a gamma seta on the Md, whereas the Japanese specimens have a gamma seta. 4. B. lineata has six spine-like setae on the endite of the L5, in contrast to the c. 13 normal setae of the Japanese specimens. 5. The length of the claw of the L6 of B. lineata is proportionally longer than that of the Japanese specimens. Savatenlinton & Martens (2010) assigned Thai specimens to Bradleytriebella lineata , but also noted that there were differences between the original description of B. lineata and their specimens. They suggested that the types of B. lineata are juveniles and this accounts for the differences.

For this study we investigated three whole paratypes of B. lineata (from a total of ten deposited, numbered CMNC 1982-0082), the carapaces of which were completely decalcified. One specimen was dissected and revealed that the body shows a degree of deterioration, with some appendages easily breaking apart or falling off. The paratype has characteristics very similar to those of the Japanese specimens, including the presence of a slen- der gamma seta on the Md, at least ten setae on the endite of the L5, and no evidence of a ‘suture’ on the second exopodal segment of the antennae. A minor difference is that the claw on the L6 of the paratype is proportionally slightly longer than that of the Lake Biwa specimens. If all the type material has a similar level of preservation as the dissected paratype then this may account for the discrepancies between the original description of the holotype and the paratype; setae can become detached and lost, and limbs can become creased (resembling ‘sutures’) in poorly preserved material. Additionally, it appears that the original description of the appendages was based on only one dissected specimen, the holotype, thus without comparisons with additional material such discrepancies could have gone unnoticed.

Traces of ornamentation on the paratypes’ carapaces resemble that of the Japanese specimens, although it was not possible to confidently identify a groove or list on the decalcified left valve. The carapaces are translucent, with a yellowish-brown tinge towards the margins, with no evidence of any purple patches similar to those of the Japanese specimens. However, carapace colouration of the types could have been lost when the specimens were fixed with formalin, which tends to bleach, as well as decalcify, valves (documents enclosed with the paratypes detail that formalin was the fixative). Victor and Fernando (1981) were not the collectors of the types, so it is unlikely that they saw fresh specimens, and hence their natural colouration, prior to fixing in formalin.

Based on our observations of the paratypes, we are confident that the specimens from Lake Biwa are B. lineata . It should be noted that the paratypes viewed by us are all adults, and the five long and one short natatory setae on the antenna figured by Victor and Fernando (1981) indicates that the holotype is also an adult, conflicting with Savatenalinton and Martens’ (2010) opinion that the types are juveniles.

Bradleytriebella lineata has previously been reported from the Philippines (Victor & Fernando 1981 as Strandesia lineata ), Sudan ( Martens 1984, as Paracypretta amati ), Thailand ( Savatenalinton and Martens 2010) and Japan ( Okubo 2004; Smith & Matzke-Karasz 2008, as Strandesia biwaensis ). A figured specimen collected from Taihu Lake, eastern China and assigned to Zonocypris sp. by Yu et al. (2005) shows a strong resemblance to B. lineata , although we cannot confirm its synonymy at present.

In Lake Biwa B. lineata was found between August and November, with highest abundances during August. It was mostly found in shallow, sandy substrates near macrophytes. Localities ( Fig. 1 ): 1, 2, 5, 18, 25, 32.

Figures

FIGURE 1. Location of Lake Biwa and sampling localities that yielded Cyprididae and Ilyocyprididae species.

FIGURE 3. Bradleytriebella lineata. A—left valve, internal view. B—right valve, internal view. C—lateral and dorsal views of carapace showing colouration. D—antennule (LBM 1430003543). E—antenna (LBM 1430003543). F—detail of antenna (LBM 1430003543). G—mandible (LBM 1430003543). H—alpha, beta and gamma setae of mandible (LBM 1430003543). Imaxillula palp and endites (setae on endites not drawn) (LBM 1430003543). J—fifth limb (LBM 1430003542). g = groove, li = list.

FIGURE 4. Bradleytriebella lineata. A—sixth limb (LBM 1430003543). B—seventh limb (LBM 1430003543). C—caudal ramus (LBM 1430003543). D—caudal ramus attachment (LBM 1430003543).

FIGURE 2. A – E Bradleytriebella lineata. A—right lateral view of whole carapace (LBM 1430003539). B—internal view of right valve (LBM 1430003541). C—internal view of left valve (LBM 1430003541). D—dorsal view of whole carapace, anterior to top (LBM 1430003540). E—detail of surface of carapace (LBM 1430003539). F & G Bradleycypris vittata. F—right lateral view of whole carapace (LBM 1430003544). G—dorsal view of whole carapace, anterior to right (LBM 1430003545). H & I Cypridopsis vidua. H—left valve, external view (LBM 1430003546). I—dorsal view of whole carapace, anterior to right (LBM 1430003547). J & K Cypris sp. J—right lateral view of whole carapace (LBM 1430003548). K—dorsal view of whole carapace, anterior to right (LBM 1430003549). Scale bar = 268 µm for A – D, 103 µm for E, 393 µm for F & G, 359 µm for H & I, and 634 µm for J & K.