Loxoconcha noharai, Dung & Tsukagoshi, 2014

Dung, Le Doan & Tsukagoshi, Akira, 2014, Three new species of the genus Loxoconcha (Crustacea, Ostracoda, Podocopida) from the Okinawa Islands, southern Japan, Zootaxa 3796 (1), pp. 147-165 : 149-153

publication ID	https://doi.org/ 10.11646/zootaxa.3796.1.7
publication LSID	lsid:zoobank.org:pub:100761B6-225E-48AF-97F4-8E3824348915
DOI	https://doi.org/10.5281/zenodo.5083040
persistent identifier	https://treatment.plazi.org/id/A51A1114-FF89-8368-C0CC-6BDE15CF8EA7
treatment provided by	Felipe
scientific name	Loxoconcha noharai
status	sp. nov.

Treatment

Loxoconcha noharai View in CoL sp. nov.

( Figs 2–5 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 )

Type series. All specimens were collected at Ohura estuary ( Fig. 1C View FIGURE 1 ), Okinawa Island, southern Japan, 26°33’0”N, 128°2’30”E on 19 March 1992. Holotype: SUM-CO-2137 (soft parts and a right valve of adult male; soft parts were enveloped on a slide glass in the “Neo Sigaral” as mounting agent and carapace was on a cardboard slide with single hole). Paratypes: 8 males (SUM-CO-2135, 2136, 2138, 2141, 2143, 2144, 2147, 2148), 5 females (SUM- CO-2139, 2140, 2142, 2145, 2146) and one an A-1 instar (SUM-CO-2149); also as for the dissected specimens, soft parts were mounted on a slide glass in the “Neo Sigaral” agent and carapaces were on a cardboard slide with single hole; other specimens, carapaces were kept on a cardboard slide with single hole.

Etymology. Named in honour of the late Prof. Tomohide Nohara (University of the Ryukyus), in recognition of his significant contribution to ostracod research in Okinawa.

Diagnosis. Carapace rhomboid in lateral view, covered with distinct reticulations and sieve-type pore canals sparsely distributed. Number of pore systems 74 per valve. 4 adductor muscle scars in little curved sub-vertical row, concave anteriorly. Possessing gongylodont hingement with clear crenulations in median element. Plumose seta at posterior margin of first podomere of the three limbs bears several long setulae. In the male, copulatory organ with large and thin distal lobe (Dl); clasping apparatus (Ca) large, thin and partly overlapping the distal lobe, and copulatory duct (Cd) not clear, fine and short, about one fourth as long as length of copulatory organ itself.

Description. Carapace ( Figs 2 View FIGURE 2 , 3 View FIGURE 3 ). Carapace rhomboid in lateral view, showing distinct sexual dimorphism; male more elongate and with less compressed postero-ventral marginal area than female. Surface covered with distinct reticulations. Right and left valves showing asymmetry in outline. Both valves slightly tapering backward; greatest height at anterior-most third. Dorsal margin very slightly convex. Ventral margin nearly straight. Anterior margin broadly rounded. Posterior margin somewhat narrowly rounded, extremity at more than half of height, with slight caudal process. Marginal infold moderately developed. List developing along middle of marginal infold in both valves. Shallow vestibula in anterior and posterior areas of valves ( Fig. 2 View FIGURE 2 ). Fused zone almost as wide as infold ( Fig. 2 View FIGURE 2 ). All lateral pore canals of sieve-type and scattered sparsely with 74 pores per valve. Muscle scars ( Fig. 3I, L View FIGURE 3 ): the smaller one of 2 separate frontal scars round and larger one with curved shape, opening anteriorly; 2 mandibular scars of equal dimensions; 4 adductor muscle scars in weakly curved sub-vertical row, concave anteriorly. Hinge gongylodont with clear crenulations in median element.

Antennula ( Fig. 4A View FIGURE 4 ). Five articulated podomeres, length ratios from proximal to distal 16:15:6:13:13, width decreasing gradually in this order. First podomere stout without seta. Second podomere with 1 postero-distal seta and setulae along anterior margin. Third podomere with 1 seta antero-distally. Fourth podomere showing vestigium of segmentation as a ledge with 1 seta and median one, and with 1 very long postero-distal seta, 3 setae anterodistally. Fifth podomere slender, with 3 long setae and 1 aesthetasc distally.

Antenna ( Fig. 4B View FIGURE 4 ). Four articulated podomeres, length ratios from proximal to distal 25:12:38:5, width decreasing gradually in this order. First podomere stout with very long exopodite (=spinneret) at anterior distal end. Second podomere with 1 long seta postero-distally and a bunch of long setulae along anterior proximal margin. Third podomere very long, with 2 setae on anterior margin, 2 setae and 1 aesthetasc on posterior ledge, 1 seta at postero-distal end, and setulae along posterior margin. Fourth podomere very small and short with 2 distal claws of sub-equal length.

Mandibula ( Fig. 4C View FIGURE 4 , C’). Five articulated podomeres. Coxa stout, bearing teeth on medial edge and 1 long seta on anterior margin. Basis bearing exopodite as bunch of 4 plumose setae (3 long plumose and 1 shorter setae) and 1 long ventro-distal seta. First podomere of endopodite with 1 annulated seta antero-distally, 2 very long and 2 short setae ventrally. Second podomere of endopodite with 5 annulated setae antero-distally, 2 setae of unequal length ventrally. Third podomere of endopodite bearing 4 simple setae.

Maxillula ( Fig. 4D View FIGURE 4 , D’). Thin branchial plate with 16 long plumose setae. Basal podomere bearing a palp and 3 endites; palp with 4 setulous annulated setae antero-distally, 1 seta ventro-distally, 1 strong claw-like and 2 stout setae on distal end; 3 endites bearing 6, 6, and 4 setae, respectively; especially most ventral seta of 3rd endite bearing long setuleae arranged in a cluster and terminating in a club-like process.

Fifth limb ( Fig. 4E View FIGURE 4 ). Four articulated podomeres, length ratios from proximal to distal 26:23:12:15. First podomere with 2 setulous setae at anterior margin, 2 short setulous setae at anterior distal end, and 1 setulous seta with several long setulae at posterior margin. Second podomere with 1 simple seta on anterior distal corner, and setulae along anterior margin. Third podomere with very short setulae along anterior margin. Fourth podomere with 1 long, stout distal claw and setulae along anterior margin.

Sixth limb ( Fig. 4F View FIGURE 4 ). Four articulated podomeres, length ratios from proximal to distal 34:32:11:16. First podomere with 2 setulous setae along anterior margin, 1 setulous seta at anterior distal end, and 1 setulous seta at one third from proximal end of posterior margin consisting of several long setulae. Second podomere with 1 long simple seta on anterior distal corner, and setulae along anterior margin. Third podomere with very short setulae along anterior margin. Fourth podomere with 1 long, stout distal claw and setulae along anterior margin.

Seventh limb ( Fig. 4G View FIGURE 4 ). Four articulated podomeres, length ratios from proximal to distal 29:28:13:19. First podomere with 2 setulous setae along anterior margin, 1 short setulous seta at anterior distal end, and 1 setulous seta with several long setulae at posterior proximal end. Second podomere with 1 simple seta on anterior distal corner, and setulae along anterior margin. Third podomere with very short setulae along anterior margin, posterior distal end extending to make small process. Fourth podomere with 1 long and stout distal claw and setulae along anterior margin.

Male copulatory organ ( Fig. 5 View FIGURE 5 ). Outline sub-circular. Basal part relatively large, and as a blunt triangle. Thin distal lobe triangular. Clasping apparatus thin and large, overlapping partly with the distal lobe, with distal end extending posteriorly. Copulatory duct not clear, fine structure, folded inside and short, about one fourth as long as length of copulatory organ itself.

Dimensions. See Table 1 View TABLE 1 .

Abbreviations: F, Female; M, Male; LV, left valve; RV, right valve.

Remarks. No brush-shaped organ was observed in any of the 7 male dry specimens and 4 male wet specimens examined. This new species resembles Loxoconcha uranouchiensis Ishizaki, 1968 in features of the carapace morphology, but it can be clearly distinguished from this species by some features of the male copulatory organ (see Okubo 1980), and small differences which are found in the chaetotaxy of 5th to 7th limbs and maxillula. In the male copulatory organ, the distal lobe of Loxoconcha noharai sp. nov. has a blunt triangular-like shape, whereas that of L. uranouchiensis is sub-quadrangular in shape and forming a small process at the anterior end. Clasping apparatus of both species overlapping the distal lobe, however, part of the clasping apparatus extending outside the distal margin of Loxoconcha noharai sp. nov. is longer and larger than that of L. uranouchiensis . In L. noharai sp. nov., the plumose setae at the posterior margins of the first podomeres of all three limbs bears several long setulae. The maxillula of this new species has the ventral-most seta of the 3rd endite bearing long setulae arranged in a cluster and terminating in a club-like process.