Loxoconcha damensis Dung & Tsukagoshi 2018, sp. nov.
Creators: name: Dung, Le Doan
name: Tsukagoshi, Akira
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Ostracoda
Podocopida
Loxoconchidae
Loxoconcha
Loxoconcha damensis

description: Loxoconcha damensis sp. nov.
(Figs 2–5)
Type series. All specimens were collected at the coral reef in Dam Ngoai Island, Phu Quoc Marine Protected Area in Phu Quoc Island, southwest of Vietnam, 9°59'42"N, 104°02'17"E (Fig. 1A, B), in November 2014. The substrate consisted mainly of very coarse sand, dead coral and algae. Holotype: SUM-CO-2421 (soft parts and a right valve of adult male; soft parts were mounted on a glass slide using “Neo Shigaral” as mounting agent, and the carapace on a cardboard slide with single hole). Paratypes: 4 males (SUM-CO-2420, 2422, 2423, 2428), 4 females (SUM- CO-2424, 2425, 2426, 2427); soft parts mounted on a glass slide and carapaces on a cardboard slide; other specimens (carapaces) are kept on a cardboard slide with single hole.
Etymology. Named after the type locality, Dam Ngoai Island, where this species was collected.
Diagnosis. Carapace covered with conspicuous reticulations with thick ridges and sparsely distributed sievetype pore systems. Semicircular ridge developed at postero-dorsal corner. Number of sieve pore systems 80 per valve. In lateral view, carapace rhomboid, that of female more oval than that of male. Dorsum arched in female, straight in male. Anterior margin rounded, posterior upward rounded terminating in subdorsal caudal process. Right and left valves showing weak asymmetry in lateral outline. Ventral marginal line of right valve more concave than left valve (Fig. 3A, B, D, E). Second adductor muscle scar from top longer than other three in both sex (Fig. 3I, L). Hinge gongylodont with clear crenulations in median element (Fig. 3N, O). In male copulatory organ, distal lobe (Dl) thin, large with a triangular shape and distal end pointed. Clasping apparatus (Ca) thin and very large with distal end extending posteriorly, forming a tip. Copulatory duct (Cd) short and folded inside (Fig. 5).
Description. Carapace (Figs 2, 3). Carapace rhomboid in lateral view as typical Loxoconcha species, showing sexual dimorphism; male relatively elongated compared to female. Lateral surface covered with conspicuous reticulation of thick ridges and lateral about 80 pore systems per valve. Eye spot clear. Semicircular ridge developed at postero-dorsal corner. Dorsum arched in female, almost straight in male. Anterior margin well rounded and inflexed anteroventrally. Posterior margin upward rounded forming a caudal process. Ventral margin gently curved. Right and left valves showing weak asymmetry in lateral outline. Ventral marginal line of right valve more concave than left valve (Fig. 3A, B, D, E). Marginal infold (calcified inner lamella) well developed with conspicuous list. Very narrow vestibula along anterior and posterior inner margins. Around 25 well-spaced marginal pore canals (Fig. 2). Fused zone almost as wide as marginal infold (Fig. 2). All lateral pore systems consisting of sieve-type (Fig. 3P), with 80 pores per valve. Muscle scars (Fig. 3I, L): frontal scar C-shaped, opening anteriorly; 2 separated mandibular scars of unequal dimensions with oval shape; 4 adductor muscle scars arranged in curved sub-vertical row, concave anteriorly, second scar from top longer than other three in both male and female (Fig. 3I, L). Hinge gongylodont with very clear crenulations in median element (Fig. 3N, O).
Antennula (Fig. 4A). Consisting of 5 articulated podomeres, length ratios from proximal to distal 31:19:10:29:17, gradually narrowing in this order. First podomere stout without seta. Second podomere with 1 seta at posterior-distal end and setulae along anterior margin. Third podomere with 1 seta antero-distally. Fourth podomere showing vestigium of segmentation as ledge with 1 long seta on posterior side and 1 short seta on anterior side, 1 long seta postero-distally, and with 3 setae antero-distally. Fifth podomere small, slender, with 3 long setae and 1 aesthetasc on distal end.
Antenna (Fig. 4B). Four articulated podomeres, length ratios from proximal to distal 17:6:21:3, width decreasing in this order. First podomere very stout bearing very long two-joined exopodite (spinneret seta) at anterior distal end. Second podomere rectangular with 1 long seta postero-distally and long setulae along anterior proximal corner. Third podomere very long, with 2 setae on anterior margin, 2 setae and 1 aesthetasc on posterior ledge, 1 seta at posterior-distal end, and setulae along posterior margin. Fourth podomere very short and small with 2 distal claws of sub-equal length.
Mandibula (Fig. 4C, C’). Five articulated podomeres. Coxa stout, bearing about 11 teeth on medial edge and 1 seta on anterior margin. Basis bearing exopodite as bunch of 4 plumose setae (3 long and 1 shorter setae), and 1 ventro-distal seta. First podomere of endopodite with 1 annulated seta antero-distally, 2 very long and 2 shorter setae ventrally. Second podomere of endopodite bearing 5 annulated setae antero-distally, 2 setae of unequal length at ventral distal end. Third podomere of endopodite with 4 simple setae of unequal sizes, one of them stouter than others at distal end.
Maxillula (Fig. 4D, D’). Exopodite a thin branchial plate, with 17 long plumose setae. Basal podomere bearing one endopodite and 3 endites. Endopodite consisting of 2 podomeres. First podore with 4 setulous annulated setae at anterior distal end and 1 simple seta on ventral distal end. Second podomere carrying 3 hook-shaped setae at distal end. Three endites bearing 5, 5 and 4 setulous setae at distal end, respectively. Third endite also bearing seta on ventral proximal margin, stout proximally with medium-length setulae, and thinning distally.
Fifth limb (Fig. 4E). Four articulated podomeres, length ratios from proximal to distal 20:15:6:8. First podomere carrying 2 setulous setae on anterior margin, 2 short anterior distal setae, and 1 long setulous seta on posterior margin nearly proximal end. Second podomere with 1 simple, short small seta on anterior distal end, and setulae along anterior margin. Third podomere with very short setulae along anterior margin. Fourth podomere with 1 long, stout terminal claw and setulae along anterior margin.
Sixth limb (Fig. 4F). Four articulated podomeres, length ratios from proximal to distal 15:12:5:7. First podomere bearing long 2 setae on anterior margin, each with setulae distally, 1 short anterior distal seta, and 1 long setulous seta at one fourth of the length from the proximal end of posterior margin. Second podomere with 1 simple seta at anterior distal corner, and setulae along anterior margin. Third podomere with short setulae along anterior margin. Fourth podomere with 1 long, stout terminal claw and setulae along anterior margin.
Seventh limb (Fig. 4G). Four articulated podomeres, length ratios from proximal to distal 11:8:3:6. First podomere with 2 long setulous setae on anterior margin, 1 setulous seta at anterior distal end, and 1 long setulous seta at one fifth of the length from the proximal end of posterior margin. Second podomere with 1 simple seta at anterior distal corner, and setulae along anterior margin. Third podomere with short setulae along anterior margin. Fourth podomere with 1 long stout terminal claw and setulae along anterior margin.
Male copulatory organ (Fig. 5). Basal capsule with elliptical outline. Thin but large distal lobe triangular in shape with pointed distal end. Clasping apparatus thin and large extending distally to form a tip. Copulatory duct clear, folded inside and short.
Dimensions. See Table 1.
Remarks. No brush-shaped organ was observed in any of the 5 male Loxoconcha damensis specimens examined. This species generally resembles Loxoconcha australis Brady, 1880 (e.g. Yassini & Jones 1995) in carapace morphology; however, it exhibits a marginal difference in the external lateral view of a semicircular ridge at the postero-dorsal corner. Furthermore, the frontal scar of this species is C-shaped (Fig. 3I, L), whereas that of L. australis is V-shaped (see Yassini & Jones 1995). Loxoconcha damensis s p. nov. has a gongylodont-type hingement (Fig. 4N, O), while L. australis has amphidont-type hingement (see Yassini & Jones 1995).
description: Published as part of Dung, Le Doan & Tsukagoshi, Akira, 2018, Three new species of the genera Loxoconcha and Xestoleberis (Crustacea, Ostracoda, Podocopida) from central and southern Vietnam, pp. 111-126 in Zootaxa 4472 (1) on pages 112-116, DOI: 10.11646/zootaxa.4472.1.5, http://zenodo.org/record/1440042