Microloxoconcha sublittoralis, Tanaka & Ohtsuka, 2019

Tanaka, Hayato & Ohtsuka, Susumu, 2019, Two New Species of Microloxoconcha (Crustacea: Ostracoda) from the Sublittoral Zone in Western Japan, Species Diversity 24, pp. 217-228 : 223-225

publication ID	https://doi.org/ 10.12782/specdiv.24.217
publication LSID	lsid:zoobank.org:pub:B327B697-2B0F-4C93-80E7-DFAD1EEB4B77
persistent identifier	https://treatment.plazi.org/id/E0789955-E412-49B3-978A-6A4028C8FAA6
taxon LSID	lsid:zoobank.org:act:E0789955-E412-49B3-978A-6A4028C8FAA6
treatment provided by	Felipe
scientific name	Microloxoconcha sublittoralis
status	sp. nov.

Treatment

Microloxoconcha sublittoralis View in CoL n. sp.

( Figs 7–11 View Fig View Fig View Fig View Fig View Fig )

Type series. Holotype: adult male (NSMT-Cr 26689), RV length 0.24 mm, height 0.10 mm, LV length 0.24 mm, height 0.09 mm, soft parts mounted on a slide and valves preserved in a cardboard cell slide. The holotype specimen was collect- ed from the bottom consisting of coarse coral sand off south of Nagannu Island, Okinawa Prefecture, Japan (26°14′20″N, 127°32′17″E) at depth 52 m on 21 May 2016 GoogleMaps . Paratype: 1 adult female (NSMT-Cr 26690), RV length 0.24 mm, height 0.10 mm, LV length 0.24 mm, height 0.10 mm, same data as in holotype.

Diagnosis. Carapace in lateral view, elongate and beanshaped, anterior margin rounded, postero-dorsal margin gently inclined toward posterior end. Marginal infold broad in both anterior and posterior regions. Vestibula broad in anterior and narrow in posterior regions, respectively. Seventh limb much longer than fifth and sixth limbs. Copulatory duct of male copulatory organ long flagellum shape. In female, sclerotized framework of paired genital openings liver-like shape.

Description of adult male. Carapace ( Figs 7A, B View Fig , 8 View Fig ). Carapace elongate and bean-shaped in lateral view, anterior margin rounded, postero-dorsal margin gently inclined toward posterior end ( Figs 7A, B View Fig , 8 View Fig ). Surface smooth. Marginal infold broad in both anterior and posterior regions ( Fig. 8 View Fig ). Vestibula broad in anterior and narrow in posterior regions, respectively ( Fig. 8 View Fig ). Adductor muscle scar pattern consisting of row of four closely spaced scars and two frontal scars ( Fig. 8 View Fig ). Hingement weak adont type.

Antennula ( Fig. 9A View Fig ). Consists of five slender articulated podomeres. First podomere bare. Second podomere with row of setulae on anterior margin. Third podomere with one antero-distal seta. Fourth podomere with one short anteromiddle seta and one long antero-distal seta. Fifth podomere with one slender seta and two spatulate setae (aesthetascs) at distal end.

Antenna ( Fig. 9B View Fig ). Four articulated podomeres. First podomere (basis) bare, with a long, thick, three-segmented exopodite (spinneret seta). Second (first endopodial) podomere with one short seta on postero-distal end. Third (second endopodial) podomere with one medium postero-middle seta, one short postero-distal spine, and one stout claw at postero-distal end. Fourth (third endopodial) podomere small, with one stout distal claw.

Mandibula ( Fig. 9C View Fig ). Coxa with one short setulous seta on anterior margin. Coxal endite consisting of six teeth. Palp consisting of four articulated podomeres. First podomere of palp (Basis) with thick nib-like plate (exopodite) near postero-middle margin and short seta on antero-middle margin. Second podomere of palp (first endopodite) with one thick antero-distal seta, and one thick and one slender postero-distal setae. Third podomere of palp (second endopodite) with two setae near antero-proximal margin, one thick and one slender antero-distal setae, and one short postero-distal seta. Fourth (third endopodite) podomere of palp slender, with three distal setae.

Maxillula ( Fig. 9D View Fig ). Thin branchial plate bearing 11 plumose setae. Basal podomere with one palp (endopodite) and three endites. Palp consisting of two distinct podomeres: first podomere with one distal seta; second podomere with three distal setae. Endite: dorsal one with five setae; middle one with four setae; ventral one with five setae.

Fifth limb ( Fig. 10A View Fig ). Four articulated podomeres. First podomere with one antero-distal seta, one stout setulous antero-middle seta and one slender postero-middle seta. Second podomere with one short antero-distal spine. Third podomere bare. Fourth podomere with one stout distal claw.

Sixth limb ( Fig. 10B View Fig ). Four articulated podomeres. First podomere with one antero-distal seta, one antero-middle seta and postero-middle seta. Second podomere with one antero-distal seta. Third podomere bare. Fourth podomere with one stout distal claw.

Seventh limb ( Fig. 10C View Fig ). Four thick articulated podomeres. First podomere with one antero-distal seta, one short antero-middle spine, and short seta on near posteroproximal part. Second podomere with one stout antero-distal spine and rows of setulae on anterior and distal margin. Third podomere small, with rows of setulae on anterior and distal margin. Fourth podomere small, with rows of setulae on anterior and distal margin and one distal claw.

Male brush-shaped organ ( Fig. 10D View Fig ). Consisting of two branches (right and left) each with 11 setae on distal margin.

Male copulatory organ ( Fig. 10E View Fig ). Consisting of spindleshaped basal capsule, with very thin and semi-triangular distal lobe; copulatory duct long flagellum shape, approximately half lengths as capsule.

Description of adult female. Carapace ( Fig. 7C, D View Fig ). Carapace elongate and bean-shaped in lateral view, anterior margin rounded, postero-dorsal margin gently inclined toward posterior end ( Fig. 7C, D View Fig ).

Posterior part of body and female genitalia ( Fig. 11 View Fig ). Sclerotized framework of paired genital openings liver-like shape. Spermathecal duct long, connecting with genital opening and receptaculum seminis. Rows of tiny setulae on abdominal end.

Occurrence. So far known only from the type locality.

Etymology. Sublittoral, referring to the habitat of this species.

Remarks. Microloxoconcha sublittoralis n. sp. has unique morphology of the male copulatory organ: a long flagellated copulatory duct has never been reported from any other Microloxoconcha species. It most closely resembles M. santacruzensis Gottwald, 1983 in the shape of the carapace. However, the appendages differ between these species: distal end of the antennula has one slender seta and two spatulate setae in M. sublittoralis n. sp. versus two slender setae and one spatulate seta in M. santacruzensis ; posterior seta on the third podomere of the antenna has one slender seta in M. sublittoralis n. sp. versus one stout and one spoon-like setae in M. santacruzensis ; basal capsule of the male copulatory organ is spindle-shaped in M. sublittoralis n. sp. versus teardrop-shaped in M. santacruzensis . Microloxoconcha sublittoralis n. sp. is similar with M. toyoshioae n. sp. by the chae- totaxy of antennula and a three segmented spinneret seta. However, Microloxoconcha sublittoralis n. sp. and M. toyoshioae n. sp. can be distinguished by the carapace shape (elongate and bean-shaped versus round-subcrescent) and the appendage morphologies (the mandibula has a 4 segmented palp versus 3 segmented palp; the branchial plate bears 11 setae versus 16 setae).