Microloxoconcha toyoshioae, 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 : 219-223

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/5A740D78-FF24-FFA6-FC6C-2499FD673E8E
treatment provided by	Felipe
scientific name	Microloxoconcha toyoshioae
status	sp. nov.

Treatment

Subclass Podocopa Sars, 1866 View in CoL Order Podocopida Sars, 1866 Superfamily Cytheroidea Baird, 1850 Family Cytheromatidae Elofson, 1938 Genus Microloxoconcha Hartmann, 1954 Microloxoconcha toyoshioae n. sp. ( Figs 2–6 View Fig View Fig View Fig View Fig View Fig )

Type series. Holotype: adult male (NSMT-Cr 26685), RV length 0.30 mm, height 0.13 mm, LV length 0.30 mm, height 0.13 mm, soft parts mounted on a slide and valves preserved in a cardboard cell slide. The holotype specimen was collected from the bottom consisting of coarse granite sand off north of Hosonosu sand bank, Hiroshima Prefecture, Japan (34°22′29″N, 133°07′36″E) at depth 19–28 m, on 4 November 2014 GoogleMaps . Paratypes: adult male (NSMT-Cr 26686), RV length 0.28 mm, height 0.12 mm, LV length 0.29 mm, height 0.12 mm; adult male (NSMT-Cr 26687), RV length 0.30 mm, height 0.13 mm, LV length 0.30 mm, height 0.13 mm; and adult female (NSMT-Cr 26688), RV length 0.28 mm, height 0.12 mm, LV length 0.28 mm, height 0.12 mm . Same data as in holotype.

Diagnosis. Carapace round-subcrescent in lateral view. Marginal infold and vestibula broad in both anterior and posterior regions. Seventh limb much longer than fifth and sixth limbs. Upper ramus shape of male copulatory organ gently bending spoon-like with one protrusion on anteromiddle margin. In female, Sclerotized framework of paired genital openings elongated triangle shape.

Description of adult male. Carapace ( Figs 2A, B View Fig , 3 View Fig ). Carapace round-subcrescent in lateral view ( Figs 2A, B View Fig , 3 View Fig ). Surface smooth. Anterior and posterior margins rounded in lateral view ( Figs 2A, B View Fig , 3 View Fig ). Marginal infold and vestibula broad in both anterior and posterior regions ( Fig. 3 View Fig ). Adductor muscle scar pattern consisting of row of four closely spaced scars and two frontal scars ( Fig. 3 View Fig ). Hingement weak adont type.

Antennula ( Fig. 4A View Fig ). Consists of five slender articulated podomeres. First and second podomere bare. Third podomere with one antero-distal seta. Fourth podomere with one short antero-middle seta and two long antero-distal setae. Fifth podomere with one long slender seta and two spatulate setae (aesthetascs) at distal end.

Antenna ( Fig. 4B View Fig ). Four articulated podomeres. First podomere (basis) bare, with a long, thick, three-segmented exopodite (spinneret seta). Second (first endopodial) podomere with one medium seta on postero-distal end. Third (second endopodial) podomere with one medium posteromiddle 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. 4C View Fig ). Coxa with one short seta on anterior margin. Coxal endite consisting of seven teeth with two short setae. Palp consisting of four indistinct podomeres. First podomere of palp (Basis) with thick nib-like plate (exopodite) near postero-middle margin and short anterodistal seta. Second and third podomeres of palp fused. Second podomere of palp (first endopodite) with one posterodistal setulous seta and two antero-distal setulous setae. Third podomere of palp (second endopodite) with three long setae at antero-distal end. Fourth podomere of palp (third endopodite) slender, with three distal setae.

Maxillula ( Fig. 4D View Fig ). Thin branchial plate with 16 plumose setae. Basal podomere with one palp (endopodite) and three endites. Palp consisting of two distinct podomeres: first podomere with two distal setae; second podomere with three distal setae. Endite: dorsal one with four setae; middle one with five setae; ventral one with five setae.

Fifth limb ( Fig. 5A View Fig ). Four articulated podomeres. First podomere with one antero-distal seta, one setulous anteromiddle seta and setulous postero-middle seta. Second and third podomeres with rows of setulae on distal margin. Fourth podomere with rows of setulae on anterior surface and one distal claw.

Sixth limb ( Fig. 5B View Fig ). Four articulated podomeres. First podomere with one antero-distal seta, one setulous anteromiddle seta and postero-middle seta. Second podomere with one antero-distal seta and rows of setulae on distal margin. Third podomere with rows of setulae on distal margin. Fourth podomere with rows of setulae on anterior surface and one distal claw.

Seventh limb ( Fig. 5C View Fig ). Four thick articulated podomeres. First podomere with one stout antero-distal seta, one short antero-middle spine, and short seta on near postero-proximal 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 long distal claw.

Male brush-shaped organ ( Fig. 5D View Fig ). Consisting of two branches (right and left) each with 13 setae on distal margin.

Male copulatory organ ( Fig. 5E View Fig ). Consisting of semiquadrilateral basal capsule, with very thin and semi-triangular distal lobe; copulatory duct short, approximately one fourth as long as length of capsule; upper ramus gently bending spoon-like with one protrusion on antero-middle margin; and clasping apparatus thick, parallelogram with a concave on posterior margin.

Description of adult female. Carapace ( Fig. 2C, D View Fig ). Carapace round-subcrescent in lateral view ( Fig. 2C, D View Fig ). Surface smooth. Anterior and posterior margin rounded in lateral view ( Fig. 2C, D View Fig ).

Posterior part of body and female genitalia ( Fig. 6 View Fig ). Sclerotized framework of paired genital openings elongated triangle in 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. The species was named after TRV Toyoshiomaru, the ship deployed for the sample collection.

Remarks. The carapace shape and pattern of the anteri- or vestibule of Microloxoconcha toyoshioae n. sp. resembles those of M. dimorpha Higashi et al., 2011 . Microloxoconcha dimorpha has genetically indistinguishable two morphotypes in the male (Higashi et al. 2011). However, this new species can be easily distinguished from M. dimorpha by the shape of the upper ramus of the male copulatory organ: a gently bending spoon-like in M. toyoshioae n. sp. versus elliptical in M. dimorpha . In addition, the terminal claw of the seventh limb is different in length between M. toyoshioae n. sp. and M. dimorpha ; 1.5 and 2.5 times as long as fourth podomere, respectively.

Co-occurring species. Following ostracod species were found in the same sample: Cobanocythere sp. 1 , Microcythere sp. 1 , Parvocythere sp. , and Cobanocytheridae gen. et sp.