Loxoconcha bizenensis Okubo, 1980

Karanovic, Hyunsu Yoo and Ivana, 2019, Six species of the ostracod families Loxoconchidae and Cushmanideidae from South Korea, Journal of Species Research 8 (1), pp. 116-127 : 118

1. Loxoconcha bizenensis Okubo, 1980 ( Fig. 1 )

Synonymy

Loxoconcha bizenensis sp. nov. ­ Okubo (1980): p. 418, Figs. 14, 18e­j.

Material examined. One male dissected on slide ( NIBR IV0000813442), shell of on micropalaeontology slide ( NIBRIV 0000813442).

Locality in Korea. Jeollanam­do, Jindo­gun , littoral, 34° 24.678 ʹ N 126°19.415 ʹ E, 04/04/2012, coll. I. Karanovic.

Identifier. Ivana Karanovic.

Diagnosis. Small ostracod, less than 1 mm long ( Fig. 1A ). Dorsal margin sinusoid, with greatest height in front of middle. One small hump present anteriorly to caudal process. Posterior margin rounded but with one caudal process terminated at 2/3 of height. Anterior margin rounded. Ventral margin convex and steeply passing into posterior margin. Valves slightly asymmetrical. Surface irregularly reticulated with two ventral ridges. Except for clearly present bulge in eye region, one more smooth bulge posteriorly. Marginal zone with long, straight canals. Hinge of Loxoconcha type (gongylodont). Antennula slender 6­ segmented all setae thin ( Fig. 1B ). Antenna 4­segmented with two distal claws ( Fig. 1C ). Hemipenis robust ( Fig. 1D ) with broad triangular distal lobe and proximally with additional triangular process tucked closely to distal process.

Distribution. According to Okubo (1980), the species is common in the intertidal zones of rocky shores in the Inland Sea in Japan. This is the first report for Korea.

Remarks. There are a few differences between the original description and our record: the posterior smooth bulge on the shell seems not to be present in the Japanese populations. Contrary to the original description we only detected two (instead of three) ventral ridges on the shell. However, Okubo (1980) did not provide any SEM photographs, therefore the posterior bulge might have been overlooked. Our identification was primarily based on the similarity in hemipenis between Japanese and Korean populations. According to Tanaka and Ikeya (2002) L. bizenensis belongs to the ozawai species group.

Figures

Fig. 1. Loxoconcha bizenensis Okubo, 1980. Male. A, Left valve; B, Antennule and Antenna; C, Antenna (High maginification); D, Male copulatory organ.