Curidia japonica, Ariyama, 2024

Ariyama, Hiroyuki, 2024, Curidia japonica sp. nov., the First Species of the Family Ochlesidae from the Northwest Pacific (Crustacea: Amphipoda), Species Diversity 29 (2), pp. 199-207 : 200-205

publication ID	https://doi.org/ 10.12782/specdiv.29.199
publication LSID	lsid:zoobank.org:pub:6542F721-F151-4F8A-AA1D-AB52E1BD7869
persistent identifier	https://treatment.plazi.org/id/4C9AA2C7-B8B3-4B8E-8F73-CA568E16F8DE
taxon LSID	lsid:zoobank.org:act:4C9AA2C7-B8B3-4B8E-8F73-CA568E16F8DE
treatment provided by	Felipe
scientific name	Curidia japonica
status	sp. nov.

Treatment

Curidia japonica sp. nov.

[New Japanese name: Ōgi-yokoebi-modoki] ( Figs 1–6 View Fig View Fig View Fig View Fig View Fig View Fig )

Material examined. Holotype: female, 1.4mm (OMNH-

Ar-12915), southwestern coast of Kamishima Island, Toba City , Mie Prefecture, 34°32′41″N, 136°58′47″E, 2 m depth, among red algae Corallina pilulifera Postels and Ruprecht and Amphiroa beauvoisii J GoogleMaps . V. Lamouroux, 25 July 2014. Paratypes: male, 1.1 mm (OMNH-Ar-12916), same locality, 2 m depth, among a bryozoan Bugula neritina (Linnaeus, 1758) , same date; female, 1.5 mm (OMNH-Ar-12917, damaged), Oura in Hidaka , Wakayama Prefecture, 33°55.5′N, 135°04′E, 1.5 m depth, among a red alga Corallina aberrans (Yendo) K GoogleMaps . R. Hind and G. W. Saunders, 31 July 2016; male, 1.2 mm (OMNH-Ar-12918), same locality, 2 m depth, among a red alga Gelidium elegans Kützing , same date; male, 1.1 mm (OMNH-Ar-12919), same locality, 4.5 m depth, among a red alga G GoogleMaps . elegans, same date; male, 1.3 mm (OMNH-Ar-12920), Hikigawa in Shirahama , Wakayama Prefecture, 33°33′N, 135°27′E, 7 m depth, among a red alga G GoogleMaps . elegans, 2 August 2003; male, 1.0 mm (OMNH-Ar-12921), same locality, 3 m depth, among a red alga G GoogleMaps . elegans, same date.

Type locality. Kamishima Island , Toba City, Mie Prefecture, Japan .

Description. Based on holotype, female, 1.4 mm (OMNH-Ar-12915); paratype, male 1.2 mm (OMNH-Ar- 12918), for upper lip, maxilla 1 and maxilliped; and paratype, male, 1.3 mm (OMNH-Ar-12920) for mandibles.

Head ( Figs 1 View Fig , 2 View Fig ). Rostrum strongly projected ventrally. Eyes oval, partially covered with pereonite 1. Antenna 1 stout; length ratio of peduncular articles 1–3 (excluding processes) 1: 0.65:0.2, lengths of posterodistal processes on articles 1 and 2 ca. 0.4 and 0.6 times of article proper, respectively; flagellum with 3 articles, article 1 long, article 3 minute, posterodistal part of article 1 and distal ends of articles 2, 3 bearing many aesthetascs. Antenna 2 also stout, but shorter than antenna 1, with ratio of lengths of peduncular articles 3–5 1: 1.55: 1.7, posterodistal process of peduncular article 4 very short, 15% length of article 5; flagellum with 3 articles, article 1 long, article 3 minute, distal end of each article setose. Upper lip triangular, tip pointed. Mandibles slender, incisors and left lacinia mobilis without denticles; length ratio of palp articles 1–3 1: 1.3: 1.55, article 3 with numerous fine setae on lateral surface and 3 thick setae on tip. Lower lip, outer lobes with narrow mandibular process. Maxilla 1, inner plate narrowed distally, tip without setae; outer plate bearing 5 mostly-fused robust setae, tip pleated; palp minute, with a long seta. Maxilla 2, outer and inner plates with 10 and 6 distal setae, respectively. Maxilliped with narrow inner plate bearing apical short robust seta and several distal and many dorsodistal setae; outer plate broad, with 2 median and 6 subdistal setae; palp narrow, apical seta very long, ca. 1.7–1.8 times length of palp proper.

Pereon ( Figs 1 View Fig , 3 View Fig ). Dorsal margins smooth, pereonite 1 strongly projected anterodorsally; pereonite 7 posterodorsal margin not projected, posteroventral corner bluntly projected. Coxae of gnathopods and pereopods, and bases and ischia of pereopods 5–7 double-structured. Gnathopod 1 slender; coxa small, curved anteriorly, anteroproximal corner swollen, ventral margin rounded; basis proximal half widened; ischium ca. 0.65 times length of basis; carpus and propodus almost same length, posterodistal margin of propodus with minute projection and a feather seta and 3 slender setae; dactylus very short, with 3 feather setae and 2 slender and 1 robust setae. Gnathopod 2 shorter than gnathopod 1; coxa elongate, ca. 1.65 times (estimated) length of coxa 1, anteroproximal corner weakly swollen; basis wide, lateral surface bearing many minute setae; ischium short; carpus posterodistal corner produced, tip with 3 setae; propodus narrow, shorter than carpus, bearing several setae distally; dactylus triangular, ca. 0.2 times as long as propodus, tip with robust seta forming chela. Pereopod 3 far larg- er than gnathopod 2, coxa elongate, ca. 1.05 times (estimat- ed) length of coxa 2, anteroproximal corner swollen; basis wide, posterolateral surface bearing many minute setae; merus wide, projected anterodistally; carpus with 1 + 2 robust setae posteriorly; propodus ca. 1.35 times length of carpus, bearing 1 + 1 + 2 + 2 posterior robust setae; dactylus with unguis. Pereopod 4 slightly smaller than pereopod 3; coxa short, ca. 0.6 times (estimated) length of coxa 3, anteroproximal corner inflated anteriorly and anterodistal corner strongly swollen distally, posteroproximal corner weakly inflated; basis–dactylus almost same as those of pereopod 3, but carpus with 1 + 1 + 2 posterior robust setae. Pereopod 5 almost same length as pereopod 4; coxa short, anterodistal corner swollen anteriorly and posterodistal corner inflated distally; basis expanded posteriorly, with 2 rounded posteroproximal projections and large posterodistal lobe; merus wide, posterodistal corner projected; carpus with 1 + 2 robust setae anteriorly; propodus ca. 1.4 times length of carpus, bearing 1 + 1 + 2 + 2 anterior robust setae; dactylus with unguis. Pereopod 6 slightly longer than pereopod 5; coxa narrow and short, posterodistal corner swollen; basis expanded posteriorly, with 1 triangular and 1 rounded posteroproximal projections and large posterodistal lobe; ischium–dactylus almost same as those of pereopod 5, but carpus and propodus with 1 + 1 + 2 and 1 + 1 + 1 + 2 + 2 anterior robust setae, respectively. Pereopod 7 a little longer than pereopod 6; coxa narrow and short, posteroproximal corner swollen; basis expanded posteriorly, with angular posteroproximal projection and large posterodistal lobe; ischium– dactylus almost same as those of pereopod 6, but propodus bearing 1 + 2 + 1 + 1 + 2 anterior robust setae.

Pleon ( Figs 1 View Fig , 4 View Fig ). Dorsal margins with posterior hump in pleonites 1 and 2, and median hump in pleonite 3; posteroventral corners of pleonites 1 and 2 with acute and triangular projections, respectively, posteroventral corner of pleonite 3 without projection, posterolateral margins bearing rounded projection each on pleonites 1, 2 and upward pointed tooth on pleonite 3, respectively. Pleopods gradually shortened; peduncles each with 2 coupling hooks; outer rami longer than inner rami, outer and inner rami with 6 and 5 articles, respectively. Uropod 1 slender; peduncle with 5 lateral and 1 mediodistal robust setae; outer ramus ca. 0.75 times length of peduncle, bearing 4 lateral and 2 medial robust setae; inner ramus 1.25 times as long as outer ramus, with 2 lateral and 2 medial robust setae. Uropod 2 about 0.8 times (estimated) length of uropod 1; peduncle with 1 lateral and 3 medial robust setae; outer ramus ca. 0.85 times length of peduncle, bearing 2 lateral and 2 medial robust setae; inner ramus longer and wider than outer ramus, with 1 lateral and 1 medial robust setae. Uropod 3 about 0.8 times (estimated) length of uropod 2; peduncle without robust setae; outer ramus ca. 0.65 times as long as peduncle, lanceolate, bare; inner ramus ca. 1.7 times length as long as outer ramus, with 2 dorsal and 2 medial setae. Telson roundish triangular, tip acute (damaged).

Sexually dimorphic characters in males. Based on paratype, 1.3 mm (OMNH-Ar-12920), and paratype, 1.2 mm (OMNH-Ar-12918) only for antenna 2. Antenna 1 ( Fig. 4M View Fig 1 View Fig -RA1), length ratio of peduncular articles 1–3 (excluding processes) 1: 0.55: 0.2, lengths of posterodistal processes on articles 1 and 2 ca. 0.3 and 1.2 times of article proper, respectively, peduncular article 2 shorter and posterodistal process of article 2 longer than those of female; flagellum with 4 articles, article 1 long, article 4 minute, posterior surface of each article bearing numerous aesthetascs. Antenna 2 ( Fig. 4M View Fig 2-A2 View Fig ) more slender than that of female, with ratio of lengths of peduncular articles 3–5 1: 1.8: 2.1, posterodistal process of peduncular article 4 short, 25% length of article 5; flagellum with 4 articles, article 1 long, article 4 minute. Coxa 3 ( Fig. 4M View Fig 1-C View Fig 3 View Fig ) long, anteroproximal lobe smaller than that of female. Coxa 4 ( Fig. 4M View Fig 1-C View Fig 4 View Fig ) short, anteroproximal and anterodistal lobes smaller than those of female, posteroproximal lobe absent. Gnathopods ( Fig. 4M View Fig 1-G1 View Fig , G 2 View Fig ) almost same as those of female.

Shape changes in coxae. Based on paratype, female, 1.5 mm (OMNH-Ar-12917) ( Fig. 5 View Fig ). Shapes of coxae 2–6 changing probably with growth: coxa 2 posteroproximal corner projected; coxa 3 anteroproximal lobe larger, posteroproximal corner projected; coxa 4 anteroproximal lobe longer, posterodistal corner projected; coxa 5 anterodistal lobe longer, posteroproximal corner projected; coxa 6 anteroproximal corner weakly projected.

Coloration of recently fixed specimen. Based on paratype, male, 1.2 mm (OMNH-Ar-12918) ( Fig. 6 View Fig ). Head and pereonites white, light orange internal organs seen through, dorsal margins of pereonites each with dark-red mark; eyes red. Pleonites and urosomites white and partly pale orange, dorsal margins of pleonites 1–3 each with small dark-red mark. Antenna 1 peduncular articles 2, 3 and flagellar article 1 orange, other parts white. Antenna 2 peduncular article 5 and flagellar article 1 dark brown, other parts white. Mouthparts including mandibular palp white. Pereopods and uropods white and pale orange.

Remarks. Curidia japonica sp. nov. can be clearly distinguished from its congeners by the very short posterodistal process of the antenna 2 peduncular article 4. Length of the process in this new species is 15% and 25% length of article 5 in female and male, respectively, whereas in the other Curidia species, lengths of the process are ca. 0.45–0.95 times length of article 5 in females and ca. 0.45–1.1 times length of article 5 in males.

Habitat. 1.5–7 m depth, among red algae and bryozoans.

Distribution. Japan: Mie and Wakayama Prefectures.