Cyproidea liodactyla Hirayama 1978
Creators: name: Ariyama, Hiroyuki
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Amphipoda
Cyproideidae
Cyproidea
Cyproidea liodactyla

description: Cyproidea liodactyla Hirayama, 1978
[Japanese name: Hosozume-hoteiyokoebi] (Figs 2–6)
Cyproidea liodactyla Hirayama, 1978: 245, figs 1–3 (type locality: Tomioka Bay, Amakusa, Kumamoto Prefecture, Japan).— Hirayama, 1983: 124.— Barnard & Karaman, 1991: 259.— Ishimaru, 1994: 53.
Material examined. One male (OMNH-Ar-9940), 3.6 mm, off Jogashima Island, Miura City, Kanagawa Prefecture, 35°07'49"N, 139°33'57"E, 97.3–100 m in depth, sand and shell bottom, using dredge, 19 April 2012, coll. H. Kohtsuka; 1 female (OMNH-Ar-9941), 3.0 mm, Ariake Sea, 32°30'56"N, 130°16'58"E, 18 m in depth, sandy-muddy bottom, using dredge, 17 September 2005, coll. K. Mori; 1 male (OMNH-Ar-9942), 3.3 mm, Ariake Sea, 32°31'11"N, 130°20'02"E, 15 m in depth, sandy-muddy bottom, using Smith-McIntyre grab, 12 May 2006, coll. K. Mori; 1 female (OMNH-Ar-9943), 3.6 mm, Ariake Sea, 32°30'56"N, 130°16'58"E, 18 m in depth, sandymuddy bottom, using Smith-McIntyre grab, 17 September 2005, coll. K. Mori; 1 female and 2 juveniles (OMNH- Ar-9944–9946), 2.7, 2.0, 1.9 mm, Koganezaki-park beach, Nishi-izu Town, Shizuoka Prefecture, 34°50'37"N, 138°45'49"E, 10–12 m in depth, sandy bottom, using SCUBA, 17 July 2012, coll. M. Fujii; 3 males and 1 juvenile (OMNH-Ar-9947–9950), 2.5, 2.5, 2.4, 2.0 mm, off Moroiso Bay, Misaki City, Kanagawa Prefecture, 10 m in depth, sandy bottom, using dredge, 1 July 2014, coll. H. Kohtsuka. Paratypes 1–7 (not dissected), sex unknown, 3.0, 3.3, 3.8, 3.2, 2.2, 3.5, 3.5 mm, Tomioka Bay, Amakusa, Kumamoto Prefecture, 10 m in depth, sandy bottom, 15 July 1978.
Description. Male [based on 3.6 mm (OMNH-Ar-9940), and 3.3 mm (OMNH-Ar-9942) for lower lip and pleonal epimera]. Body (Fig. 2) oval; head shorter than pereonite 1, eyes large, diameter about 0.7 times as long as head; pereonites 1, 4 and 5 dorsally long, posteroventral corners of pereonites 5–7 protruded; coxa 5 far exceeding posteroventral corner of pereonite 6; pleonites 1–3 each with dorsolateral ridge extending to urosomite 1; urosome slender.
Antenna 1 (Fig. 3 A, A1) short, with ratio of lengths of peduncular articles 1–3 1:1.2:0.7, tooth of article 2 occupying 30% of whole length; accessory flagellum vestigial, with 4 setae; primary flagellum with 7 articles, articles 1–6 with 2, 2, 2, 2, 2, 1 aesthetascs at each distal end, respectively. Antenna 2 (Fig. 3 B) short, with ratio of lengths of peduncular articles 3–5 1:2.2:2.0; flagellum with 3 articles.
Upper lip (Fig. 3 C), ventrolateral margins with short setae. Mandible (Fig. 3 D, D1, E, E1), each incisor bearing 6 cusps, left lacinia mobilis fan-shaped, distal margin minutely serrated, right lacinia mobilis lacking, number of accessory blades 5 in left and 4 in right; molar conical; palp article length ratio 1:1.6: 1.4 in left and 1:1.4: 1.2 in right, article 2 with 2–3 short setae, tip of article 3 with 1 long seta, ventral surfaces of articles 2–3 covered with minute setae. Lower lip (Fig. 3 F), inner lobes indistinct; anteromedial corners of outer lobes each with 1 acute and 1 truncate projections, mandibular processes small. Maxilla 1 (Fig. 3 G, G1 – 2), inner plate roundish triangular, without setae; mediodistal corner of outer plate acutely projected, distal margin with 7 robust setae, medial margin bearing 3 robust setae; distal end of palp projected in middle, with 2 minutely-serrated robust setae and 4 robust setae. Maxilla 2 (Fig. 3 H), inner plate shorter than outer, terminal ends of both plates each with a few setae, dorsal surfaces of both plates setose. Maxilliped (Fig. 3 I, I1 – 2), inner plate truncate, mediodistal corner with 1 robust seta dorsally; outer plate with 2 distal and 2 ventral robust setae, mediodistal margin serrated; palp articles 1 – 2 with 1 and 4 setae, respectively, article 3 covered with short setae dorsally, with 1 robust seta on mediodistal corner, article 4 slender.
Gnathopod 1 (Fig. 4 A, A1), coxa quadrate; basis long, narrow; posterodistal corner of ischium not projected; merus short; carpus long, posterodistal corner slightly protruded, bearing several long setae, posteromedial surface covered with thin setae; propodus long, about 1.6 times as long as carpus, palm with many acute denticles, anteromedial surface covered with thin setae; dactylus very long, gradually curved, posteroproximal margin bearing 1 long and 6 short acute spines. Gnathopod 2 (Fig. 4 B, B1) stouter than gnathopod 1; coxa roundish quadrate; posterodistal corner of ischium projected, with several setae; merus short; posterodistal projection of carpus as long as carpus proper, bearing 4 medial setae, posteromedial surface covered with thin setae; distal half of propodus slightly swollen posteriorly, palm with many blunt denticles; dactylus strongly flexed at a point of one third, gradually narrower, posteroproximal margin bearing 8 acute denticles.
Pereopod 3 (Fig. 4 C), coxa triangular, anterior margin rounded, posterior margin slightly concave, posteroproximal corner with small projection, posteroventral corner with small medial hollow; basis and merus – propodus long. Pereopod 4 (Fig. 4 D), coxa extremely wide, swollen posteriorly, anterior margin slightly convex, with small projection on anteroventral corner, ventral margin also slightly convex, posteroproximal corner a little projected; basis and merus long. Pereopod 5 (Fig. 4 E), coxa lanceolate, width about 3.1 times of length, anterior margin with small hollow, posterior end pointed; basis and merus – propodus long. Pereopod 6 (Fig. 4 F) almost same length as pereopod 5; coxa roundish trapezoidal; basis and merus – propodus long. Pereopod 7 (Fig. 4 G), coxa roundish rectangular; basis and merus long.
Pleonal epimera (Fig. 5 A), epimera 1 – 2 projected bluntly on posteroventral corner, each with oblique lateral ridge, epimeron 3 rounded posteroventrally, all ventral margins bare. Pleopods (Fig. 5 B – D) almost same length; inner rami with 6 articles, outer rami with 8, 8, 7 articles in pleopods 1 – 3, respectively. Uropods (Fig. 5 E – G), peduncle and both rami without robust setae, but bearing minute denticles on edges of dorsal surfaces; peduncle of uropod 1 long, both rami about 0.7 times as long as peduncle; uropod 2 about 0.8 times length of uropod 1, both rami 93% as long as peduncle; uropod 3 short, 55% length of uropod 1, peduncle relatively short, inner ramus about 1.3 times as long as peduncle, outer ramus almost same length as peduncle. Telson (Fig. 5 G) ovoid, breadth about 0.6 times of length, without setae.
Female [3.6 mm (OMNH-Ar-9943)]. Generally similar to male except for antenna 1 and oostegites. Antenna 1, peduncular article 2 cuspidate, flagellum 6-articulated. Gnathopods 1–2 (Fig. 5 H–I) almost same as those in male except for oostegite on coxa 2, but carpi–dactyli shorter.
Paratypes-1–7 (sex unknown, 2.2 – 3.8 mm). Antenna 1 (Fig. 5 J), peduncular articles 2 in all paratypes cuspidate, flagellum in paratype-2 (3.3 mm) with 6 articles.
Coloration in fixed specimen (Fig. 6). Eyes red; dorsal surfaces from head to pereonite 5 dark brown, lateral surfaces of them translucent, lateral surfaces from pereonite 6 to pleonite 2 partly dark brown; proximal–middle part of coxa 3 dark brown, with several red pigments; proximal part of coxa 4 dark brown, middle–distal part translucent, with a few orange pigments; coxa 5 dark brown; from posterior part of urosomite 1 to peduncles of uropods also dark brown.
Remarks. Morphological characters of the examined specimens almost agree with the original description and figures of Cyproidea liodactyla, except for the shape of antenna 1. Although Hirayama (1978) stated on the antenna 1 “distal margin of peduncle 2 produced into two pointed and triangular processes” and “flagellum four segmented”, the examined specimens including the paratypes have a 1-pointed large acute projection similar to the other Cyproidea species, and a 6–7-articulated flagellum. However, the examined specimens can be identified as C. liodactyla because of the following reasons: (1) the morphological characters except for the antenna 1 are similar to the original description, (2) the shape of antenna 1 is the same in all the specimens including the paratypes, and (3) the distribution of brown pigments resembles well Hirayama’s Fig. 1. The antenna 1 in the holotype is considered to be abnormal caused by omission and regeneration.
Distribution (Fig. 1). Japan: Miura City in Kanagawa Prefecture, Nishi-izu Town in Shizuoka Prefecture, Ariake Sea (present study); Amakusa in Kumamoto Prefecture (Hirayama 1978).
Habitat. Sandy or sandy-muddy bottom, 10–100 m in depth. This species occurs together with Terepeltopes dolichorhunia in Nishi-izu Town.
description: Published as part of Ariyama, Hiroyuki, 2016, Five species of the family Cyproideidae (Crustacea: Amphipoda) from Japan, with the description of a new genus and two new species, pp. 301-331 in Zootaxa 4097 (3) on pages 303-309, DOI: 10.11646/zootaxa.4097.3.1, http://zenodo.org/record/263937