Indopinnixa kumejima Naruse & Maenosono 2012
Creators: name: Komai, Tomoyuki
name: Naruse, Tohru
name: Yokooka, Hiroyuki
name: Taru, Masanori
name: Shimetsugu, Miho
name: Watanabe, Tetsuya
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Pinnotheridae
Indopinnixa
Indopinnixa kumejima

description: Indopinnixa kumejima Naruse & Maenosono, 2012
(Figs. 9–16)
Indopinnixa kumejima Naruse & Maenosono, 2012: 223, figs. 1–3.— Naruse 2017: 2.— Palacios Theil & Felder 2020: 88, 90.
Type material. Holotype: RUMF-ZC-1397, male (2.7× 6.5 mm), off Shimajiri, Kume Island, Ryukyu Islands, Japan, 26°19.054´N, 126°48.702´E to 26°18.958´N, 126°48.724´E, 5.6–13.1 m, mud, KUMEJIMA 2009 Expedition, stn Dredge 69, 18 November 2009.
Other material examined. Amami-ohshima Island: RUMF-ZC-7321, 1 female (2.7× 5.6 mm), Shirahama, Setouchi, sand, SCUBA & yabby pump, 6 August 2015, coll. T. Naruse. Okinawa Islands: CBM-ZC 16587, 1 male (2.4 × 5.1 mm), Sumuide, Yagaji Island, Okinawa Islands, 26°40.50’N, 128°01.18’E, intertidal, sand, 11 February 2016, coll. H. Yokooka; RUMF-ZC-5958, 1 male (2.8×6.0 mm), Sashiki, Okinawa Island, 20 May 2019, coll. H. Nakajima. Kume Island (all by SCUBA & yabby pump): CBM-ZC 16588, Tatami-ishi, Oh-jima, 2 females (3.0 × 6.4 mm, 3.6× 7.8 mm, latter specimen DNA voucher), 14 November 2016, coll. T. Naruse; CBM-ZC 16589, 1 male (3.6× 8.1 mm), 1 female (3.9× 8.7 mm), same data. Iheya Island: RUMF-ZC-5957, 2 females (2.1×4.3, 2.2× 4.3 mm), SE Shimajiri Fishery Port, 3 July 2020, coll. H. Nakajima. Yaeyama Islands: RUMF-ZC-7322, 1 male (2.2× 4.7 mm), 1 female (4.0× 9.4 mm, DNA voucher), Midara, Iriomote Island, Yaeyama Islands, intertidal sand flat, associated with sipunculid worm, 17 May 2014, yabby pump, coll. T. Komai; RUMF-ZC 3666, 1 intersexual specimen (2.3× 4.9 mm), same locality, 15 August 2014, coll. T. Naruse; RUMF-ZC 3667, 1 male (2.9× 5.8 mm), Midara, Iriomote Island, 14 August 2014, coll. T. Naruse; RUMF-ZC-7323, 2 males (2.0×5.5, 2.7× 5.8 mm, latter specimen DNA voucher), Sotopanari Islet, Iriomote Island, 2 December 2014, coll. T. Naruse; RUMF-ZC 3668, 1 male (2.1× 4.2 mm), Amitori Bay, Iriomote Island, 20 August 2014, coll. T. Naruse; CBM-ZC 16590, 1 male (3.4× 8.2 mm), 2 females (3.6×8.0, 3.6× 8.1 mm; latter specimen DNA voucher), Tsukiga-hama Beach, 1–2 m, 24 January 2021, coll. H. Nakajima, T. Sato and R. Ueda; RUMF-ZC-5968, 2 males (3.3×6.7, 3.6× 7.5 mm), 5 ovigerous females (3.2×6.7–3.8× 8.2 mm), same data.
Ogasawara Islands. Haha-jima Island (all by SCUBA & yabby pump): RUMF-ZC 4733, 1 male (3.6× 7.6 mm), 1 ovigerous female (3.6× 7.4 mm), Iguma Bay, 21 February 2016, coll. T. Naruse; RUMF-ZC-7324, 1 male (3.4× 7.2 mm), Iwashi-ne, Iguma Bay, 26.6613N 142.1457E, 21 February 2016, coll. T. Naruse; CBM-ZC 16591, 1 male (3.4× 7.2 mm), 1 female (3.3×7.0 mm), Inarizushi-ne, Iguma Bay, 26.6655N, 142.1466E, 20 February 2016, coll. T. Naruse; RUMF-ZC-7325, 1 male (3.8× 8.5 mm), 1 female (3.9× 8.8 mm, DNA voucher), same locality, 21 February 2016, coll. T. Naruse. Chichi-jima Island: CBM-ZC 16592, 1 female (3.1× 6.8 mm; DNA voucher), Sakai-ura, 1 m, 14 December 2020, yabby pump, coll. H. Yokooka; CBM-ZC 16691, CBM-ZC 16691, 5 males (1.9×3.7–3.0× 6.6 mm), 2 females (2.5×5.1, 2.6× 5.3 mm), same data.
Redescription. Male. Body and appendages well-sclerotized.
Carapace (Figs. 9A; 10A) transversely ovate, 2.1–2.3 times wider than long; dorsal surface gently convex in general, sparsely punctate, with very short, pigmented setae on front and adjacent to anterior margin; regions poorly defined, only shallow, median gastrocardiac groove discernible; cardiac region transversely elevated, with low but clearly delimited transverse ridge falling far short of posterolateral margins. Front slightly bilobed, slightly more than 0.1 times carapace width; lateral angle bluntly angular. Supraorbital margin entire, slightly limbed laterally, confluent with suborbital margin; suborbital margin smooth, entire. Hepatic region slightly swollen. Anterolateral margin gently arcuate, defined by granular ridge not confluent with supraorbital margin, starting some distance from orbit, forming distinct projection at juncture with posterolateral margin; posterolateral margin smooth, slightly sinuous, distinctly converging towards almost straight posterior carapace margin. Subhepatic region with low oblique ridge obscured by numerous short, plumose setae; suborbital region narrow; pterygostomial regions smooth.
Ocular peduncle (Figs. 9A; 10A) filling orbit, stout, with scattered very short, darkly pigmented setae on dorsal surface; cornea narrower than ocular peduncle, darkly pigmented.
Antennule with basal articles sub-globular, separated by median septum; distal 2 articles folded transversely; article 3 slightly longer than article 2; upper and lower flagella both shorter than article 3. Antenna with subquadrate basal article in contact with orbit; flagellum short.
Epistome longitudinally very narrow, posteromedian margin protruded into buccal space as short ridge; anterior buccal flame gently convex on either side of median ridge, with distinct suture at base of antennal article 1.
Maxillipeds 3 with large propodi and dactyli (Fig. 10E), endopod and its setae filling most of buccal space. Ischiomerus completely fused to form subtriangular plate, external surface without median sulcus, but keeled along inner margin, outer margin obscured by numerous short to long plumose setae. Carpus shorter than ischium-merus fused article, outer surface with numerous short plumose setae. Propodus subovate, spatuliform, with scattered short plumose setae on external surface. Dactylus also spatuliform, articulated at middle portion of flexor margin of propodus, widest at distal 0.25 length, distal part wider than proximal, tip rounded. Inner margins of ischio-merus and carpus, inner to distal margins of propodus, and inner margin of dactylus with very long, thick setae for filter feeding. Exopod completely hidden by outer margin of ischio-merus, shorter than ischio-merus, tapering distally, outer margin with subtriangular lobiform structure at about midlength; flagellum much shorter than exopod.
Chelipeds (Figs. 9A, B; 12A) not enlarged; subequal and similar, outer and inner surfaces of merus and carpus concealed by numerous short plumose setae. Basis and ischium fused but suture visible, surfaces almost glabrous. Merus relatively short, almost surfaces obscured by plumose setae, without conspicuous armature; upper surface almost flat, with few granules, on proximal outer portion; inner margin convex, with row of granules; outer surface rounded; lower surface glabrous, with row of granules along outer side. Carpus short, cup-shaped, also without conspicuous armature; upper surface with few short setae. Chela 1.9–2.2 times as long as high, fairly compressed. Palm 1.3–1.4 times as long as high; upper margin delimited by row of granules, and with short, pigmented, stiff setae; outer surface with numerous short plumose setae and scattered granules dorsally and with median longitudinal row of granules accompanied by short setae; inner surface with sparse, very short setae on dorsal side and numerous short to long plumose setae adjacent to lower margin; lower margin not carinate; fingers with wide hiatus filled by plumose setae; fixed finger nearly straight, not deflexed, terminating in small curved tip, occlusal margin with 1 or 2 small subterminal teeth. Dactylus 0.8 times as long as palm, noticeably curved, leaving distinct hiatus when closed; upper margin smooth or with row of minute granules and numerous plumose setae, occlusal margin unarmed or armed with 1 small tooth at midlength.
Ambulatory legs moderately long, pereopod 4 largest, pereopod 5 smallest. Pereopod 2 (Figs. 9A, B; 12B) moderately slender. Basis-ischium fused article short, with few granules on posterior margin. Merus slightly recurved, slightly narrowed distally, subtriangular in cross section; anterior surface non-carinate, with row of plumose setae; posterior surface with row of setae on upper side, otherwise almost glabrous. Carpus with extensor margin sharply carinate, flexor margin rounded with row of plumose seta on upper side. Propodus almost glabrous, 1.5 times as long as wide; extensor margin sharply carinate, gently convex; flexor margin also sharply carinate, gently convex. Dactylus nearly straight, 1.4–1.5 times as long as propodus, tapering to small corneous tip, with 4 distinct longitudinal carinae (extensor and flexor margins sharply carinate, upper and lower surfaces also each with median carina); extensor margin with short sparse setae.
Pereopod 3 (Figs. 9A, B; 12C) moderately slender. Basis-ischium fused article short, with some granules on posterior face. Merus fairly compressed, anterior margin bluntly carinate, nearly straight, with row of short to long plumose setae over entire length and row of small granules at least on proximal half; posterior surface bicarinate distally, with row of plumose setae on over entire length and row of granules at least on proximal half of upper side; upper and lower surfaces glabrous. Carpus with extensor margin gently convex and sharply carinate; flexor surface rounded with row of short to long plumose setae. Propodus 1.8 times as long as wide, almost glabrous except for row of short setae on flexor margin; extensor margin gently convex, sharply carinate; flexor margin slightly convex, sharply carinate. Dactylus nearly straight, 1.4 times as long as propodus, tapering to small corneous tip, with 4 distinct longitudinal carinae (extensor and flexor margins sharply carinate, outer and inner surfaces also each with median carina); upper surface with row of short stiff setae on space between extensor and upper carinae.
Pereopod 4 (Figs. 9A, B; 12D, F) stout, large, compressed. Coxa enlarged, with prominent, glabrous lobe anterodorsally (Fig. 10F). Basis-ischium fused article with flat posterior surface, with few granules distally. Merus subovate, fairly compressed, 2.1–2.3 times longer than wide; anterior margin nearly straight in proximal two-thirds and distal one-third weakly sloping, carinate over entire length, with row of coarse granules and of plumose setae; upper surface with scattered coarse granules adjacent to anterior and posterior margins; lower surface smooth, glabrous; posterior surface concealed by dense plumose setae, flanked by carinae, upper carina delimited with single or double row of granules, becoming obsolete proximally, and with row of plumose setae; lower carina distinct over entire length, slightly sinuous, bordered with coarse granules. Carpus short, widened distally; extensor margin sharply carinate; upper surface with scattered short plumose setae; lower surface glabrous; flexor surface forming shallow concavity accommodating posterodistal angle of merus, defined on upper side by row of granules. Propodus tapering distally, 1.7 times as long as wide; extensor margin slightly convex, sharply carinate; upper surface with scattered short plumose setae; lower surface glabrous; flexor surface flanked by sharp, granulate carinae, with dense plumose setae. Dactylus almost straight, subequal in length to propodus, tapering to small corneous claw, with 5 longitudinal carinae and sparse short setae; flexor surface narrow, with 2 longitudinal rows of short setae.
Pereopod 5 (Figs. 9A, B; 12G) short, compressed, falling far short of distal margin of merus of pereopod 4 when extended, with numerous long plumose setae on margins. Coxa with prominent knob-like protuberance on dorsodistal margin (Fig. 10F). Basis-ischium fused article with few granules on posterior surface. Merus anterior margin bluntly carinate; upper and lower surfaces almost glabrous; posterior surface flanked by sharp, granulate carinae, with numerous plumose setae. Carpus extensor margin non-carinate; upper and lower surfaces almost glabrous. Propodus subquadrate, 1.3 times as long as wide, extensor margin not carinate; upper and lower surfaces almost glabrous; posterior surface thickly setose. Dactylus subequal in length to propodus, subconical, with 2 rows of short stiff setae on extensor margin.
Thoracic sternum (Fig. 9B) wide, polished, edges of sternites abutting sutures granular or smooth. Sternites 1 and 2 incompletely fused, deeply sunken into buccal cavity together with anteromedian part of sternite 3, obscured by thick setae; only lateral parts of sternite 3 clearly visible. Sternite 3 and 4 (Fig. 10B) clearly separated by distinct, granulate ridge; distal part of gonopod 1 fitted into oblique lateral part of sternite 3. Sternite 4 with granules anteriorly; each anterolateral margin produced into rounded lobe, separated by anterolateral angle of sternite 3 by deep notch. Sternites 5–7 almost smooth, sternite 7 longitudinally widest. Sternite 8 (Fig. 10D) wide, fully exposed, widened toward lateral margin, nearly perpendicular against horizontal plane of carapace, but partially visible in dorsal view, with transverse rows of setae, not extending to lateral margin, on midline and on morphologically anterior margin along suture, extending over entire width. Sterno-pleonal cavity deep, reaching to base of buccal cavity, marked by distinct ridges where sternites fit against lateral margins of closed pleon; margins of sterno-pleonal cavity along sternites 4–6 smooth, not granular; margin on sternite 6 (and occasionally margin on sternite 5) posteriorly raised to form distinct tubercles that grip closed pleon (Fig. 10C); press-button pleonal locking mechanism reduced into tiny tubercle inside of sterno-pleonal cavity of sternite 5, located near suture between sternites 4/5. Penis sternal.
Pleon (Fig. 10G) narrow, constricted, outer surface polished. Somites 1 and 2 transversely wide and very short, somite 1 with transverse row of short setae on midline. Somite 3 widest, trapezoidal, lateral margins rounded proximally. Somites 4–6 functionally fused, immobile although sutures clearly visible; somite 4 trapezoidal, lateral margins with shallow concavity corresponding to ledge-like structure on thoracic sternite 6; somite 5 subquadrate, lateral margins sinuous, concavities corresponding to ledge-like structure on thoracic sternite 5; somite 6 widened distally, with lateral margins concave; gonopodal plate absent. Telson covering posterior part of buccal cavity, almost as wide as pleomere 3, about 2 times as wide as long; lateral margin strongly convex, distal margin bilobed with shallow median notch.
Male gonopod 1 (Fig. 10H, I; 11A, B) relatively long, somewhat compressed, reaching posterior end of buccal cavity, gently curved outward, outer and inner margins with row of numerous long, plumose setae; distal process delimited by slight constriction at base, strongly compressed, faintly recurved, terminal margin blunt, with patch of dense very short stiff setae on distal half of dorsal surface; shoulder at base of distal process with tuft of numerous long setae reaching to terminus of distal process. Male gonopod 2 similar to that of I. haematosticta, very short, gently curved, with slightly inflated, spatuliform tip, less than 0.2 length of gonopod 1; base strongly inflated.
Female. Carapace (Fig. 13A) generally similar to that of males, but anterolateral margins slightly more sloping.
Chela (Fig. 13A, B; 14B) proportionally smaller than in males. Palm 1.6 times as long as high; upper margin with row of granules; outer surface with scattered granules superior to median line of setae; occlusal margin of fixed finger with row of 3–5 small blunt teeth. Dactylus 0.7–0.8 times as long as palm, curved distally, terminating in acute tip; upper margin gently arcuate, with row of granules; occlusal margin with 1 small but conspicuous tooth at about mid-length, and with row of minute teeth distal to median tooth.
Pereopods 2–5 relatively shorter than in males (Fig. 13A, B versus Fig 9A, B; Fig. 15A versus 15B). Pereopod 2 propodus 1.3–1.5 times as long as wide. Pereopod 3 propodus 1.5–1.8 times as long as wide. Pereopod 4 merus 2.1–2.3 times longer than wide.
Female thoracic sternum (Fig. 13B) with most surfaces smooth or only slightly punctate, sometimes with sparse setae partially; lateral parts of sternites 4–8 exposed, not concealed by closed pleon (but setae on lateral margins of pleon covering lateral parts of sternite). Sternites 3 and 4 completely fused; widely concave anterior margin fringed with dense setae. Gonopore tubercle (vulva) small, low, generally rounded, extending anteriorly across half-length of sternite 6, reaching or falling slightly short of midlength of sternite 5; gonopore rounded (Fig. 14A).
Pleon (Figs. 13B; 14C) relatively narrow (lateral parts of thoracic sternum exposed), subcircular, somite 4 widest; in ovigerous females, lateral margins fringed with thick setae covering lateral parts of thoracic sternum. Telson (Fig. 14C) 3.3 times as wide as long, reaching to bases of maxilliped 3, distal margin straight or slightly concave.
Colouration in life. Carapace and pereopods generally yellowish brown or gray on dorsal side; carapace occasionally mottled; pereopods paler than carapace; sternum and pleon whitish, with scattered gray or brown chromatophores; lower surfaces of pereopods similarly coloured to sternites and pleon (Fig. 15A, B).
Size. Males 2.4 × 5.1–3.6 × 8.1 mm; ovigerous females 3.2 × 6.7–3.8 × 8.2 mm, largest female (non-ovigerous) 3.9 × 8.8 mm.
Distribution. Known from the Ryukyu Islands and Ogasawara Islands; intertidal to 13.1 m.
Habitat. Most specimens examined were extracted from soft sediments with yabby pump operation. The two specimens from Midara, Iriomote Island (RUMF-ZC-7322), were collected from a burrow inhabited by a large sipunculid worm.
Remarks. As noted above, Indopinnixa kumejima is morphologically very similar to I. haematosticta. Initially, it was considered that the structure of the male gonopod 1 was substantially different between the two taxa, but reexamination of the holotype of I. kumejima has clarified that the figure in the original description (Naruse & Maenosono 2021: fig. 3b, c) was not very accurate. The gonopod 1 of the holotype is re-figured herein (Fig. 11A, B), and it is in fact very similar to that of I. haematosticta (Fig. 5G, H).
In order to test if more than one species are mixed up in the present series of specimens, nine 16S sequences (520–534 bp) were newly obtained from four specimens from the Ryukyu Islands, two specimens from the Ogasawara Islands, and three specimens from the Japanese mainland. The topology of ML and NJ trees (Fig. 16) reveals that specimens from the Japanese mainland and those from the Ryukyu and Ogasawara Islands form reciprocal clades with 1.4–2.2% sequence divergence with relatively high bootstrap support (94/98% for the Japanese mainland clade, 69/88% for the Ryukyu and Ogasawara Islands clade (ML /NJ bootstrap value)). Genetic divergence within the Japanese mainland clade is 0.6–0.8%, whereas that within the Ryukyu-Ogasawara clade is 0–0.8%. Therefore, we conclude that the two clades represent two species: the clade consisting of specimens from the Japanese mainland corresponds to I. haematosticta (type locality: Shimoda, Shizuoka Prefecture); and the clade consisting of specimens from the Ryukyu Islands and Ogasawara Islands corresponds to I. kumejima (type locality: Kume Island, Ryukyu Islands). Specimens from the Ogasawara Islands also form a subclade with high bootstrap support, but nested among specimens from the Ryukyu Islands. For the time being, we refer specimens from the Ogasawara Islands to I. kumejima.
Examination of specimens following the phylogenetic results has also revealed minor morphological differences between I. haematosticta and I. kumejima. The most notable difference is seen in the shape of the merus of the pereopod 4. The merus of the pereopod 4 is proportionally more slender with a less convex anterior margin in I. kumejima than in I. haematosticta (2.1–2.3 times as long as wide versus 1.7–1.9 times as long) (Fig. 12E versus Figs. 4E, 7G). The propodi of the pereopods 2 and 3 tend to be proportionally wider in I. haematosticta than in I. kumejima, particularly in the case when large specimens are compared, but significance of this character is less useful as there is some overlap of characters in small specimens. The female vulva seems to be more anteriorly produced in I. haematosticta than in I. kumejima (cf. Fig. 7A versus Fig. 14A).
One specimen (RUMF-ZC 3666; 2.3× 4.9 mm) is intersexual, being similar to those androgynous specimens of I. haematosticta n. comb. (see above). We consider this specimen of I. kumejima represents an abnormal condition, as well as the example of I. haematosticta.
description: Published as part of Komai, Tomoyuki, Naruse, Tohru, Yokooka, Hiroyuki, Taru, Masanori, Shimetsugu, Miho & Watanabe, Tetsuya, 2022, Redescription of Pinnixa haematosticta Sakai, 1934, its transfer to Indopinnixa Manning & Morton, 1987, and a reappraisal of Indopinnixa kumejima Naruse & Maenosono, 2012 (Decapoda: Brachyura: Pinnotheridae), pp. 361-389 in Zootaxa 5100 (3) on pages 376-384, DOI: 10.11646/zootaxa.5100.3.3, http://zenodo.org/record/6201604