Heterosignum ohtsukai, Shimomura & Mawatari, 2002

Shimomura, M & Mawatari, SF, 2002, A revision of Heterosignum (Asellota, Isopoda, Paramunnidae) with descriptions of three new species, Journal of Natural History 36 (17), pp. 2103-2126 : 2113-2117

Heterosignum ohtsukai sp. nov.

(gures 7–9)

Material examined

TR/ V ‘ Toyoshio-maru ’, St. 11, oV Yaku Shima Island, Kagoshima Prefecture, Japan, 30° 12.00°N, 130° 30.80°E, 135 m, sledge net (mesh size 0.33 mm), 4 June 1996: holotype, one male, 1.4 mm (ZIHU-01916); other material, two males, 1.1 mm (ZIHU-01917), 1.2 mm (ZIHU-01918) .

Description

Male. Body (gure 7A, C) about 2.5 times as long as maximum width (except spine-like processes). Head as long as pereonite 1, with one stout mid-dorsal spine bearing two setae, with a pair of narrow long preorbital lobes; frontal margin of head convex, with two setae; labrum dorsally invisible; posterior margin of head convex. Eyestalks stout, arising from posterior part of head, reaching proximal onethird of peduncular article 2 of antenna 1. Pereonites 1–7 each with a mid-dorsal spine, and with a few dorsal and lateral setae. Pereonites 1, 2, 4, 5 and 7 each with a pair of moderately short single lateral spine-like processes; pereonites 3 and 6 with a pair of long single lateral spine-like processes. Pereonites 1–4 subequal in length; pereonite 5 about two-thirds as long as pereonite 4; pereonite 6 slightly longer than pereonite 5; pereonite 7 as long as pereonite 6. Pereonites 1–3 slightly increasing in width (except spine-like processes); pereonites 4–7 decreasing in width (except spine-like processes). Coxal plates dorsally invisible on all pereonites. Pleonite 1 small, with a pair of dorsal setae, without mid-dorsal spine. Pleotelson consisting of two parts, with scattered small dorsal setae, 1.5 times as long as wide; anterior part of pleotelson short, cylindrical, about one- fth length of posterior; posterior part of pleotelson bulbous, with 13 lateral teeth. Uropod (gure 7D) biramous, cylindrical; ventral ramus, 1.5 times as long as broad, apically with one simple and ve pappose setae, and two lateral simple setae; dorsal ramus one- fth length of ventral ramus, with two apical setae.

Antenna 1 (gure 8A) with three-articulate peduncle and three-articulate agellum. Peduncular article 1 half length of article 2, with three distal setae; article 2 longest, widest, with distolateral protrusion bearing single seta, and with two simple and four pappose setae distomesially; article 3 about one-third length of article 2, with one distomesial seta. Flagellum article 1 shortest, with one distolateral seta; article 2 longer than article 1, without setae; article 3 longer than article 2, distally with one long, two short setae and one aesthetasc.

Antenna 2 (gure 7E) with peduncle composed of six articles: article 1 not visible dorsally; article 2 widest, longer than broad, mesially curved slightly, with one lateral seta and some distomesial irregular short teeth; article 3 longer than article 2, with convex proximal protrusion bearing single seta, and with two distomesial setae; article 4 half length of article 3, with two mesial and one dorsal setae; article 5 three times as long as article 4, with six simple setae; article 6 longest, with 11 setae. Flagellum slightly shorter than peduncular article 6, composed of six articles, each with a few setae.

Left mandible (gure 8C) incisor with four cusps; lacinia mobilis with four teeth; spine row with four spines; molar process with two setae. Right mandible (gure 8D) lacking lacinia mobilis; incisor with ve cusps; spine row with three spines; molar process with single seta.

Maxilla 1 (gure 8E) with inner lobe bearing four apical setae; outer lobe with 12 apical setae. Maxilla 2 (gure 8F) with inner lobe bearing eight apical and two mesial setae; outer two lobes each with three apical setae.

Maxilliped (gure 8G) with narrow palp composed of ve articles; article 1 broader than long, with one mesial seta; article 2 trapezoidal, as wide as article 1, with two distomesial setae; article 3 longer than article 2, with three mesial and one distolateral setae; article 4 longest, with one distomesial seta; article 5 narrowest, with four apical setae; endite rectangular, bearing three pectinate setae distally and two coupling hooks mesially; epipod broad, subtriangular, reaching third article of palp, with rounded apex.

Pereopod 1 (gure 8H) shorter than pereopods 2–7: basis the longest article, 1.7 times as long as ischium, ventrally with two setae, dorsally with two setae and irregular short teeth; ischium with one ventral and one distal setae and one dorsal robust seta; merus trapezoidal, with two short and one robust seta dorsally, two ventrodistal setae; carpus ovate, ventrally with one robust, two robust sensory, and three simple setae, two short acute teeth, and one dorsodistal seta; propodus ovate, ventrally with two robust sensory and three simple setae and one short blunt tooth; dactylus narrowest, shorter than propodus, with four distal setae, one robust and short unguis, and one acute accessory claw.

Pereopods 2–7 (gure 8I, J) subequal in shape and length; bases longest, with one dorsal and two or three ventral setae; ischia slightly shorter and narrower than bases, with one or two dorsal, two ventral and one distal setae; meri trapezoidal, half as long as ischia, with one long and two short setae ventrally, one long seta dorsodistally; carpi as long as ischia, with three dorsal and one distal setae, and with three robust sensory and one or two simple setae ventrally; propodi slightly narrower than carpi, with three robust sensory and two simple setae ventrally, three simple setae dorsally; dactyli shortest, narrowest, distally with three simple setae, one robust unguis, and one minute accessory claw.

Pleopod 1 (gure 9A) 2.5 times as long as broad, with two pairs of ventrolateral setae and two pairs of apical setae, with a pair of short lateral projections, each projection bearing seven setae. Pleopod 2 (gure 9B) with broad protopod, lateral margin convex, with about 23 lateral setae; endopod surpassing apex of protopod, with slender, long, curved second article; exopod stout. Pleopod 3 (gure 9C) with endopod bearing three stout plumose setae distally; exopod composed of two articles, as long as endopod, narrower than endopod; article 2 with one terminal seta. Pleopod 4 (gure 9D) slightly narrower than endopod, tapering to pointed apex, without setae; endopod narrow. Pleopod 5 (gure 10E) narrow, uniramous, 5.3 times as long as broad.

Juvenile male. Similar to type specimen in morphology of all appendages except for antenna 1. Body (gure 7B) about 2.7 times as long as maximum width (except spine-like processes). Head with one stout mid-dorsal spine; pereonites 1–7 without mid-dorsal spines. Pleotelson with 17 lateral teeth. Peduncular article 2 of antenna 1 (gure 8B) without convex distolateral protrusion.