Longipedis fragilis, Larsen, Kim & Shimomura, Michitaka, 2006

Larsen, Kim & Shimomura, Michitaka, 2006, Tanaidacea (Crustacea: Peracarida) from Japan. I. Apseudomorpha from the East China Sea, Seto Inland Sea, and Nansei Islands, Zootaxa 1341, pp. 29-48 : 41-46

Longipedis fragilis n. sp.

( Figs 5–6 )

Material examined

Holotype female (KMNH­IvR­700,131) Station 9, 26 °49.50’N, 127°42.00’E, West of Okinawa, East China Sea, 202– 199 m. Beam Trawl, 22 May­2003. Paratype, 1 female (KMNH­IvR­700,132) same locality as holotype (dissected).

Diagnosis

Monotypic genus, no diagnosis given.

Etymology

This species is named after the incredibly fragile nature of this species whose appendages detach seemingly merely by contact with photons. (Latin: Fragilis = fragile).

Description (body from holotype, appendages from dissected paratype)

FEMALE. Body length 2.95 mm).

Body ( Fig. 5 A). About five times as long as as wide.

Cephalothorax. Longer (including rostrum) than pereonites 1–3 combined. Eyes present with 2–3 ommatida but without visual pigmentation. Anterior margin smooth. Ventrally with large curved hyposphenium. Epistome three quarters as long as rostrum. Pereonites. Pereonite 5 as long as wide. Other pereonites wider than long, without anterolateral spines or lateral shoulders. Pereonites with sparse setation. Pereonites 1–3 with medium hyposphenium, other pereonites without hyposphenia.

Pleon. About 0.25 times total body length. Pleonites all wider than long, with blunt epimera bearing only few dorsal setae. All pleonites with pleopods but without ventral keel. Pleotelson as long as all pleonites combined.

Antennule ( Fig. 5 C). Twice as long as carapace. Peduncle article 1 broken but without spines; article 2 less than twice as long as article 3, with several simple setae, without spines; article 3 less than twice as long as common article, with several simple setae. Common article naked. Inner flagellum longer than first peduncle article, about seven articles. Outer flagellum only marginally longer than outer flagellum and of about ten articles, article 6 and 8 with multiarticulated aesthetascs.

Antenna ( Fig. 5 D, 5d1). With about 13 articles. As long as antennular rami. Article 1 and 3 with bifurcate apophyses, article 2 with simple apophysis. Squama attached distally on article 2, reaching beyond end of article 4, with seven distal simple setae. Articles 4–10 serially repeating with simple and plumose setae.

Mouthparts. Labrum ( Fig. 5 E) articulated from clypeus, distal margin finely setose. Mandibles, molar process strongly denticulate with two protruding spines, straight. Palp short (less than half of mandibular body), with three articles; article 1 with one prominent seta; article 2 with four simple distal setae; article 3 with mediodistal row of setae. Left mandible ( Fig. 5 F) incisor multidenticulated; lacinia mobilis smaller and multidenticulated; setal row of four bi­ or multifurcate setae arising from common peduncle. Right mandible ( Fig. 5 G) setal row of five bi­ or multifurcate setae arising from common peduncle; incisor with five denticles. Labium ( Fig. 5 H) palp with numerous setules and simple terminal setae. Lobes with lateral spines and few setules. Maxillule ( Fig. 5 I) palp with two articles, distal article with three setae. Outer endite with nine spiniform distal setae and scattered setae/setules; inner endite with five setulose distal setae. Maxilla ( Fig. 5 J) outer lobe of movable endite with four setae and lateral spines. Inner lobe of movable endite with six simple setae. Outer lobe of fixed endite with five multifurcate spiniform setae. Inner lobe of fixed endite with row of numerous distally curved setae. Maxilliped ( Fig. 5 K) basis without spines. Endite with three complex setae and three simple spiniform setae on distal margin: inner margin with two coupling hooks, and row of eight setulated setae. Palp article 1 without spine on inner margin; article 2–4 with row of simple setae; Epignath ( Fig. 5 L) body naked, terminal seta short and circumplumose.

Cheliped ( Fig. 6 G). Basis shorter than carpus with only one ventrodistal seta but with one prominent ventromedial spine. Merus half as long as carpus, with ventrodistal setae, without ventrodistal spines. Carpus slender (approximately six times as long as broad) with few setae and without ventral spines. Propodus with outer transverse row of setae leading to dactylus insertion. Fixed finger with row of setae on ventral margin and on cutting surface. Dactylus as long as fixed finger, with two subdistal setae. Exopod distal article with four plumose setae.

Pereopod 1 ( Fig. 6 A). Only marginally longer and wider than pereopods 2 and 3. Coxa ( Fig 5 B) with small blunt apophysis with two terminal setae. Basis about 3.1 times as long as wide and as long as ischium, merus and carpus combined, with one ventrodistal spiniform seta, scattered simple setae, and dorsoproximal plumose setae. Ischium with two ventral setae. Merus longer than carpus, with scattered simple setae on both margins and one spiniform ventrodistal seta. Carpus as long as propodus, with one dorsal and two ventral spiniform setae and several simple setae. Propodus marginally shorter than dactylus/unguis, with row of five ventral and two dorsal spiniform setae, scattered simple setae and one setulose seta. Dactylus 0.8 times as long as propodus, with serrations and dorsal seta. Unguis one third the length of dactylus. The spiniform setae of this appendage are much more robust than on the following pereopods. Exopod with four plumose setae (not illustrated).

Pereopod 2 ( Fig. 6 B). As pereopod 1 except: Coxa with one seta. Ischium with simple ventral setae. Merus shorter than carpus, with two ventral spiniform setae and few simple setae. Carpus with shorter than propodus, with several simple and four ventral and two dorsal spiniform setae. Propodus with three spiniform setae and more simple setae than pereopod 1, and one dorsal setulated seta. Dactylus without serration or setae. Dactylus and unguis combined shorter than propodus.

Pereopod 3 ( Fig. 6 C). As pereopod 2 except: basis without setulated setae. Carpus spiniform setae shorter and narrower than on pereopod 2. Dactylus with one ventral seta at unguis insertion.

Pereopod 4 ( Fig. 6 D). Basis longer than and twice as wide as on pereopods 1–3, with few distal setae. Ischium with ventral setae. Merus shorter than carpus, with one spiniform seta and only few simple setae. Carpus longer than propodus, with many simple and spiniform ventral setae. Propodus with multiple ventral setae and one dorsal setulated seta, with long saber­like setae dorsally. Dactylus and unguis slightly reduced, combined shorter than propodus.

Pereopod 5 ( Fig. 6 E). As pereopod 4 except: basis with three setulated setae proximal. Dactylus not reduced, with one small ventral and dorsal setae.

Pereopod 6 ( Fig. 6 F). As pereopod 4 except: basis with several plumose setae on dorsal margin. Merus with one long plumose seta and scattered simple setae. Carpus with two plumose setae on dorsal margin and seven spiniform setae. Propodus with dorsal setulated setae, transverse row of identically repeating stout setae and two ventral spiniform setae. Dactylus with one dorsal seta.

Pleopods ( Fig. 6 H). Basal article biarticulated, with four plumose setae. Exopod uniarticulated, with eight plumose setae. Endopod longer than exopod, with nine plumose setae.

Uropod ( Fig. 5 A). Basal article three times as long as wide, several setae along outer margin. Endopod broken on both specimens. Exopod longer than pleotelson, of about ten articles, each with zero–two simple setae.

Remarks

The antenna peduncle spination is very unusual. A somewhat similar spination is found in the metapseudid genus Calozodion Gardiner, 1973 (particularly C. multispinosum Gutu, 1984 ) and the parapseudid genus Biroplastoma Gutu & Angsupanich, 2004, but L. fragilis clearly does not belong to those genera owing to cheliped and mandible morphology respectively. Also some species of the apseudid genus Bunakenia Gutu, 1995 b displays spination on the antenna, but the pereopod 1 is much larger in Bunakenia .

Figures

FIGURE 5. Longipedis fragilis n. sp. A, holotype, male, dorsal view, scale bar = 0.1 mm. B, same, lateral view; C, antennule; D, antenna; d 1 antenna peduncle; E, labrum; F, left mandible; G, right mandible; H, labium; I, maxillule; J, maxilla; K, maxilliped; L, epignath. Scale bars antennae = 0.2 mm, scale bars mouthparts = 0.4 mm.

FIGURE 6. Longipedis fragilis n. sp. A, pereopod 1; B, pereopod 2; C, pereopod 3; D, pereopod 4; E, pereopod 5; F, pereopod 6; G, cheliped; H, pleopod. Scale bar = 0.2 mm.