Typhlotanais ohtsukae, Larsen, Kim & Shimomura, Michitaka, 2007

Larsen, Kim & Shimomura, Michitaka, 2007, Tanaidacea (Crustacea: Peracarida) from Japan. II. Tanaidomorpha from the East China Sea, the West Pacific Ocean and the Nansei Islands, Zootaxa 1464, pp. 1-43 : 24-28

Typhlotanais ohtsukae n. sp.

( Figs 11–13 )

Holotype, non-ovigerous female ( KMNH IvR 700.187), Station 12, 31°14.28’N, 131°32.68’E, 367– 254 m, shell sand, East of Cape Miyazaki, 29 May 2006. Paratypes, 1 non-ovigerous female ( KMNH IvR 700.188)(dissected), same locality; 1 ovigerous, 1 non-ovigerous females, 1 male, ( KMNH IvR 700.189– 700.190), same data.

Diagnosis. Female. Lateral shield prominent on posterior pereonites. Antennule article 3 without apical spiniform process. Chelipeds basis not reaching edge of pereonite 1, with a wide groove at the cheliped insertion. Chela shorter than carpus. Pereopod 4–6 unguis serrated but not bifurcate. Uropods longer than pleotelson; endopod and exopod biarticulated, exopod more than half as long as endopod.

Etymology. This species is named after Professor S. Ohtsuka, Hiroshima University, who collected this material during the yearly Toyoshio-maru cruises.

Description (body of holotype, appendages of dissected paratype).

FEMALE.

Body ( Fig. 11 A). Body length 1.6 mm Cylindrical, about 7 times as long as broad.

Cephalothorax. Longer than combined length of pereonites 1 and 2. Eye-lobes absent.

Pereonites. Pereonites 1, 2 and 6 wider than long. Pereonite 3 as wide as long. Pereonites 4–5 longer than wide. Pereonite 1 lateral shield not reaching beyond posterior margin of Cephalothorax. Lateral shield present on all pereonites and pleonites.

Pleon. Not wider than pereon, short (including pleotelson about 22% of total body length). All pleonites subequal, carrying pleopods. Pleotelson longer than combined length of two pleonites.

Antennule ( Fig. 11 B). Longer than cephalothorax. Article 1 longer than rest of antennule, with several simple and setulated setae. Article 2 less than 0.25 times as long as article 1, with three simple distal setae. Article 3 more than twice as long as article 2, with five simple setae and one aesthetasc.

Antenna ( Fig. 11 C). About 0.8 times as long as antennule. Article 1 broader than following articles, with one seta and small setules; article 2 longer than half of article 1, with two small setae. Article 3 longer than other articles, with three simple and two setulose distal setae. Article 4 twice as long as article 2, with one distal seta. Article 6 minute, with two distal setae and one aesthetasc.

Mouthparts. Labrum ( Fig. 11 D) with setulate apex. Mandibles ( Fig. 11 E-G) molar broad, with terminal ring of blunt denticles. Left mandible ( Fig. 11 G) lacinia mobilis longer than incisor, without denticles; incisor broad, with four outer denticles. Right mandible ( Fig. 11 E, F) incisor simple, with inner denticles. Labium ( Fig. 12 H) without outer processes, with pointed, setulated apex. Maxillule ( Fig. 11 I) endite with eight distal spiniform setae, palp shorter than endite, with two terminal setae. Maxilla ( Fig. 11 J) ovoid and featureless. Maxilliped ( Fig. 11 K) basis with one seta at palp insertion. Endites with inner processes and one seta, almost as wide as basis. Palp article 1 naked; article 2 with one outer and three inner setae; article 3 with three inner setae; article 4 with one outer and five inner setae; all inner palp setae setulose. Epignath ( Fig.11 L) shorter than maxillule endite.

Cheliped ( Fig. 12 A). Basis divided unequally by small sclerite attached to the proximal part of basis, shorter than carpus, with one dorsomedial seta. Merus with one ventral seta. Carpus as long as propodus including fixed finger and only slightly wider, with two ventral and two small dorsal setae. Propodus with one seta at dactylus insertion. Fixed finger with two ventral setae and three on inner margin, with one small denticle on inner margin. Dactylus as long as fixed finger.

Pereopod 1 ( Fig. 12 B). Coxa naked. Basis longer than three succeeding articles combined, with three small simple setae. Ischium with one seta. Merus as long as carpus, with one distal seta. Carpus three-quarters length of propodus, with four distal setae. Propodus longer than half of basis, with three subdistal setae. Dactylus and unguis shorter than propodus, not fused into a claw. Dactylus shorter than unguis.

Pereopod 2 ( Fig. 12 C). As pereopod 1 except: coxa with one seta. Merus with two distal setae. Carpus half as long as propodus, with two setae and one tubercle. Propodus with three distal setae.

Pereopod 3 ( Fig. 12 D). As pereopod 2 except: coxa naked; carpus with four distal setae; propodus with ventrodistal spiniform seta and serrated dorsal margin.

Pereopod 4 ( Fig. 12 E). Coxa not present. Basis twice as wide as on pereopods 1–3, naked. Ischium with two setae. Merus with one spiniform distal seta and many small spines. Carpus with one spiniform distal seta, clinging apparatus surrounded by small spines. Propodus with two ventrodistal spiniform setae, one dorsoproximal setulated seta, one dorsodistal robust seta and dorsal spine. Dactylus and unguis shorter than propodus and incompletely fused into an elongate claw. Unguis much shorter than dactylus.

Pereopod 5 ( Fig. 12 F). As pereopod 4.

Pereopod 6 ( Fig. 12 G). As pereopod 4 except: basis with one seta; propodus with three dorsodistal setae.

Pleopod ( Fig. 12 H). Basal article naked. Exopod with one outer and many inner plumose setae. Endopod with many inner plumose setae, small gap between proximal seta and other setae.

Uropods ( Fig. 12 I). Basal article more than half as long as exopod, naked. Endopod biarticulated, longer than pleotelson; with one or two simple and one pinnate medial setae, with four to five simple and one setulate distal setae. Exopod biarticulated, longer than half as long as endopod, first article with one small seta, distal article with one short simple and one long thick distal setae.

MALE ( Fig. 13 A)

Body. Laterally compressed, almost amphipod-like.

Pereonites. Reduced.

Pleonites. Enlarged.

Pleotelson. Narrow and tapering into a pointed apex.

Antennule. With seven articles; articles 3, 4 and 5 densely covered with aesthetascs (many more than illustrated).

Mouthparts. Without functional mouthparts.

Pereopods. Much slimmer and less armored than those of female.

Pleopods. Better developed than in female.

Remarks. This species shares a number of characters with Peraeospinosus adipatus ( Tzareva, 1982) , notably the microsetae on the antenna. Typhlotanais ohtsukae differ, however, in the biarticulated uropods, the pereopod 2 and 3 carpal process and in the presence of a small clinging apperatus on pereopods 4–6.

The status of P. adipatus is somewhat confused. When Sieg (1986a) erected the genus Peraeospinosus , he included P. adipatus . During her revision of the genus, BłaŻewicz-Paszkowycz (2006) removed P. adipatus from the genus but did not assign another position of this species.

Typhlotanais ohtsukae cannot be included into the Peraeospinosus as is currently diagnosed (BłaŻewicz- Paszkowycz 2006) because it does not display the row of minute setae on the dorsal margin of the cheliped carpus; the epignath is not sharply tipped or bifurcated; the distal seta on propodus of pereopods 4 and 5 is not longer than unguis; and the uropods are not uniarticulated. It is possible that an intermediate genus, consisting of T. ohtsukae and P. adipatus could possibly be justified, but because the typhlotanaids are currently undergoing revision, no such action is taken here.

The male corresponds to the male described by Sieg (1986a:95) for P. adipatus and is thus referred to T. ohtsukae as it was found in the same sample. However, as with all ‘swimming males’, only with a molecular analysis can conspecificity be confirmed ( Larsen 2001).

Figures

FIGURE 11. Typhlotanais ohtsukae n. sp. A, holotype, female, lateral view, scale bar = 0.5 mm. B, antennule; C, antenna; D, labrum; E, left mandible, incisor; F, same, molar; G, right mandible; H, labium; I, maxillule; J, maxilla; K, maxilliped; L, epignath. Scale bars 0.2 = mm.

FIGURE 12. Typhlotanais ohtsukae n. sp. A, cheliped; B, pereopod 1; C, pereopod 2; D, pereopod 3; E, pereopod 4; F, pereopod 5; G, pereopod 6; H, pleopod; I, Telson and uropods. Scale bars = 0.2 mm.

FIGURE 13. Typhlotanais ohtsukae n. sp. A, male, lateral view, scale bar = 0.5 mm.