Pseudosphyrapus quintolongus, Kakui, Keiichi, Kajihara, Hiroshi & Mawatari, Shunsuke F., 2007

Kakui, Keiichi, Kajihara, Hiroshi & Mawatari, Shunsuke F., 2007, Two new sphyrapodid species (Crustacea: Tanaidacea: Apseudomorpha) from southwestern Japan, Zootaxa 1563, pp. 37-54 : 43-53

Pseudosphyrapus quintolongus n. sp.

( Figs 4–9 )

Material examined. Holotype, adult male (ZIHU-3253), 26°33.50’N, 127°44.98’E, west of Okinawa Island, East China Sea, 386 m depth, beam trawl, 22 May 2005. Paratype, ovigerous female (ZIHU-3254), 31°27.04’N, 131°40.12’E, east of Toi Cape, Pacific Ocean, 521 m depth, beam trawl, 19 May 2005; with three mancas in the marsupium (ZIHU-3255 and -3256; one destroyed during dissection).

Diagnosis. Pleonites with laterally pointed epimera, unusually large on pereonite 5.

Etymology. The specific epithet, an adjective referring to the long lateral process on pleonite 5, is a composite word derived from the Latin adjectives quintus (fifth) and longus (long).

Description of male. Body ( Fig. 4 A, 4a1). Dorsoventrally flattened, gradually narrowing posteriorly, 3.20 mm in length, about 5 times as long as carapace width.

Cephalothorax. About 0.23 times total body length. Eyes well developed, without any ommatidia or visual pigmentation. Rostrum pointed, almost triangular in shape.

Pereonites. Wider than long; pereonite 1 rectangular, wider than carapace and other pereonites, intimately joined with carapace; succeeding five free pereonites trapezoidal in shape, wider posteriorly.

Pleon. About 0.25 times total body length, with five pleonites and pleotelson. Pleonites all wider than long, with acute lateral process, pleopod, and ventral keel; lateral process on pleonite 5 much larger than others. Pleotelson as long as wide, and shorter than two pleonites combined; with two simple setae at tip.

Antennule ( Fig. 5 A, 5a1). 1.12 times as long as carapace. Article 1 thick, almost as long as remaining articles and outer flagellum combined, with four outer and three inner simple setae, and five outer broom setae; article 2 one-third length of article 1, with two outer and two inner simple setae, and three outer broom setae; article 3 one-third length of article 2, with three simple setae; article 4 (common article) with one seta, and one simple seta at insertion of inner flagellum. Outer flagellum five-articulate; article 1 and 2 wider than long, with a tuft of aesthetascs; article 3 half as wide as article 2, longer than wide, with one distal aesthetasc; article 4 much longer than wide, with one simple seta and one distal aesthetasc; article 5 with four simple setae and one broom seta at tip, and one medial simple seta. Inner flagellum biarticulate; article 1 with two simple setae; article 2 with three simple setae and one broom seta at tip.

Antenna ( Fig. 5 B). Narrow and shorter than antennule. Article 1 distally widens; articles 2 and 3 naked; article 4 longest, with two simple setae and nine broom setae; articles 5 and 6 naked; articles 7 and 8 with two simple setae; article 9 with one short and three long simple setae.

Mouthparts. Labrum ( Fig. 5 E) unipartite and naked. Mandibles ( Fig. 5 F–I). Molar process well developed, without any denticles or setae. Left mandible ( Fig. 5 F) incisor with two distal denticles; setiferous lobe digitate in shape; lacinia mobilis well developed, triangular in shape. Right mandible ( Fig. 5 G) incisor with two distal denticles; setiferous lobe digitate in shape; lacinia mobilis absent. Palp ( Fig. 5 I) three-articulate; article 1 naked; article 2 with one outer seta; article 3 with three pinnate setae. Labium lost during dissection. Maxillule ( Fig. 5 J). Palp biarticulate, with one subdistal seta and one terminal hook-tipped seta. Outer endite with 11 distal spiniform setae and two subdistal setulated setae. Inner endite with four distal setae. Maxilla ( Fig. 5 K). Outer lobe of movable endite with five setae (three of them pinnate, the others with the ends missing); with several minute spines on outer subdistal margin. Inner lobe of movable endite with eight simple setae. Outer lobe of fixed endite with eight simple setae. Inner lobe of fixed endite reduced, with one simple seta. Maxilliped ( Fig. 5 L, 5l1). Coxa well developed, naked. Basis naked. Endite with three simple setae, four basally setulated spiniform setae, and two spiniform setae on distal margin; one setulated seta and three coupling hooks on inner margin. Palp article 1 with one outer and one inner (very long) simple setae; article 2 with one outer and eight (seven medium-length and one long) inner simple setae; article 3 with seven inner simple setae; article 4 with seven distal simple setae. Epignath ( Fig. 5 M). Body setulated; terminal seta setulated on distal half.

Cheliped ( Fig. 6 A). Basis slightly smaller than carpus, 1.5 times as long as wide, with one distal simple seta. Merus narrow, as long as basis, with one ventromedial simple seta and one distal triangular process. Carpus with one ventral triangular process that bears two ventromedial simple setae; also with one ventro-subdistal and one dorsodistal simple setae. Propodus large, longer than basis or carpus, with two simple setae at dactylus insertion; fixed finger with three simple setae on ventral margin, and three simple, several short spiniform setae and blunt spines on cutting surface. Dactylus slightly longer than fixed finger, with three subterminal inner simple setae; several short spiniform setae and blunt spines on cutting surface. Exopod threearticulate; distal article with four plumose setae.

Pereopod 1 ( Fig. 6 B). About 2.4 mm long, far longer than other pereopods. Coxa present. Basis shorter than combined length of merus and carpus, with several short setae. Ischium much wider than long, with one ventrodistal simple seta. Merus 1.5 times as long as carpus, with several dorsal and ventral simple setae, and one ventrodistal spiniform seta. Carpus longer than propodus, with five dorsal and three (one short and two long) ventral simple setae, and one dorsodistal and two ventral spiniform setae. Propodus slightly shorter than dactylus, with three dorsal and one ventral simple setae, and two dorsodistal and three ventral spiniform setae. Dactylus ventrally serrate; unguis less than one-fourth length of dactylus. Exopod three-articulate; distal article with four plumose setae.

Pereopod 2 ( Fig. 6 C). Less than two-thirds length of pereopod 1. Coxa with one simple seta. Basis long and thin, with two short setae and two broom setae. Ischium wider than long, with one ventrodistal seta. Merus slightly shorter than carpus, with four simple setae. Carpus a little longer than propodus, with five (one short and four long) dorsal, four ventral, and one distal simple setae, and one ventral spiniform seta. Propodus with three dorsal and one ventral simple setae, and three ventral spiniform setae. Dactylus slender, longer than propodus, with two ventromedial setae; unguis one-third length of dactylus.

Pereopod 3 ( Fig. 6 D). Shorter than pereopod 2. Otherwise like pereopod 2, except basis with one simple seta and three broom setae, and merus much shorter than carpus; merus with three simple setae; propodus with two dorsal and one ventral simple setae, one dorsal broom seta, and three ventral spiniform setae; dactylus with one ventromedial simple seta; unguis one-third length of dactylus.

Pereopod 4 ( Fig. 6 E). Shorter than pereopod 2. Coxa with one simple seta. Basis with one simple seta and four broom setae. Ischium like that of pereopod 3. Merus shorter than carpus, with two ventrodistal simple setae. Carpus longer than propodus, with two dorsal and four ventral simple setae. Propodus shorter than dactylus, with two ventral spiniform setae and 19 serrate setae. Dactylus like that of pereopod 3.

Pereopod 5 ( Fig. 6 F). Almost as long as pereonite 3. Coxa with one simple seta. Basis with two simple setae and three plumose setae. Ischium like that of pereopod 4. Merus shorter than carpus, with three distal simple setae. Carpus longer than propodus, with six ventral simple setae. Propodus shorter than dactylus, with three distal spiniform setae, one distal serrate seta, and four outer dendrite setae. Dactylus like that of pereopod 4.

Pereopod 6 ( Fig. 6 G). Shortest pereopod. Basis with one simple seta and six plumose setae. Ischium like that of pereopod 5. Merus shorter than carpus, with two distal setae. Carpus longer than propodus, with four simple setae. Propodus and dactylus like those of pereopod 5.

Pleopods ( Fig. 5 C). Biramous in five pairs. Basal article with one ventral plumose seta. Exopod biarticulate; article 1 with one dorsal plumose seta; article 2 with about seven distal plumose setae. Endopod uniarticulate, with one ventral distally hooked plumose seta at midpoint and about seven distal plumose setae.

Uropod ( Fig. 5 D). Basal article and endopod combined slightly shorter than pleon. Basal article with three simple setae. Exopod short, three-articulate, two simple setae at tip. Endopod with serially repeated articles, with simple setae and broom setae as illustrated; distal article with four simple setae and two broom setae at tip.

Description of female. Body ( Fig. 4 B, 4b1). Dorsoventrally flattened, gradually narrowing posteriorly, 2.42 mm in length, about 4.3 times as long as carapace width; with three mancas in marsupium.

Cephalothorax. About 0.25 times total body length. Eyes well developed, without any ommatidia or visual pigmentation. Rostrum pointed, sides slightly concave.

Pereonites. Like those of male.

Pleon. About 0.24 times total body length, with five pleonites and pleotelson. Pleonites like those of male. Pleotelson as long as wide, and as long as two pleonites combined; with three simple setae at tip.

Antennule ( Fig. 7 A, 7a1). 1.06 times as long as carapace. Article 1 thick, longer than remaining articles and outer flagellum combined, with four outer and three inner simple setae, and eight broom setae; article 2 one-fourth length of article 1, with one outer and two inner simple setae, and six broom setae; article 3 onefourth length of article 2, with three simple setae; article 4 (common article) with one broom seta, and one simple seta at insertion of inner flagellum. Outer flagellum three-articulate, all articles longer than wide; article 1 with one aesthetasc; article 2 with one simple seta and one aesthetasc; article 3 with three distal and one medial simple setae, and one distal broom seta. Inner flagellum biarticulate; article 1 with one simple seta; article 2 with three simple and two broom setae at tip.

Antenna ( Fig. 7 B). Narrow and shorter than antennule. Articles 1–5 like those of male; article 6 with two simple setae and one broom seta; article 7 with two simple setae; article 8 with three simple setae.

Mouthparts. Labrum ( Fig. 7 E) unipartite, setulated on distal margin. Mandibles ( Fig. 7 F, 7G). Molar process well developed, bearing distal row of denticles and several setulated setae. Left mandible ( Fig. 7 F) incisor with four distal denticles; setiferous lobe with five serrate setae; lacinia mobilis well developed, with four teeth. Right mandible ( Fig. 7 G) incisor with distal denticles; setiferous lobe with one four-pronged seta much stronger than others, and three serrate setae; lacinia mobilis absent. Palp three-articulate; article 1 naked; article 2 with one bipinnate seta; article 3 with three pinnate setae. Labium ( Fig. 7 H, 7h1). Lobe with setulated spines on outer margin. Palp with several simple setae and two bifurcate setae at tip. Maxillule ( Fig. 7 I). Palp biarticulate, with one subdistal and one terminal hook-tipped seta. Outer endite with 11 distal spiniform setae, two subdistal setulated setae, and several clumps of setae. Inner endite with four distal setulated setae and one outer process. Maxilla ( Fig. 7 J, 7j1). Outer lobe of movable endite with five setulated setae; with several minute spines on outer subdistal margin. Inner lobe of movable endite with four simple setae and four setulated setae. Outer lobe of fixed endite with six setulated setae, two setulated spiniform setae, two basally setulated trifurcate spiniform setae, and one four-pronged spiniform seta. Inner lobe of fixed endite with about 24 bifid-tipped setae and four biserrate setae. Maxilliped ( Fig. 7 K, 7k1, 7k2). Coxa well developed. Basis setulate on outer margin, with one ventral simple setae; seven setulated setae along dorso-outer margin of coxa and basis (origin of specific setae from coxa or basis was obscure and remains uncertain). Endite with four basally setulated spiniform setae and five setulated setae on distal margin; five basally setulated setae, one setulated seta, one setulated bifid-tipped seta, and two coupling hooks on inner margin. Palp like that of male. Epignath ( Fig. 7 L). Body setulated; terminal seta setulated on distal margin.

Cheliped ( Fig. 8 A, 8a1). Basis almost as long as carpus, 1.9 times as long as wide, with one ventromedial and one distal simple setae. Merus shorter than basis, with one ventromedial simple seta. Carpus with two ventromedial, one ventro-subdistal, and one dorsodistal simple setae. Propodus and dactylus like those of male, except cutting surface flat, with row of lamellae instead of short spiniform setae. Exopod like that of male.

Pereopod 1 ( Fig. 8 B). About 1.5 mm long, far longer than other pereopods. Coxa with two simple setae. Basis as long as combined length of merus and carpus, with one broom seta. Ischium much wider than long, naked. Merus 1.3 times as long as carpus, with two dorsal and six ventral simple setae, and one ventrodistal spiniform seta. Carpus slightly longer than propodus, with five (one short and four long) dorsal and five ventral simple setae, and one dorsodistal and two ventral spiniform setae. Propodus longer than dactylus, with four dorsal and two ventral simple setae, and two dorsodistal and four ventral spiniform setae. Dactylus ventrally serrate; unguis one-fourth length of dactylus. Exopod like that of male.

Pereopod 2 ( Fig. 8 C). Two-thirds length of pereopod 1. Coxa, basis and ischium like those of male. Merus as long as carpus, with three simple setae. Carpus like that of male. Propodus with four dorsal and one ventral simple setae, and four ventral spiniform setae. Dactylus with one ventromedial seta; unguis one-third length of dactylus.

Pereopod 3 ( Fig. 8 D). Shortest pereopod. Coxa like that of male. Basis with four broom setae. Ischium naked. Merus shorter than carpus, with two simple setae. Carpus longer than propodus, with four (one short and three long) dorsal, four ventral, and one distal simple setae, and one ventral spiniform seta. Propodus like that of male. Dactylus with two ventromedial setae; unguis one-third length of dactylus.

Pereopod 4 ( Fig. 8 E). Like that of male, except the number of serrate setae on propodus is 20; dactylus with one dorsal and one ventromedial simple setae.

Pereopod 5 ( Fig. 8 F). Shorter than pereonite 4. Coxa, ischium, merus and dactylus like those of male. Basis with one distal simple seta and five broom setae. Carpus longer than propodus, with four simple setae. Propodus as long as dactylus, with three distal spiniform setae, one distal serrate seta, and three outer dendrite setae.

Pereopod 6 ( Fig. 8 G). Almost as long as pereopod 3. Ischium and carpus like those of male. Basis with six broom setae. Merus shorter than carpus, with two dorsodistal and one ventrodistal setae. Propodus like that of pereopod 5. Dactylus like that of pereopod 4.

Pleopods ( Fig. 7 C). Like those of male, except for the number of distal plumose setae on exopod (about five) and endopod (about four).

Uropod ( Fig. 7 D). Basal article and endopod combined slightly longer than pleon. Basal article with two simple setae. Exopod and endopod like those of male.

Manca I hatchling. Length 0.5 mm. Rostrum pointed, sides concave. Cheliped carpus with one simple seta. Five pereopods present. Single exopods present on cheliped; pereopods 1, 4, and 5; several setae on the its distal end; exopods on cheliped and pereopod 1 shorter than those on pereopods 4 and 5 ( Fig. 9 A–C). Propodus of pereopod 1 with two ventral spiniform setae.

Remarks. Pseudosphyrapus quintolongus n. sp. is the sixth known species of the genus; it is characterized by pointed epimera, which are much larger on pleonite 5. As with P. quintolongus , P. serratus ( G.O. Sars, 1882) and P. vladimiri Guţu, 1989 are reported to have pointed epimera, but their lateral processes are all equal in length ( G.O. Sars 1885; Guţu 1989). The other congeners, viz., P. anomalus ( G.O. Sars, 1869) , P. c e n - tobi Băcescu, 1981, and P. g u t u i Kudinova-Pasternak, 1985, have rounded epimera ( G.O. Sars 1899; Băcescu 1981; Kudinova-Pasternak 1985) and can thus easily be distinguished from P. quintolongus .

Our specimens, comprising one male and one female, were collected from two localities 650 km apart. We identified these two individuals as conspecific, since 1) both possess the large lateral process on pleonite 5; 2) both have two setae on the maxillular palp; 3) both have two ventromedial and one ventro-subdistal simple setae on the cheliped carpus ( Figs 6 A, 8A); and 4) both have similar setation patterns on the appendages.

Among the five known species of the genus Pseudosphyrapus , P. anomalus and P. serratus have been described for both sexes ( G.O. Sars 1869, 1882, 1885, 1899). Sexual dimorphism in these species involves body shape (males longer and much more slender than females), the antennule (males have more articles in outer flagellum than females), the general shape of the cheliped (e.g., males have a longer merus than females), pereopod 1 (the carpus is longer in males than in females), and the pleopods (males have more distal plumose setae on the exopod and endopod than do females). In addition to these differences, P. quintolongus shows sexual dimorphism in the mouthparts; that is, the mandibles, maxillae, and maxillipeds are simpler in structure in the male. The male maxillipeds in Pseudosphyrapus sp. A described by Larsen (2005) are also simpler than those of the female (the inner margin of the endite lacks setae).

The manca I hatchling (sensu Larsen 2003) from the female paratype has one ventral simple seta on the cheliped carpus and two ventral spiniform setae on the propodus of pereopod 1; since adults have more setae on these articles, these setae must increase in number during development (see Larsen 2005). On the other hand, there are two ventral spiniform setae on the carpus of pereopod 1 in both the manca I hatchling and the adult, so this character may not be ontogenetic. Furthermore, this character is consistent among species, and thus can be used as one of the diagnostic characters for this genus.

Figures

FIGURE 4. Pseudosphyrapus quintolongus n. sp. Holotype, male (ZIHU- 3253): A, dorsal view; a 1, lateral view of pereonite 6 and pleon, after detachment of appendages. Paratype, female (ZIHU- 3254): B, dorsal view; b 1, lateral view of pleon, after detachment of appendages. Scale bar: 1 mm.

FIGURE 5. Pseudosphyrapus quintolongus n. sp. Holotype, male (ZIHU- 3253): A, antennule; a 1, same, article 5 of outer flagellum; B, antenna; C, pleopod 1; D, uropod; E, labrum; F, left mandible incisor and lacinia mobilis; G, right mandible incisor; H, mandible molar process; I, mandibular palp; J, maxillule; K, maxilla; L, maxilliped; l 1, same, distal margin of endite; M, epignath. Scale bars: 0.1 mm.

FIGURE 6. Pseudosphyrapus quintolongus n. sp. Holotype, male (ZIHU- 3253): A, cheliped; B, pereopod 1; C, pereopod 2; D, pereopod 3; E, pereopod 4; F, pereopod 5; G, pereopod 6. Scale bar: 0.5 mm.

FIGURE 7. Pseudosphyrapus quintolongus n. sp. Paratype, female (ZIHU- 3254): A, antennule; a 1, same, article 3 of outer flagellum; B, antenna; C, pleopod 2; D, uropod; E, labrum; F, left mandible; G, right mandible; H, labium; h 1, same, tip of palp; I, maxillule; J, maxilla; j 1, same, outer lobe of fixed endite; K, maxilliped; k 1, same, distal margin of endite, excluding setae on inner margin; k 2, same, inner margin of endite, excluding setae on distal margin; L, epignath. Scale bars: 0.1 mm.

FIGURE 8. Pseudosphyrapus quintolongus n. sp. Paratype, female (ZIHU- 3254): A, cheliped, excluding exopod; a 1, same, exopod; B, pereopod 1; C, pereopod 2; D, pereopod 3; E, pereopod 4; F, pereopod 5; G, pereopod 6. Scale bar: 0.5 mm.

FIGURE 9. Pseudosphyrapus quintolongus n. sp. Paratype, manca I hatchling (ZIHU- 3255): A, lateral view (arrows: exopods); B, exopods of cheliped (left arrow) and pereopod 1 (right arrow); C, exopods of pereopods 4 (right arrow) and 5 (left arrow). Scale bars: A, 200 µm; B and C, 30 µm.