Peraeospinosus acruxi, Błażewicz-Paszkowycz, 2007

Błażewicz-Paszkowycz, Magdalena, 2007, Figure 6. Typhlotanais Compactus, Female A In Family Nototanaidae Sieg, 1976 And Typhlotanaidae Sieg, 1984, Zootaxa 1598, pp. 1-141 : 47-51

Peraeospinosus acruxi n. sp.

( Figs 23-25 )

Material examined: Holotype: one female, ( K 41347 ), ANT XXII /3 , PS 67/74-5, 71°18.35'S – 71°18.28'S, 13°57.71'– 13°57.31'W, depth 1030–1040 m, epibenthos sledge, 20 Feb 2005 ; Paratypes: two females, two mancae, ( K 41349 ), the same locality; one manca, ( K 41348 ), ANT XXII/3 , PS 67/153-7, 63°19.31'S – 63°19.15'S, 64°36.94'– 64°37.18' W, depth 2092–2118 m, epibenthic sledge, 29 Mar 2005 .

Diagnosis: Body long, about ten times as long as wide; carapace smooth, not swollen, 1.2 times as long as wide, 1.5 times as long as pereonite-1. Pereonites 2–3 rectangular; pereonite-6 short (1.7 times as wide as long). Pleon a little wider than pereonites, as long as carapace, over twice as long as pereonite-6; pleotelson rectangular. Antennule article-3 twice as long as article-2. Propodus of pereopod-2 length:width ratio 4.8: pereopods 4–6 merus and carpus with microtrichae; distal setae on pereopod-6 propodus well-calcified, just as long as dactylus. Pleopods normally developed. Uropod exopod slightly longer than endopod.

Etymology: Acrux is the biggest star in the constellation ‘The Southern Cross’.

Description: Female holotype body length 5.7 mm. Body ten times as long as wide. Pereonite-1 about as long as wide, tapering distally; pereonites 2–4 longer than wide ( Fig. 23A,B ), narrower in the middle and wider at proximal and distal margin; pereonite-5 as long as wide; pereonite-6 1.7 as wide as long. Pleon as long as carapace, a little wider than pereonites; all pleonites the same size; pleotelson rectangular.

Antennule ( Fig. 24A ): three-articled; article-1 stout, about 1.3 times as long as articles 2 and 3 combined, with two groups of pinnate setae and two simple setae along article; article-2 half as long as article-3, with two simple and one pinnate setae distally; article-3 with three apical setae.

Antenna ( Fig. 24B ): Article-2 twice as long as article-3, with one simple seta; article-4 eight times as long as wide, less than twice as long as article-5, with three minute setae distally; article-5 with one simple seta distally; article-6 very short, with six terminal setae.

Mouth parts: Labrum lost during dissection. Mandible ( Fig. 24C,D ) stout; molar process well-developed, with strongly crenulated edges, bunch of small spines at “lower” margin; lacinia mobilis well-developed, crenulated. Maxillule ( Fig. 24E ) endite longer than palp, with eight apical spiniform setae; two of them are semi-fused; palp with two terminal setae. Maxilla ( Fig. 24F ) semi-triangular. Lobes of labium ( Fig. 24G ) poorly separated and setose in distal parts; outer lobe with row of short setae along outer margin. Maxilliped ( Fig. 24H ): coxa reduced; basis fused into heart-shaped plate, as long as wide, with seta reaching half of endites; endite with two simple setae and two small tubercles distally; palp article-1 naked; article-2 wedgeshaped, with two weakly serrated and one strongly serrated setae on inner margin and one minute seta on outer margin; article-3 trapezoidal, with two weakly serrated and two simple setae on inner margin; article-4 slender, with one simple seta on outer margin and five weakly serrated setae distally. Epignath ( Fig. 24I ) curved, distally simple.

Cheliped ( Fig. 25A ): Basis robust, slightly rounded, twice as long as wide; merus wedge-shaped, with one rod seta; carpus with row of eight small rod setae dorsally and two rod setae ventrally; propodus with seta near fixed finger insertion; fixed finger (propodus projection) tipped with a strong spine, with well-calcified inner margin, and with three setae dorsally and two setae ventrally; dactylus slightly curved, with one short rod seta proximally on dorsal margin.

Pereopod-1 ( Fig. 25B ): Slender (walking type); basis with five short setae along article; ischium short with one seta; merus 1.25 times as long as propodus, with two setae distally; carpus with one simple and two rod setae (dorsal seta long); merus and carpus combined longer than propodus; propodus length: width ratio 7, with one rod setae distally and one minute spiniform seta ventrally; dactylus less than half of unguis length, with long seta.

Pereopod-2 ( Fig. 25C ): Slender (walking type); basis little shorter than rest of articles combined, with three minute setae along article; ischium with short seta ventrally; merus little longer than carpus, each with two simple setae and thick spiniform seta distally; carpus with microtrichia; propodus little longer than merus and carpus combined length, with spiniform seta ventrally and one simple and one thick rod seta dorsally; propodus length: width ratio 4.8; dactylus with one simple seta.

Pereopod-3 ( Fig. 25D ): Similar to pereopod-2, but merus and carpus subequal, merus with only one simple seta distally.

Pereopod-4 ( Fig. 25E ): Clinging type; basis twice as long as wide, with one simple and two pinnate setae dorsally and one pinnate seta ventrally; ischium with two setae; merus almost as long as to carpus, with two strong spiniform setae on ventral margin; carpus with two distal tooth, one seta distally and large prickly tubercle covered by little spines and surrounded by dense row of well-calcified blunt spines ventrally; propo-

dus with two spiniform setae ventrally and with distal seta twice as long as propodus and dactylus combined length; dactylus tipped by weakly bifurcated unguis.

Pereopod-5 ( Fig. 25F ): Similar to pereopod-4.

Pereopod-6 ( Fig. 25G ): Similar to pereopod-5; propodus tipped by three terminal setae just as long as dactylus (two coarsely, one finely serrated).

Pleopods 1–5 ( Fig. 25H ): Rami similar in structure; endopod with row of eighteen setae and exopod with row of six plumose setae on outer margin (length: width ratio of both exopod and endopod 2.7); clear gap between the most proximal and other setae in both rami.

Uropod ( Fig. 25I ): Both rami one-articled. Exopod little longer than endopod; endopod with one pinnate seta at middle, tipped by two simple terminal setae and one pinnate seta; exopod with pinnate seta on outer margin, tipped by strong simple setae.

Distribution: Antarctic: Eastern part of the Weddell Sea and off Palmer Archipelago, at depths of 1030– 2118 m.

Remarks: Peraeospinosus acruxi n. sp. is the seventh species of Peraeospinosus recorded in the Antarctic. It can be distinguished from the other six species ( Peraeospinosus kerguelenensis , P. pushkini , P. emergensis , P. exiliremis , P. magnificus , P. subtigaleatus ) by its narrow carapace (longer than wide), by its pereonites 2–4 being longer than wide and by the long dorso-distal rod seta on the carpus of pereopod-1. From the list above, only P. emergensis has elongate pereonites and a similar rod seta on the propodus of pereopod-1, but it has also a round carapace, a more compact carpus of the cheliped (1.25 times as long as wide), a narrower propodus on pereopod-2 (width: length 8), and sixteen setae on the pleopod exopod. In contrast, P. acruxi has a cheliped carpus twice as long as wide, a compact propodus on pereopod-2 (width: length 4.8) and only six setae on the pleopod exopod. Similar elongate pereonites can be observed in P. magnificus , although that species has one long distal seta on the propodus of pereopod-6, while P.acruxi has all three setae shorter than the dactylus. Kudinova-Pasternak (1969; 1970; 1973; 1993) recorded P. magnificus at various localities in the North Pacific (off California, off Japan and Alaska), the South Atlantic ( Argentina), and the West Antarctic (Bransfield Strait) as well (see Błażewicz-Paszkowycz, 2005). That material is not available for study, so the apparently wide distribution of the species cannot be confirmed. However, it seems likely that Kudinova-Pasternak dealt with two (or more) species with distinct areas of distribution (North Pacific and West Antarctic).

Figures

FIGURE 23. Peraeospinosus acruxi n. sp., holotype, female. A) dorsal view; B) lateral view. Scale =1 mm.

FIGURE 24. Peraeospinosus acruxi n. sp., female paratype. A) Antennule; B) Antenna; C) Left mandible; D) Right mandible; E) Maxillule; F) Maxilla; G) Labium; H) Maxilliped; I) Epignath. Scale = 0.1 mm.

FIGURE 25. Peraeospinosus acruxi n. sp., female paratype. A) Cheliped; B) Pereopod-1; C) Pereopod-2; D) Pereopod- 3; E) Pereopod-4; F) Pereopod-5; G) Pereopod-6; G’); H) Pleopod; I) Uropod. Scale = 0.1 mm.