Pentaceration spinosissima, Just, Jean, 2009

Just, Jean, 2009, Pentaceration, an unusual new genus of Paramunnidae from Australia (Isopoda, Asellota), Zootaxa 2134, pp. 36-48 : 43-46

Pentaceration spinosissima sp. nov.

Figs 5–6

Type fixation. Holotype, male; here designated; Museum Victoria: NMV J20085 .

Etymology. The epithet reflects the many large and small spines and denticles characteristic of this species.

Material examined. Holotype. 3, 2.2 mm, Australia, Eastern Bass Strait, 63 km E of North Point, Flinders Island, 39o44.8'S, 148o40.6'E, 124 m, muddy sand, grab, sled or trawl, R.S. Wilson, RV Tangaroa , stn BSS 167, 14 November 1981, Museum Victoria NMV J20085 (with 2 slides).

Paratypes ( Australia, 37 specimens) Same data as holotype, NMV J20084 (14 ƤƤ, mostly ovigerous, 4 33). Victoria, South of Point Hicks, 38o17.70'S, 149o11.30'E, 400 m, coarse sand, gravel, mud, many sponges, epibenthic sled, M.F. Gomon et al., CSIRO RV Franklin, stn SL 40, 24 July 1986, NMV J20080 (2 ƤƤ, 3 33) and J20079 (single 3). New South Wales, 44 km E of Nowra, 34o55.79'S, 151o08.06'E, 429-466 m, muddy coarse shell, epibenthic sled, G.C.B. Poore et al., CSIRO RV Franklin, stn SL 56, 22 October 1988, NMV J20081 (2 ƤƤ, 3 33). Victoria, 76 km S of Point Hicks, 38o29.33'S, 149o19.98'E, 1840- 1750 m, sandy mud, fine shell, epibenthic sled, G.C.B. Poore et al., CSIRO RV Franklin, stn SLOPE 69, 26 October 1988, NMV J20082 (5 ƤƤ, ovigerous, 4 33).

Description (adult male, holotype). Body, excluding lateral spines, elongate ovate, slightly tapering towards pleon; width 0.26 length, widest between pereonites 2 and 3. Head length 0.28 width, length posterior to eyestalks 0.67 anterior length. Frontal margin mid-spine length approximately as pereonite 1–2 combined, acute, with serrate margins and a few dorsal denticles, lateral spines as long as pereonites 1–3 combined, slightly inward-upward curved in distal half, with coarse marginal and dorsal denticles. Eyestalks overreaching pereonite 1 by about half their length, pointing laterad at approximately 90º to head midline with slight backward curve in distal half, tapering to acute point, anterior and posterior margins irregularly serrate, ventral surface with row of coarse denticles; without visual elements.

Pereonite 1 mid-length equalling pereonite 2 and half of 3, dorsolaterally with moderately inflated ‘shoulders’, pereonites 2–4 of subequal length, all about 1.25 longer than subequal pereonites 5–7. Pereonites 1–4 with single middorsal long vertical to slightly backward leaning spine, 1–2 middle spines with single denticle on shaft near anterior base, pereonites 1–4 with mid-lateral spine each side of middle spine; pereonites 5–7 with 2 short, conical middorsal spines. Pereonite 1 lateral margins rounded truncate with denticles in anterior corners and in proximal half; pereonites 2–3 and 5–6 with acute lateral spines, approximately as long as 2/3 pereonite width, base of spines approximately as wide as half pereonite length, with marginal and dorsal coarse denticles; pereonite 4 width moderately reduced compared to 3 and 5, lateral margin spines short, about half pereonite length; pereonites 5–6 with lateral spines similar to pereonites 2–3; pereonite 7 width approximately 0.75 pereonite 6, lateral margin spines length as in pereonite 4 spines, pointing backward at approximately 45º.

Pleon length 1.7 width. Pleonite 1 width 0.6 distance between uropods, length 0.3 width. Pleotelson with short proximal neck; dorsal surface with several short spines in midline and a few scattered more laterally; proximal and lateral margins forming distinct angle, lateral margins nearly straight, slightly diverging posteriorly, with 12–13 denticles; posterior margin drawn out to long spine forming half the length of entire pleotelson (measured from line between distal corners of lateral margins), with midlateral rows of small denticles.

Antennula articles 1 and 2 combined reaching approximately to apex of eyestalks; article 1 0.6 length of and about twice width of 2, tubular; 3 and 4 of equal length, both half length of subequal 5 and 6.

Antenna article 2 in ventral view approximately three times length of 1, length 1.85 width, with medial and distolateral denticles; 3 width 0.4 length, narrowest in proximal 1/3, with medial, distolateral and distal denticles; 5 length 3 times 4; 6 length 1.8 of 5; flagellum with 9 articles, proximal article length twice second article.

Pereopod I basis anterior margin with row of 5 blunt spines in distal half, length 4 times width (not including spines); ischium 0.6 length of basis, anterior margin with 3 blunt spines of varying length; merus with single blunt spine on anterior margin; carpus rectangular, distal margin width 1.35 posterior margin length, distal margin concave in posterior half, with two broad rounded spines, posterior margin with small hyaline flanges at base of robust setae; propodus narrowing distally to insertion of dactylus, with 2 robust setae and 2 crenate ridges on opposing margin. Pereopods II–VII basis with 2–4 blunt spines on anterior margin; propodus with 3 slender robust setae on posterior margin.

Pleopod I proximal lateral sublobe prominent, rounded, width 0.26 distance to midline; distal sublobe approximately half length of proximal one, acutely pointed, set apart from proximal sublobe; with tuft of a few simple setae between sublobes; distal projection length 0.34 pleopod total length, forming acute angle, with pointed apices. Pleopod II protopod rounded distally, lateral margin with simple setae; endopod article 2 (stylet) forming approximately 230° curve.

Uropods recessed into large protruding cuticle tube with medial projection about twice length of endopod, lateral projection 4/5 length of endopod; exopod vestigial with single simple seta.

Female. Females are similar to males in general body shape, though ovigerous females are wider relative to length: 0.35–0.37, have less strongly developed pereonite 1 lateral parts, and with a more bulging pereon. Antenna article 3 is more slender than in males, with row of lateral and row of medial marginal denticles. Pereopod I ischium anterior spines are more numerous and acute, merus has an anterior group of small acute spines, carpus is narrow oval. The operculum is ovoid with slightly concave distal margins, width 0.68 length.

General variation. The length of the mid-dorsal spines vary; specimens from stn SL40, especially, have somewhat shorter spines. The number and position of denticles on the main head and body projections and on the pleotelson dorsum vary with size and among specimens of similar size; large females generally have more such denticles. The number and shape of anterior spines on pereopod I vary.

Size. Largest male, 2.2 mm; largest ovigerous female, 2.5 mm.

Distribution. Australia, Eastern Bass Strait and south-east slope towards the Tasman Sea, 124–1840 m.

Figures

FIGURE 5. Pentaceration spinosissima gen. et sp. nov. Holotype, terminal male, except op, paratype, ovigerous female. a, antenna; au, antennula; cv, head ventral view; op, operculum; pl 1 – 4, pleopod 1 – 4; up, uropod. Scale bar for habitus: 0.5 mm.

FIGURE 6. Pentaceration spinosissima gen. et sp. nov. Holotype, male, except F, paratype, ovigerous female. md, mandible (l, left; r, right); p 1, 2 and 6, pereopods 1, 2 and 6.