Pentaceration bassiana, Just, Jean, 2009

Just, Jean, 2009, Pentaceration, an unusual new genus of Paramunnidae from Australia (Isopoda, Asellota), Zootaxa 2134, pp. 36-48 : 37-43

Pentaceration bassiana sp. nov.

Figs 1–4

Type fixation. Holotype, male, here designated; Museum Victoria: NMV 20091.

Etymology. The epithet denotes the wide distribution of the species in the Bass Strait.

Material examined. Holotype, 3, 1.4 mm, Australia, central Bass Strait, 20 km NNE of North Point, 40o38.0'S, 145o23'E, 36 m, muddy shell grit, Smith-McIntyre grab, M.F. Gomon & G.C.B. Poore, RV Sarda , stn BSS 117, 4 November 1980, Museum Victoria, NMV J20091 (with 2 slides).

Paratypes. (South-eastern Australia, Bass Strait, 48 specimens). 48 km WNW of Stokes Point, King Island, 40o4.00'S, 143o22.00'E, 108 m, coarse sand, carbonate, Smith-McIntyre grab, G.C.B. Poore, HMAS Kimbla , stn BSS 89, 11 October 1980, NMV J20086 (1 ovigerous Ƥ). 70 km W of Cape Farewell, King Island, 39o38.2'S, 143o07.2'E, 127 m, mainly sand, R.S. Wilson, RV Tangaroa , stn BSS 195, 21 November 1981, NMV J20087 (1 preparatory Ƥ). 23 km E of Cape Rochon, Three Hummock Island, 40o22.2'S, 145o17'E, 40 m, mainly sand, epibenthic dredge, M.F. Gomon & G.C.B. Poore, RV Sarda , stn BSS 112, 3 November 1980, NMV J20088 (1 young 3, 1 near terminal 3). 20 km NNE of North Point, 40o32.0'S, 145o23'E, 43 m, muddy shell grit, Smith-McIntyre grab, M.F. Gomon & G.C.B. Poore, RV Sarda , stn BSS 116, 4 November 1980, NMV J20089 (1 preparatory Ƥ). 20 km NNE of North Point, 40o38.0'S, 145o23'E, 36 m, muddy shell grit, epibenthic sled, M.F. Gomon & G.C.B. Poore, RV Sarda , stn BSS 117, 4 November 1980, NMV J20090 (1 ovigerous Ƥ). 5 km SW of Bluff Point, 40o48.1'S, 144o38.0'E, 42 m, bryozoans, Smith- McIntyre grab, M.F. Gomon et al., RV Hai Kung, stn BSS 126, 2 February 1981, NMV J20092 (1 preparatory Ƥ). 38 km SW of Cape Paterson, 38o55.5'S, 145o17.0'E, 70 m, fine sand, R.S. Wilson, RV Tangaroa , stn BSS 155, 12 November 1981, NMV J20093 (1 ovigerous Ƥ). 38 km SW of Cape Paterson, 38o55.5'S, 145o17.0'E, 70 m, fine sand, R.S. Wilson, RV Tangaroa , stn BSS 155, 12 November 1981, NMV J20094 (4 ovigerous ƤƤ). 66 km S of Rodondo Island, 39o48.6'S, 146o18.8'E, 82 m, sand, silt and mud, R.S. Wilson, RV Tangaroa , stn BSS 158, 13 November 1981, NMV J20096 (1 terminal 3). 66 km S of Rodondo Island, 39o48.6'S, 146o18.8'E, 82 m, sand, silt and mud, epibenthic sled, R.S. Wilson, RV Tangaroa , stn BSS 158, 13 November 1981, NMV J20097 (1 small 3, 1 ovigerous Ƥ). 66 km S of Rodondo Island, 39o48.6'S, 146o18.8'E, 82 m, sand, silt and mud, R.S. Wilson, RV Tangaroa , stn BSS 158, 13 November 1981, NMV J20098 (4 33, 16 ƤƤ ovigerous and preparatory, including Ƥ Fig. 1 F). 57 km S of Rodondo Island, 39o43.5'S, 146o18.8'E, 80 m, muddy shell, Smith-McIntyre grab, R.S. Wilson, RV Tangaroa , stn BSS 159, 13 November 1981, NMV J20099 (3 33, 4 preparatory ƤƤ). 57 km S of Rodondo Island, 39o43.5'S, 146o18.8'E, 80 m, muddy shell, R.S. Wilson, RV Tangaroa , stn BSS 159, 13 November 1981, NMV J20100 (1 specimen). 50 km SE of Port Albert, 38o54.3'S, 147o13.4'E, 58 m, coarse shell, R.S. Wilson, RV Tangaroa , stn BSS 176, 18 November 1981, NMV J20101 (1 ovigerous Ƥ). 40 km SSW of Lakes Entrance, 38o18.0'S, 147o37.0'E, 55 m, muddy fine shell, trawl or sled, M.F. Gomon & R.S. Wilson, FV Silver Gull, stn BSS 209, 31 July 1983, NMV J20102 (1 ovigerous Ƥ). Maria Island 2 km E of Cape Boulanger, 42o34.00'S, 148o6.00'E, 50 m, fine Bryozoa and shell, epibenthic sled, R.S. Wilson, RV Challenger, stn TAS 29, 23 April 1985, NMV J20104 (1 preparatory Ƥ). E of Maria Island, 42o36.00'S, 148o10.00'E, 75 m, fine bryozoans and shell, epibenthic sled, R.S. Wilson, RV Challenger, stn TAS 30, 23 April 1985, NMV J20105 (2 preparatory ƤƤ).

Description (adult male, holotype). Body elongate ovate, slightly tapering towards pleon; width 0.35 length, widest between pereonites 1 and 2. Head length 0.35 width; length posterior to eyestalks 1.20 anterior length. Frontal margin mid-spine length subequal to head length, with minutely truncate apex, margins serrate; lateral spines as long as mid-spine, straight, with coarse marginal denticles. Eyestalks overreaching pereonite 1 by about half their length, pointing laterad at approximately 90º to head midline, anterior and posterior margins parallel or slightly expanding distally, apex rounded, distally microserrate; with a few ocelli.

Pereonites 1–5 and 7 of equal mid-length, 6 slightly longer; pereonite 1 dorsolaterally with moderately inflated ‘shoulders’; pereonites 1–7 with single short conical mid-dorsal spine. Pereonite 1 lateral margins irregularly rounded truncate with short irregular denticles; pereonite 2 with broad marginally denticulate spine as long as half pereonite width; pereonite 3 with short pointed spine a little less than half pereonite 2 spine length; pereonite 4 with pointed spine approximately 0.25 length of pereonite 3 spine; pereonites 5–6 lateral spines similar to pereonite 2; pereonite 7 with spine similar to pereonite 4 spine. Pereonites 6 and 7 with tumaculae arising from ventrolateral anterior surfaces of pereonite, projecting into cavity between adjoining pereonites.

Pleon length equal to width. Pleonite 1 with single dorsal spine; width 0.54 distance between uropods, length 0.2 width. Pleotelson with short proximal neck; dorsal surface at neck with single rounded spine; proximal and lateral margins forming distinct angle, lateral margins diverging distally, with approximately 20 denticles, mid-laterally concave, distally forming projecting corners with hook-like denticle pointing mediad, reaching as far back as posterior margin, producing deep concavities either side of posterior margin; posterior margin broad, triangular at 70°, apex rounded, 0.25 length of entire pleotelson.

Antennula articles 1 and 2 combined reaching about 2/3 along eyestalk; article 1 shorter and slightly wider than 2, tubular; 3 and 4 of equal length, both 2/3 length of subequal 5 and 6.

Antenna article 2 in ventral view approximately four times length of 1; 3 width 0.3 length, narrowing in distal 1/3; 5 length 2.6 times 4; 6 length 1.6 of 5; flagellum with 9 articles, proximal article 1.2 length of second article.

Pereopod I basis length 4 times width; ischium half length of basis, anterior margin with single acute spine; carpus oval, distal margin width 1.3 posterior margin length, distal margin weakly concave, distal robust seta with small hyaline flanges at base; propodus narrowing distally to insertion of dactylus, with 2 robust setae on opposing margin. Pereopods II–VII propodus with 1–2 slender robust setae on posterior margin.

Pleopod I lateral sublobes overlapping, proximal one broadly rounded, distal one more angular; width 0.26 distance to midline; distal projection length 0.28 pleopod total length, forming acute angle, with pointed apices. Pleopod II protopod bluntly rounded distally, lateral margin with simple setae; endopod article 2 (stylet) forming 130° curve.

Uropods recessed into protruding cuticle tube with large mediodistal projection, reaching to apex of endopod; exopod vestigial with single simple seta.

Variation. Males appear to become terminal at a larger size than the holotype. Terminal males differ from the holotype in the somewhat more bulky shoulders and a different pereopod I. While pereopod I of the holotype is broadly similar to that of females, males of 1.7–1.8 mm from the type locality have a more rectangular carpus with the proximal half of the posterior margin projecting, and 1 large and 1 smaller blunt spines just distal to the distalmost robust seta. Pereopod I from a 1.78 mm specimen ( Fig. 3 M) has 2 blunt anterodistal spines on basis, a single similar mid-anterior spine on ischium, 1 anterior and 2 posterior acutely pointed spines on merus, and a small posterodistal denticle on propodus. The pattern of pereopod I spines differ among terminal males with some spines occasionally lacking.

Females. Females are similar to males in general body shape, although ovigerous females are wider relative to length: 0.42, have less strongly developed pereonite 1 lateral parts, and with a more bulging pereon. Head length/width is 0.28, length posterior to eyestalks 1.4 anterior length. Head frontal margin spines are shorter than in males relative to eyestalks. Lateral spines on pereonite 3 are equal to those of pereonite 2. Pereopod I carpus is narrow oval; propodus has a single robust seta on opposing margin in specimens examined. The operculum is ovoid with slightly concave distal margins, width 0.68 length.

General variation. Mid-dorsal spines in both sexes vary in size and shape from low humps to irregular spines ( Fig. 4 a–d). The mid-cephalic spine may be somewhat shorter than the lateral ones, and all three cephalic spines vary between straight and moderately downward curved.

Size. Largest male (terminal), 1.8 mm; largest ovigerous female, 2.1 mm.

Distribution. Australia, Bass Strait, 36– 127 m.

Figures

FIGURE 1. Pentaceration bassiana gen. et sp. nov. Holotype, male, except F, paratype, ovigerous female (NMV J 20098). a, antenna; au, antennula; cv, head ventral view; pe, pereonite, lateral parts, tumaculum in pocket between pereonites shown; up, uropod. Scale bars for habitus figures: 0.5 mm.

FIGURE 2. Pentaceration bassiana Holotype, male., mandible (, left; r, right); mx 1 – 2, maxilla 1 and 2; mxp, maxilliped.

FIGURE 3. Pentaceration bassiana gen. et sp. nov. Holotype, male, except F, paratype, ovigerous female, and M, paratype, terminal male. p 1, 2 and 6, pereopods 1, 2 and 6.

FIGURE 4. Pentaceration bassiana gen. et sp. nov. Holotype, male, except op, paratype, ovigerous female, and a – d, paratype females. op, operculum; pl 1 – 4, pleopods 1 – 4 (*, tip of pleopod 2 stylet); pt, pleotelson; vv, ventral view; a – d, lateral view of dorsal armature in 4 paratype females, a – c, ovigerous, d, preparatory.