Pentaceration serrata, Just, Jean, 2011

Just, Jean, 2011, Remarkable Australasian marine diversity: 18 new species in Pentaceration Just, 2009 (Crustacea, Isopoda, Paramunnidae), Zootaxa 2813, pp. 1-54 : 27-29

Pentaceration serrata sp. nov.

Figure 19

Type fixation. Holotype, male, here designated.

Etymology. The epithet alludes to the regularly serrate margins of head and pereonite spines.

Material examined. Holotype, 3, 1.70 mm, Australia, New South Wales, off Nowra, 34o54.68'S, 151o11.36'E, 800–850 m, 5 m otter trawl, M.F. Gomon et al, RV Franklin, 15 July 1986, stn SL 5, NMV J20078 (with 2 slides).

Paratype. Same data as holotype, NMV J20077 , (1 3, 1.85 mm).

Description. Body barely tapering from pereonite 2 towards pleon; width 0.35 length, widest between pereonites 2 and 3. Head length 0.35 width; length posterior to eyestalks 1.1 anterior length. Frontal margin middle spine length 0.75 head length; lateral spines 1.7 middle spine length, slightly forward-inward curving, diverging at 130°; all 3 spines with coarsely but regularly denticulate margins. Eyestalks reaching lateral margin of pereonite 1, pointing forward at 15º, apex pointed spine, anterodistally denticulate.

Pereonite 1 lateral margins rounded, denticulate; pereonites 2 and 3 lateral spines diverging at 30° pereonite 2 with broad pointed lateral spines of 1.67 pereonite width, pointing forward at approximately 30º; pereonite 3 with similar spines pointing directly laterad; pereonite 4 with tiny lateral spines, smooth; pereonite 5 lateral spines similar to pereonite 3 spines; pereonite 6 lateral spine similar to pereonite 2 spines, but pointing backwards at approximately 40º; pereonite 1–6 spines with regularly denticulate margins; pereonite 7 lateral spines half length of 6, pointed with small lateral denticles.

Pleon length 0.95 width. Pleonite 1 width 0.8 distance between uropods, length 0.14 width.

Pleotelson proximal and lateral margins evenly merging, lateral margins evenly rounded, with 17 denticles; distal projection triangular at 70°, 0.35 length of entire pleotelson, apex pointed.

Antennula articles 1 and 2 combined reaching 0.8 along eyestalks; article 1 shorter and slightly wider than 2, tubular; 3 and 4 of subequal length, both 0.7 length of subequal 5 and 6.

Antenna article 2 in ventral view approximately 4 times length of 1; 3 width 0.38 length. Pereopod I basis length 3.6 width, anterior margin with 2 distal short blunt spines; ischium 0.6 length of basis, anterior margin with single acute spines; merus with single acute spine on anterior margin; carpus oval, distal margin straight, with small translucent flanges posterior to robust setae, and more complex one in front of distal robust seta; propodus narrowing distally to insertion of dactylus, with single robust setae on opposing margin. Pereopod II slender, propodus without robust setae on posterior margin.

Pleopod I lateral sublobes rounded, similar, strongly overlapping, distal sublobe with row of simple setae, width 0.22 distance to midline; distal projection length 0.3 pleopod total length, forming acute angle, with pointed apices. Pleopod II protopod pointed distally; endopod article 2 (stylet) forming 105° curve.

Uropods recessed into simple cuticle hood with slight medial rim bulge; endopod very short,, barely protruding from cuticle hood, apex rounded, exopod and protopod apparently absent; length 0.67 width.

Variation. The paratype male has moderately larger pereonite 1 shoulders, and lateral pereonite spines are slightly longer than in the holotype. Otherwise there are no differences. The specimens are adult, but it is uncertain if they have reached the terminal stage (e.g. changes in pereopod I carpus).

Size. Largest male, 1.85 mm.

Distribution. Australia, south-east coast, 850 m.

Figures

FIGURE 19. Pentaceration serrata sp. nov. Holotype, 3. a, antenna; au, antennula; cv, head ventral view; md l, left mandible; pl 1 – 2, pereopods 1 and 2 (1 enlarged); pl 1 – 2, pleopods 1 and 2; up, uropod. Habitus scale: 0.5 mm.