Austronanus aucklandensis, Just, Jean & Wilson, George D. F., 2006

Just, Jean & Wilson, George D. F., 2006, Revision of Southern Hemisphere Austronanus Hodgson, 1910, with two new genera and five new species of Paramunnidae (Crustacea: Isopoda: Asellota), Zootaxa 1111, pp. 21-58 : 32-35

Austronanus aucklandensis sp. nov.

( Figs 6–7 )

Etymology. The species is named for Auckland Island south of New Zealand.

Material examined

Holotype. Ovigerous Ψ, 1.14 mm, Auckland Island, New Zealand, Ranui Cove, 166°17'E 50°32.5'S, 7 February 1973, Macrocystis pyrifera holdfasts and red algae on anchor of “Acheron”, J.K. Lowry, stn SA­1485, NIWA 18949.

Paratypes. Same data as holotype, AM P70534 (ɗB, 0.77 mm), AM P70535 (8 specimens).

Description. Body width 0.42 length in female, 0.43 length in male, widest in female at pereonite 2 or 3, widest in male at pereonite 2.

Head length 0.74 and 0.79 width (ɗ, Ψ); length posterior to eyestalks 1.1 anterior length in female and male. Frontal margin lobe length 0.29–0.31 head length (Ψ, ɗ); apex bluntly angular in dorsal view. Eyestalks lateral apex somewhat flattened, long axis angling forward at approximately 30° in female, 10° in male.

Pereonite lateral margin 1–4 linear, 5–7 rounded. Pereonite 5 in dorsal view distinctly narrower than pereonites 4 and 6.

Pleon length 0.94–0.95 width. Pleotelson proximal margin length shorter than lateral margin length. Pleonite 1 width 1.0 distance between uropods; length 0.17 width. Pleotelson proximal margin in dorsal view forming 60° angle with medial axis of pleon; lateral margins denticulate, with 10–11 denticles per side, denticles low and posteriorly directed; posterior margin in female forming 110° angle, in male forming 120° angle, posterior margin with uniformly fine denticles laterally, with 3 denticles each side.

Antennula with 5 articles, 1 and 2 combined shorter than eyestalk; article 1 longer and broader than 2, inflated, article 5 longer than articles 3 and 4 combined. Antenna article 2 lateral margin with two spines; article 3 in ventral view distally expanded, lateral distal margin angular, width 0.56 length, with 1 spine distally, fine cuticular combs on ventral side; article 5 only slightly longer than article 4; flagellum with 7 articles, proximal article subequal to more distal articles.

Pereopod I basis with crenate ridge on anterior margin (fine denticles only), length 1.5 width; merus with 2 spines on anterior margin, 1 spine on posterior margin; carpus distal width 1.0 posterior margin length, with 2 denticles proximal to robust setae (1 large, 1 small), one denticle between robust setae (massive, larger than other denticles), one denticle distal to robust setae (medium sized); propodus narrowing distally to insertion of dactylus, with 2 robust setae, with crenate ridge. Pereopod VII coxa lateral margin with small denticle.

Male pleopods I lateral lobes distinctly projecting from midlateral margin, width 0.46 distance to midline; distal projection length 0.30 pleopod total length, forming obtuse angle, with pointed apices. Female operculum distal part tapering with concave distolateral margins, width 0.96 length.

Uropods on lateral margin of pleotelson.

Size. Largest female 1.14 mm, largest male 0.77 mm.

Distribution. Known only from the type locality.

Remarks. Austronanus aucklandensis is unusual in having an exceptionally short and stocky basis to pereopod I. Although the lateral margin of the broad pleotelson is denticulate, the lateral spines are low and directed posteriorly. This species shares with A. dentatus a 5­articulate antennula (all other species in have 6; note that A. specimen A, see below, also has 5). Austronanus aucklandensis differs from A. dentatus in the shape of the frontal margin of the head, and in the latter having laterally projecting coxae on pereopods V–VII.

Figures

FIGURE 6. Austronanus aucklandensis, sp. nov. A, holotype, female; B, paratype, male B. cl, lateral view of head; cx 1, coxa I; dv, dorsal view; p 1, pereopod I; pe 5 ­ 7, pereonites 5 ­ 7 with coxae; pt, pleotelson; up, uropod; vv, ventral view. Habitus scale bar for both: 0.5 mm.

FIGURE 7. Austronanus aucklandensis, sp. nov. A, holotype, female; B, paratype, male B. a, antenna; au, antennula; cv, ventral view of head; mdp, mandible palp; op, operculum; pl 1 ­ 2, pleopods I and II.