Holodentata triangulata, Doti, Choudhury & Brandt, 2009

Doti, Brenda Lía, Choudhury, Madhumita & Brandt, Angelika, 2009, Holodentata gen. nov. (Isopoda: Asellota: Paramunnidae) with a description of two new species: H. caeca and H. triangulata from the Southern Ocean *, Zootaxa 2096 (1), pp. 395-412 : 404-410

Holodentata triangulata sp. nov.

( Figs. 6–9 , 10A–C )

Holotype: 1 adult ♀ ( ZMH –41972); Ross Sea, RV Italica , station H out 4, 72°18.5’S, 170°26.8’E, 235 m depth, 12 Feb 2004.

Paratypes: same locality as holotype: 25 brooding ♀♀ (1.4–1.8 mm), 26 preparatory ♀♀ (1–1.7 mm), 12 adult ♂♂ (1.1–1.5 mm) and 7 juveniles (0.9–1 mm); ( ZMH –41973). Station H out 2, 72°17.5’S, 170°29.4’E, 353 m depth, 11 Feb 2004: 7 brooding ♀♀ (1.5–1.7 mm), 5 preparatory ♀♀ (1.1–1.5 mm), 3 juvenile ♀♀ (0.9–1 mm) and 3 adult ♂♂ (1.1–1.2 mm). Station H in 3, 72°17.0’S, 170°13.1’E, 316 m depth, 16 Feb 2004: 3 preparatory ♀♀ (1–1.4 mm) and 2 adult ♂♂ (1.4–1.5 mm). Station H in 4, 72°17.1’S, 170°14.0’E, 196 m depth, 16 Feb 2004: 5 brooding ♀♀ (1.3–1.7 mm), 9 preparatory ♀♀ (1–1.6 mm), 2 adult ♂♂ (1.2–1.3mm) and 7 juveniles (0.8–1 mm). Station H in 5, 72°17.2’S, 170°17.9’E, 84 m depth, 16 Feb 2004: 4 preparatory ♀♀ (1.3–1.4 mm), 1 juvenile ♀ (0.9 mm) and 2 adult ♂♂ (0.9–1.1 mm). Station H out 1, 72°14.8’ S, 170°15.2’E, 542 m depth, 9 Feb 2009: 4 preparatory ♀♀ (1.2–1.6 mm) and 1 juvenile ♀ (1 mm) .

Diagnosis. Head anterior lobe triangular with blunt apex, and curving upward in lateral view. Eyestalk long axis pointing laterally, with 4 ommatidia. Lateral margin of pereonites 1–3 expanded into a subquadrate projection, 4 rounded and 5–7 produced into single processes. Coxal plates produced into processes. Pereopod 7, carpus with 1 robust seta distoventrally.

Description of brooding female (habitus description based on the holotype ZMH–41972, description of appendages on the paratype ZMH–41973). Length: 1.9 mm ( Fig. 6A, B ). Body width 0.6 length, widest at pereonite 3. Head width 2.4 length; anterior lobe triangular with blunt apex, curving upward in lateral view, marginally denticulated ( Figs. 6C , 10B ). Eyestalks long axis pointing laterally, with 4 ommatidia. Lateral margin of pereonites 1–3 expanded into a subquadrate projection, 4 rounded and 5–7 produced into single processes. Total length of all pereonites and free pleonite combined subequal to pleotelson length. Coxal plates produced into processes and denticulated, visible in dorsal view in all pereonites. Pleotelson width 1.2 length, marginally with 20–25 denticles on each side, apex truncate.

Antennula ( Fig. 7A ), article 1 largest, with 1 broom seta, and 3 and 1 robust denticles on each side; article 2 0.6 length of article 1, with 2 broom and 3 simple setae; article 3 0.7 length of article 2 and subequal in length to article 5 (and 6); article 4 shortest, with 1 simple seta; article 6 with 3 simple setae and 1 aesthetasc.

Antenna ( Figs. 7B , 10C ), articles 1 and 2 glabrous; article 3 short distally broadened, with 2 simple setae and several robust denticles; article 4 with 1 simple seta; article 5 subequal in length to article 6, with 1 simple seta; article 6 with 3 broom and 3 simple setae; flagellum with 9 articles, each article with numerous setae.

Right mandible ( Fig. 7C ), incisor process with 4 blunt cusps (proximal one quadrate); spine row with 5 serrate setae; molar process with 1 row of teeth and 1 serrate seta on distal edge. Left mandible ( Fig. 7C detail) as right except for: incisor process with a 4-cusped lacinia mobilis (1 of these cusps minute) and spine row with 4 serrate setae; molar process without setation.

Maxillula ( Fig. 7D ), lateral lobe with 1 simple seta close to distal margin and 12 cuspidate setae distally (2 of these setulated), mesial lobe with 5 setulated setae distally and 4 slender simple setae.

Maxilla ( Fig. 7E ), lateral and middle lobe protruding distomedially, with 1 pectinated and 3 simple setae distally; mesial lobe with 2 pectinated, 1 setulated and 6 simple (with pore-bearing tip) setae on distal margin, 1 setulated seta and numerous slender simple setae on mesial margin.

Maxilliped ( Fig. 7F ), endite with 2 coupling hooks, distal margin with 4 setulated setae, ventral surface with 2 fan setae and 1 setulated seta, dorsal surface with 3 setulated setae (see detail). Epipod ovate, width 0.6 of length.

Pereopod 1 ( Fig. 8A, B ), basis longest article with 3 simple setae. Ischium 0.5 basis length, with 2 simple setae and 1 cuticular comb. Merus cup-shaped, with 5 simple setae and 2 cuticular combs. Carpus oval, 0.8 ischium length; dorsal margin with 1 simple seta distally; ventral margin with 2 robust and 6 simple setae, anterior surface with 1 cuticular comb. Propodus 0.8 ischium length, dorsal margin with 4 simple setae (1 at half length article and 3 distal), ventral margin with 7 simple setae, anterior surface with 1 simple seta and 4 cuticular combs. Dactylus with 3 simple setae near distal end and 2 simple setae between unguis and supplementary claw, unguis slightly shorter than dactylus, supplementary claw 0.8 unguis length.

Pereopods 2–7 ( Figs. 8C–E , 9A–C ). Bases with 2–3 simple setae. Ischia with 2–4 simple setae. Meri with

3–5 simple setae. Carpi with 2 simple setae at half length article, and 3–6 simple setae and 1 broom seta on distal end; carpus of pereopod 7 with 1 robust seta distoventrally and some cuticular combs. Propodi with 2–3 simple setae half way along the length of article, 2–4 simple setae and 1 broom seta on distal end; propodus of pereopod 7 with some cuticular combs. Dactyli with 4–5 simple setae, unguis slightly longer than dactylus, supplementary claw absent.

Operculum ( Fig. 9D ) ovoid and acuminating distomedially, width 0.9 length; lateral margins with several simple setae (many of these broken).

Pleopod 3 ( Fig. 9E ), endopod width 0.6 length, with 3 plumose setae distally. Exopod with 2 articles; distal one with 3 minute setae and 1 distal simple seta, which extends towards the tips of the endopod setae.

Pleopod 4 ( Fig. 9F ), endopod width 0.5 length, exopod reaching half length of endopod.

Pleopod 5 ( Fig. 9G ) width 0.5 length.

Uropod ( Fig. 9H ) exopod 0.3 endopod length, with 2 simple setae distally; endopod with 3 simple setae subapically and 5 broom setae distally.

Description of adult male (paratype ZMH–41973). Pleopod 1 ( Fig. 9I ) maximum width 0.6 length; lateral lobes at 0.7 of its length from proximal end, each one with 6–7 simple setae; distal projection with 2 simple setae; ventral surface with 4 simple setae (2 of these close to lateral margins).

Pleopod 2 ( Fig. 9J ), protopod width 0.4 length, with 17 simple setae on lateral margin. Endopod slightly surpassing protopod. Exopod bilobed.

Remarks. H. triangulata is most similar to H. caeca , but it can be easily distinguished from the latter by having (features dealing with H. caeca are in parentheses): Head anterior lobe triangular (anterior lobe rounded), eyestalks with ommatidia (blind), antenna article 3 with denticles on one side (article 3 with denticles on both margins), carpus pereopod 7 with one distal robust seta on ventral margin (robust seta absent).

Distribution. Only known from type locality.

Etymology. The epithet is derived from Latin triangulus meaning triangular alluding to the triangular shape of the head.

Figures

FIGURE 6. Holodentata triangulata sp. nov., holotype ♀, ZMH–41972, A, dorsal view; B, lateral view. Scale bar = 1 mm. C, head in ventral view. Scale bar = 0.5 mm. D, Pleotelson in ventral view. Scale bar = 0.5 mm.

FIGURE 7. Holodentata triangulata sp. nov., paratype ♀, ZMH–41973, A, antennula. Scale bar = 0.05 mm. B, antenna. Scale bar = 0.1 mm. C, right mandible and detail of the incisor process of left mandible; D, maxillula; E, maxilla. Scale bars = 0.05 mm. F, maxilliped. Scale bar = 0.1 mm.

FIGURE 8. Holodentata triangulata sp. nov., paratype ♀, ZMH–41973, A, pereopod 1; B, dactylus of pereopod 1; C, pereopod 2; D, pereopod 3; E, pereopod 4. Scale bars = 0.1 mm.

FIGURE 9. Holodentata triangulata sp. nov., paratype ♀, ZMH–41973, A, pereopod 5; B, pereopod 6; C, pereopod 7. Scale bar = 0.1 mm. D, operculum; E, pleopod 3; F, pleopod 4; G, pleopod 5. Scale bars = 0.2 mm. H, uropod. Scale bar = 0.05 mm. Paratype ♂, ZMH–41973. I, pleopod 1; J, pleopod 2. Scale bars = 0.2 mm.

FIGURE 10. SEM photographs. Holodentata triangulata sp. nov., paratype ♀, ZMH–41973. A, dorsal view and detail of the uropod. Scale bar = 100 µm. B, frontal margin of head in dorsal view; C, antenna. Scale bars = 20 µm. H. caeca sp. nov., paratype ♀, ZMH–41971. D, dorsal view and details of the lateral margins of the pereonites. Scale bar = 100 µm.