Monoculodes tropicalis, Hughes & Lowry, 2009

Hughes, L. E. & Lowry, J. K., 2009, Oedicerotidae *, Zootaxa 2260 (1), pp. 746-758 : 750-751

Monoculodes tropicalis sp. nov.

( Figs 3 , 4 )

Type material. Holotype, female (dissected), 4 slides, 6.0 mm, AM P78134, Blue Lagoon , Lizard Island, Queensland, Australia (~ 14°40’S 145°28’E), plankton tow, night, no moon, 6 m, J.M. Leis, 20 October 1979 ( JML 20-10 - 1 ) . Paratypes: 3 unsexed, AM P78135 ( JML 20-10 - 1 ) .

Additional material examined. 1 unsexed, AM P28309 (HI-3); 16 unsexed, AM P28310 (HI-3); 1 unsexed, AM P78136 (78 LIZ PBW-2); 1 unsexed, AM P78137 (78 LIZ PBW-6); 8 unsexed, AM P78138 ( JDT / OPH 6c); 1 unsexed, AM P78139 ( JML 7-10-1); 1 unsexed, AM P78140 ( JML 7-10-2); 1 unsexed, AM P78141 ( JML 16-10-7); 1 unsexed, AM P78142 ( JML 16-10-8); 1 unsexed, AM P78143 ( JML 16-10-9); 2 unsexed, AM P78144 ( JML 20-10-2); 2 unsexed, AM P78145 ( QLD 33); 3 unsexed, AM P78147 ( QLD 63); 1 unsexed, AM P70873 ( QLD 1654); 1 unsexed, AM P78148 ( QLD 1900); 2 unsexed, AM P78149 ( QLD 1922); 3 unsexed, AM P78150.

Type locality. Blue Lagoon , Lizard Island, Great Barrier Reef, Queensland, Australia (~ 14°40’S 145°28’E) .

Etymology. The name signals the first record of Monoculodes from the tropical Indo-West Pacific.

Description. Based on holotype, female (dissected), 6.0 mm, AM P78134.

Head. Head rostrum well developed, broad, strongly deflexed, apically acute; eyes ovate, coalesced at top of head, situated fully within head; lateral cephalic lobe truncate. Antenna 1 peduncle sparsely setose; peduncular article 1 without tooth, longer than article 2, longer than article 3; peduncular article 3 elongate, subequal to article 2; flagellum without callynophore, without calceoli. Antenna 2 peduncle sparsely setose; calceoli with separated proximal and distal elements, proximal element convex, turret-shaped, broad lamellar receptacle with two apical cusps. Mandible molar well developed, triturative; left incisor a straight weakly serrate blade; palp elongate, article 2 straight, article 3 slightly shorter than article 2, with many marginal setae. Lower lip inner lobes separated. Maxilla 1 outer plate with 9 setal-teeth. Maxilla 2 inner plate without oblique setal row. Maxilliped inner plate present; palp article 2 expanded along midmedial margin.

Pereon. Gnathopods 1–2 well developed; propodi similar in shape, subchelate. Gnathopod 1 subequal to gnathopod 2; carpal lobe short (extending less than half the length of the propodus), broad (as broad as long), divergent from propodus margin; propodus ovate, posterodistal margin smooth, palm acute, margin smooth. Gnathopod 2 carpus elongate, longer than broad, carpal lobe short (extending less than half the length of propodus), broad (as broad as long), divergent from propodus margin; propodus ovate (about 2 x as long as broad), posterodistal margin smooth, palm acute margin smooth, setose. Pereopods 3–4 carpi shorter than propodi; propodi posterior margins without setae, dactyli well developed, shorter than propodi, without apical setae. Pereopod 3 coxa anterior margin rounded, anteroventral corner not produced, ventral margin convex. Pereopod 4 coxa posterior margin excavate, with posteroventral lobe. Pereopods 5–6 similar in form; propodi posterior margins sparsely setose; dactyli slender, tapering, each with circular unguis. Pereopod 5 coxa small, depth distinctly less than coxa 4; dactylus longer than propodus. Pereopod 6 dactylus longer than propodus. Pereopod 7 basis with posteroproximal lobe, posterior margin straight, posterodistal lobe absent.

Pleon. Epimeron 3 posterodistal corner narrowly rounded to subquadrate. Uropod 1 subequal in length to uropod 2; peduncle, lateral margin with 19 robust setae; rami subequal in length, with small robust setae; inner ramus margins smooth. Uropod 2 shorter than uropod 3; rami subequal in length, with small robust setae. Uropod 3 greatly enlarged; rami subequal in length, with small robust setae. Telson entire, apically truncate, with apical setae.

Habitat. Monoculodes tropicalis sp. nov. has been found swimming in the water column at night and on shallow coarse to fine sand bottoms (1 to 17 m) during the day.

Remarks. According to Bousfield & Chevrier (1996) the genus Monoculodes is still poorly defined because of the limited description of the type species, M. demissus Stimpson, 1853 . Monoculodes tropicalis sp. nov. is placed in Monoculodes (sensu stricto) based on the subsimilar gnathopods with short carpal lobes ( Bousfield & Chevrier 1996).

Monoculodes tropicalis differs significantly from the other Indo-West Pacific species of Monoculodes ( M. abacus J.L. Barnard, 1961 , M. dentimanus Jo, 1990 , M. koreanus Jo, 1990 , M. muwoni Jo, 1990 ) as follows: gnathopods 1–2 propodi more broadly subovoid in shape, and pereopod 7 basis with posterior proximal lobe and without posterodistal lobe. The presence of calceoli on the flagellum of antenna 2 ( Fig. 3 A, B ) is apparently the first record of calceoli for the genus Monoculodes . The structure of the calceolus conforms to the oedicerotid type seven as described by Lincoln & Hurley (1981) with separated proximal and distal elements. The broad lamellar receptacle around the proximal element has two apical cusps like those noted on Oediceropsis bicornuta Bellan-Santini, 2007 . This appears to be the first type seven calceolus reported with a convex, turret-shaped proximal element. Previously documented oedicerotid calceoli have a concave cupshaped proximal element.

Monoculodes tropicalis can be separated from other oedicerotids on the GBR by the short, subchelate gnathopods with subovoid propodi and short-lobed carpi.

Monoculodes tropicalis is the first tropical species described in the genus. Ledoyer (1984) reported a single specimen of Monoculodes sp. from New Caledonia, but did not illustrate or describe the material.

Distribution. Australia. Queensland: Goodes and Hawkesbury Islands, Torres Strait (current study); Eagle and Lizard Islands (current study); Fantome Island (current study); Heron Island (current study).

Figures

FIGURE 3. Monoculodes tropicalis sp. nov., holotype, female, 6.0 mm, AM P78134, Blue Lagoon, Lizard Island, Great Barrier Reef. A - SEM picture length 15 µm, B - SEM picture length 180 µm.

FIGURE 4. Monoculodes tropicalis sp. nov., holotype, female, 6.0 mm, AM P78134, Blue Lagoon, Lizard Island, Great Barrier Reef.