Dexaminoculus grobbeni ( Spandl, 1923 ), 1981

Myers, Alan A., 2009, Dexaminidae *, Zootaxa 2260 (1), pp. 393-424 : 394-397

Dexaminoculus grobbeni ( Spandl, 1923)

( Figs 1 , 2 )

Sphaerophthalmus grobbeni Spandl, 1923: 14 . — Spandl, 1924: 61–63, fig. 23. —J.L. Barnard, 1969: 480, fig. 173a. Dexaminoculus grobbeni . — Lowry, 1981: 191–197, figs 1–5. — Ledoyer, 1984: 44–45, fig. 21.

Material examined. 2 males, 5 females, 1 juvenile, AM P78017 ( JDT / LIZ 9 ) ; 4 males, 2 females, 1 juvenile, GCRL 2881 ( JDT / LIZ 10 ) ; 1 male, 1 female, AM P78018 ( JDT / OPH 4 ) ; 4 males, 4 females, 1 juvenile, AM P78019 ( JDT / OPH 8 ) ; 1 female, AM P78020 ( JDT / OPH 11 ) ; 1 female, AM P70867 ( QLD 1654 ) ; 1 female, AM P70845 ( QLD 1666 ) ; 1 female, AM P70914 ( QLD 1672 ) ; 1 juvenile, AM P71133 ( QLD 1742 ) ; 1 male,

AM P71341 ( QLD 1805 ) ; 5 males, 1 female, AM P71424 ( QLD 1805 ) ; 34 males, AM P71515 ( QLD 1805 ) ; 15 males, AM P71520 ( QLD 1805 ) .

Type Locality. Gulf of Suez, Red Sea (~ 28°40'N, 32°57'E) .

Description. Based on 1 female, 2.6 mm, AM P71424; 2 females, 2.3–2.4 mm, GCRL 2881.

Head. Head ocular spine absent or weak. Antenna 1 peduncle article 1 with posteroproximal acute or subacute process. Antenna 2 poorly developed, very short, 4-articulate; peduncle article 4, anterior margin sparsely setose. Maxilla 1 palp very stout, about twice as long as broad. Maxilla 2 inner plate subequal to outer plate in length, with dense apical slender setae, inner margin without setae. Maxilliped palp 3-articulate.

Pereon. Gnathopod 1 propodus subtriangular, broadest distally, anterior margin convex, palm convex; dactylus posterior margin entire. Gnathopod 2 coxa subtriangular, anterodistal margin entire; merus shorter than carpus. Pereopods 3–7 simple or scarcely prehensile. Pereopod 4 coxa truncate distally, posterodistal corner slightly produced, subacute. Pereopods 5–7 of diverse morphology. Pereopod 6 basis, posterior lobe moderately expanded, rounded posterodistally. Pereopod 7 coxal gill present.

Pleon. Epimeron 3 posterodistal excavation deep, posteroventral spine large. Urosomite 1 posterodorsal spine small, acute. Telson lobes with apices minutely serrate.

Colour in life. Eyes red. Antennal peduncles translucent grey flecked with white; flagellum of antenna 2 pale rust. Head, pereon, pleon and urosome translucent pale olive green, heavily flecked with white, sparsely flecked with rust. Pereopods translucent grey banded with white.

Male (sexually dimorphic characters). Based on 5 males, 2.8–3.3 mm, AM P71424; 1 male, 3.0 mm, AM P7515 ; 4 males, 2.4–2.8 mm, GCRL 2881 . Antenna 2 well-developed, elongate; peduncle article 4, anterior margin densely setose. Gnathopod 1 propodus L-shaped, broadest proximally, anterior margin weakly emarginate, palm deeply excavate, broadly angled, without pectinate slender seta .

Habitat. Sand or algal turf bottoms along reef front or on patch reefs at depths of 1– 25 m. Males often found in night plankton.

Remarks. Dexaminoculus grobbeni can be distinguished from two of the other three known species in the genus ( D. acutipes Ledoyer, 1979 and D. cavimana Ledoyer, 1983 from Madagascar) by the weakly emarginate anterior margin of the propodus of gnathopod 2 in the male (margin convex in the other species) and by the deeply excavate posterodistal margin and large posterodistal spine on epimeron 3 (weakly excavate with a small spine in the other species). It is very similar to D. lacinimanus Ortiz and Lalana, 1999 from Indonesia, from which it can be distinguished by the 4-articulate antenna 2 of the female (5+-articulate in D. lacinimanus ), the distally subtruncate coxa 4 (rounded in D. lacinimanus ) and the minutely serrate apices on the telson lobes (apices entire in D. lacinimanus ). Although Lowry (1981) does not illustrate the posteroproximal process on antenna 1, peduncle article 1, a re-examination of the Lizard Island material used in his description has confirmed its presence (J.K. Lowry, pers. com.).

Distribution. Australia. Queensland: Lizard Island, Orpheus Island, One Tree Island ( Lowry 1981, current study). New Caledonia. Noumea ( Ledoyer 1984). Red Sea. Gulf of Suez ( Spandl 1923, 1924).

Figures

FIGURE 1. Dexaminoculus grobbeni (Spandl, 1923), female, 3.6 mm, Lizard Island, Great Barrier Reef (after Lowry 1981).

FIGURE 2. Dexaminoculus grobbeni (Spandl, 1923), lectotype, female, 2.9 mm, Gulf of Suez, Red Sea (after Lowry 1981); female 2, 2.3 mm, GCRL 2881, North Point, Lizard Island; male, 3.9 mm, Lizard Island (after Lowry 1981); male 2, 3.0 mm, AM P71515, Third Beach, Lizard Island, Great Barrier Reef.