Guernea yamminye Thomas & Barnard, 1991

Myers, Alan A., 2009, Dexaminidae *, Zootaxa 2260 (1), pp. 393-424 : 400-403

Guernea yamminye Thomas & Barnard, 1991

( Figs 5 , 6 , Pl. 3B)

Guernea yamminye Thomas & Barnard, 1991: 306–309 , figs 4(part)–6.

Material examined. 1 male, AM P70893 ( QLD 1653 ) ; 1 female, AM P71216 ( QLD 1758 ) ; 1 female, AM P71257 ( QLD 1771 ) ; 1 male, AM P71302 ( QLD 1761 ) ; 1 female, 1 juvenile, AM P71305 ( QLD 1772 ) ; 1 male, AM P71309 ( QLD 1756 ) ; 1 juvenile, AM P71313 ( QLD 1779 ) ; 1 male, AM P71342 ( QLD 1805 ) ; 97 males, AM P71408 ( QLD 1805 ) ; 2 females, AM P71446 ( QLD 1814 ) ; 6 males, AM P71514 ( QLD 1805 ) .

Type Locality. Near Mermaid Beach , Lizard Island, Queensland, Australia (~ 14°39’S 145°27’E) .

Description. Based on 1 female, 2.6 mm, AM P71216; 1 female, 2.1 mm, AM P71257; 1 female, 3.5 mm, AM P71305.

Head. Head lateral lobes acute or subacute. Eye medium, smaller than lateral lobe. Antenna 1 peduncle article 1 without short, dense brush setae lining posterior margin. Antenna 2 short, not longer than head; peduncle article 4 without short, dense brush setae lining anterior margin; flagellum short, 3-articulate. Mandible palp absent. Maxilla 1 palp stout, about three times as long as broad, without apical spout, with 1 apical slender seta. Maxilla 2 inner plate shorter than outer plate, with sparse apical slender setae, inner margin without setae. Maxilliped palp 4-articulate.

Pereon. Gnathopod 2 carpus approximately one and one-half times length of propodus. Pereopods 3–7 simple or scarcely prehensile. Pereopod 3 carpus with large robust setae on posterior margin. Pereopod 5 coxa posterior lobe well-developed, subequal to anterior lobe in depth. Pereopods 5–7 of diverse morphology. Pereopod 6 basis, posterior margin concave. Pereopod 7 coxal gill absent; merus and carpus expanded; carpus broadly ovate, partially enveloping propodus; propodus approximately one-half length of carpus.

Pleon. Urosomite 1 with dorsal hump, without dorsal keel, with 1 median dorsal carina. Urosomite 2–3 fused, with 2 dorsal humps, with 2 dorsolateral carinae, without dorsal robust setae. Uropods 1–2 inner ramus subequal in length to outer; apical robust setae of rami elongate, at least one-half length of corresponding ramus. Uropod 1 peduncle with basofacial slender setae. Uropod 3 peduncle with distolateral robust seta; inner ramus, inner margin with single short plumose slender seta; outer ramus, inner margin without long plumose slender setae, outer margin with robust seta. Telson lobes with slender apical setae.

Colour in life. Ivory overall, with a few small scattered rusty spots and faint banding on the antennae. The eye is mostly white, with a few red or rust-coloured ommatidia. Juveniles are similarly coloured

Male (sexually dimorphic characters). Based on 1 male, 2.2 mm, AM P71302; 1 male, 2.3 mm, AM P71309; 6 males, 2.1–2.6 mm, AM P71514. Eye bright red. Antenna 1–2 peduncle, all body segments and proximal parts of the coxae, pale rusty orange with darker markings in some areas. Eye very large, covering most of lateral lobe. Antenna 2 moderately long, approximately half length of body; peduncle article 4 with short, dense brush setae lining anterior margin; flagellum long, multiarticulate. Maxilla 1 palp without apical slender setae. Uropod 3 inner ramus, inner margin with long plumose slender setae; outer ramus, inner margin with long plumose slender setae .

Habitat. On rubble, sand or mud bottoms, occasionally with algae or seagrasses, on patch reefs or in back reef areas. Occurs at depths of 1– 25 m. Males often found in night plankton.

Remarks. Guernea yamminye can be distinguished from all other Australian members of the genus by the distinctive "triple-humped" morphology of the urosome. Only four other known species of Guernea exhibit this urosomal morphology: G. coalita ( Norman, 1868) from the north-eastern Atlantic and Mediterranean; G. longicornis Ledoyer, 1983 from Madagascar; G. reticulata ( Schellenberg, 1938) from the Bismarck Archipelago; and G. tumulosa Griffiths, 1976 from South Africa. Guernea yamminye differs from G. coalita in the 1-articulate palp of maxilla 1 (palp 2-articulate in G. coalita ), the excavate posterior margin of pereopod 6 (not excavate in G. coalita ) and the short propodus of pereopod 7 partially enveloped by the carpus ((propodus long, not enveloped by the carpus in G. coalita ). It differs from G. longicornis in the excavate posterior margin of the basis of pereopod 6 (not excavate in G. longicornis ) and the presence of a short robust seta on the outer margin of the outer ramus of uropod 3 in both sexes and a short plumose slender seta on the inner margin of the inner ramus in the female (these are lacking in G. longicornis ). Guernea yamminye differs from G reticulata in the lack of crenulations on the posterior margin of the basis of pereopod 7 (margin crenulate in G. reticulata ) and by having a less well-developed posterodistal lobe on the carpus of that appendage. It can be distinguished from G. tumulosa by the 1-articulate palp of maxilla 1 (2-articulate in G. tumulosa ) and by the subequal rami and elongate apical robust setae of uropods 1–2 (inner ramus shorter than outer and apical robust setae short in G. tumulosa ).

Distribution. Australia. Queensland: Lizard Island, Yonge Reef ( Thomas & Barnard 1991, current study).

Figures

FIGURE 5. Guernea yamminye Thomas & Barnard, 1991, holotype, male, 1.8 mm, NMV J20496, near Mermaid Beach, Lizard Island, Great Barrier Reef (after Thomas & Barnard, 1991).

FIGURE 6. Guernea yamminye Thomas & Barnard, 1991, female, 2.1 mm, AM P71257, Casuarina Beach, Lizard Island; female 2, 3.5 mm, AM P71305, Horseshoe Reef, Lizard Island; holotype, male, 1.8 mm, NMV J20496, near Mermaid Beach, Lizard Island, Great Barrier Reef (after Thomas & Barnard, 1991).