Melita sampsonae, Lowry & Springthorpe, 2009

Lowry, J. K. & Springthorpe, R. T., 2009, Melitidae, the Melita group *, Zootaxa 2260 (1), pp. 718-735 : 726-730

Melita sampsonae sp. nov.

( Figs 6 , 7 )

Type material. Holotype, male, 4.2 mm, AM P77779, Mermaid Cove , Lizard Island (14°38.90'S 145°27.26’E), swash/subtidal, protected beach with patch reefs offshore, coarse coral sand with pieces of coral, 0.5–1.0 m, S.E. LeCroy, 2 July 2001 ( SEL /LZI-1-1) . Paratypes: female ovigerous, 3.4 mm, AM P77780, male, 4.8 mm, AM P77781, type locality .

Type locality. Mermaid Cove , Lizard Island (14°38.90'S 145°27.26'E) .

Etymology. Named for Marilyn Sampson (Australian Museum Members), in recognition of the support of the Australian Museum Members for the Lizard Island Amphipod Workshop in 2005.

Description. Based on holotype, male, 4.2 mm, AM P77779.

Head. Head lateral cephalic lobe broad, apically rounded; eyes well developed, ovate; anteroventral margin with anteroventral notch, anteroventral margin with small ventral notch, anteroventral corner rounded. Antenna 1 slightly longer than antenna 2; peduncular article 1 subequal in length to article 2, with 3 robust setae along posterior margin; peduncular article 2 not geniculate, article 2 longer than article 3; accessory flagellum short, minute, with 3 articles (third tiny); flagellum with 15 articles. Antenna 2 not strongly setose; peduncular article 4 longer than article 5; flagellum with 6 articles. Mandible molar medium size; accessory setal row well developed; palp well developed, 3-articulate; article 1 about as long as broad, not produced distally; article 2 subequal to article 3; article 3 well developed, slightly tapering distally, setae along both margins and terminal. Maxilla 1 inner plate long, subrectangular, with 7 mainly apical setae. Maxilla 2 inner plate without oblique setal row on inner face, with marginal setal row. Lower lip inner lobes vestigial or absent. Maxilliped palp article 3, about 1.5 x as long as wide.

Pereon. Gnathopod 1 sexually dimorphic; coxa anteroventral corner not produced, anterior margin straight; merus without posterodistal tooth; carpus about 2 x as long as broad, carpus longer than propodus, length 1.3 x propodus; propodus without hump along anterior margin, anterodistal projection forming triangular hood over dactylus, palm nearly transverse, straight, entire, without anterodistal projection near base of dactylus, posterodistal margin not swollen, defined by posterodistal corner, corner without posterodistal robust setae; dactylus articulating distinctly with propodus, fitting palm, posterior margin swollen at base. Gnathopod 2 significantly enlarged in male, not in female, sexually dimorphic (size and shape); subchelate; carpus compressed, length 0.8 x breadth, lobate, projecting between merus and propodus; merus acutely produced distoventrally; propodus expanded, with strong setal bunch, with medial depression, forming posteromedial channel, palm acute in male and female, extremely acute without corner, convex, smooth, lined with robust setae, without posteroventral corner, with posterodistal robust setae; dactylus closing across medial surface of propodus, reaching end of palm, without setae on anterior margin. Pereopod 4 coxa posteroventral lobe well developed, subrectangular. Pereopod 5 basis expanded; posterior margin convex, posteroventral corner broadly rounded; carpus and propodus with few (or none) long, slender setae along anterior margin. Pereopod 6 coxa slightly produced, rounded; basis slightly convex, posteroventral corner narrowly rounded or subquadrate. Pereopod 7 basis posterior margin convex, with posterior margin smooth or minutely castelloserrate, evenly rounded posteriorly, produced posterodistally (lobate), posteroventral corner insignificant.

Pleon. Pleonites 1–3 without dorsal spines or seta. Urosomites 1–3 without dorsal spines. Epimeron 1 anteroventral corner rounded, posteroventral corner subquadrate. Epimeron 2 posteroventral corner subquadrate. Epimeron 3 ventral margin smooth, posteroventral corner with small acute spine, posteroventral margin smooth. Urosomite 2 posterior margin smooth; dorsally smooth, with 2 groups of 3 tiny robust setae. Urosomite 3 without dorsal setae. Uropod 1 with basofacial robust seta. Uropod 3 rami distally truncated; inner ramus scale-like, much shorter than outer ramus; outer ramus long, length 3 x breadth, about 2 x peduncle, 2-articulate, article 2 short. Telson cleft, as long as broad, tapering distally, lobes apically acute or subacute, without dorsal robust setae, with apical/subapical robust setae, each lobe with 3 or more short and long apical/subapical robust setae, with robust setae on outer margins and inner margins, apical conical extension absent.

Female (sexually dimorphic characters). Based on paratype, female, 3.4 mm, AM P77780. Gnathopod 1 propodus without anterodistal projection, palm convex. Gnathopod 2 propodus without strong concentration of setae, without medial depression, without medial pad, acute with well defined corner, with sparse robust setae, defined by posteroventral corner; dactylus closing along palm, with 1 or 2 setae on anterior margin. Pereopod 6 coxa anterior lobe ventral margin strongly produced, hooked .

Habitat. Brackish littoral. Remarks. Melita sampsonae appears to be part of a closely related group of species: M. bingoensis

Yamato, 1987, M. koreana Stephensen, 1944, M. nagatai Yamato, 1987 (from Japan and Korea), M. pahuwai

J.L. Barnard, 1970 (from Hawaii) and B. intermedia Sheridan, 1979 (from Florida, USA). These species all have a triangular-shaped posterodistal hood on the propodus of male gnathopod 1, an uproduced anterodistal corner on the coxa of gnathopod 1, a medial depression on the propodus of gnathopod 2, a well developed posteroventral lobe on coxa 4, sexually dimorphic coxa 6 and a small acute spine defining the posteroventral corner of epimeron 3. Melita sampsonae differs from all of these species in the relatively short, broad outer ramus on uropod 3.

Melita sampsonae differs most obviously from M. myersi , the only other Melita known from the GBR as follows: antenna 1 about as long as antenna 2 (much longer in M. myersi ); anterodistal hood on propodus of male gnathopod 1 triangular (rounded in M. myersi ); dactylus closing across palm of strongly setose propodus of male gnathopod 2 (dactylus closing along palm of sparsely setose propodus in M. myersi ); coxa of pereopod 4 with well developed posteroventral lobe (lobe absent in M. myersi ); posteroventral corner of epimeron 3 a small acute spine (a strongly produced spine in M. myersi ); and the outer ramus of uropod 3 has 2 articles (1 article in M. myersi ).

Distribution. Australia. Queensland: Mermaid Cove, Lizard Island (current study).

Figures

FIGURE 6. Melita sampsonae sp. nov., holotype, male, 4.2 mm, AM P77779, *paratype, male, 4.8 mm, AM P77781, Mermaid Cove, Lizard Island, Great Barrier Reef.

FIGURE 7. Melita sampsonae sp. nov., holotype, male, 4.2 mm, AM P77779, paratype, female, 3.4 mm, AM P77780, Mermaid Cove, Lizard Island, Great Barrier Reef.