Mallacoota worimi, Hughes, 2011

HUGHES, L. E., 2011, New species of Hoho, Mallacoota and Parelasmopus (Maeridae: Amphipoda) from Australian waters, Zootaxa 2955 (1), pp. 1-79 : 65-68

Mallacoota worimi sp. nov

(Figs 42, 43)

Type material. Holotype, male, 9.2 mm, dissected,4 slides, AM P.85245 . Paratypes: female, 9.0 mm, dissected, 1 slide, AM P.85246; 1 male, 2 female, 1 immature, AM P.85247, south-west side of Boondelbah Island , east of Port Stephens (32°42”29’S 152°13”32’E), 10 m, corallimorphs and red algae on barnacles scraped off large boulder, sloping boulder reef meeting flat sand bottom, 10 March 2006, coll. A. Murray, RV Baragula ( NSW 2917 ) .

Type locality. South-west side of Boondelbah Island, east of Port Stephens , New South Wales (32°42”29’S 152°13”32’E).

Etymology. Named from the indigenous tribe of the Port Stephens region.

Description. Based on holotype, male, 9.2 mm, AM P.85245.

Head. Eyes ovate; lateral cephalic lobe broad, truncated, anteroventral margin with notch/slit. Antenna 1 longer than antenna 2; peduncular article 1 shorter than article 2, without robust setae along posterior margin; article 2 longer than article 3; flagellum articles broader than long, with 30 articles; accessory flagellum minute, with 3 articles. Antenna 2 peduncular article 2 cone gland not reaching to end of peduncular article 3; article 4 subequal in length to article 5; flagellum with 11 articles. Maxilla 1 inner plate subtriangular, with 2 apical plumose setae. Lower lip outer lobes with two pair of ducts, mandibular lobes apically subacute. Mandible accessory setal row well developed with 4 setae; molar well developed, triturative; mandibular palp well developed, 3-articulate; article 1 three times as long as broad, shorter than article 2; article 2 subequal to article 3, without setae; article 3 rectolinear, short (3 times as long as broad), subequal to article 1, with 2 apical setae.

Pereon. Gnathopod 1 coxa anterior margin concave, anteroventral corner produced, rounded; carpus about twice as long as broad, subequal in length to propodus; propodus medial surface with comb, palm acute, convex, entire, defined by posterodistal corner with 2 robust setae. Gnathopod 2 subchelate; basis slender, anterodistal corner subquadrate; merus with subquadrate distoventral corner; carpus compressed, lobate, projecting between merus teeth, palm defined by posteroventral tooth, without posterodistal robust setae, subpalmar surface smooth; dactylus without posteroproximal shelf, apically truncated, hammer-like, closing along palm. Pereopod 4 coxa posteroventral lobe well developed, with subrectangular posteromedial corner. Pereopods 5–7 basis slightly expanded, posterior margin convex, minutely castelloserrate, without long slender setae, posteroventral corner broadly rounded; merus and carpus weakly broadened; carpus and propodus with long, slender setae along posterior margin; propodus not expanded posterodistally; dactylar ungues simple. Pereonite 7 without carina.

Pleon. Pleonites 1–3 without carina. Epimera 1–2 posteroventral corner with small acute tooth. Epimeron 3 ventral margin smooth, posteroventral margin smooth, posteroventral corner subquadrate. Urosomite 1 bicarinate, subtriangular. Urosomites 2–3 without carina. Uropod 1 peduncle with 1 basofacial seta; outer ramus slightly shorter than inner ramus. Uropod 2 outer ramus slightly shorter than inner ramus. Uropod 3 rami distally truncated, apical robust setae long; inner ramus short (length 1.8 times breadth), slightly shorter than outer ramus; outer ramus longer than peduncle. Telson deeply cleft, as long as broad, tapering distally, apical margins concave, each lobe with 3 long and 1 short apical robust setae.

Female (sexually dimorphic characters), based on AM P.85246. Gnathopod 2 propodus without sparse setal bunches along posterior margin, palm without proximal shelf, defined by corner, with 2 robust setae; dactylus closing along palm.

Remarks. Mallacoota worimi sp. nov. is most similar to M. malua with the male gnathopod 2 propodus having a dense medial setal bunch, midmedial tooth and palm defining tooth. Mallacoota worimi sp. nov. can be separated by the presence of a small third tooth at the end of the palm and the large apically blunt dactylus. The blunt hammer-like dactylus is also known from M. nananui and M. latidactylus however the palmar tooth formula of gnathopod 2 differs between these species.

Distribution. Australia. New South Wales: Port Stephens (current study).