Australian Amphipoda: Melitae

J.K. Lowry, P.B Berents & R.T. Springthorpe

Mallacoota diemenensis (Haswell, 1879)

Megamoera diemenensis Haswell, 1879a: 266, pl. 11, fig. 3. --Haswell, 1882: 259.

Elasmopus diemenensis. --Stebbing, 1906: 442. --Sheard, 1937: 24.

? Elasmopus subcarinatus. --Tattersall, 1922: 9.

Mallacoota diemenensis. --J.L. Barnard, 1972a: 244, figs 142-143. --Barnard & Barnard, 1983: 631.

not Elasmopus diemenensis. --Chilton, 1921: 74, fig. 10a-c.

Type material. SYNTYPES: 1 specimen, P18498 (apparently lost).

Type locality. Tasmania.

Description. Based on J.L. Barnard, 1972a: 244, figs 142-143. Head lateral cephalic lobes broad, truncated, with anteroventral notch or slit, anteroventral corner rounded. Antenna 1 longer than antenna 2; peduncular article 1 not geniculate with article 2, subequal in length to article 2, with 4 or more robust setae along posterior margin; flagellum with 50 articles (about); accessory flagellum with 5 articles (about). Antenna 2 peduncular article 2 cone gland reaching at least to end of peduncular article 3; article 4 longer than article 5; flagellum with 15 articles (about). Mandible palp present, well developed, article 3 rectolinear, with setae mostly terminal, longer than article 1 (slightly) or subequal to article 1, article 2 subequal to article 3, article 1 not produced, subequal to article 2, about twice as long as broad. Maxilla 1 inner plate with setae mainly terminal.

Pereon. Gnathopod 1 not sexually dimorphic; coxa anteroventral corner produced, rounded (slightly), coxa posteroventral corner notch present (weak); merus without posterodistal tooth; carpus about 2 x as long as broad; propodus without anterodistal projection, posterodistal margin not swollen, palm acute, straight, defined by posterodistal corner, defined by posterodistal robust setae. Gnathopod 2 sexually dimorphic; subchelate; left and right gnathopods subequal in size; coxa posteroventral corner notch present (weak); merus with sharp posteroventral tooth; carpus compressed; propodus without medial depression, with strong setal bunch, palm extremely acute, convex, sculptured (distally), without robust setae, without posterodistal robust setae, without posteroventral corner; dactylus closing along palm, not reaching end of palm, apically blunt. Peraeopod 5 basis posterior margin straight. Peraeopod 5 basis posteroventral corner narrowly rounded or subquadrate. Peraeopod 6 coxa anterior lobe ventral margin slightly produced, rounded. Peraeopod 6 basis posterior margin straight. Peraeopod 6 basis posteroventral corner narrowly rounded or subquadrate. Peraeopod 6 propodus not expanded posterodistally. Peraeopod 7 basis posterior margin convex. Peraeopod 7 basis with posterior margin smooth or minutely castelloserrate, posteroventral corner narrowly rounded or subquadrate. Peraeopod 7 propodus not expanded posterodistally.

Pleon. Pleonite 1 without dorsal serrations, without dorsodistal spines, dorsally bicarinate. Pleonite 2 without dorsal serrations, without dorsodistal spines, dorsally bicarinate. Pleonite 3 without dorsal serrations, without dorsodistal spines, dorsally bicarinate. Epimeron 1 anteroventral corner without curved spine. Epimera 1-2 posteroventral margin without spines above posteroventral corner. Epimeron 3 posterior margin smooth, posteroventral corner with strongly produced acute spine, posteroventral margin smooth. Urosomite 1 without dorsal carina, without a small dorsal hump, without dorsal serrations, without spines or gape, dorsally bicarinate. Urosomite 1 without posterodorsal spine. Urosomite 2 posterior margin smooth, without dorsolateral robust setae. Urosomite 3 without dorsal robust setae. Uropod 1 peduncle with basofacial robust seta, without distoventral spur. Uropod 3 subequal or slightly exceeding length of uropods 1 and 2; inner ramus subequal in length to outer ramus; outer ramus medium length (1.1 to about 1.5 x longer than peducle), 1-articulate. Telson cleft. Telson without robust setae on inner margins. Telson each lobe with 3 or more apical/subapical robust setae, apical conical extension reaching at least halfway along longest seta.

Habitat. Marine; algae.

Depth zone. Littoral, or Continental shelf.

Remarks. No known species of Mallacoota has an acutely produced anteroventral corner of coxa 1, such as the one illustrated for M. diemenensis by Chilton (1921). Based on the few illustrations available, Chilton's (1921) specimen may be an undescribed species of Parelasmopus.

Distribution. Victoria: Port Phillip (J.L. Barnard, 1972a). Tasmania: (Haswell, 1879a); Bass Strait (Chilton, 1921). South Australia: Pearson Islands (J.L. Barnard, 1972a); West Island (J.L. Barnard, 1972a).

Australian geographic areas. South-eastern Australia, or Southern Australia.

Pereon. Gnathopod 2 carpus long; without strong concentration of setae, palm acute, straight, smooth, defined by posterodistal robust setae; reaching end of palm, apically acute/subacute.

Cite this publication as: 'J.K. Lowry, P.B Berents & R.T. Springthorpe (2000 onwards). Australian Amphipoda: Melitae Descriptions, Illustrations, Identification and Information Retrieval. Version: 2 October 2000. https://crustacea.net'.