Australian Amphipoda: Melitae

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

Mallacoota euroka Lowry & Springthorpe

Mallacoota subcarinata. --J.L. Barnard, 1972a: 247, fig. 144. --Barnard & Barnard, 1983: 632 (in part).

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Type material. HOLOTYPE: male, 10.1 mm, AM P60561. PARATYPES: female, AM P60562; 8 specimens, AM P27034.

Type locality. Between Troubridge Light and Cape Jervis, South Australia (35º20'S 137º40'E), sponge on mud bottom, 20 m.

Description. Based on holotype male, AM P60561 and paratype female, AM P60562. 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 29 articles (about); accessory flagellum with 3-4 articles. Antenna 2 peduncular article 2 cone gland reaching at least to end of peduncular article 3; article 4 longer than article 5, or article 4 subequal to article 5; flagellum with 10 articles (about). Mandible palp present, well developed, article 3 cone-like, with setae mostly terminal, longer than article 1, article 2 shorter than article 3, article 1 not produced, subequal to article 2, about twice as long as broad. Maxilla 1 inner plate with setae mainly terminal (about 5).

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

Pleon. Pleonite 1 without dorsal serrations, without dorsodistal spines, not dorsally bicarinate. Pleonite 2 without dorsal serrations, without dorsodistal spines, not dorsally bicarinate. Pleonite 3 without dorsal serrations, without dorsodistal spines, dorsally smooth. 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 scarcely one third along longest seta.

Habitat. Marine; sponges on mud bottom.

Depth zone. Littoral (20 m).

Remarks. This species was originally described as Mallacoota subcarinata phenotype A by J.L. Barnard (1972a). It has a large spine on epimeron 3, like M. subcarinata and M. diemenensis. Mallacoota euroka differs from M. diemenensis in having no dorsal spines on pleonites 1 to 3. It differs from M. subcarinata in the number of robust setae on the first pedunclular article of antenna 1 (five in M. euroka and one to three in M. subcarinata), in having posteroventral notches on coxae 1 and 2 and in having a convex posterior margin on the basis of peraeopod 7.

Distribution. Victoria: Port Phillip (J.L. Barnard, 1972a). South Australia: Cape Jervis (AM).

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

Type material. HOLOTYPE: male, AM P60561. PARATYPES: female, AM P60562; 8 specimens, AM P27034.

Pereon. Gnathopod 2 carpus short; setose, smooth, without robust setae, defined by posterodistal robust setae, defined by posteroventral corner; 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'.