Metopoides typicus (Walker, 1906)

Krapp-Schickel, Traudl, 2011, On the Austral-Antarctic stenothoids Proboloides, Metopoides, Torometopa and Scaphodactylus (Crustacea Amphipoda) Part 2: the genus Proboloides, with description of two new genera and the transfer of two nominal species to Metopoides, ZooKeys 86, pp. 11-45 : 19-21

Metopoides typicus (Walker, 1906) Figs 34

Proboliella typica Walker 1906: 14; 1907: 20-21 t.6 fig. 10

Proboloides typica Schellenberg 1926: 323-24 fig, 41; De Broyer et al. 2007: 213 not Proboloides typica KH. Barnard 1932: 109, f. 57

Metopoides sp. Bellan-Santini and Ledoyer 1974: 700 fig. 38 B

Material examined:

Cape Bird, EBS, C3-C4, 70-100m, 14.12. 1971, several spec.; tide crack, near Cape Spencer, White Island, Ross Ice Shelf, 78°01'0"S, 167°20'0"E, 28.XII. 1976, coll. P. Ensor (AMS P 25504); Southern Rookery, Cape Bird, Ross Island, Antarctica (approx. 77°13'0"S, 166°27'0"E) AM P.80875 (1 slide); slide of " Metopoides sp. ", Kerguelen,MNVCR.

Redescription after material from the Australian and Verona Museum:

Body

smooth. Eyes rounded, medium size.

Length.

3-3,5 mm.

Antennae.

A1 less than 2/3 of body length, peduncle robust, art 1 shorter than three times wide; acc. flag. with 2 (very small) articles, flagellum 10 arts. A2 subequal in length to A1, peduncle robust, art 4 somewhat> art 5, flagellum about as long as peduncle art 5, with 7 arts (Walker: without acc. flag., A1 reaching to the middle of the flagellum of A2).

Mouthparts.

Md incisor and raker spine row well developed; no clear molar cusp; palp with 3 arts, art 3 about 1/3-1/2 length of art 2, with 3 distal long setae (Walker: Md palp lacking third art, therefore creating a new genus Proboliella; but Schellenberg already noticed 1926: 323 fig. 41, that there is a well-developed third article). Mx 1 IP with 1 distal seta, OP with 6 strong robust setae, palp with 2 arts; Mx 2 inner plate ordinary, shorter than outer; Mxp IP not fused, 2/3 length of ischium; OP narrow, well developed, reaching more than half of merus length; dactylus long, subequal to propodus.

Coxae.

Cx2 with rounded anterior margin straight behind, angle rounded with small tooth; Cx3 narrow with parallel margins, Cx4 not excavated, inferior and posterior margin rounded, about as long as wide.

Gnathopods.

Gn1, 2 propodi different in size and shape. Gn1 dactylus ordinary; propodus with parallel margins, palm well defined (corner about 120°), somewhat longer than half length of propodus, about twice as long as wide; carpus shorter than propodus, triangular, longer than wide, merus incipiently chelate. Gn2 length of propodus more than 2/3 of basis in male, less in female; propodus subelliptical, twice the size of propodus Gn1; hind margin half length of palm which is in male and female with incisions, palmar corner well defined by acute tooth-shaped prolongation and U-shaped incision. Dactylus clearly shorter than palm, probably working together with robust setae of palmar corner. Gn2 carpus shorter than wide, cup-shaped, merus not lobate.

Peraeopods.

P4 merus anterodistal margin somewhat lengthened. P5 dactylus long, weak, much longer than half of slim propodus; merus posterodistal margin not reaching half of carpus length, basis slender without lobe. P6 basis hind margin harmonically rounded, clearly longer than wide, merus posterodistal corner acutely lengthened but not widened, not reaching to half of carpus length. P7 basis and merus similar to P6.

Epimeral plates.

Ep3 posterodistally lengthened to triangular corner.

Uropods.

U1 peduncle slightly longer than subequal rami, with many robust setae; U2 peduncle longer than shorter ramus, rami clearly unequal; U3 peduncle shorter than ramus, first article of ramus shorter than peduncle, ramus art 2 about ¾ of art 1.

Telson.

Not reaching end of peduncle U3; about twice as long as wide; distally triangulary pointed, medio-laterally with 2-3 robust setae.

Sexual differences.

Probably small.

Distribution.

Antarctica, Hut Point near Mc Murdo, 77.47°S ( Walker 1906, 1907); S-Victoria Land, Gauß Station ( Schellenberg 1926); White Island, Ross Ice Shelf, 78°01'0"S, 167°20'0"E, (AMS P 25504); Cape Bird, Ross Island, Southern Rookery, 77°13'0"S, 166°28'0"E (AMS P 80875).

Ecology.

Steeply sloping rock bottom with encrusted bryozoans and hydroids.

Remarks:

As this species clearly has an accessory flagellum (although tiny), unspecialized gnathopod propodi and neither much lengthened nor widened merus on P5-7, it has to be placed in the genus Metopoides, and even is a very “typical” representative of that genus.