Metandania islandica Stephensen, 1925

Berge, JØrgen, 2001, Revision of the Amphipod (Crustacea: Stegocephalidae) genera Andaniotes Stebbing, 1897 and Metandania Stephensen, 1925, Journal of Natural History 35 (6), pp. 787-832 : 825-829

Metandania islandica Stephensen, 1925

(®gures 25±27)

Metandania islandica Stephensen, 1925: 136 .

Metandania islandica: Schellenberg, 1953: 187 .

Andaniotes islandica: Barnard and Karaman, 1991: 678 ( A. islandica synonymized with A. corpulentus ).

Material examined

HOLOTYPE: Zoological Museum, Copenhagen: immature 7 mm, 65 ss 14 ¾ N, 30 ss 39 ¾ W, 1318 m.

Additional material: Naturhistorisk a Museet, Gotenborg, Sweden: Female 22 mm ( Schellenberg, 1953: 187), 19 ss 49 ¾ N, 65 ss 01 ¾ W, 7900± 7625 m.

Distribution Known only from two localities in the north Atlantic, 1318±7900 m.

Description

The following description and ®gures are all from Schellenberg’s female, 22 mm.

Rostrum very small.

Antennae elongate. Antenna 1 shorter than antenna 2; ¯agellum four-articulate; accessory ¯agellum article 2 absent. Antenna 2 peduncle (articles 3±5) shorter than ¯agellum; article 3 short, about as long as broad; article 4 shorter than article 5.

Epistome curved (convex) and smooth; epistomal plate (medial keel) produced into a large conspicuous medial keel.

Mouthparts not elongate or pointed.

Mandible incisor transverse; smooth and toothed; left lacinia mobilis present; powerful; laterally straight; not conical.

Maxilla 1 palp uni-articulate, oval, setae short, robust, cuspidate, apex reaching above the apex of outer plate; outer plate distally rounded; ST in two parallel rows, ®rst marginal and second submarginal, ST ®rst row with six setae (ST1±5, ST7), ST 1 ordinary (similar to ST 2±4), gap between ST 5 and ST 7, ST A±C present, part of second row; inner plate without a well developed shoulder, setae pappopectinate.

Maxilla 2 ordinary; outer plate setae without distal hooks or cleft; inner plate setae row A covering the entire margin, appressed to row B, row A setae pappose, ®rst three or four setae diOEerentiated from the other setae (weakly pappopectinate); row B setae proximally pappose, distally with cusps; row C present; row D absent.

Maxilliped palp four-articulate; article 2 distally unproduced; dactylus distally simple (pointed); inner plate not exceeding base of palp article 1, with six nodular setae; medial setae-row present, not reduced, transverse, setae cuspidate; distal setaerow present; inner setae-row present, row not reduced (more than two setae), setae conspicuously large and strong; outer plate outer setae-row present, marginal, setae attached normally; setae short, straight; inner setae-row present but strongly reduced, parallel but not appressed to outer row, setae short simple, slender; distal setaegroup present, setae attached normally; setae long robust.

Labrum elongate; lobes asymmetrical; right lobe ordinary; left lobe reduced.

Labium distally broad, oval.

Coxal plates and basis on the pereopods smooth. Coxae 1±3 contiguous.

Pereopod 1 coxal plate not as deep as basis; propodus subovate.

Pereopod 2 longer and thinner than pereopod 1; ischium not elongate, ratio length:breadth not exceeding 1.5; ischium distal posterior margin with plumose setae; propodus subrectangular; palm absent.

Pereopod 4 coxa posteroventral lobe small, reaching about the base of pereon segment 6; basis anterior and posterior margins with long setae, plumose setae on distal anterior margin, no plumose setae on distal posterior margin; ischium with plumose setae on posterior distal margin.

Pereopod 6 basis posteriorly expanded, expansion conspicuous, rounded posteriorly; with a row of long plumose setae.

Pereopod 7 basis anterior margin straight, distally rounded; with a medial row of setae present, setae short and robust.

Oostegites on pereopod 2±5. Gills on pereopods 2±7.

Pleonites 1±3 dorsally smooth.

Urosomites 2 and 3 free. Uropod 1 peduncle longer than rami, outer ramus as long as inner. Uropod 2 peduncle longer than rami, outer ramus shorter than inner. Uropod 3 peduncle longer than half the length of rami, outer ramus uni-articulate, outer ramus shorter than inner.

Telson as long as broad; shorter than uropod 3 peduncle, cleft, apically rounded, submarginal setae on apex of each lobe.

Males. Unknown.

Remarks

Stephensen (1925) described the present species based on a single immature female captured west of Iceland. Later, Schellenberg (1953) identi®ed a mature female captured at 19 ss 49 ¾ N 65 ss 01 ¾ W. The two specimens show some very important diOEerences (see table 1), but due to lack of material, it is impossible to determine whether the two specimens belong to two diOEerent species or if the diOEerences are due to one of them being immature.

However, both specimens also share some very important character-states that clearly group them together and at the same time separate them from Andaniotes . First, the epistome is convex, not laterally produced as in all species belonging to the genera Andaniexis , Andaniotes and Parandaniexis . The epistomal plate is large and conspicuous, and the labrum is not reduced, with the right lobe well developed. Furthermore, the mandibular incisor is partly toothed, resembling the state found in Andaniella , Andaniopsis and Bathystegocephalus , and the setae on the palp of the ®rst maxilla are short robust with cusps (versus long simple and slender in Andaniotes ). Examination of the left mandible has also revealed a lacinia mobilis of a very diOEerent morphology than found in any other stegocephalid species (this state was impossible to verify for the holotype, as it was partly damaged, but Stephensen’s original description is similar to the state found on Schellenberg’s female): the lacinia mobilis is almost totally reduced, but the mandibular body itself is produced, thus the lacinia mobilis appear to have gone through ®rst a reduction and then a secondary enlargement. Finally, the accessory ¯agellum on the ®rst antenna is conspicuously large, with lateral setae-groups.