Andaniopsis isaki, Berge, 2004

Berge, Jørgen, 2004, The subfamily Andaniopsinae (Crustacea: Amphipoda: Stegocephalidae): description of one new species and redescription of Steleuthera maremboca, Journal of Natural History 38 (11), pp. 1385-1395 : 1386-1389

Andaniopsis isaki sp. n.

( figures 1–3 )

HOLOTYPE: female, 4 mm. 31 ‡ 54 ’ N, 79 ‡ 05 ’ W, 29 October 1958, depth 413 m. Collected on Vema , station 15-01, standard benthic trawl.

PARATYPES: female, 4 mm, immature, 3 mm. Same station as holotype ( Vema 15-01) .

Etymology. This species is named after the author’s godson Isak Aglen.

Diagnosis. The present species resembles A. nordlandica in the partly toothed incisor on the mandibles and the enlarged merus on pereopod 7. The two species are separated by the rounded and minutely incised apex of the telson in the new species. In addition, the second article of the accessory flagellum in A. isaki is long and conspicuous, versus the strongly reduced state in A. nordlandica .

Description Head. Head retractable under pereonite 1. Rostrum rudimentary.

Antennae. Accessory flagellum shorter than flagellum article 1, two-articulate. Antenna 2 peduncle article 3 short, about as long as broad. Peduncle article 4 as long as article 5.

Epistome. Epistome laterally smooth. Epistomal plate (medial keel) produced into a small elongate medial ridge covering the entire epistome.

Mouthparts. Mouthparts not elongate. Mandibles with incisors transverse, partly toothed; left lacinia mobilis present, strongly toothed and distally produced.

Maxilla 1 palp articulation absent, distally with short simple setae. Outer plate distally subrectangular, ST in a 6/3 arrangement with two parallel rows: first row with ST 1–5 present, ST 6 absent and ST 7 present. Second row with ST A–C present. Inner plate with shoulder weakly developed, setae pappose.

Maxilla 2 outer plate not gaping and geniculate, setae distally straight. Inner plate with setae rows A and B apressed together. Row B with the three first setae differentiated from the other setae. Rows C and D absent.

Maxilliped palp four-articulate, article 2 distally unproduced. Articles 1–3 with long slender setae. Inner plate distally with inner corner produced, one nodular seta present. Outer plate with inner and outer setae-row present, both with short simple setae. Distal setae-group present, setae short and simple.

Labrum about as long as broad, both lobes reduced.

Labium distally broad, distal finger absent.

Pereopods and coxae. Coxal plates and basis on the pereopods smooth. Pereopod 1 coxal plate about as deep as basis; basis anterior margin not expanded; propodus subrectangular, posteriorly without submarginal row of setae. Pereopod 2 ischium not elongate, distal posterior margin with plumose setae; propodus subrectangular. Pereopod 4 coxa without locking process; basis without long setae, distally with plumose setae on anterior and posterior margins; ischium without long plumose setae. Pereopod 6 basis posteriorly rudimentary expanded, medially without a row of long plumose setae; posterior margin of basis smooth. Pereopod 7 conspicuously differentiated from pereopod 6; basis posteriorly serrate, medially with a row of short simple setae; merus more than twice as long as carpus.

Oostegites and gills. Gills present on pereopods 2–7, oostegites on pereopods 2–5.

Pleonites. Pleonites 1–3 dorsally smooth. Epimeral plate 3 weakly produced and rounded posteriorly, serrations absent.

Urosome. Articulation between urosomites 2 and 3 present. Uropods 1–3 rami without setae; uropod 3 peduncle longer than telson, outer ramus two-articulate. Telson entire (but minutely incised) and rounded distally, submarginal setae on apex present.

Males. Unknown.

Remarks. The present species is a typical member of the subfamily Andaniopsinae with its distally produced and toothed lacinia mobilis on the left mandible, in addition to the relatively long outer plate on the second maxilla. Furthermore, the palp of the first maxilla is uniarticulate and reduced, although not as much as in its congeners. The telson of this new species has a small apical notch ( figure 3 ), a character state not found in any other species within the subfamily, except to some degree in Steleuthera maremboca . The entire condition is typical for the present genus, whereas the telson in the other Andaniopsinae genus, Steleuthera Barnard, 1964 is either deeply or weakly cleft. Thus, the character state of A. isaki does in this respect represent some sort of intermediate state. In another species of the genus, A. pectinata ( Sars, 1883) , that was originally described as possessing an entire telson, a similar state was later described by Shoemaker (1931: figure 3 ). However, such a partially cleft telson has not been observed for A. pectinata in the material available to me. Furthermore, the two species are easily separated on the pectinated dactyla on the gnathopods in addition to the heart-shaped coxa 4 of A. pectinata (versus the distally broad in A. isaki ).

Figures

FIG. 1. Andaniopsis isaki n. sp. holotype.

FIG. 2. Andaniopsis isaki n. sp. holotype.

FIG. 3. Andaniopsis isaki n. sp. holotype.