Amathillopsis Heller, 1875

Loerz, Anne-Nina & Horton, Tammy, 2021, Investigation of the Amathillopsidae (Amphipoda, Crustacea), including the description of a new species, reveals a clinging lifestyle in the deep sea worldwide, ZooKeys 1031, pp. 19-39 : 19

Amathillopsis Heller, 1875

Amathillopsis Heller, 1875: 35. - Stebbing 1906: 384. - Gurjanova 1955: 209 (key). - J.L. Barnard 1969: 394. - J.L. Barnard and Karaman 1991: 390.

Acanthopleustes Holmes, 1908: 533 ( Acanthopleustes annectens Holmes, 1908 by original designation).

Type species.

Amathillopsis spinigera Heller, 1875 (by original designation).

Diagnosis

(after Lowry 2006). Head. Deeper than long; lateral cephalic lobe subquadrate, truncated apically; anteroventral margin straight, anteroventral margin moderately recessed, anteroventral margin moderately excavate; rostrum short or moderate length; eyes present (round or ovoid) or absent. Body smooth, or dorsally carinate. Antenna 1 subequal in length or longer than antenna 2; peduncle with sparse slender setae; peduncular article 1 shorter than or subequal to article 2; article 2 longer than article 3; article 3 shorter than article 1; accessory flagellum short or minute, 1- or 2-articulate; calceoli present. Antenna 2 medium length; peduncle with sparse slender setae or none; flagellum shorter than or as long as peduncle.

Pereon. Coxae 1-4 longer than broad, overlapping, coxae 1-3 or coxae 1-4 ventrally acute. Coxae 1-3 similar in size or progressively larger. Gnathopod 1 subchelate; carpus shorter than or subequal to propodus; propodus with or without peg-like robust setae along palmar margin. Gnathopod 2 subchelate; coxa smaller than but not hidden by coxa 3 or subequal to but not hidden by coxa 3; carpus short, shorter than propodus. Pereopods: some or none prehensile. Pereopod 4 coxa ventrally acute, with or without small posteroventral lobe. Pereopod 5 coxa equilobate, with posteroventral lobe or with acute posterodistal lobe; basis slightly expanded or linear. Pereopod 6 subequal in length to, or longer than pereopod 7; basis slightly expanded or linear. Pereopod 7 shorter than or subequal in length to pereopod 5; basis slightly expanded or linear.

Pleon. Urosomite 1 carinate, urosomites 1-2 carinate or urosomites not carinate. Uropods 1-2 apices of rami without robust setae. Telson notched, emarginate or entire; dorsal or lateral robust setae absent; apical robust setae absent.

Remarks.

Amathillopsis is the type genus of the family Amathillopsidae and the genus has a cosmopolitan distribution ( Wakabara and Serejo 1999). It currently contains 12 species, five of which are known from the Pacific, A. annectens (Holmes, 1908), A. australis Stebbing, 1883, A. grevei J.L. Barnard, 1961, A. takahashiae Tomikawa & Mawatari, 2006 and A. pacifica Gurjanova, 1955 (and the sub species A. pacifica margo J.L. Barnard, 1967),; two from the Antarctic, A. roroi Coleman & Coleman, 2008 and A. charlottae Coleman, 1998; two from the Indian Ocean, A. septemdentata Ledoyer, 1978 and A. comorensis Ledoyer, 1986; and three from the North Atlantic and Arctic, A. affinis Miers, 1881, A. spinigera Heller, 1875 and A. atlantica Chevreux, 1908. Amathillopsis is a deep-sea specialist, with the shallowest records of the large species, A. spinigera , coming from colder Arctic waters at 248 m. All other species are found at depths of 500 to 3580 m. The new species, A. inkenae , described here, provides the deepest confirmed records of an Amathillopsis to date, at 4622 m and 4844 m. Table 1 summarises the known species in the genus along with the type locality and depth.

Species.

Amathillopsis affinis Miers, 1881, A. annectens (Holmes, 1908), A. atlantica Chevreux, 1908, A. australis Stebbing, 1883, A. charlottae Coleman, 1998, A. comorensis Ledoyer, 1986, A. grevei J.L. Barnard, 1961, A. pacifica Gurjanova, 1955, A. pacifica margo J.L. Barnard, 1967, A. roroi Coleman & Coleman, 2008, A. septemdentata Ledoyer, 1978, A. spinigera Heller, 1875, A. takahashiae Tomikawa & Mawatari, 2006.