Anisocallisoma armigera, Hendrycks & Conlan, 2003

Hendrycks, EA & Conlan, KE, 2003, New and unusual abyssal gammaridean Amphipoda from the north-east Pacific, Journal of Natural History 37, pp. 2303-2368 : 2314-2321

Anisocallisoma armigera sp. nov.

(figures 4–6)

Type material

H  : adult W, 5.5 mm, (appendages on one slide), CMNC 2002-0003 , Sta. 1706, Cup# 11, 34°47.20∞N, 123°03.00∞W, 3450 m, 8 November 1993 . A  : adult X, 3.7 mm, (appendages on one slide), CMNC 2002-0004 , Sta. 118, Cup# 2, 34°47.83∞N, 123°01.35∞W, 4050 m, 23 July 1989 ; P    : W, 4.1 mm, (appendages on one slide), CMNC 2002-0005 , Sta. 439, Cup# 3, 34°50.97∞N, 122°59.79∞W, 4000 m, 17 July 1990 ; W, 5.7 mm, (appendages on one slide), CMNC 2002-0006 , Sta. 1216, Cup# 8, 34°47.94∞N, 123°03.80∞W, 3500 m, 3 September 1992 ; W, ZMUC-CRU-3722, Sta. 2030, Cup# 4, 34°53.80∞N, 123°10.31∞W, 4050 m, 23 October 1994.

Description

H  , male, CMNC 2002-0003.

Head: much deeper than long, midcephalic margin of head slightly convex; eye absent; rostrum short, rounded; lateral cephalic lobe narrowly rounded, positioned near ventral margin of head. Antenna 1: short, length about one-fifth body, peduncular article 1 short, deep, ventrolaterally lobate, depth about 1.3×length, length about 3×peduncular articles 2–3, dorsal and ventral margins with sensory setules, peduncular article 2 with ventromedial cusp with one penicillate seta apically; accessory flagellum conical, short, length about 0.5×article 1 of primary flagellum, one-articulate, lacking distal, brush setae; primary flagellum six-articulate, articles 2–6 with stiff setae anterodistally, callynophore strong, length about 0.7×peduncles, densely covered in aesthetascs medially, article 6 acute apically, calceoli absent. Antenna 2: short, length about equal to antenna 1, peduncles with brush setae, article 4 longer than 5; flagellum eight-articulate, articles with short setae anterodistally, calceoli absent.

Peraeon and pleon: smooth. Urosomite 1 and 3: dorsal margin concave. Urosomite 2: posterodorsal margin produced into a weak tooth.

Epistome: with bulbous process above upper lip. Upper lip: slightly produced, rounded, separated from midcephalic margin, ventral margin with small protuberance. Lower lip: outer lobes narrow, medially setulose; inner lobes absent. Mandible: incisors symmetric with smooth, convex margins; left lacinia mobilis a simple spine; right lacinia absent; accessory spine row with three short, curved spines; molar present as a broadly triangular, flap-like process, non-triturative; mandibular palp long, length about 2.1×mandible body, attached level with molar, article 1 short, length 0.6×width, article 2 long, length 4.1×width, with 20 submarginal, posterodistal setae, article 3 spatulate-shaped, with 13 setae along posterior margin and two apical setae. Maxilla 1: inner plate ovate, with one subapical plumose seta; outer plate with 11 multi-cusped spine-teeth in a 7/4 arrangement; palp longer than outer plate, one-articulate with 3 strongly hooked, apical spines, one subapical seta and one distolateral spine. Maxilla 2: plates short, rounded, inner plate slightly shorter, with two medial plumose setae, and about 10 apical setae and spines; outer plate with about 12 apical setae and spines. Maxilliped: inner plate small, narrowing distally with three to four apical nodular spines medially, with three plumose setae; outer plate subovate, lateral margin with fine setules, with one small apical spine, medial margin crenate with six small spines and six submarginal setae; palp fourarticulate, article 2 longest with five medial setae, article 3 with medial setae on distal half, dactylus reduced, length 0.25×article 3, with three long, apical setae.

Gnathopod 1: coxa small, anterior margin concave, narrowing distally, rounded; basis swollen, appearing to contain glandular tissue, width about 0.6×length, margins smooth; ischium long, length 1.6×width; carpus rectangular, long, length 1.3×propodus, with two ventral setae and one apicodorsal seta; propodus simple, tapering distally to a point, length 0.8×carpus, with five fine apical setae, four fine setae on ventral margin proximal to dactylus and three setae on dorsal margin; dactylus minute, with two accessory spines anteriorly, dactylus attached subterminally. Gnathopod 2: coxa short, reaching slightly more than 0.3×length of basis, rectangular, anterior margin convex; basis length 5.2×width, margins smooth; ischium long, length 2.1×width; carpus long, length 1.5×propodus, distal half of dorsal margin with three long, bifurcate setae and covered with patch of fine setules, distally with three bifurcate setae, ventral margin with 11 bifurcate setae and covered with patch of fine setules; propodus subchelate, subrectangular, length 2.6×width, palm short, length 0.1×propodus, weakly oblique, palm corner lacking spines, with three mediofacial and three lateral setae, proximal corner with one strong seta, ventral margin with five long, bifurcate setae and patch of fine setules, dorsal margin with long, bifurcate setae, anterodistally with four clusters of strong lateral and medial, bifurcate setae; dactylus about equal to palm, inserted slightly less than half way down the distal margin, inner margin lined distally with fine serrations and three very fine setules, tip bifurcate.

Peraeopod 3: coxa slightly deeper than coxa 2, length about 0.5×basis, anterior margin of coxa convex; basis, posterodistal corner with one long seta; merus weakly expanded, length 1.4×carpus; posterodistal corner of carpus with two fine setae; propodus longer than carpus, slightly expanded midway, distal half of posterior margin with three long, blunt spines and two short, locking spines; dactylus long, length 0.6×propodus. Peraeopod 4: similar to peraeopod 3 except coxa small, length about 0.5×basis, slightly tapering ventrally, rounded, with a very weak posteroventral lobe, posterior margin shallowly excavate. Peraeopod 5: length about 0.75×peraeopod 7, coxa equilobate, wider than deep; basis small, ovate, deeper than wide, distal half of anterior margin with two small spines, posterior margin with one proximal notch, posteroventral lobe broadly rounded, weak, not exceeding half of ischium; merus weakly expanded, anterior and posterior margins weakly spinose; carpus short, length 0.9×merus, anterior margin with weak spination, posterior margin smooth; propodus longer than carpus, anterior margin with five clusters of double spines and two distal blade-like, locking spines; dactylus long, length 0.5×propodus. Peraeopod 6: length about 1.2×peraeopod 5, coxa not lobate, wider than deep; basis narrowing distally, deeper than wide, anterior margin convex with two small spines midway, posterior margin straight with one proximal notch, posteroventral lobe rounded, weak, not exceeding half of ischium; merus as above; carpus long, length 1.5×merus, anterior margin with three clusters of spines, distal corner with two spines, posterior margin smooth; propodus very slightly shorter than carpus, anterior margin with one single and four clusters of double spines and two distal blade-like, locking spines, posterior margin with five strong setae, distal corner with one strong seta; dactylus as above. Peraeopod 7: long, length 1.3×peraeopod 5, coxa not lobate, ventral margin convex, wider than deep; basis large, triangular, much deeper than wide, anterior margin with two small spines, anterodistal corner with two spines, posterior margin expanded, proximally with two notches, posteroventral lobe weak, rounded, not exceeding half of ischium; merus not expanded, anterior and posterior margins with two clusters of spines; carpus long, length 1.4×merus, anterior margin with three clusters of spines, anterodistal corner with two spines, posterior margin smooth, posterodistal corner with two spines; propodus slightly shorter than carpus, anterior margin with five clusters of double spines and two distal blade-like, locking spines, posterior margin with one distal spine; dactylus as above.

Gills: on peraeopods 2–7. Pleopods: anterior margin of inner ramus with fanlike clusters of setae on distal segments. Epimeron 2: large, deep, anteroventral margin broadly rounded, ventral margin concave with setal fringe, posteroventral corner subquadrate. Epimeron 3: posteroventral corner rounded.

Uropod 1: peduncle length 1.4×inner ramus, with one apicolateral spine, two dorsomedial spines and one apicomedial spine; rami lanceolate, lacking spines, outer shorter. Uropod 2: peduncle length 0.8×inner ramus, with one apicolateral and one apicomedial spine; rami lacking spines, outer shorter. Uropod 3: peduncle short, length 0.4×outer ramus; outer ramus two-articulate, article 1 with one lateral and one apicolateral spine, distal half of medial margin with plumose setae; article 2 length about 0.3×ramus; inner ramus, lateral margin smooth, medial margin with plumose setae. Telson: short, reaching about half length of uropod 3, widest at midpoint, tapering distally, cleft 52%, lobes with subapical notch.

A  , adult female, 3.7 mm. Similar to adult male, except the following. Antenna 1: callynophore very weak with few aesthetascs; accessory flagellum shorter, rounder; primary flagellum five-articulate. Mandible: palp shorter, with six submarginal, posterodistal setae on article 2, posterior margin of article 3 with eight setae. Maxilliped: outer plate slightly longer. Peraeopods 3–4: carpus short, length 0.6×merus; propodus with two posterodistal spines and two distal, locking spines. Brood plates: slender, with long brood setae, found on peraeopods 2–5. Pleopods: anterior margin of inner ramus with weakly developed, fan-like clusters of setae on distal segments. Urosomites 1 and 3: dorsal depressions weak. Uropod 3: setation of rami weak.

Etymology

The species is named from the Latin armigera (armed), referring to the spination of the propodus of peraeopods 3 and 4.

Condition

Male with all appendages. Female with all appendages and setose brood plates, but not ovigerous. The left gnathopod 1 was dissected instead of the right.

Variation

Male. The telson can be cleft slightly less than 50% (vs 52%). The callynophore of one male is slightly deeper. The number of apical nodular spines on the inner plate of the maxilliped ranges from two to four. The number of spines on the medial margin of the maxilliped outer plate varies from four to six. The propodus of peraeopods 3 and 4 can have four posterior marginal spines (vs three).

Remarks

This remarkable species is superficially similar to Eucallisoma glandulosa, J. L. Barnard, 1961. Lowry and Stoddart (1993) described another species, E. barnardi from the Philippines, the type specimen being a 40 mm female. There is no doubt that A. armigera is very different from both these species, although all three share the glandular basis of gnathopod 1.

Anisocallisoma armigera is distinguished easily from E. glandulosa and E. barnardi as follows: size, up to 5.7 mm (vs 10 and 40 mm); accessory flagellum, one-articulate (vs two-articulate); maxilla 1, inner plate with only one subapical seta (vs 10+medial setae), palp one-articulate (vs two-articulate); maxilliped, outer plate lacking apical setae, medial margin crenate with four to six small spines (vs with apical setae, medial margin smooth and>12 strong spines); peraeopods 3–4, propodi spinose (vs lacking spines); peraeopod 5 much shorter than 6–7 (vs subequal); coxa 4, posteroventral lobe very weakly developed (vs strong); uropods 1–2, rami lack spines (vs rami spinose), and telson widest midway, cleft 52% (vs widest proximally, cleft>63%).

Distribution North-east Pacific off Point Conception, California in 3450–4050 m depth.