Cyphocaris latirama, 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 : 2306-2311

Cyphocaris latirama sp. nov.

(figures 1, 2) Type material

H: adult W, 22.6 mm, (appendages on two slides), CMNC 2001-0004 , Sta. 621, Cup# 1, 34°50.88∞N, 122°58.68∞W, 4050 m, 25 February 1991. P : juvenile, 14 mm, (appendages on one slide), CMNC 2001-0006 , Sta. 1619, Cup# 6, 34°46.48∞N, 123°00.78∞W, 3450 m, 16 or 26 April 1993; adult W , CMNC 2001-0005 , Sta. 1014, Cup# 3, 34°53.22∞N, 123°02.13∞W, 4000 m, 14 November 1991; juvenile , CMNC 2001-0007 , Sta. 208, Cup# 1, 34°46.59∞N, 123°04.04∞W, 3500 m, 23 October, 1989 .

Diagnosis

Peraeonite 1, anterior margin rounded, not produced anterodorsally beyond head; lateral cephalic lobe shallowly concave; antenna 1, accessory flagellum ninearticulate, about 0.5×length of article 1 of primary flagellum, article 1 of accessory flagellum short, length about 0.5×articles 2–9; coxa 5, posterior margin shallowly concave; peraeopods 5–7, basis with serrate, posterior margins; uropod 3, outer ramus length 0.9×inner, article 1 proximally wide, about 0.4×length; telson length 2.3×width, cleft 84%, lobes distally acute, not reaching ends of uropod 3.

Description

H, male, CMNC 2001-0004.

Head: positioned under peraeonite 1, narrow, much deeper than long; midcephalic margin of head straight; eye indistinct, lacking ommatidia; rostrum short, acute, length about 0.3×peduncular article 1 of antenna 1; lateral cephalic lobe broad, margin shallowly concave. Antenna 1: medium length, about 0.3×body, peduncular article 1 about twice as long as peduncular articles 2–3 combined; accessory flagellum short, length about 0.5×article 1 of primary flagellum, ninearticulate, article 1 short, about half as long as remaining articles; primary flagellum 33-articulate, articles with fine setules anterodistally, callynophore strong, length about twice peduncles, densely covered with aesthetascs medially, flagellar article 2 with a long stiff seta anterodistally, calceoli present. Antenna 2: long, length about 3×antenna 1, peduncular articles 4–5 with brush setae, article 4 strongly broadened, longer than 5; flagellum 315-articulate, calceoli present.

Peraeon and pleon: smooth. Peraeonite 1: about as long as peraeonites 2–3 combined, produced anterodorsally about 0.7×over head, anterior margin rounded. Urosomite 1: with an anterodorsal notch. Urosomite 2: with a slight dorsal hump.

Upper lip: slightly produced, rounded, separated from midcephalic margin, ventral margin narrowly rounded in the middle. Lower lip: outer lobes broad, furnished with setules, mandibular lobes narrow; inner lobes weak. Mandible: incisors symmetric with smooth, convex margins; left lacinia present as a distally seven-cusped blade, right lacinia absent; accessory spine row with four to six slender spines; molar strong, proximally setose, triturative; mandibular palp attached distally to molar, article 1 short, article 2 strongly expanded in the middle with a distinct protuberance, with 38 submarginal, posterodistal setae, article 3 blade-like, with about 50 setae along posterior margin and three to four subapical setae. Maxilla 1: inner plate tapering distally, distal half of medial margin with 15 stout, plumose setae; outer plate rectangular with 11 multi-cusped spine-teeth in a 6/5 arrangement; palp longer than outer plate, broadening distally, two-articulate, with 16 stout, apical spines and 16 long, subapical setae. Maxilla 2: inner plate triangular, broad, fully setose medially; outer plate narrow, slightly longer than inner, with subapical spines and setae. Maxilliped: inner plate rectangular, with three apical nodular spines, with two distolateral spines near medial margin, medial margin fully lined with long, plumose setae; outer plate subovate, apicolateral margin with 10 plumose setae, medial margin with 24 close-packed blunt spines, submarginal setae present; palp large, fourarticulate, articles 1–3 setose medially, article 3 shortest, dactylus large, blade-like, with four medial plumose setae and one apical seta, unguis absent.

Gnathopod 1: coxa small, wider than deep; basis long, widening distally, length 4.8×width, anterior and posterior margins smooth; ischium and merus short; carpus subrectangular, length 1.3×propodus, dorsal and ventral margins with clusters of long setae, ventral margin with patch of very fine setules; propodus weakly subchelate, short, subtriangular, length 0.7×carpus, ventral margin slightly convex, finely serrate with about 10 slender spines and long setae, strong pectinate setae along medial face, dorsal margin with clusters of long setae; dactylus with large, subterminal tooth, posterior margin finely denticulate. Gnathopod 2: coxa small, depth 1.5×width, narrowing ventrally; basis long, length 6.6×width, strongly bent, margins smooth; ischium long, length 3×width; carpus long, about twice width, ventral margin with about ten clusters of long setae and covered with patch of fine setules, dorsal margin with patch of fine setules, distally with long setae; propodus subchelate, subrectangular, length 3.2×width, palm short, length 0.2×propodus, oblique, finely serrated, palm corner defined by one medial and one lateral spine, ventral margin with about 18 clusters of long, pectinate setae curled forward at the tips, anterodistally with two strong clusters of pectinate setae, dorsal margin with eight clusters of setae; dactylus slightly shorter than palm, posterior margin smooth with subterminal setae.

Peraeopod 3: coxa small, anterior margin produced midway, narrowly rounded; merus with convex anterior margin, posterior margin with clusters of setae increasing in length distally; carpus shorter than merus, posterior margin with clusters of setae; propodus longer than carpus, posterior margin with four clusters of spines, anterior margin with four clusters of setae and spines; dactylus long, slender. Peraeopod 4: coxa very large, partly covering coxae 2–3, deeper than wide, anterior margin broadly rounded, posterior margin strongly excavated, posteroventral lobe narrowly rounded; merus with slightly concave anterior margin, anterodistally with cluster of setae, posterior margin with three clusters of setae distally; carpus, posterior margin with clusters of strong setae and spines, anterior margin with a cluster of setae; propodus shorter than carpus, posterior margin with four clusters of setae and spines, anterior margin with about five slender spines; dactylus as above. Peraeopod 5: coxa large, wider than deep, bilobate, posterior lobe truncate ventrally, posterior margin slightly concave; basis broad, about as wide as deep, anterior margin with 26 small spines, posterior margin serrate with 21 broad teeth, posteroventral lobe produced 0.6×along merus, anterior margin of lobe sinusoidal and lacking teeth; merus spinose along both margins; propodus longer than carpus, anterior and posterior margins spinose; dactylus slender, length 0.4×propodus. Peraeopod 6: coxa not lobate, posterior margin slightly convex; basis deep, 1.4×width, anterior margin lacking spines, posterior margin serrate with 19 teeth that broaden distally, posteroventral lobe acute, produced 0.3×along merus, anterior margin of lobe smoothly convex and lacking teeth; merus, anterior margin strongly spinose, posterior margin weakly spinose; propodus as above; dactylus as above. Peraeopod 7: coxa not lobate, rounded; basis deep, 1.6×width, anterior margin shallowly concave distally, lacking spines, posterior margin serrate with 19 broad teeth, posteroventral lobe acute, produced 0.4×along merus, anterior margin of lobe convex lacking teeth; ischium short, length 0.6×width; merus slightly expanded proximally, anterior and posterior margins strongly spinose; propodus longer than carpus, anterior margin with eight to nine clusters of spines, posterior margin with four clusters of spines; dactylus as above.

Gills: on peraeopods 2–7. Pleopods: powerful. Epimeron 3: posterior margin concave, posteroventral corner produced into a broad point, anteroventral margin broadly rounded.

Uropod 1: peduncle 1.7×length of inner ramus, with three dorsomedial spines and two apicomedial spines; rami lanceolate, outer ramus slightly shorter than inner, with 11 lateral spines; inner ramus with 11 medial spines. Uropod 2: peduncle 1.2×length of inner ramus, with four dorsolateral spines, one dorsomedial spine and four apicomedial spines; outer ramus 0.8×length of inner ramus, with 10 lateral spines; inner ramus with six medial spines. Uropod 3: peduncle short, 0.5×length of outer ramus, with medial setae and apicomedial spines; outer ramus two-articulate, article 1 wide, 0.4×length with two lateral and three medial spines, distal two-thirds of inner margin with long, plumose setae; article 2 short; inner ramus slightly longer and narrower than outer, with six lateral and six medial spines, medial margin with long, plumose setae. Telson: elongate, length 2.3×width, cleft 84%, lobes narrowing distally with about five small, dorsal spines and one subapical spine, tips acute.

P, juvenile, 14 mm. Similar to adult male, except the following. Antenna 1: callynophore short with fewer aesthetascs; accessory flagellum six-articulate, about 0.75×length of article 1 of primary flagellum, flagellum with fewer articles, calceoli absent. Antenna 2: peduncular article 4 narrow, not broadened, lacking brush setae; flagellum with fewer articles, calceoli absent. Peraeopods 5–7: posterior marginal teeth on the basis are longer, narrower and more numerous (see figure 2). Uropods 1–2: rami with fewer spines. Uropod 3: outer ramus is narrower proximally, article 2 longer; rami with few plumose setae on medial margin.

Etymology

The species name is from the Latin latus (broad) and ramus (branch, antler) referring to the expanded condition of the outer ramus of uropod 3.

Condition

All appendages present. The head and peraeonite 1 are broken off, but remain with the body.

Variation

No females were collected, so brood plate morphology and sexual dimorphism could not be documented, but would likely occur in the antennae and uropod 3. These differences would be expected in pelagic species such as Cyphocaris , which have a terminal, reproductive male stage and mate in the water column.

Remarks

This species appears to be closely related to Cyphocaris polaris Gurjanova, 1951 described from the Greenland Sea (78°04.2∞N, 3°51.4∞E), at 2460 m depth but not collected since. Cyphocaris polaris was described from an incomplete female specimen, with everything posterior to pleonite 2 missing. The paratype male specimen of about 38 mm has a long, acute process of peraeonite 1 that extends to the end of the accessory flagellum of antenna 1 (N. Tzvetkova, personal communication). Dr Nina Tzvetkova of the Zoological Institute of the Russian Academy of Sciences kindly compared our drawings of C. latirama to the holotype of C. polaris , as the type specimens could not be borrowed.

Cyphocaris latirama differs from all other Cyphocaris species which have an unproduced peraeonite 1, by the absence of a spur on the posterior margin of the basis of peraeopod 5. It differs from C. polaris as follows: the adult male is smaller in size (22.6 mm vs 38 mm), peraeonite 1 is not produced (vs produced), the accessory flagellum reaches only half of article 1 of antenna 1 flagellum (vs>two-thirds), the lateral cephalic lobe is shallowly concave (vs subacute), gnathopod 1 propodus is broader, coxa 5 has a shallowly concave, posterior margin (vs convex) and the maxilliped dactylus has four setae on the medial margin (vs six).

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