Vemana cuspidata, Hendrycks & Thurston, 2025

Hendrycks, Ed A. & Thurston, Michael H., 2025, Two new species of Vemana Barnard, 1964 (Crustacea, Amphipoda, Vemanidae) from abyssal depths in the eastern tropical Atlantic Ocean, Zootaxa 5653 (1), pp. 97-115 : 99-106

Vemana cuspidata sp. nov.

( Figs. 1–5)

Type material. Holotype: Mature female, length 10.0 mm, carcass plus 2 microscope slides ( CMNC 2025-0858 ); DIVA-2 M63/2 Expedition , RV Meteor , Station #69 ( Guinea Basin), 0.25m ² USNEL box corer, 17 March 2005, 0°26.7’ S 2°20.5’ W, 5060 m . Paratype: Male, posterior fragment (pereonite 5 to telson), total length of complete specimen ca 9.5 mm ( NHMUK 2025.1102 ), Discovery Cruise 63, Station 8524#1, 28 June 1974, 20°45.5’ N 22°42.5’ W to 20°46.6’ N 22°42.0’ W, BN1.5/5C, 4412 m .

Etymology. The specific epithet, cuspidata , refers to the strong distoventral tooth on peduncle 2 of antenna 1.

Diagnosis. Lateral cephalic lobe narrowly rounded, about as long as rostrum; antenna 1 peduncle article 2 with distoventral tooth; coxa 1 produced anteroventrally, apically rounded, depth greater than length, anterior margin straight; coxa 4 lacking posterodistal lobe; gnathopod 1 carpus and propodus subequal; gnathopod 2 palm oblique; pereopod 7 posterior margin of basis convex; epimeron 3 strongly produced posteriorly with strong acute tooth at posteroventral corner; telson cleft about 20%, lobes not tapering.

Description. Holotype, mature female, 10 mm, CMNC 2025-0858.

Body ( Fig.1) vaulted, pereonites broader than deep. Urosome ( Figs.1, 4) urosomite 1 gently rounded posterodorsally, with small boss and lateral ridge; urosomite 2 very short; urosomite 3 shorter than urosomite 1, slightly convex, with lateral ridge.

Head ( Fig. 1) eyes absent; rostrum short, apically rounded, weakly downcurved; lateral cephalic lobe, triangular, subacute. Antenna 1 ( Fig. 1) longer than length of head and pereonites 1–3 combined, peduncle article 2 with distoventral tooth, peduncle article 3 very short; accessory flagellum slender, biarticulate, about half as long as callynophore; flagellum 9-articulate. Antenna 2 ( Fig. 1) 1.3x length of antenna 1, peduncle article 5 slightly shorter than articles 3 and 4 combined; flagellum 13-articulate.

Upper lip ( Fig. 2) rounded distally, smooth with fine marginal setules. Mandible ( Fig. 2), incisor processes strongly toothed, 4-dentate; left lacinia mobilis 5-dentate, right stout, transversally truncate, multidentate; accessory spine row, left of about 8 pectinate or setose stout setae, right with 4 spines, the three adjacent to the lacinia broadened into blade-like structures; molar process broad, triturative; palp attached level with molar, article 1 short, article 2 length 4.6x width with 15 A2 setae, article 3 length 0.6x article 2 with 1 A3 seta, 15 D3 setae and 3 E3 setae. Lower lip ( Fig. 2) distal mesial margin with dense fine setules overlying simple setae, mandibular lobes oval. Maxilla 1 ( Fig. 2) inner plate subtriangular, tapering distally with 22 plumose setae along inner margin; outer plate with 9 bifurcate or multidentate stout spine-teeth in a 5/4 arrangement, palp article 2 broad with 7 stout nodular spines on mesiodistal margin of left palp; right palp slender with 5–6 slender spines on mesiodistal margin. Maxilla 2 ( Fig. 2) inner plate slightly shorter than outer with parallel margins, distally narrowly rounded, with strong mediofacial row of 24 plumose setae; outer plate lateral margin convex, apically setose. Maxilliped ( Fig. 2) inner plate broad, slightly exceeding distal end of palp article 1, with 3 nodular spines apically and 7 long plumose setae on medial margin; outer plate broad, not reaching end of palp article 2, setose apically, with 11 elongated spines distally on medial margin; palp 4-articulate, article 2 longest, stout, inner margins setose, article 3 broad, 0.6x length of article 2, setose distally, dactyl short, unguis prominent.

Gnathopod 1 ( Fig. 3), coxa subquadrangular, length more than twice width, anteroventral corner produced, narrowly rounded; basis, with long setae at midpoint of anterior margin, posterior margin lacking setae; ischium and merus short, setose ventrally; carpus, posterior margin setose; propodus, length 1.1x carpus, posterior margin weakly sinuous, setose; dactylus 0.8x propodus. Gnathopod 2 ( Fig. 3), coxa, length 1.5x width, anterior margin convex, posterior margin straight, small tooth at posterodistal corner; basis straight, anterior margin with small setules; ischium and merus short, setose ventrally; carpus, posterior margin setose; propodus subovate, length 0.9x carpus, palm very oblique, defined by three stout spines, ventral margin setose; dactylus slender, length 0.5x propodus. Pereopod 3 ( Fig. 4) coxa slightly narrowing distally, length greater than width, anterior and ventral margins convex, posterior margin sinuous, anteroventral corner broadly rounded, posteroventral corner with incipient tooth; basis 1.5x length of coxa, with margins slightly setose; merus posterior margin with long setae; carpus and propodus together just longer than merus, posterior margins strongly setose; dactylus slightly shorter than propodus, with unguis. Pereopod 4 ( Fig. 4), coxa slightly narrowing distally, length about 1.5x width, anterior and distal margins broadly rounded, posterior margin weakly concave; other articles as in pereopod 3. Pereopod 5 ( Fig. 4), coxa width less than twice length, anterolobate; basis, posterior margin with small tooth at 20% length, posterodistal margin weakly concave; merus 0.6x basis; carpus just shorter than merus, 0.5x basis; propodus shorter than carpus; anterior margins of merus to propodus with long setae; dactylus slender, subequal to propodus length. Pereopod 6 ( Fig. 4) coxa width about twice length, bilobed, lobes subequal; basis, posterior margin convex proximally, straight distally; distal articles as in pereopod 5. Pereopod 7 ( Fig. 4) a little shorter than pereopod 6; coxa oval, width twice length; basis broad, width more than half length, posterior margin convex, with about 10 fine crenulations; merus 0.4x basis, merus and carpus subequal, slightly stouter than in pereopods 5–6; propodus a little shorter than carpus; anterior margins of merus to propodus with clusters of strong spines; dactylus slender, a little shorter than propodus.

Oostegites ( Figs. 3–4) present on gnathopod 2 and pereopods 3–5, long and slender, largest on gnathopod 2 and pereopods 3–4, slightly smaller on pereopod 5, with long curved apical and subapical brood setae ranging in number from 7–8. Gills ( Figs. 3–4) suboval on gnathopod 2 and pereopods 3–4, broadly triangular on pereopods 5–6 and small, heart shaped on pereopod 7.

Epimeron 1 ( Fig. 1) broadly rounded. Epimeron 2 ( Fig. 1) subquadrangular, anterodistal corner rounded, distal margin straight, posterodistal corner with small acute tooth, posterior margin weakly sinuous. Epimeron 3 ( Fig. 1) anterior corner rounded, distal margin straight, posterodistal corner produced into strong acute tooth, posterior margin straight.

Uropod 1 missing. Uropod 2 ( Figs. 1, 5) peduncle stout, subequal to inner ramus, with 8 lateral and 1 distomedial spines; rami lanceolate, outer shorter than inner, both with small inset apical spine; inner ramus as long as peduncle with 6 medial and 3 lateral spines; outer ramus 0.9x peduncle with 3 lateral spines. Uropod 3 ( Figs. 1, 5) peduncle very short, about 0.5x rami, with 2 distolateral and distomedial spines; rami of equal length, much longer than peduncle, inner ramus with 6 plumose setae on medial margin, 1 lateral spine; outer ramus biarticulate, second article short, length 0.2x rami, with 2 lateral and 1 medial spine. Telson ( Figs. 1, 4–5) subrectangular, length 1.2x breadth, margins with 1 proximolateral spine, cleft 19%, lobes broadly rounded, with 1 small distal spine; surface with prominent microstructure.

Distribution. Known from eastern Atlantic, Guinea Basin and off the northwest continental margin of Africa.

Remarks. Vemana cuspidata sp. nov. is separated from all other species in the genus by the form of the telson; subrectangular in shape, shallowly and widely cleft (less than 25%) and with broadly rounded, non-tapered lobes. The new species and V. touzeti Ortiz & Winfield, 2022 both possess a distoventral tooth on antenna 1 peduncle article 2 but the latter is clearly distinguished by the prominent lateral cephalic lobe, gnathopod 2 lacking palm, strongly cusped posteroventral corner of coxa 4, dentate pereopod 7 basis and deeply cleft telson. Ortiz & Winfield (2022, fig. 2) illustrate the distoventral tooth of antenna 1 peduncle article 2, but this distinctive character is not mentioned in their species description.

Also of note, Ortiz & Winfield (2022, fig 2, also p. 587) reference a callynophore on antenna 1 article 1 flagellum lower margin. However, the callynophore encompasses the whole article, and is not just confined to the lower margin as stated. All Vemana species possess a callynophore in both sexes. In common with many other alicelloids, the callynophore is larger in males and the dorsal boss on urosomite 1 is a little more prominent. Otherwise, the sexes are very similar (see Barnard 1967, p. 190).

This collection of Vemana cuspidata sp. nov. is also the deepest published occurrence of the genus, extending the depth range to 5060 m.