Vemana hortonae, 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 : 106-107

Vemana hortonae sp. nov.

( Figs. 6–9)

Type material. Holotype: (based on the least damaged specimen). Juvenile female, length 12.6 mm, carcass plus 13 microscope slides ( NHMUK 2025.1103 ); 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 . Paratypes: 1 immature female, 15.6 mm and 1 juvenile female, 12.5 mm, ( NHMUK 2025.1105 ); same data as above . 1 adult female, 16.3 mm, ( NHMUK 2025.1104 ); Discovery Cruise 63, Station 8524#6, 28 June 1974, 20°44.3’ N 22°44.4’ W to 20°44.9’ N 22°44.3’ W, BN1.5/5C, 4414–4416 m .

Etymology. Named in honour for Tammy Horton, in recognition of her important contributions on the ecology and taxonomy of amphipod necrophages, particularly in the eastern North Atlantic Ocean. In addition, she has had a major input into the development of the World Register of Marine Species (WoRMS) having chaired the Steering Committee for five years and has entered and checked more amphipod records (currently greater than 22,717) than any other contributor.

Diagnosis. Lateral cephalic lobe rounded, about as long as rostrum; maxilla 2 outer plate strongly convex and broadened, wider than inner plate; antenna 1 peduncle article 2 lacking distoventral tooth; coxa 1 subrectangular, length and depth subequal, anteroventral angle lacking tooth, anterior margin weakly concave; coxa 4 with prominent rounded posterodistal lobe; gnathopod 1 propodus one-third longer than carpus; gnathopod 2 palm oblique; pereopod 7 posterior margin of basis constricted; epimeron 3 produced posterodistally with small rounded tooth; telson cleft 67%, lobes tapering, subtriangular.

Description. Holotype, juvenile female, 12.6 mm, NHMUK 2025.1103.

Body ( Fig. 6) vaulted, pereonites broader than deep. Urosome ( Fig. 6), urosomite 1 gently rounded posterodorsally, with small boss; urosomite 2 short; urosomite 3 shorter than urosomite 1.

Head ( Fig. 6) eyes absent; rostrum short, acute, not down-curved; lateral cephalic lobe short, triangular, rounded apically. Antenna 1 ( Fig. 6) shorter than length of head and pereonites 1–4 combined, peduncle article 2 lacking distoventral tooth, peduncle article 3 shorter than 2; accessory flagellum slender, biarticulate, about half as long as callynophore; flagellum 14-articulate. Antenna 2 ( Fig. 6) length 1.2x antenna 1, peduncle article 5 slightly longer than articles 3 and 4 combined; flagellum 19-articulate.

Mandible ( Fig. 7), incisor processes strongly toothed, 6-dentate; left lacinia mobilis 6-dentate, right 4-dentate; accessory spine row, left of about 17 pectinate or setose stout setae, right with 10 stout spines, the five adjacent to the lacinia broadened into blade-like structures; molar process broad, triturative; palp attached just distal to molar, article 1 short, article 2 length 3.5–3.8x width with 18 A2 setae in 2 groups, article 3 length 0.7x article 2 with 21 D3 setae and 2 E3 setae. Lower lip ( Fig. 7) distal medial margin with dense fine setules overlying simple, bifurcate and trifurcate setae, mandibular lobes oval. Maxilla 1 ( Fig. 7) inner plate tapering distally, strongly setose with 42 plumose setae along inner margin; outer plate with 11 bidentate or simple spine teeth in a 7/4 arrangement, palp article 2 broad with 9 stout spines on mesiodistal margin. Maxilla 2 ( Fig. 7) inner plate slightly shorter than outer with parallel margins and strong mediofacial row of 59 plumose setae; outer plate unusually shaped, lateral margin strongly bulged, convex, apically setose, much wider than inner plate. Maxilliped ( Fig. 7) inner plate narrow, nearly reaching one-third length of palp article 2, with 2 nodular spine teeth apically and 14 long setae on medial margin; outer plate broad, not reaching end of palp article 2, setose apically, 8 spine teeth distally on medial margin; palp 4-articulate, article 2 longest, stout, setose medially, article 3 broad, 0.7x length of article 2, setose distally, dactyl short, length 0.8x article 3, unguis prominent.

Gnathopod 1 ( Fig. 8) coxa subquadrangular, length and width about equal, anteroventral corner weakly produced, narrowly rounded; basis, with long setae on anterior and posterior margins; ischium and merus short, posterior distal margins setose; carpus, posterior margin strongly setose; propodus, length 1.3x carpus, posterior margin straight, with 11 setae; dactylus long, subequal in length to propodus. Gnathopod 2 ( Fig. 8) a little longer than gnathopod 1; coxa, length just greater than width, anterior and ventral margins convex, corners rounded; basis, with long setae on posterior margin; ischium and merus short, posterior distal margins setose; carpus longer than propodus, with 6 posterior marginal clusters of setae; propodus oval, length 0.9x carpus, palm oblique, finely pectinate, defined by 3 stout spines, posterior margin with 4 clusters of long setae; dactylus length 0.5x propodus. Pereopod 3 ( Fig. 8) coxa length and width subequal, anterior and ventral margins convex, posterior margin concave, distal corners broadly rounded; merus, length 0.6x basis; propodus longer than carpus, length 0.8x merus; dactylus slender, length 0.9x propodus; merus, carpus and propodus posterior margins with long setae. Pereopod 4 ( Fig. 8), coxa length less than width, anterior margin broadly rounded, distal margin straight, oblique, with rounded, strong posterodistal lobe; other articles as in pereopod 3. Pereopod 5 ( Fig. 9), coxa width about twice length; basis smooth, length about twice breadth; merus 0.7x basis; carpus just shorter than merus, 0.6x basis; propodus shorter than carpus; anterior margins of merus to propodus setose; dactylus slender, 0.9x propodus. Pereopod 6 ( Fig. 9) about 1.2x length of pereopod 5; coxa, width about twice length, bilobed, lobes subequal; basis, posterior margin with obtuse angle at 25% length, distally sinuous; merus 0.6x basis; carpus as long as merus; propodus shorter than carpus; anterior margins of merus to propodus setose; dactylus slender. Pereopod 7 ( Fig. 9) slightly shorter than pereopod 6; coxa much wider than long, greatest length anteriorly; basis, posterior margin with obtuse angle at 60% length, distally concave; merus 0.4x basis; carpus 1.3x merus; propodus shorter than carpus; anterior margins of merus to propodus with slender spines; dactylus slender, 0.8x propodus.

Epimeron 1 ( Fig. 6) subquadrate, posterodistal corner angled, posterior margin weakly convex. Epimeron 2 ( Fig. 6) anterodistal corner rounded, distal margin convex, posterodistal corner with small, rounded tooth, posterior margin weakly convex. Epimeron 3 ( Figs. 6, 9) anterior corner rounded, distal margin straight, posterodistal corner produced into a small subacute tooth, posterior margin straight.

Uropod 1 ( Fig. 9) peduncle stout, with 1 mediodistal spine and 2 proximolateral slender setae; inner ramus 1.6x maximum length of peduncle with 4 medial and 3 lateral spines, tapering to slender apex; outer ramus smooth [broken], but much shorter than inner. Uropod 2 ( Fig. 9) peduncle stout with 16 slender lateral and 2 distolateral spines; rami lanceolate, both with small inset apical spine; inner ramus 0.8x peduncle with 6 medial and 5 lateral spines; outer ramus with 2 medial and 8 lateral spines. Uropod 3 ( Fig. 9) peduncle short, stout, with 3 distomedial, 5 lateral and 1 distolateral spine; [rami probably damaged and regenerated] inner ramus longer than peduncle, medial margin with 8 plumose setae and 4 spines, lateral margin with 2 spines; outer ramus a little longer than inner, biarticulate, second article short, length 0.2x rami, first article with 2 medial, 4 lateral and 2 distolateral spines. Telson ( Fig. 9) length and breadth subequal, proximolateral margins with 1 small spine, cleft 67%, lobes tapering, each with a small apical spine.

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

Remarks. Vemana hortonae sp. nov. shares with V. lemuresa Barnard, 1967 the distally constricted basis of pereopod 7 but differs from that species in the strong posterodistal lobation of coxa 4. The only other species in the genus in which coxa 4 is produced is V. touzeti Ortiz & Winfield, 2022 but in this species the projection is a strong posteriorly directed tooth, not a rounded lobe. The new species has a very unusual morphology of maxilla 2, in which the outer plate lateral margin is strongly convex and bowed outward resulting in a much-broadened plate. This character is unique among Vemana species. Vemana hortonae is the largest species recorded in the genus, attaining a length substantially greater than the 10 mm females of V. lemuresa and V. cuspidata sp. nov. herein. Oostegites in the adult female paratype are typical of other alicelloids; long, narrow and with relatively few apical and subapical setae.