Vemana touzeti, Ortiz & Winfield, 2022

Ortiz, M. & Winfield, I., 2022, A new deep-sea species of Vemana J. L. Barnard, 1964 (Amphipoda, Amphilochidea, Vemanidae) from off southern Gulf of Mexico, Zootaxa 5205 (6), pp. 585-593 : 587-592

Vemana touzeti sp. nov.

( Figs 2–5 )

Type Material. Holotype male 7.5 mm ( CNCR36469 ); collected from the type locality on 20 September 2010; María Teresa Herrera-Dorantes, collector.

Type locality. Bay of Campeche, SW Gulf of Mexico, cruise site Ch-25 at 20 15’ 57.59”N, 94 05’ 34.80”W. The material was collected from soft-bottom characterized by mud (silty-clay) sediments of terrigenous origin at 1492 m in depth .

Etymology. This new species is named to honour René Touzet Monté, for his valuable contribution to Latin-American music. It is derived from the noun “touzet” in the genitive case.

Diagnosis. Based on the male holotype (CNCR36469). Body laterally compressed, pereon and pleon smooth dorsally, first urosome segment convex with a diminutive hump. Antenna 1 shorter than 2, accessory flagellum 2–article, primary flagellum 10–article, article 1 lower margin with callynophore. Antenna 2 peduncle article 5 longer than 4, flagellum 11–article. Gnathopod 1 smaller than 2, subchelate, coxa 1 anteroventral corner with point. Gnathopod 2 is not mitten-shaped, palm transverse. Coxa 4 posteroventral corner prolonged in a big and acute tooth. Basis posterior margin of pereopod 7 with six evident teeth. Uropod 3 outer ramus 2–article, article 2 shorter than peduncle, inner ramus with 3 long plumose setae. Epimeron 3 posteroventral corner forming small acute tooth. Telson longer than wide, 33% cleft.

Description. Head ( Fig. 2 ). Eyes absent, cephalic lobe acute, anteroventral margin recessed, rostrum poorly developed. Body ( Fig. 2 ). Laterally compressed, pereon and pleon smooth dorsally, urosomite 1–3 free. First urosome dorsal convex, a diminutive hump. Epimera ( Fig. 2 ). Epimeron 1 posteroventral corner forming a right angle, epimeron 2 without plumose setae, epimeron 3 posteroventral corner forming small acute tooth. Antennae ( Fig. 2 ). Antenna 1 shorter than 2, peduncle article 1 longer than 2–3 combined, accessory flagellum 2–article, flagellum 10–article, article 1 lower margin with callynophore.

Mouthparts ( Fig. 3 ). Maxilla 1 ( Fig. 3A ) outer plate 8 robust distal setae; inner plate strongly setose along medial margin, 17 setae out of which 2 shortest; palp 2–article, article 2 distal margin 7 robust and one simple setae. Maxilla 2 ( Fig. 3B ) outer plate 15 straight and 7 curved distal setae, 7 marginal setae distally, and 18 facial setae. Lower lip ( Fig. 3C ) inner plate absent, mandible lobes poorly developed, and several distal short setae. Upper lip ( Fig. 3D ) asymmetrical. Maxilliped ( Fig. 3E ) inner plate separated, with 5 molariform robust setae and 5 simple setae; outer plate 6 molariform robust setae and 3 distal simple setae; palp 4–article, long setae on article 2 inner margin; article 3 shorter than 2; article 4 shortest, with sparse distal setae. Mandibles ( Fig. 3F, G ); right mandible ( Fig. 3G ) 2 teeth lacinia mobilis, 5 incisors, 9 accessory setae; molar large, triturative, setose; palp article 2, 2x longer than 3, inner margin distal half 13 long setae, article 3 falcate, 16 marginal setae and one facial large setae; left mandible ( Fig. 3F ) 6 teeth lacinia mobilis, 6 incisors, and 10 accessory setae.

Gnathopod 1 ( Fig. 4A ) smaller than 2, subchelate; coxa 1 anteroventral corner with point; basis longer than ischium-carpus combined; one tuft of setae on posterior margin merus, other 2 on carpus; propodus as long as carpus, palmar margin absent; dactylus long. Gnathopod 2 ( Fig. 4B ) not mitten-shaped; coxa without anteroventral point; basis as long as ischium and carpus in length combined; merus anteroventral lobe discreet; carpus-propodus densely setose on posterior margin; palm transverse; dactylus short, as long as palmar margin. Pereopod 3 ( Fig. 4C ) coxa posteroventral corner slightly protruded, rounded; ischium as long as merus and carpus combined; merus equal to carpus and propodus in length combined; dactylus as long as carpus. Pereopod 4 ( Fig. 4D ) coxa posteroventral corner prolonged in a big and acute tooth; ischium as long as merus and carpus in length combined; merus equal to carpus and propodus in length combined; dactylus as long as carpus. Pereopod 5 ( Fig. 4E ) coxa with anteroventral lobe well developed; basis longer than ischium and merus combined; carpus and propodus subequal in length; vestigial dactylus. Pereopod 6 ( Fig. 4F ) coxa with anteroventral lobe poorly developed; basis narrow, posterior margin with one tooth sub-basally, shorter than ischium and merus combined; carpus, propodus, and dactylus equal in length. Pereopod 7 (Fig, 4G) coxa devoid of lobe, wider than high, posteroventral corner with small tooth; basis wide, posterior margin 6 dentate; merus, carpus, and propodus subequal in length, anterior margins setose; dactylus as long as propodus.

Uropod 1 ( Fig. 5A ) peduncle rectangular, shorter than inner ramus, one distal outer corner robust seta; rami curved, tapering distally; outer ramus with 3 outer margin robust setae; inner ramus with apical setae. Uropod 2 ( Fig. 5B ) peduncle 7 outer margin robust setae, other antero and posterodistally; outer ramus 6 outer and 3 inner marginal robust setae; inner ramus naked; both rami with terminal setae. Uropod 3 ( Fig. 5C ) peduncle 3 simple and 3 robust setae; outer ramus 2–article, rami overlapping; basal article with 2 short robust setae on each margin, each distal corners with one short robust seta; article 2 shorter than peduncle; inner ramus with 4 long plumose setae. Telson ( Fig. 5D ) laminar, longer than wide, 33% cleft; each lobe with one robust and 2 simple distal setae.

Remarks. The distribution patterns and biodiversity of the benthic amphipods along the bathymetric gradient have been documented in several ocean basins. Recently, Jażdżewska & Mamos (2019) proposed that the diversity and abundance of these peracarids are high throughout the bathyal zone decreasing towards abyssal and hadal depths, recording 400 species below 2000 m in depth. However, our knowledge of the deep-sea amphipod fauna is still limited in most ocean regions due to its origin and complex geomorphology. The Gulf of Mexico has been recognized as a hotspot for biodiversity with some areas of endemism located in the SW sector (Bay of Campeche) as of result of complex tectonic history, sedimentary discharges, and vicariance events, which have promoted a high rate of speciation with the description of numerous new deep-sea genera and species of benthic amphipods ( Winfield et al., 2016, 2021; Ortiz et al., 2018).

Genus Vemana was described by Barnard in 1964, which joined Vitjaziana were placed in the family Vitjazinidae . Later, both genera were compared, and several morphological dissimilarities were found ( Ledoyer, 1986). As a result of phylogenetic analysis, Lowry & Myers (2017) erected the family Vemanidae to receive the genus Vemana , which includes 5 species, so far.

Species of Vemana have been characterized as deep-sea amphipods recorded between 1492 to 5379 m depth. The geographic distribution includes Madagascar, western Indian Ocean, western North Atlantic, Caribbean Sea basin, tropical western Atlantic ( Lowry & Myers, 2017), Kuri-Kamschatka trench, northeastern Pacific Ocean ( Golovan et al., 2019; Jazdzewska & Mamos, 2019), and southern Gulf of Mexico (the present study).

Vemana touzeti sp. nov., mainly differs from the 4 other described Vemana species by the following features: coxa 4 posteroventral corner prolonged forming an acute tooth, basis posterior margin of pereopod 7 with 6 evident teeth, antenna 1 article 1 lower margin with callynophore, and first urosome segment convex with a diminutive hump. In contrast, the new species is morphologically closest to Vemana lizata previously described for the deep-sea Caribbean Sea, based on the third pleonal epimeron, lower lip, and calynophores on the article 1 of the antenna 1. Major differences among the now present 5 Vemana species worldwide are considered in the dichotomic key.

Figures

FIGURE 2. Vemana touzeti sp. nov. Holotype male 7.5 mm (CNCR36469). Lateral view of body.

FIGURE 3. Vemana touzeti sp. nov. Holotype male 7.5 mm (CNCR36469). A, maxilla 1; B, maxilla 2; C, lower lip; D, upper lip; E, maxilliped; F, left mandible; G, rigth mandible.

FIGURE 4. Vemana touzeti sp. nov. Holotype male 7.5 mm (CNCR36469). A, antennae; B, gnathopod 1; C, gnathopod 2; D, pereopod 3; E, pereopod 4; F, pereopod 5; G, pereopod 6; H, pereopod 7.

FIGURE 5. Vemana touzeti sp. nov. Holotype male 7.5 mm (CNCR36469). A, uropod 1; B, urpodod 2; C, uropod 3 D, telson.