Gennadas scutatus Bouvier, 1906

Alves-Júnior, Flavio De Almeida, Lemos, Rachel De Jesus Feio De, Cardoso, Irene Azevedo, Araújo, Marina De Sá Leitão Câmara De, Bertrand, Arnaud & Souza-Filho, Jesser F., 2018, New records of deep-sea prawn of the genus Gennadas Spence Bate, 1881 (Crustacea: Decapoda: Benthesicymidae) from Southwestern Atlantic, Zootaxa 4450 (3), pp. 376-384 : 381-382

Gennadas scutatus Bouvier, 1906

( Figure 4 A‒C )

Gennadas scutatus Bouvier, 1906: 748 ; 1908: 42–44, plate VIII; A. Milne-Edwards & Bouvier 1909: 193, 194, fig. 10–12.— Kemp 1909: 727, 728, plate LXXV fig. 2; 1910: 178, plate XIII fig. 9,10; 1913: 61, 62.— Lenz & Strunk 1914: 310, 311, 341.— Calman 1925: 4.— Burkenroad 1938: 59, 60.— Crosnier & Forest 1969: 549, 550; 1973: 281–283, fig. 94a, 95a, b.— Kensley 1971: 288, 289, fig. 10; 1972, figs. 4d, 6g.— Kensley et al. 1987: 279.— Dall 2001: 434, 435, fig. 20.— Guzmán 2008: 29.— Hendrickx 2015: 423.

Material examined. Superstation 3, serial 1013, 1 Male (CL, 5.18 mm) and 1 Female (CL, 4.98 mm), Mid-Atlantic Ridge, 04°16’42’’S, 12°22’39’’W, 3093 m, MNRJ 22569. ST47, 2 Females (CL, 3.6 mm, 3.4 mm), Fernando de Noronha Archipelago, 4°25'5''S, 32°57'51''W, 505 m, 30 April 2017, MOUFPE 18769. ST56C, Seamounts- Ceará Chain, 3 Females (CL, 3.3 mm ‒ 3.5 mm), 3°58'46''S, 35°23'2''W, 260 m, 0 4 May 2017, MOUFPE 18770.

Diagnosis. Carapace thin. Antennal and infra-antennal angles acute. Spine on external margin of scaphocerite reaching beyond its apex. Thelycum of female with elongated flap on 8th sternite, stretching forward to cover the 7th and 6th sternites, with these last two showing a triangle-shape; 6th sternite with seminal receptacles visible under flap of 5th sternite. Petasma internal lobe with 2 short rounded lobules with hooks. Median lobe broad, outer lobule slender and inner broadly rounded lobule with tiny lobe on outer margin, internal lobe with 2 rounded lobules.

Distribution. Western Atlantic: Caribbean Sea and Brazil (Seamounts- Ceará Chain and Fernando de Noronha Archipelago), Mid-Atlantic Ridge ( Figure 2 ). Eastern Atlantic: off Cape Peninsula, West coast of South Africa, Agulhas Basin. Indo-Pacific Oceans: East Australia, Mexico, Peru, Chile ( Kensley et al. 1987; Guzmán 2008; Hendrickx 2015).

Bathymetric Distribution. Maximum of 3400 m depth ( Kensley 1971; Kensley et al. 1987).

Remarks. According to Kensley (1971), in the specimens collected along the African coast the antennal and infra-antennal angles were acute. In the material examined herein, these angles are rather rounded. In the individuals analyzed by Kemp (1910) the accessory lobe of the petasma is triangle-shape, although on the specimens analyzed by Kensley (1971) and herein the accessory lobe of the petasma is broadly rounded.

The closest species of G. scutatus is G. propinquus Rathbun, 1906 , but these two species can be distinguished as follows: thelycum of G. scutatus with an elongated flap in the 8th sternite, while in G. propinquus this flap is absent; the petasma of G. scutatus shows the median lobe apically rounded, vs. acute in G. propinquus . Gennadas scutatus has a cosmopolitan distribution, including the Atlantic Ocean, but it has never been documented in the southwestern Atlantic and its distribution is expanded to the Mid-Atlantic Ridge.

Figures

FIGURE 2. Sampling stations visited during this study where specimens of Gennadas were collected (Abracos 2 and MAR- ECO Projects).

FIGURE 4. Gennadas scutatus Bouvier, 1906, Female (CL, 4.98 mm), Carapace (A) (AA= Antenal Angle; IAA= Infra- Antenal Angle), Thelycum (B) (Cx = Coxa); Male (CL, 5.18 mm), Petasma (C) (EL= External Lobe; ML: Median Lobe; IL= Internal Lobe), MAR-ECO, Superstation 3, serial 1013, Mid-Atlantic Ridge, 3093 m, MNRJ 22569.