Fagegnathophausia gracilis (Willemoes-Suhm, 1875)

Hendrickx, Michel E., 2019, Species of Gnathophausiidae (Crustacea, Lophogastrida) collected off the west coast of Baja California, Mexico, during the TALUD cruises, Zootaxa 4609 (3), pp. 449-468 : 458-459

Fagegnathophausia gracilis (Willemoes-Suhm, 1875)

( Figs. 2 C–D, 8)

Gnathophausia gracilis Willemoes-Suhm, 1875b: 33 , 37, pl. IX, fig. 1.

Gnathophausia gracilis . ―G.O. Sars, 1885: 48, pl. VII, figs. 6–10.― Ortmann, 1906: 39.― Hansen, 1912: 185.―W.M. Tattersall, 1939: 223.― Fage, 1941: 27, fig. 27.―O.S. Tattersall, 1955: 39.― Gordan, 1957: 333.― Pequegnat, 1965: 400, 402 (key), 409, fig. 6, Tables 1 , 4, 411–420 (passim).―Childress, 1971b: 104.― Mauchline & Murano, 1977: 57, Table 1 .― Quetin & Childress, 1980: 383, figs. 4–5.― Udrescu, 1984: 6 2–64, figs. 2A, 3C, 4B.―Casanova, 1996b: 132, fig. 3; 1997: 92 (list), 93 ( Table 1 ), 96, fig. 2C, E.― De Jong & Casanova, 1997: 1032 –1038 (passim), fig. 3d, g, fig 4c.―Wirtz, 1998: 512 (list).― Casanova et al., 1998: 60, fig. 1a.― Nouvel et al. 1999: 63, fig. 4.2 3F. ― van der Land & Brattegard, 2001: 293 (list).― Richter et al., 2002: 345, figs. 9–12.― Haroun & Garrido, 2003: 68.― Lowry & Stoddart, 2003: 426.― Sawamoto & Fukuoka, 2005: 81, Table 1 .― Ibarra Rivera & Hendrickx, 2008: 57 (list), 65 (key), 67, figs. 18, 19A– F.― Price et al., 2009: 923 –924 (passim), 928 (list).― Wittmann & Riera, 2012: 68.― Meland & Aas, 2013: 204 , fig. 3, 219 (key).― Sawamoto, 2015: 4, Table 1 .― San Vicente, 2016: 485, 495 (key).― Letessier et al., 2017: 90, Table 2 .

Gnathophausia var. brevispinis Wood-Mason & Alcock, 1891a: 187 .

Gnathophausia brevispinis .―Wood-Mason & Alcock, 1891b: 269.― Faxon, 1895: 216, pl. J.

Gnathophausia dentata Faxon, 1893: 217 .

Gnathophausia bidentata Illig, 1906: 229 , fig. 2.

Gnathophausia sp.― Chun, 1900: 289 –531 (partim); 1903: 551.

Gnathophausia dentate.― Meland & Aas, 2013: 205 .

Gnathophausia bidentate .― Meland & Aas, 2013: 205.

Fagegnathophausia gracilis .― Petryashov, 2015: 239, figs. 1–2, 242 (list).― Fernández, 2017: 13 (list).

Material examined. TALUD XV, St. 5F (22°58'15"N, 110°40'17"W), Aug 5, 2012, 1 juv. (CL 24 mm), BS operated at 1035–1108 m (ICML-EMU-12315A) ; St. 10 (24º20'42"N, 112º44'48"), Jul 29, 2012, 1 male (CL 20 mm), BS operated at 2088–2125 m (ICML-EMU-12316) ; St. 16 (25º13'11"N, 113º15'56"W), Aug 3, 2012, 1 female (CL 21 mm), BS operated at 1770–1810 m (ICML-EMU-12313A) ; St. 17 (26º20'24"N, 114º13'07"W), July 31, 2012, 1 male (CL 19 mm) and 1 female (CL 29 mm), BS operated at 2111–2136 m (ICML-EMU-12313B) ; St. 25 (26º57'06"N, 114º34'31"W), Aug 1, 2012, 2 females (CL 28 mm; one damaged), BS operated at 1370–1518 m (ICML-EMU-12317). TALUD XVI , St. 3 (28º39'N, 115º49'W), Jul 31, 2013, 1 male (CL 28 mm), 1 female (CL 31 mm), and 2 damaged specimens (CL ca. 15 mm), BS operated at 1397–1408 m (ICML-EMU-12318) . TALUD XVI-B, St. 1 (28º27'24"N, 115º48'55"W), May 23, 2014, 2 females (CL 15–24 mm), BS operated at 2038–2054 m (ICML-EMU-12319) ; St. 8 (29º23'48"N, 115º45'16"W), May 31, 2014, 1 male (CL 22 mm), BS operated at 1416– 1480 m (ICML-EMU-12314A) ; St. 11 (29º16'48"N, 116º13'46"W), May 29, 2014, 2 males (CL 20–21 mm), 2 females (CL 28–32 mm) and 1 juv. (CL ca. 8 mm), BS operated at 1679–1698 m (ICML-EMU-12320) ; St. 20 (30º51'16"N, 116º42'11"W), May 26, 2014, 1 female (CL 26 mm), BS operated at 2075–2090 m (ICML-EMU- 12322) ; St. 21 (30º49'24"N, 116º47'48"W), May 28, 2014, 2 males (CL 26–27 mm), BS operated at 2018–2093 m (ICML-EMU-12314B) ; St. 28 (31º22'N, 117º02'W), May 27, 2014, 1 juv. (CL 16 mm), BS operated at 1461–1532 m (ICML-EMU-12315B).

Distribution. Cosmopolitan, almost exclusively in tropical waters (Medan & Ass 2013). According to Ibarra Rivera & Hendrickx (2008: fig. 18), F. gracilis is one of the most commonly collected species in the California Current area, thus confirming its presence in temperate waters, at least in the eastern Pacific. This is fully confirmed by the abundant and widely distributed material collected during this survey ( Fig. 3 ).

Remarks. Illustrations of this species by G.O. Sars (1885) were reproduced by Meland & Ass (2013). The base of the rostrum, on the anterior part of the carapace, is showed as slightly elevated but without spines (G.O. Sars 1885: pl. VII, fig. 6; Meland & Ass 2013: fig. 3A). Revision of the original description and figure by Willemoes- Suhm (1875: 33, pl. IX, fig. 1), based on a single male (CL 24 mm; 41 mm total length), indicates that there is indeed a spiny ridge (or crest) with 2–3 spines on the anterior part of the carapace, at the base of the rostrum. While examining the type material of G. gracilis, G.O. Sars emphasized that "the carapace [has] been partly crushed" and that "it has therefore been somewhat difficult [...] to give correct figures of the general appearance and form of the body". This might explain the absence of a ridge in G.O. Sars figure. The illustration provided for F. gracilis by Petryashov (2015: fig. 1, 1–2) clearly shows a strong, elevated spiniferous ridge (crest) at the base of the rostrum. This character coincides with our material in which an elevated crest, armed with a strong spine is visible, in large and small specimens ( Figs. 2 C–D, 8A–C), this spine followed by a cluster of 1–3 smaller spines (occasionally lacking).

The branchiostegal spines of the carapace are strikingly different in G.O. Sars figure (G.O. Sars 1885: pl. VII, fig. 7; Meland & Ass 2013: fig. 3B), with the anterior spine small and the posterior spine larger, leaf-like, with a sharp tip ("... enormously developed" and projecting like "... strong wing-like expansions"; fide G.O. Sars, 1885: 49). In Petryashov illustration (2015: fig. 1, 1), the branchiostegal spines of the carapace are both very slender, sharp, the posterior being about twice as long as the anterior. Material examined herein features two well marked anterolateral "leaf-like" projections, each ending in sharp spine ( Fig. 8 G ), the anteriormost being considerably larger than the one illustrated by G.O. Sars (1885).

The abdominal somites 1–2 of G.O. Sars illustration (G.O. Sars, 1885: pl. VII, fig. 6; Meland & Ass 2013, fig. 3A) appears intermediate between the illustrations provided by Petryashov (2015: fig. 2, 1–2) of these somites ("pleomeres") in a male and a female specimens, which are very different. The material examined herein match the illustrations provided by Willemoes-Suhm (1875: pl. IX, fig. 1) and of G.O. Sars (1885), including a pair of sharp dorsal spines on somites 1–2 in a male (CL 27 mm), a female (CL 31 mm), and a juvenile (CL ca. 15 mm) ( Fig. 8 D–F). The original description refers to "the presence of spines at the top of the first, second, and fifth abdominal ring" (Willemoes-Suhm, 1875: 34 and pl. IX, fig. 1), while in the illustrations of G.O. Sars (1885) and of Meland & Ass (2013) a spine is present on abdominal somites 3–5. G.O. Sars (1885: 49) also clearly stated this characteristic in the text: "... caudal segments [...] five anterior ones are armed with dorsal projections ...". Petryashov (2015: 240) also emphasized the presence of " ... large spiniform processus in middle of dorsal part of tergites of pleomeres 1–5". The material examined herein clearly features a posterodorsal, triangular process ending in a spine on somites 3–5 ( Fig. 8D ).

The forked tip of the telson in G.O. Sars (1885: pl. VII, fig. 10) is composed of four teeth, a pattern also reported by Petryashov (2015: fig. 2, 5) and observed in our material (telson tip is often damaged). The pair of lateral teeth, however, consists of movable spines and there is a pair of series of spinules obliquely set near the base of the fork ( Fig. 8H ), as observed by Petryashov (2015). The distolateral series of spines on the telson illustrated by G.O. Sars (1885) is mostly made of minute spines, while Petryashov (2015) illustration figures larger spines, and the material examined features intercalated minute and larger spines ( Fig. 8H ).

Figures

FIGURE 2. A, B, Gnathophausia childressi Casanova, 1996. C, D, Fagegnathophausia gracilis (Willemoes-Suhm, 1875). A, lateral view, male (CL 27 mm) (ICML-EMU-12294); B, lateral view, male (CL 22 mm) (ICML-EMU-12293); C, lateral view, female (CL 28 mm) (ICML-EMU-12320); D, same, dorsal view.

FIGURE 3. Localities where Gnathophausia childressi Casanova, 1996 and Fagegnathophausia gracilis (Willemoes-Suhm, 1875) were collected during this survey.

FIGURE 8. Fagegnathophausia gracilis (Willemoes-Suhm, 1875). A, upper part of carapace and base of rostrum, male (CL 27 mm) (ICML-EMU-12314B); B, anterior part of carapace and base of rostrum, female (CL 31 mm) (ICML-EMU-12318); C, same, juvenile (CL ca. 15 mm) (ICML-EMU-12318); D, lateral view of somites 1–5, male (CL 27 mm) (ICML-EMU- 12314B); E, lateral view of somites 2–3, female (CL 31 mm) (ICML-EMU-12318); F, same, juvenile (CL ca. 15 mm) (ICML- EMU-12318). G, dorsal view of branchiostegal spines, right, male (CL 26 mm) (ICML-MU-12314B); H, dorsal view of tip of telson, female (CL 28 mm) (ICML-EMU-12320).