Diuplax sigsbei (A. Milne-Edwards, 1880 ) L. & Castro & Rodríguez & Moreno, 2024

L., Peter K., Castro, Ng Peter, Rodríguez, Paula A. & Moreno, 2024, Notes on the taxonomy of Frevillea A. Milne-Edwards, 1880 (Crustacea, Brachyura, Goneplacoidea), with the description of a new genus for F. sigsbei A. Milne-Edwards, 1880, Zoosystema 46 (29), pp. 733-748 : 743-746

publication ID	https://doi.org/ 10.5252/zoosystema2024v46a29
publication LSID	lsid:zoobank.org:pub:B8FB5A89-4811-4DB1-819B-442067652F3E
persistent identifier	https://treatment.plazi.org/id/03D287C2-7D59-9C10-2E8F-FC06FC66F976
treatment provided by	Plazi
scientific name	Diuplax sigsbei (A. Milne-Edwards, 1880 )
status	comb. nov.

Treatment

Diuplax sigsbei (A. Milne-Edwards, 1880) n. comb.

( Figs 5 View FIG ; 6 View FIG )

Frevillea sigsbei A. Milne-Edwards, 1880: 16 . — A. Milne-Edwards & Bouvier 1923: 337, fig. 3, pl. 6, fig. 2.

Goneplax sigsbei View in CoL – Rathbun 1918: 25, 26, pl. 4, figs 2, 4. — Williams et al. 1968: 54, fig. 10. — Guinot 1969b: 520, figs 63, 68, 71a, b, 72; 1971: 1081 [in list]. — Williams 1984: 433, fig. 345. — Boschi 2000: 84 [in list]. — Nizinski 2003: 137. — Castro 2007: 692 View Cited Treatment . — Ng et al. 2008: 80.

HISTORY. — Alphonse Milne-Edwards (1880: 16) described F.sigsbei View in CoL from Blake ’s station 253 in Grenada, Lesser Antilles from a depth of 92 fathoms (= 168 m). One ovigerous female was measured, 14.0 × 9.0 mm but no type was indicated. Rathbun (1918: 26) stated: “type-locality, Grenada. 92 fathoms, station 253, Blake; holotype in Paris Mus.” and although she did not examine the specimen; her action constitutes the first valid designation of a name-bearing specimen or lectotype for the species. Rathbun (1918: 27), however, did examine one of the Blake specimens in MCZ: “Off Grenada; Lat. 11° 27’ 00” N.; long. 62° 11’ 00” W.; 164 fathoms; S. Sh.; temp. 57° F.; Feb. 27, 1879; station 254, Str. Blake; 1 female (Cat- No. 4117, M.-C. Z.).” Alphonse Milne-Edwards & Bouvier (1923: 337) stated that they studied two males and two females, including the measured ovigerous female type, 14.0 × 9.0 mm, which was figured (A. Milne-Edwards & Bouvier 1923: pl. 6 fig. 2); they also figured the frontal view of the carapace of a “type male” (A. Milne-Edwards & Bouvier 1923: fig. 3) ( Figs 5A View FIG ; 6A View FIG ). This action is confusing because they do not specifically identify one specimen as the “type”. Rathbun (1918) is therefore the only author who selected a valid name-bearing specimen or lectotype. The 14.0 × 9.0 mm ovigerous female is therefore the lectotype of F. sigsbei View in CoL .

There are two specimens in MNHN listed as “ syntypes ” of F. sigsbei : a male (13.0 × 8.5 mm) and a female (10.8 × 7.3 mm), both registered as MNHN-B10199. The original labels list the two specimens as “cotypes” and have been accepted as such by all subsequent workers including Guinot (1969b) and Castro (2007). The male specimen, 13.0 × 8.5 mm, from station 287 in Barbados, was figured and described by Guinot (1969b: 521, 523, 525, figs 63, 68, 71, 72) and is cited as a syntype. These two specimens, however, cannot be syntypes as they were from station 287 off Barbados; A. Milne-Edwards (1880) and A. Milne-Edwards & Bouvier (1923) clearly stated that the type series, including the lectotype ovigerous female was from station 253 in Grenada (but see discussion later). MCZ is depository of two specimens from station 253, an ovigerous female (15.3 × 9.5 mm) (MCZ-IZ-CRU-10991) and a male (14.1 × 8.4 mm) (MCZ-IZ-CRU-10992), labelled as holotype and paratype, respectively; but in the database, both are listed as “ syntypes.”

TYPE MATERIAL. — The ovigerous female measuring 14.0 × 9.0 mm from station 253 is the lectotype of F. sigsbei A. Milne-Edwards, 1880 . This specimen is the 15.3 × 9.5 mm ovigerous female specimen in MCZ (MCZ-IZ-CRU-10991) ( Figs 5B, C View FIG ; 6A View FIG ), the differences in measurements easily accounted for by different measurement methods (see discussion for F. barbata ). It agrees very well with the figures in A. Milne-Edwards & Bouvier (1923: pl. 6 fig. 2). The other male specimen in MCZ is here regarded as a paralectotype ( Fig. 5D, E View FIG ). As noted earlier, the two MNHN specimens from station 287 ( Figs 5F, G View FIG ; 6 View FIG B-I) cannot be regarded as types for the time being. It does seem coincidental, however, that A. Milne-Edwards & Bouvier (1923) had two male and two female specimens in total, and since we know that specimens were shared between MCZ and MNHN in most cases, it would make sense that each institution kept one pair each. It is noteworthy that between MCZ and MNHN, we have found all the other specimens of Frevillea . It is possible the station number for the two MNHN specimens of F. sigsbei had been incorrectly recorded and they are actually from station 253 as well, but we may never know.

MATERIAL EXAMINED. — Lectotype (by inference of holotype by Rathbun 1918: 26, as Goneplax sigsbei ; A. Milne-Edwards & Bouvier 1923: 337 as F. sigsbei ). Caribbean Sea • ovigerous ♀ (15.3 × 9.5 mm); station 253, off Grenada; 92 fathoms (168 m); 11°25’0”N, 62°04’15”W; coll. USCGS; George S. Blake cruise; 27.II.1879; MCZ-IZ-CRU-10991.

Paralectotype. Caribbean Sea • 1 ♂ (14.1 × 8.4 mm); same data as lectotype; MCZ-IZ-CRU-10992 .

ADDITIONAL MATERIAL. — Caribbean Sea • 1 ♂ (13.0 × 8.5 mm), 1 ♀ (10.8 × 7.3 mm); station 287, off Barbados; 7.5-50 fathoms (14-91 m); 13°11’25”N, 59°38’20”W; coll. USCGS; George S. Blake cruise, 8.III.1879; MNHN-IU-2014-11828 (= MNHN-B10199) GoogleMaps .

GEOGRAPHICAL DISTRIBUTION. — Western Atlantic region: Grenada, Barbados and off South Carolina, United States.

TAXONOMY

In transferring to Goneplax, Guinot (1969b: 520-522) wrote: “Par contre, la F. sigsbei A. Milne Edwards, 1880 (p. 16), ouest-atlantique, conservée dans Frevillea par A. MILNE EDWARDS et BOUVIER (1923, p. 337, fig. 3, pl. 6, fig. 2) mais placée (en même temps que les autres Frevillea , mais celles-là authentiques) dans Goneplax par RATHBUN (1918, p. 26, pl. 4, fig. 2, 4), et par WILLIAMS et al. (1968, p. 54, fig. 10), peut être laissée pour le moment dans le genre de LEACH. Il est vrai qu’à première vue le faciès de sigsbei rappelle advantage une Frevillea que Goneplax rhomboides . Pourtant, les caractères de sigsbei , nullement euryplaciens, sont gonéplaciens (s. str.), notamment la région antennaorbitaire (fig. 68); l’abdomen mâle; le pl 1 mâle (fig. 71), fort sur toute sa longueur et à peine effilé vers l’apex; ainsi que le pl 2 mâle (fig. 72), plus long que le pl 1. Chez sigsbei (fig. 63), comme chez rhomboides (fig. 64), l’orifice mâle s’ouvre sur la coxa de p5 mais, par suite du début de réunion des sternites 8 et 7, le pénis se trouve dans une gouttière imparfaitement close, ménagée entre ces deux régions. A noter que chez rhomboides , la portion latérale du sternite 8 non recouverte par l’abdomen est importante et s’intercale largement entre toute la partie basilaire, étroite, de l’abdomen (segments 1 et 2) et les coxae des p5; par contre, chez sigsbei , les premiers segments abdominaux, plus étendus, occupent pratiquement tout l’espace entre les coxae des p5, à l’exception d’une petite partie du sternite 8 qui est laissée à découvert. Par ailleurs, il ne semble pas que chez sigsbei le flagelle du pl 2, qui est recourbé, soit bifide comme chez G. rhomboides . ” [On the other hand, the F. sigsbei A. Milne Edwards, 1880 (p. 16), West Atlantic, kept in Frevillea by A. MILNE EDWARDS and BOUVIER (1923, p. 337, fig. 3, pl. 6, fig. 2) but placed (together with the other Frevillea , but those authentic) in Goneplax by RATHBUN (1918, p. 26, pl. 4, fig. 2, 4), and by WILLIAMS et al. (1968, p. 54, fig. 10), may be left for the time being in the genus of LEACH. It is true that at first glance the facies of sigsbei is more reminiscent of a Frevillea than Goneplax rhomboides . The characters of sigsbei are nevertheless goneplacian (s. str.), not euryplacian, notably the antennaorbital region (fig. 68); the male abdomen [pleon]; the pl 1 male (fig. 71), strong along its entire length and barely tapering towards the apex; as well as the male pl 2 (fig. 72), longer than the pl 1. In sigsbei (fig. 63), as in rhomboides (fig. 64), the male orifice opens on the coxa of p5 but, as a result of the beginning of the union of sternites 8 and 7, the penis is in an imperfectly closed gutter, formed between these two regions. It should be noted that in rhomboides , the lateral portion of sternite 8 not covered by the abdomen is important and is widely inserted between the entire basilar, narrow part of the abdomen (segments 1 and 2) and the coxae of p5; on the other hand, in sigsbei , the first abdominal segments, more extended, occupy practically all the space between the coxae of p5, with the exception of a small part of sternite 8 which is left uncovered. Moreover, it does not seem that in sigsbei the flagellum of pl 2, which is curved, is bifid as in G. rhomboides .]

Frevillea sigsbei A. Milne-Edwards, 1880 is clearly a member of Goneplacidae MacLeay, 1838 View in CoL , s. str. (cf. Castro 2007). Comparing the specimens of F. sigsbei also shows that Guinot’s (1969b) doubts about transferring it to Goneplax View in CoL are justified. The differences in the pleon, sternal and gonopodal structures, as well as differences in the carapace and chelipeds with Goneplax View in CoL s. str. argue for treating F. sigsbei as a separate new genus. It is here made the type species for a new genus, Diuplax n. gen.

MCZ	Museum of Comparative Zoology
MNHN	Museum National d'Histoire Naturelle

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Taxonomy

Kingdom	Animalia
Phylum	Arthropoda
Class	Malacostraca
Order	Decapoda
Family	Goneplacidae
Genus	Diuplax