Notonyx vitreus Alcock, 1900

Castro, Peter, 2007, A reappraisal of the family Goneplacidae MacLeay, 1838 (Crustacea, Decapoda, Brachyura) and revision of the subfamily Goneplacinae, with the description of 10 new genera and 18 new species, Zoosystema 29 (4), pp. 609-774 : 755-757

publication ID	https://doi.org/ 10.5281/zenodo.4525564
persistent identifier	https://treatment.plazi.org/id/102B87CB-FF10-25F6-FCB0-FE3FFBBEF97B
treatment provided by	Felipe
scientific name	Notonyx vitreus Alcock, 1900
status

Treatment

Notonyx vitreus Alcock, 1900 View in CoL

Notonyx vitreus Alcock, 1900: 319 View in CoL [Andaman Is]. — Alcock & McArdle 1903: pl. 61, fig. 3 [Andaman Is]. — Tesch 1918: 219 [in key], 221 [ Indonesia]. — Balss 1924: 14 [Red Sea]. — Serène & Soh 1976: 18, fig. 16A-D [ Thailand].

? Notonyx vitreus View in CoL – Takeda 1989: 170, fig. 15 [ Japan].

TYPE MATERIAL. — Unknown deposit (Zoological Survey of India, Kolkata [Calcutta]?).

TYPE LOCALITY. — India, Andaman Is.

DISTRIBUTION. — Indo-West Pacific region from the Red Sea ( Balss 1924) to New Guinea ( Tesch 1918). Questionably from Japan ( Takeda 1989). Depth: 32-91 m ( Tesch 1918).

REMARKS

The identification of Japanese material as N. vitreus by Takeda (1989) is questionable (see Clark & Ng 2006).

REPRODUCTIVE STRUCTURES

AND THE TAXONOMY

OF THE GONEPLACIDAE

This reappraisal of the family Goneplacidae has emphasized the use of the external reproductive structures, both male and female, as taxonomic characters. Although the morphology of the brachyuran male gonopods, particularly the G1, and the male abdomen have been widely used by taxonomists for some time, practically no attention has been placed on the morphology of the female vulva as a taxonomic character. It is surprising, for instance, that few carcinologists have ever remarked on the conspicuously enlarged vulva of some goneplacids, particularly in Carcinoplax . An exception is Barnard (1950: 287), who included “Genital openings in adult ♀ very large” as one of the characters listed in his diagnosis of Carcinoplax .

The morphology of the vulva and vagina among several groups of brachyurans was studied by Hartnoll (1968), who described two general arrangements (see also Guinot 1979): those having a vagina consisting of a simple tube with flexible walls and those with a vagina that is concave in cross section and localized muscles in the wall. A sclerified vulvar cover, mobile or immobile and referred to as an operculum, was found present among species belonging to the two groups. The vagina of Goneplax rhomboides , the only goneplacid studied by Hartnoll (1968: 296), was found to be intermediate between the two major groups, concave in outline but with flexible walls without localized muscles. The vulvar cover was absent.

The morphology of the external reproductive structures goes beyond being another morphological character of practical use to taxonomists. There seems to be a correlation between the general morphology of the vulva and that of the G1 among goneplacines.

It is speculated that this apparent correlation may be an adaptation to facilitate copulation (see discussion for other groups of brachyurans by Guinot 1979: 248). A large, greatly expanded vulva only protected by a soft membrane appears to be linked to a slender and thin (distinctly dorsoventrally compressed) G1. This is the case of eight goneplacine genera: Carcinoplax (see Fig. 1 View FIG for the vulva; Figs 2A View FIG ; 4C View FIG ; 6C View FIG ; 9C View FIG for the G1), Entricoplax n. gen. ( Fig. 11 View FIG for the vulva; Takeda & Miyake 1968: fig. 5f, as Carcinoplax vestita , for the G1), Exopheticus n. gen. ( Figs 49 View FIG ; 50 View FIG for the vulva; Fig. 48C View FIG for the G1), Goneplacoides n. gen. ( Fig. 29 View FIG for the vulva; Komatsu & Takeda 2003: fig. 3c, d, as Goneplax marivenae , for the G1), Goneplax sensu stricto ( Capart 1951: figs 10-12, and Guinot 1969b: fig. 71a, b; 1989: fig. 46A, as Carcinoplax barnardi , for the G1), Hadroplax n. gen. ( Serène & Umali 1972: figs 78, 79, as Goneplax sinuatifrons , for the G1), Ommatocarcinus ( Barnard 1950: fig. 53 f, and Dai & Yang 1991: figs 199-1, 199-2, for the G1), and Paragoneplax n. gen. (G1 slender but bent in larger males, Chen 1998: fig. 12-6, as Goneplax serenei ). The large size of the vulva in these genera, however, remains unexplained.

In contrast, a small, not expanded vulva typically covered in part by a vulvar cover and linked with a stout, thick, sometimes bent, often spinous G1, is characteristic of six genera: Menoplax n. gen. ( Fig. 12 View FIG for the vulva; Chen 1984: fig. 7-4 to 7-6 and Guinot 1989: fig. 32A, as Carcinoplax longispinosa , for the G1), Neogoneplax n. gen. ( Fig. 32 View FIG for the vulva; Fig. 33 D View FIG and Chen 1998: fig. 11-4, as Goneplax renoculis , for the G1), Notonyx ( Clark & Ng 2006: figs 3H, I, 5J, K for the G1), Psopheticus ( Fig. 47 View FIG for the vulva; Zarenkov 1972: fig. 6-5, Guinot & Richer de Forges 1981b: fig. F, Guinot 1990: figs 44, 47, 50, 52, and Hsueh & Huang 2002: figs 12D, H, for the G1), Pycnoplax n. gen. ( Figs 14 View FIG ; 15 View FIG ; 18 View FIG for the vulva; Fig. 16C View FIG and Zarenkov 1972: fig. 6-2, Serène & Lohavanijaya 1973: figs 158-162, Chen 1984: figs 4-5, 4-6, Guinot 1989: fig. 30A, as C. bispinosa ; Guinot 1969b: fig. 73; 1989: fig. 31 A, Chen 1984: figs 3-5, 3-6, Dai & Yang 1991: fig. 192-1, as C. surugensis , for the G1), and Thyraplax n. gen. ( Figs 19 View FIG , 22 View FIG for the vulva; Figs 20C View FIG ; 23D View FIG ; 25C View FIG for the G1).

Some of the species of Microgoneplax n. gen. and Singhaplax present conditions that deviate from those described above. In Microgoneplax n. gen. the vulva is small, the vulvar cover is present, the G1 is thick as in the genera listed above ( Figs 41C View FIG ; 43B View FIG ; 44B View FIG ), but it is nevertheless thin and slender in one species, M. prion n. sp. ( Fig. 45B View FIG ). In Singhaplax the vulva is large, the vulvar cover is absent, but the G1 may be regarded as stout and thick in two of the species ( Figs 35B View FIG ; 38B View FIG ; Serène & Umali 1972: figs 86, 87, as Goneplax ockelmanni Serène & Soh 1976 : figs 15B, B’). In these two genera, however, females are known in only some of the species and the relative thickness of the G1 is difficult to ascertain due to the small size of the individuals. There are two other notable exceptions among the remaining goneplacine genera. In Neogoneplax costata n. sp. the vulva is small and provided with a vulvar cover ( Fig. 32 View FIG ) but the G1 is clearly slender ( Fig. 30C View FIG ), in contrast to the other two species of Neogoneplax n. gen., where the G1 is predictably stout. In Neommatocarcinus huttoni , the G1 is slender ( Takeda & Miyake 1969b: fig. 5d) but the vulva, although covered by a soft membrane and lacking a vulvar cover, is bordered by a sclerified prominence.

An alternative hypothesis is that the optimal size of the vulva is influenced more by its function as the opening through which eggs are released rather than as the location where the male pleopods deposit the sperm. Egg size, although not quantified among the goneplacines that were studied, does not seem to be noticeably or particularly larger in species with large vulvae than in those with small vulvae.

The morphology of the vulvar cover varies widely among carcinoplacines and several patterns may be observed. However, it is never as complex as the hinged operculum of some brachyurans (see Thompson & McLay 2005). The role and significance of the vulvar cover in the reproductive behavior of carcinoplacines remain unknown.

The G2 is similar among practically all goneplacines, being slender and about the same size as the G1, which was considered a more primitive character by Guinot (1979: 243). Such a long G2 is known to be involved in the insemination of the vulva in some brachyurans (see Brandis et al. 1999; Guinot & Quenette 2005). The notable exception, a G2 that is much shorter than the G1, is found in Menoplax n. gen. ( Guinot 1989: fig. 32A, B, as C. longispinosa ), Microgoneplax n. gen. ( Figs 41C, D View FIG ; 43B, C View FIG ; 44B, C View FIG ; 45B, C View FIG ), and Paragoneplax n. gen. ( Chen 1998: figs 12-6 to 12-9, as Goneplax serenei ). There is no apparent correlation between the length of the G2 and the thickness, ornamentation, or general shape of the G1. In Carcinoplax ( Figs 2A, B View FIG ; 4C, D View FIG ; 6C, D View FIG ; 9C, D View FIG ), Entricoplax n. gen. ( Takeda & Miyake 1968: fig. 5f, g, as Carcinoplax vestita ), Exopheticus n. gen. ( Fig.48C, D View FIG ), Goneplacoides n. gen. ( Komatsu & Takeda 2003: fig. 3c, d, e, as Goneplax marivenae , fig. 6c-e, as G. megalops ), Goneplax sensu stricto ( Guinot 1969b: figs 71a, b, 72; 1989: fig. 46A, B, as Carcinoplax barnardi ), Hadroplax n. gen. ( Serène & Umali 1972: figs 78-81, as Goneplax sinuatifrons ), and Ommatocarcinus a long G2 is found together with a G1 that is thin, straight, and lacking conspicuous spines or teeth, a condition pointed out for Carcinoplax and several non-goneplacid genera by Guinot (1979: 241). The same basic type of long G2, however, is found in genera with thick, conspicuously spinous G1 as in Notonyx ( Clark & Ng 2006: figs 3G, 5I), Psopheticus ( Guinot 1990: figs 44-54), Pycnoplax n. gen. ( Fig. 16C, D View FIG ), and Thyraplax n. gen. ( Figs 20C, D View FIG ; 23D, E View FIG ; 25C, D View FIG ). A long G2 is found together with a relatively slender G 1 in Neogoneplax serratipes n. sp. ( Fig. 33D, E View FIG ) and four species of Singhaplax ( Figs 36B, C View FIG ; 39B, C View FIG ; 40A, B View FIG ), but with a thick and spinous G 1 in N. costata n. sp. ( Fig. 30C, D View FIG ) and three species of Singhaplax ( Figs 35B, C View FIG ; 38B, C View FIG ; Serène & Umali 1972: figs 86-88).

The goneplacine penis always arises directly from the male opening, which is found in the P5 coxa.It is uniformly soft but the proximal portion is sclerified in Neommatocarcinus . It was described as proximally sclerified in Ommatocarcinus by Guinot (1979: 219, fig. 54H) but this could not be verified.

Sperm plugs were present on the vulvae of specimens of Pycnoplax bispinosa n. comb. ( Fig. 15 View FIG ), P. victoriensis n. comb. ( Fig. 18 View FIG ), and Psopheticus stridulans ( Fig. 47 View FIG ). They have also been reported in Entricoplax vestita n. comb. ( Doi & Watanabe 2006). The role of sperm plugs in reproductive behaviour and sperm competition among goneplacines is unknown. Although sperm plugs are supposedly placed in the vagina by the first male to mate with soft-shelled females to prevent subsequent access to the spermatheca, in some species the plugs do not necessarily occlude the vulva nor prevent subsequent copulations (see Jensen et al. 1996).

The morphology of the external reproductive structures of both sexes is unfortunately rarely available for study by paleontologists. The morphologies of these structures are not studied and are therefore missing from the descriptions and, most significantly, the suggested phylogenetic relationships that have been given by paleontologists. The importance of these structures for neontologists working with at least members of the family Goneplacidae is evidenced by the impossibility of reliably distinguishing between Microgoneplax n. gen. and Singhaplax , between Neommatocarcinus and Ommatocarcinus , and between Carcinoplax tenuidentata n. sp. and Pycnoplax bispinosa n. comb. without examining the external reproductive structures. The likely role of the structure of copulatory organs as an isolating mechanism among the sympatric species of Microgoneplax n. gen. and Singhaplax provides evidence of the obvious biological significance of these structures.