Leptograpsodes octodentatus (H. Milne Edwards, 1837)

Guinot, Danièle, Ng, Ngan Kee & Rodríguez Moreno, Paula A., 2018, Review of grapsoid families for the establishment of a new family for Leptograpsodes Montgomery, 1931, and a new genus of Gecarcinidae H. Milne Edwards, 1837 (Crustacea, Decapoda, Brachyura, Grapsoidea MacLeay, 1838), Zoosystema 40 (26), pp. 547-604 : 556-561

Leptograpsodes octodentatus (H. Milne Edwards, 1837)

( Figs 1-3 )

Cyclograpsus octodentatus H. Milne Edwards, 1837: 80 . — Lucas 1840: 71.

Heterograpsus octodentatus – H. Milne Edwards 1853: 160 [194]. — Kingsley 1880: 209. — Haswell 1882: 101.

Brachynotus octodentatus – Tesch 1918: 106 (in key and footnote). — Hale 1924: 69; 1927a: 182, fig. 183; 1927b: 312. — Balss 1935: 142. — Tweedie 1942: 16, fig. 2. — Guiler 1952: 40 (list). — Bennett 1964: 81.

Grapsus inornatus Hess, 1865: 148 , pl. 6, fig. 11. — Haswell 1882: 98. — see De Man 1887: 699.

Leptograpsodes webhaysi Montgomery, 1931: 452 , pI. 25, fig. 5, pI. 28, fig. 1, la, 1b.

Leptograpsodes octodentatus – George 1962: 71-74, unnumbered figs. — Griffin 1969: 325, figs 1, 2a-c, 3a, 8, 9, table 3; 1971: 598, 603, figs 1-3, 5, tables 2, 3, 5-12. — Davie 2002: 215. — Poore 2004: 297, 503, 506, figs 161b, f, 162d, e, pl. 29d. — Ng et al. 2008: 217. — Schubart 2011: 473, 476, fig. 1, table 1. — Ip et al. 2015: 221, 223, fig. 2, table 1.

MATERIAL EXAMINED. — Leptograpsodes octodentatus (H. Milne Edwards, 1837) : neotype (by present designation), ♂ 17.3 × 20.6 mm, Australia, Tasmania, King Island, coll. D. Alexander, 13.IV.1965 ( TMAG G1033 ); 1♂ 12.8 × 15.4 mm, 1♀ 17.1 × 20.6 mm, Australia, Tasmania, King Island, Cape Wickham, above high tide level, in freshwater, coll. D. Hird, XII.1996 ( TMAG G3854 ); 1♂ 51.8 × 68.3 mm (left-handed), Australia, South Australia, Blue Lagoon at Cactus Beach via Penong , 32°04’20”S, 132°59’24”E, coll. Brian V.Timms, 10.X.2006, by hand, G. Poore det. 2006 (ex NMV J55301 -1 , as exchange), MNHN-IU-2013 - 14993; 1 ovigerous ♀ 27.0 × 34.0 mm, South Australia, Australian Mus. , entry 1912, Heterograpsus octodentatus Edw., Bouvier typ. comp., MNHN- IU-2013 -14992 (= MNHN-B12530).

Leptograpsodes webhaysi Montgomery, 1931 : syntype, ovigerous ♀ 27.0 × 34.0 mm, Abrolhos, Western Australia, WAM C71736, with several pereipods detached or partially missing; syntype ♀ 16.0 × 20.0 mm, Long Island, Abrolhos, WAM C71737, with several pereiopods missing.

TYPE LOCALITY. — Australia, Tasmania, King Island .

DESCRIPTION

As for the genus.

SELECTION OF A NEOTYPE

The type material of Cyclograpsus octodentatus H. Milne Edwards (1837: 80) , described without any indication of sex and size, from the King Island in the Bass Strait, between southeast Australia and Tasmania (curiously, the species is indicated as from unknown locality by H. Milne Edwards himself [1853: 160] then by Kingsley [1880: 209]), could not be tracked at the MNHN. It was still deposited in the MNHN collection around 1930 since it was examined by Charles Gravier for comparison with Leptograpsodes webhaysi . Griffin (1969: 325) indicated it could be deposited in the MNHN and Davie (2002: 217) wrote “type status unknown MNHP*”, thus a probable MNHN depository. But, despite an extensive investigation, it must be today assessed as lost, and therefore the fixation of a neotype is made here (ICZN, art. 72.4.5).

An ovigerous female 28.0 ×35.0 mm, in very good condition, labelled “ Heterograpsus octodentatus Edw. , South Australia, Australian Mus.1912, Bouvier typ.comp.”, MNHN- IU-2013-14992 (= MNHN-B12530), was compared to the type of Cyclograpsus octodentatus c. 1930 by E.-L. Bouvier (director of the chair of Entomology in the MNHN from 1917 to 1931), who has perhaps helped Gravier to list the differences from Leptograpsodes webhaysi asked by Montgomery (1931: 453). Although this female could be eligible to be the name-bearing type of the species, it was preferable to choose a male, originating from the type locality. Consequently, a male 17.3× 20.6 mm from King Island (TMAG G1033) is selected here as neotype of L. octodentatus ( Fig. 2 A-D): despite its small size, it has fully developed gonopods and fulfils all the specific characteristics.

COLOUR

Carapace olivaceous, mottled or spotted with dark brown ( Hale 1927a: fig. 183; Tweedie 1942: 18); mottled with black, dark blue or purple and yellow ( George 1962: 72, unnumbered fig.). Underside of the body, chelipeds and legs usually much paler than carapace, with the mottling on the dorsal surface of the chelipeds and legs sometimes bright red ( Griffin 1969). In ethanol, carapace dirty yellow mottled with red in patches, and discontinuous rings of a similar dull red on merus, carpus, and propodus of the legs ( Montgomery 1931: 454, pl. 25, fig. 5, as Leptograpsodes webhaysi ) (see Fig. 2E ). Carapace dark brown to purple, with extensive yellow mottling; chelipeds bright red on upper surfaces ( Fig. 1A, B ) ( Poore 2004: colour fig. pl. 29, fig. f).

VARIATIONS WITH SEX AND AGE

There is a large difference in size among the specimens we examined. According to George (1962) sexual maturity is reached at a carapace breadth of about 25.0 mm, and large adult males may reach a size of 76.0 mm; a size of more than 70.0 mm is cited by Tweedie (1942) and by Poore (2004). Large-sized adult males ( Fig. 1A, B ) develop huge, heterochelous and heterodontous chelae, with curved and irregularly toothed fingers, whereas smaller adult males ( Fig. 2A, B ) and females have more reduced, homochelous and homodontous chelipeds, with straight, regularly toothed fingers. George (1962), who examined a total of 84 specimens of L. octodentatus (50 males, 34 females, carapace width 10-70 mm) throughout its geographical range, concluded that the ridges around the orbits, the prominence of the pits on the dorsal surface of the carapace, the dentition and shape of the fingers, and ornamentation of the carpus of the cheliped were subject to significant variation with either age or sex, sometimes both. According to Griffin (1969) examination of the Tasmanian material at hand fully supported George’s conclusion. Thus, since the characters listed by Montgomery (1931) as differential characters with respect to Cyclograpsus octodentatus are precisely those that are subject to significant variation, they did not support taxonomic separation of eastern and western populations.

Although we have not examined a broad sampling panel of specimens, we agree with the preceding authors and share the assertion of George (1962) that the ridges on the branchial regions become less prominent with increasing overall size. In old cave-dwelling males, the clothing of anterior thoracic sternum and pterygostomial areas has exceedingly dense geniculate setae, resembling brown fur. The genital region is similarly organised in the small male neotype 17.3× 20.6 mm and in the large male 51.8 × 68.3 mm ( Figs 1E ; 3 A-C): in both the cylindrical portion of penis (differently coloured) and a small proximal part of sternite 8 are exposed over a short distance when the pleon is closed, whereas these portions are covered and not visible at smallest size, for example in the male measuring 12.8 × 15.4 mm.

For the age-related variations of the stridulatory apparatus, see below Stridulatory structures in grapsoids.

GEOGRAPHICAL DISTRIBUTION AND ECOLOGY

Leptograpsodes octodentatus is restricted to southern and southwestern Australia as far north as the Abrolhos Islands, and quite widely distributed around Tasmania. It is a large supratidal crab, on rocky parts, found in rock-crevices; it burrows on the

beach, sometimes far from the sea ( Hale 1927a: fig. 184). It may be found under debris and stones on estuarine areas, in brackish waters ( Hale 1927a), even near freshwater streams; adults were never found immersed in the sea ( George 1962: 72, fig. p. 74), or only rarely entering the sea ( Hale 1927a). The crab is highly resistant to desiccation; old males live singly in burrow. From field observations on the coasts of Tasmania and laboratory experiments ( Griffin 1971: figs 1-3, 5, tables 2, 3, 5-12), L. octodentatus is known to occur on cliffs and platforms at some localities but more often on fully to semi-exposed boulder; to be also found at some localities on the north of Tasmania at the tops of cliffs burrowing in the earth; to show a tendency to move out of freshwater and remain out of water, being found at all areas located in freshwater seepages, always at a higher level than the ‘high tide’ level of the sea or saltlake ( George 1962). Leptograpsodes octodentatus shows a high degree of terrestrial adaptation: it gets water through tufts of hydrophilic setae located on pouches of P2-P4 coxae, to a lesser extent between P1/P2 coxae ( Figs 1C, D ; 2B ) (see Terrestrial adaptations of grapsoids).

REMARKS

The status of the monotypic genus Leptograpsodes has been controversial. On the basis of its morphology, it has been alternatively regarded as a member of several distinct families or subfamilies: Grapsidae ( Montgomery 1931; Balss 1935, as Brachynotus octodentatus ; George 1962; Griffin 1969; 1971; Cuesta & Schubart 1999; Davie 2002; Poore 2004; N. K. Ng 2006: 39; Ng et al. 2008; Pinheiro et al. 2016); Varuninae by Tweedie (1942: 16, as Brachynotus octodentatus ), who simultaneously assigned Cyclograpsu s H. Milne Edwards, 1837 to Sesarminae , such as Campbell & Griffin (1966: 139) and Haswell (1882). According to Bennett (1964: 81) Leptograpsodes was a synonym of Brachynotus De Haan, 1833 in the Varuninae , whereas Griffin (1969: 327) pointed out its strong similarities to the Australian varunines, and Griffin (1971: 327) stated that it was an exception among grapsines in possessing only fourteen gills. Brachynotus , assigned to Varuninae , is now restricted to the western Atlantic and Mediterranean Sea ( Schubart et al. 2002).

In the cladistic analysis by Sternberg & Cumberlidge (1998: 125,129, 130, 131, 134, figs 3, 5, table 3), where Sesarminae was recovered as paraphyletic, Leptograpsodes was recognised “morphologically quite distant from the other varunines”, nesting apart, and was placed in a non-varunine clade, whereas Cyclograpsus nested among varunine genera; Leptograpsodes was found more properly allied with the Gecarcinidae , Grapsidae , and Sesarmidae rather than to Varunidae (as Varuninae ). So far, the morphological generic differences between Leptograpsodes and the varunine Cyclograpsus were essentially established by Poore (2004, key: 506).

According to Schubart (2011), in excluding Leptograpsodes Grapsidae became a relatively small and monophyletic assemblage, a homogeneous family in terms of adult morphology ( Banerjee 1960; Crosnier 1965 as Grapsinae ; Guinot 1979 as Grapsinae ; Sternberg & Cumberlidge 1998; Schubart et al. 2002; Poore 2004; N. K. Ng et al. 2007), of larval features ( Cuesta & Schubart 1999; Cuesta et al. 2011 but without data for Leptograpsodes ), and of molecular data ( Schubart et al. 2000b, 2002; Schubart & Cuesta 2010). From the analysis of genetic sequences from all grapsid genera and 80% of the known grapsid species, the overall topology of the phylogenetic tree by Ip et al. (2015) provided similar results: the monophyly of Grapsidae was supported only when Leptograpsodes octodentatus was excluded but did not strongly reject the topology with L. octodentatus included in the family; Leptograpsodes was placed within the clade of the outgroup, next to Xenograpsus testudinatus . Information on the larval development of L. octodentatus that is still lacking (see Cuesta & Schubart 1999; Cuesta et al. 2011) would be crucial for a complete understanding of the phylogenetic relationships of Leptograpsodidae n. fam .

Our present re-appraisal shows that Leptograpodes can be referred to the Grapsoidea , but its comparison with the main evolutionary lineages recognised in this superfamily (gecarcinids, glyptograpsids, grapsids, percnids, plagusiids, varunids, sesarmids, xenograpsids), demonstrates it requires a separate family recognition.

Family GECARCINIDAE H. Milne Edwards, 1837

INCLUDED GENERA. — Cardisoma Latreille, 1828 ; Discoplax A. Milne- Edwards, 1867; Epigrapsus HelIer, 1862 ; Gecarcinus Leach, 1814 ; Gecarcoidea H. Milne Edwards, 1837 ; Johngarthia Türkay, 1970 ; Tuerkayana n. gen.

REMARKS

Leptograpsodes was never considered related to Gecarcinidae H. Milne Edwards, 1837 (for the authorship, see Appendix), and therefore a comparative analysis with its members is fully justified. First and foremost, a clarification about this family must be done.

Gecarcinidae is currently represented by five genera with large-sized species: Cardisoma , Discoplax , Gecarcoidea , Gecarcinus , and Johngarthia , which deserve the title of “land crabs”, although all of them have to return to the sea for larval release through a migration of reproductive individuals (Hartnoll 2010; Hartnoll et al. 2014; Rodríguez-Rey et al. 2016; Bauer 2018) and although their larval development shows no concession to a terrestrial lifestyle, even in the case of species preferring karst and cave environments. A sixth genus, Epigrapsus , with two small-sized species having a cryptic life, deviates from all gecarcinids.

Today, based on morphological characters that are too often ignored and/or overlooked (see below), the reexamination of all gecarcinids reveals a deep discrepancy from some of the recently published data, especially byTürkay (1987), Ng et al. (2000, 2001), Ng & Guinot (2001), Ng & Davie (2012), Ng & Shih (2014, 2015), and many subsequent authors. The changes that we hereby propose are related to their generic nomenclature (see Table 1), whereas the specific identifications accompanied by a remarkable iconography constitute points of agreement, but only partially, however. Change in the taxonomic status of several species will have important consequences, especially for the endemic fauna of Christmas Island, a unique marine biodiversity hotspot: its vulnerable gecarcinid population, worldwide known by its extraordinary migrations, plays an important ecological role in the terrestrial ecosystem and requires a conservation strategy ( Hicks et al. 1990; Paulay & Starmer 2011; Beeton et al. 2010; Turner et al. 2011, 2013; Bauer 2018).

The current classification of Gecarcinidae does not reflect the existence of the two main subclades supported by the congruence of morphological, larval and genetic data abovementioned. Establishment of two subfamilies is strongly required but would not be appropriate in the present paper in respect of the project announced in Ng et al. (2008: 214): “Davie & Ng, in prep.”.

Figures

FIG. 1. — Leptograpsodes octodentatus (H. Milne Edwards, 1837), ♂ 51.8 ×68.3 mm, South Australia, MNHN-IU-2013-14993 (ex NMV J55301-1): A, carapace, dorsal surface; B, chelipeds; C, thoracic sternum with pleon (setal tufts visible); D, thoracic sternum without pleon; E, genital area with male gonopore and penis; F, G1, two views; G, front, orbit, antenna (with articles 1-4 and flagellum) and suborbital ridge as pars stridens. Scale bars: 10 mm.

FIG. 2. — Leptograpsodes octodentatus (H. Milne Edwards, 1837): A-D, neotype, ♂ 17.3× 20.6 mm, Australia, Tasmania, King Island, TMAG G1033: A, dorsal view; B, ventral view; C, frontal view, with suborbital ridge as pars stridens; D, close-up view of plectrum as whitish ridge on P1 merus (see arrow); E, syntype of L. webhaysi Montgomery, 1931, ovigerous ♀ 27.0 ×34.0 mm, Abrolhos, WAM C71736. Scale bars: 10 mm.

FIG. 3. — Leptograpsodes octodentatus (H. Milne Edwards, 1837), ♂ 51.8 ×68.3 mm, South Australia, MNHN-IU-2013-14993 (ex NMV J55301-1): A, thoracic sternum (note sternite 8 not developed medially, only exposed laterally); B, genital area with male gonopore and penis; C, posterior part of thoracic sternum with pleon; D, front and orbit. Abbreviations: b, bridge; b.p., press-button; c, coxo-sternal condyle; cx1-5, P1-P5 coxae; e.p., exposed proximal portion of penis; e.t., extraorbital tooth; e4-e7, episternites 4-7; i.b., suborbital border; i.s., incomplete sulcus; i.t., suborbital tooth; m.l., median line; mxp3; third maxilliped; P1, P2, P3, pleonal somites 1-3; p, penis; p.e., posterior emargination; p.p., proximal portion of penis; p.r., pleonal rim; s.c., stridulating crest; s.p., sterno-pleonal cavity; 1-8, thoracic sternites 1-8; 1/2-7/8, thoracic sternal sutures 1/2-7/8. Scale bars: 10 mm.