Bioacoustics of Leptograpsodes octodentatus

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 ).