Ethusa hirsuta McArdle, 1900

Castro, Peter, 2005, Crabs of the subfamily Ethusinae Guinot, 1977 (Crustacea, Decapoda, Brachyura, Dorippidae) of the Indo-West Pacific region, Zoosystema 27 (3), pp. 499-600 : 524-527

Ethusa hirsuta McArdle, 1900

( Fig. 11 )

Ethusa hirsuta McArdle, 1900: 474 . — Alcock & McArdle 1902: pl. 59, fig. 2, 2a. — Alcock & MacGilchrist 1905: pl. 72, fig. 1, 1a. — MacGilchrist 1905: 257. — Ihle 1916b: 142, 151 (list), 153 (list), 156 (list). — Serène 1968: 40 (list). — Serène & Lohavanijaya 1973: 35 (key). — Chen 1993: 318 (key), 319 (list) (part).

Not Ethusa aff. hirsuta – Serène & Vadon 1981: 119, 121 (= E. latidactyla Parisi, 1914 ).

Not Ethusa hirsuta – Chen 1987: 685, pl. 1, fig. F (= E. machaera n. sp.).

Ethusa makasarica Chen, 1993: 318 (key), 327, fig. 9. Not Ethusa makasarica – Chen 2000: 427 (= E. abbreviata n. sp.).

TYPE MATERIAL. — Unknown (Zoological Survey of India, Calcutta?).

Type material of Ethusa makasarica Chen, 1993 : holotype:, damaged, CORINDON 2, stn 276 ( MNHN-B 19071 ) ; allotype: cl 7.7 mm, cw 7.2 mm, same station ( MNHN-B 22251 ) .

TYPE LOCALITY. — Gulf of Manaar between India and Sri Lanka, 07°02.5’- 07°36.0’N, 79°36.00’- 78°05.00’E, 914-1097 m.

MATERIAL EXAMINED. — Indonesia. Makassar Strait, CORINDON 2, stn 276, 01°54.6’S, 119°13.8’E, 456- 395 m, 8.XI.1980, 1 holotype of Ethusa makasarica Chen, 1993 ( MNHN-B 19071), 1 allotype ( MNHN- B 22251).

Solomon Islands. SALOMON 1, stn CP 1748, 09°20.4’S, 159°58.2’E, 509-522 m, 25.IX.2001, 2 ( MNHN-B 28539). — Stn CP 1749, 09°20.9’S, 159°56.2’E, 582-594 m, 25.IX.2001, 3 ( MNHN-B 28543). — Stn CP 1786, 09°21.3’S, 160°24.6’E, 387 m, 30.IX.2001, 3 ( MNHN-B 28544). — Stn CP 1794, 09°16.1’S, 160°07.7’E, 494-504 m, 30.IX.2001, 2 ( MNHN-B 28542). — Stn CP 1796, 09°19.2’S, 160°25.4’E, 469-481 m, 1.X.2001, 3, 1 juv., 2 ( MNHN-B 28541). — Stn CP 1798, 09°21.0’S, 160°29.2’E, 513-564 m, 1.X.2001, 3, 1 ( MNHN-B 28540). — Stn CP 1800, 09°21.4’S, 160°23.9’E, 357-359 m, 1.X.2001, 6 ( MNHN-B 28495). — Stn CP 1859, 09°32.6’S, 160°37.3’E, 283- 305 m, 7.X.2001, 1 ( MNHN-B 28523).

DISTRIBUTION. — Gulf of Manaar, between India and Sri Lanka ( McArdle 1900), off Sri Lanka ( MacGilchrist 1905), Indonesia (Makassar Strait [ Chen 1993, as Ethusa makasarica Chen, 1993 ], Timor [ Ihle 1916b]), and now from the Solomon Is ( Fig. 11 ). Depth: 112 ( Ihle 1916b)- 1097 m ( McArdle 1900) ( Fig. 34 ).

SIZE. — Maximum size: cl 15 mm, cw 15 mm ( McArdle 1900), cl 7.7 mm, cw 7.2 mm ( MNHN- B 22251).

REMARKS

Ethusa hirsuta was described from a female and a young male collected between Sri Lanka and India ( McArdle 1900: 474). The species was first illustrated by Alcock & McArdle (1902: pl. 59, fig. 2, 2a). Two males were then collected from off Sri Lanka and re-described by MacGilchrist (1905: 257); one of the males was illustrated by Alcock & MacGilchrist (1905: pl. 72, fig. 1, 1a). The type material or MacGilchrist’s specimens could not be examined and it is not known if they are still extant but the description of the species, MacGilchrist’s re-description, and the illustrations of specimens from both collections, however, provide ample information about the diagnostic characters.

Ihle (1916b) reported E. hirsuta from Indonesia. His two specimens, from Timor, were not found with the rest of the Siboga material at ZMA. Chen (1987: 685) assigned three specimens from Madagascar to E. hirsuta , but they were found to belong to E. machaera n. sp. (see below).

Chen (1993) described E. makasarica as a new species from Makassar Strait, Indonesia, and found it to be “similar to E. hirsuta McArdle ” ( Chen 1993: 328). At the same time Chen recognized that the Madagascar specimens did not belong to E. hirsuta . E. makasarica was characterized by slender and acute outer orbital teeth that nearly reach the frontal teeth ( Chen 1993: fig. 9a); very broad and nearly U-shaped orbital sinuses, with steeper sides along the inner margins of the outer orbital teeth; relatively straight, lateral borders, the branchial regions not markedly inflated along the sides. The carapace is covered with faint granules and setae along the anterior and anterolateral borders in smaller individuals. The carapace, however, is covered by abundant coarse setae in larger individuals. One important diagnostic character that was not mentioned was the extension of the anterior border of the endostome, which reaches the antennular fossae of the basal antennular articles.

E. makasarica was distinguished from E. hirsuta by six characters, which were given in a table ( Chen 1993: 329). Chen did not mention the examination of the type material of E. hirsuta so it is assumed that the characters given for this species in the table were taken from the description and from the figures. The first character was the “hirsute and not granular” carapace of E. hirsuta in contrast to being “pubescent and granular” in E. makasarica . The fine granules of E. m a k a s a r i c a a r e e v i d e n t i n t h e a l l o t y p e ( MNHN-B 22251) and they can also be seen in one of the drawings of E. hirsuta ( Alcock & MacGilchrist 1905: pl. 72, fig. 1). The presence or absence of granules is not mentioned in McArdle’s description or in MacGilchrist’s redescription. Relatively long hairs are evident in the figures of E. hirsuta by Alcock & McArdle (1902: pl. 59, fig. 2) and Alcock & MacGilchrist (1905: pl. 72, fig. 1).

A second character was the length of the outer orbital teeth, which were described in Chen’s table as “short, falling short of front and directed outwards” in E. hirsuta but “long, almost reaching to front and directed forwards [sic]”. The figures of E. hirsuta , the specimens of E. makasarica that were available for examination, and the figure of Chen (1993: fig. 9a) do not show any noticeable differences in the length of the teeth in the two species. The only difference is that the teeth are more slender in E. makasarica than those illustrated for E. hirsuta . The illustrations by both Alcock & McArdle (1902: pl. 59, fig. 2) and Alcock & MacGilchrist (1905: pl. 72, fig. 1) show V-shaped orbital sinuses and triangular outer orbital teeth. Although the teeth are triangular in the figures, they were described as “long, slender, acutely triangular” and “directed slightly outwards” ( McArdle 1900: 475). Furthermore, in explaining the placement of his new species in the key to the Indian species of Ethusa ( Alcock 1896) , E. hirsuta was separated from E. andamanica Alcock, 1894 (erroneously thought to be a junior subjective synonym of E. sexdentata ( Stimpson, 1858)) , by the outer orbital teeth being “long” and “acute” in contrast to the “broad flat triangular” teeth of E. andamanica .

The next four characters in Chen’s table, which involve the relative size of particular articles of pereopods, should not be considered as highly significant since in the case of E. hirsuta it is assumed they involved the measurement of articles from illustrations. McArdle (1900) and MacGilchrist (1905) only give the total length of chelipeds, P2, and P3, and there is no indication that Chen examined the type material. Furthermore, the figures are all close enough that it is highly probable that the differences obtained resulted largely because of the small number of specimens that were measured, the large margin of error, and the possibility that some pereopods may have been relatively shorter as a result of regeneration.

One highly significant similarity between E. hirsuta and E. makasarica is the morphology of the endostome. The anterior border of E. hirsuta was clearly shown to extend anteriorly above the level of the antennular fossae of the basal antennular articles ( Alcock & MacGilchrist 1905: pl. 72, fig. 1a) so that “there is no distinct epistome” ( McArdle 1900: 475). MacGilchrist (1905: 258) clearly described the endostome (“a noteworthy and what appears to be a specific character”) as extending “forward well between the bases of the antennules”.

Other characters are shared by E. hirsuta and E. makasarica . The frontal teeth of E. hirsuta were described as being equal in length, the median ones wider apart from each other than they are from the lateral ones. This is also shown in the two illustrations. MacGilchrist (1905: 258) added that of the frontal teeth, the median ones tended to be “stouter and longer” than the lateral ones, which is shown in the figure of Alcock & MacGilchrist (1905: pl. 72, fig. 1, 1a). The branchial region was illustrated as not being inflated, making the sides of the carapace look almost straight. This is confirmed in the description, where the borders are given as “almost straight” ( McArdle 1900: 475).

McArdle (1900: 475) described the carapace as “covered with hairs, which are particularly long and strong over the anterior and lateral borders”, and the illustration of a specimen part of the type material is shown with setae on the carapace as well as on the pereopods, including the chelipeds. This pubescence, however, is not shown in the specimens of E. makasarica that were examined. MacGilchrist (1905), however, does not mention the presence of hairs and the illustration of one of his specimens ( Alcock & MacGilchrist 1905: pl. 72, fig. 1) only shows long setae along the anterior and anterolateral borders of the carapace (but apparently the result of the cleaning of the carapace) and on the carpi and propodi of P4 and P5.

Only the comparison of the type material of E. makasarica with that of E. hirsuta will conclusively show if both species are one and the same. The type material of E. hirsuta , if still extant, was unfortunately not available. There is ample evidence, however, to consider Ethusa makasarica Chen, 1993 , as a junior subjective synonym of Ethusa hirsuta McArdle, 1900 .

There are some similarities between E. hirsuta and E. indica Alcock, 1894 . The outer orbital teeth, which in E. indica are long, acute, and are directed outwardly ( Chen 1985: fig. 8), can sometimes be nearly straight ( Chen 1985: fig. 9b) and thus very similar to those of E. hirsuta . The most reliable character to use to differentiate between both species is that the anterior border of the endostome ends well below the antennular fossae of the basal antennular articles in E. indica ( Sakai 1976: 62, 63 [key]; Chen 1985: fig. 9a) in sharp contrast to E. hirsuta , where it extends above the antennular fossae.

Figures

FIG. 11. — Geographical distribution of Ethusa hirsuta McArdle, 1900.

FIG. 34. — Bathymetric distribution of Indo-West Pacific ethusine crabs.