Thenus orientalis ( Lund, 1793 )

Burton, T. E. & Davie, P. J. F., 2007, A revision of the shovel-nosed lobsters of the genus Thenus (Crustacea: Decapoda: Scyllaridae), with descriptions of three new species, Zootaxa 1429 (1), pp. 1-38 : 15-19

Thenus orientalis ( Lund, 1793)

( Figs 10 , 11 , 12 , 18A, C, J )

The following synonymy follows Holthuis (1946: 106–108) for all the earlier literature. No attempt has been made to separate these older records into the five species identified in the present paper, but the literature is listed here for convenience and in an attempt to be inclusive. We have attempted to reallocate post-1946 literature to one of the appropriate five species, but where we are unsure of the new identity, we have continued to leave the citation within the T. orientalis synonymy. Thus the synonymy, as presented, should not be trusted to distill accurate biogeographic distributional data.

Ursa-Cancer p.p. Rumphius, 1705: 3, pl. 2 fig. D. — Rumphius, 1711: 1, pl. 2 fig. D. — Rumphius, 1739: pl. 2 fig. D. —

Rumphius, 1740: 3, pl. 2 fig. D. — Rumphius, 1741: 3, pl. 2 fig. D. Squilla lata foemina Petiver, 1713: 1 , pl. 5 fig. 1 Cancer (Astacus) arctus Herbst, 1793: 80 , pl. 30 fig. 1. Scyllarus orientalis Lund,1793: 22 . — Fabricius, 1798: 399. — Latreille, 1802: 181, pl. 52 fig. 2. — Latreille, 1818: 5,

pl. 314. — Lamarck, 1818: 213. — Desmarest, 1823: 291, atlas vol. 4, Crust., pl. 31 fig. 1. — Desmarest, 1825: 182,

pl. 31 fig. 1. — Henschel, 1833: 203. — De Haan, 1841: 150, pls. J, L. — Herklots, 1861: 142. — Tennent, 1861: 486.

Thenus orientalis H. Milne Edwards, 1837a: 120 , pl. 45 fig. 2; 1837b: 286; 1838b: 168. — Anonymous, 1845: 70. — White, 1847: 67. — Gibbes, 1850a: 193. — Gibbes, 1850b: 29. — Lucas, 1851: 167. — Heller, 1865: 93. — Hoffmann, 1874: 42.— Neumann, 1878: 34. — Hilgendorf, 1879: 849. — Miers, 1880 a: 378. — Haswell, 1882: 170. — Walker, 1887: 112. — Bate, 1888: 66. — Gavino, 1888: 6. — De Man, 1888a: 485; 1888b: 261. — Ortmann, 1891: 46. — Stearns, 1891: viii. — Henderson, 1893: 433. — Stebbing, 1893: 193. — Casto de Elera, 1895: 565. — Thurston, 1895: 120. — De Man, 1897: 501. — Nobili, 1900: 491. — Lanchester, 1901: 557. — Thompson, 1901: 18. — Alcock, 1902: 68. — De Man, 1902a: 101. — Nobili, 1903 b: 12; 1906a: 88; 1906b: 55. — Borradaile, 1910: 261. — Chilton, 1911: 549. — Babič, 1913: 273. — Balss, 1914 a: 80. — Stebbing, 1915: 65. — Balss, 1921 b: 18. — Maki & Tsuchiya, 1923: 88, pl. 8 fig. 2. — Barnard, 1926: 121. — Santucci, 1926: 19, figs 1–4. — Boone, 1935: 58, pls 14, 15. — Gordon, 1935: 629. — von Bonde & Marchand, 1935: 7. — Estampador, 1937: 496. — Serène, 1937: 71. — Suvatti, 1937: 52. — Ramadan, 1938: 127. — Barnard, 1950: 565, fig. 104e. — Chhapgar & Deshmukh, 1964: 203–207, fig. — Holthuis, 1968: 287– 288. — Lal Mohon, 1976: 109. — Nurul Huda et al., 1989: 83–91. — Holthuis, 1991: 227–228 (in part). — Davie & Burton, 2000: 84–86. — ICZN, 2002: 53.

? Scyllarus Orientalis Siebold, 1824: 15 .

non Scyllarus orientalis Bosc, 1801: 20 , pl. 10 fig. 2. — Risso, 1816: 60. — Desmarest, 1830: 53, pl. 10 fig. 2. — De Man, 1916: 73. — Ramadan, 1938: 126, fig. 2.

non Thenus orientalis Stebbing, 1920: 267 .

? Thenus orientalis Stephensen, 1923: 76 , fig. 26.

Material examined. Neotype, ZRC-1999.0481, female (69.2 x 95.8), from fishermen on beach, Padang, southern central coast Sumatera, Indonesia, 23.05.1997, T.H. T. Tan.

Non-type material. ZRC-1999.1287, male (75.1 x 89.6), Kaoshiung County, Taiwan , Tungkang Fish Port, P.K.L. Ng, 30.12.1997; ZRC-1999.1288, 2 ovig. females (68.0 x 80.5, 69.7 x 84.2), male (67.3 x 80.0), Tungkang Fish Port , Kaoshiung County, Taiwan , P.K.L. Ng, 30.05.1997; QM-W22101, female (94.0 x 113.4), southern Mindanao , Philippines , 3.04.1994; QM-W22100, male (72.7 x 85.5), southern Mindanao , Philippines , 3.04.1994; QM-W22105, female (57.5 x 71.6), Vietnam , 14.04.1994, Dr. Nguyen Tac-An; QM- W22123, female (64.1 x 78.3), Okinawa Is., Southern Japan , 16.03.1994, Dr. N. Shikatani; RMNH-D42342 , female (53.9 x 68.0), male (56.1 x 69.7), Taiwan ; QM-W22192, female (61.8 x 75.0), Singapore markets, June, 1994, P. Davie; QM-W22130, female (63.0 x 76.5), Singapore markets, June, 1994, P. Davie; QM- W22131, female (78.0 x 93.5), Singapore markets, June, 1994, P. Davie; ZRC-1995.978, 4 males (54.9 x 65.5; 58.7 x 71.0; 56.4 x 69.6; 56.0 x 67.1), 4 females (76.6 x 93.0; 53.7 x 64.2; 61.6 x 74.6; 57.0 x 70.4), off Singapore (purchased from Ponggol Fish Market ) , P.K.L. Ng, 30.11.1995; ZRC-1992.10411–10414, female (39.6 x 50.7), male (34.2 x 42.5), off Pattaya , Thailand , P.K.L. Ng & L.B. Holthuis, 25.12.1991; QM-W22278, dry female (78.5 x 101.8), between Dubai and Sharjah, about 1 km offshore, T. Burton , 1991; QM-W22279, dry female (66.8 x 85.3), between Dubai and Sharjah, about 1 km offshore, T. Burton, 1991; QM-W22280, dry female (68.2 x 85.0), between Dubai and Sharjah, about 1 km offshore, T. Burton, 1991; QM-W22281, dry female (69.3 x 87.7), between Dubai and Sharjah, about 1 km offshore, T. Burton, 1991; RMNH-D12290 , male (36.7 x 46.6), Persian Gulf; RMNH-D23004 , male (39.1 x 49.7), Ethiopia ; RMNH-D46593 , male (79.1 x 97.3), Seychelles .

Diagnosis. Obvious spots or large patches present on some or all segments of legs; outer face of propodus of P2 having upper-most longitudinal groove bearing obvious setae over at least proximal half. Merus of third maxilliped with a small spine proximally on inner ventral margin; inner margin of ischium prominently dentate along entire length. No single morphometric ratio has been isolated that will exclusively identify this species, but only T. orientalis can have ratios that fall outside the following maximum and minimum values: telson length (TL) more than 0.31 times width ( TW); width of merus of pereiopod 2 less than 0.079 times carapace length ( Table 6: Ratios 1, 3).

Remarks. The identity of Scyllarus orientalis Lund, 1793 , is somewhat confused because the original description does not provide sufficient information to distinguish it from its congenors identified here. In addition there are problems concerning the positive identification of a type specimen and the very poor condition of the specimen labelled ‘type’ in the Zoologisk Museum, Copenhagen ( ZMUC CRU 7648).

Holthuis (1991: 227) has summarised very concisely the difficulties regarding the types of Scyllarus orientalis Lund : ‘Lund’s material consisted of a specimen from Tranquebar, India, and one from China, so that both are syntypes; also a syntype is the specimen figured on pl. 2 fig. D in Rumphius’ (1705) Amboinsche Rariteitkamer, this specimen not necessarily comes from Amboina, as the figure was made in Holland after a specimen of unknown locality and subsequently added to Rumphius’ manuscript, it most likely originated from Indonesia. One of Lund’s two specimens is in UZM, it is preserved in alcohol, its condition is reasonable; the second specimen is lost. The third syntype specimen formed part of the collection of Henricus d’Acquet, burgomaster of Delft, The Netherlands, this collection was sold publicly in 1708, and the fate of the specimen of Thenus is unknown.’

Contrary to Holthuis’ statement that the specimen in the UZM, Copenhagen, is alcohol preserved and in ‘reasonable’ condition, our information from the then curator (N. Bruce, in litt.) is that it is a dry specimen, and in very poor condition. All legs and mouthparts are missing, and it is therefore impossible to attribute it reliably to any of the known Thenus species. In addition, there is no absolute certainty that this is a specimen examined by Lund. While a relatively modern label states that it is a type, there is no original labelling that could be used to provide any reasonable proof that it was examined by Lund. As it is impossible to prove or disprove its type status, and as it is useless in its present state for identifying the true T. orientalis , the most appropriate action is to erect a neotype. Recommendation 75E of the Code of Zoological Nomenclature says ‘ Neotypes should be designated to clarify the application of names when their continued existence as nomina dubia threatens the stability of other names; if, despite the existence of a holotype, or a lectotype or syntypes, it is not possible to resolve a complex zoological problem, a zoologist should refer the case to the Commission which may, by the use of the plenary power, set aside the existing type material and designate a neotype’. Such an application ( Davie & Burton 2000) was lodged with the Commission and registered as Case 3135. An official ruling was published in Opinion 1988 (International Commission of Zoological Nomenclature, 2000) that states:`Under the plenary power all previous fixations of type specimens for the nominal species Scyllarus orientalis Lund, 1793 are hereby set aside and the female specimen from Padang, Sumatra, Indonesia, no. ZRC- 1999.0481 in the Zoological Reference Collection, National university of Singapore, is designated as the neotype.’

The status of Scyllibacus orientalis Desjardins, 1831 , is unclear. As Holthuis (1991: 227) stated: “If Scyllibacus orientalis Desjardins is a new combination of Scyllarus orientalis Lund, 1793 , Scyllibacus falls as a junior objective synonym of Thenus Leach, 1815 ; if it is a new species, Scyllibacus is a nomen nudum.” Whatever the outcome it will not affect the taxonomic decisions we propose.

Thenus orientalis and T. australiensis , new species, are most easily distinguished from the other three species by the characteristic spotting on the pereiopods. However, the only method of identifying these two spe- cies from each other, in the absence of genetic data, is through the combination of morphological ratios presented in the key. This is further discussed under the remarks for T. australiensis .

The spotting on the pereiopods of T. orientalis is highly variable in both colour, shape and extent, according to locality ( Figs 10 , 11 ), although coloration is consistent within populations. There appears to be a trend towards decreased spotting in the most northern populations, with the specimens from Okinawa having only a few spots on the propodus. Philippine specimens have numerous small dark purple spots which become larger and transversely elongated on the propodi of pereiopods 2–4. Specimens from the United Arab Emirates have fewer, but larger, chocolate brown to maroon spots on all segments.

Distribution. Specimens were collected in the coastal regions of Okinawa in southern Japan, southern Vietnam, the Philippines, Taiwan, the Singapore region, and in the Indian Ocean from south-western Indonesia, and the United Arab Emirates.

Figures

FIGURE 10. Geographic variation in spotting on the pereiopods of Thenus orientalis. A, United Arab Emirates (large, sparse, individual spots); B, Philippines (numerous fine spots that tend to fuse especially on the anterior pereiopods).

FIGURE 11. Geographic variation in spotting on the pereiopods of Thenus orientalis. A, Taiwan (spots very small, more obvious on posterior legs); B, Vietnam (spotting conspicuous and of moderate size).

FIGURE 12. Map showing the distribution of Thenus orientalis (Lund, 1793).

FIGURE 18 A, C, Thenus orientalis (off Singapore); B, D, T. indicus (off Singapore); E. T. parindicus (off Darwin, Australia) F, G, H, T. unimaculatus (off Phuket, Thailand), note the variation in the extent of the purple blotch on the propodus of the pereiopods, always represented by at least a streak on P1 as on H; I, T. australiensis (off Darwin, Australia). J, live specimen presumed to be T. orientalis from Bali, Indonesia; Photographs reproduced with kind permission of Tin- Yam Chan (A, B, C, D) and Roger Steene (J).