Chelarctus virgosus, Yang & Chan, 2012

Yang, Chien-Hui & Chan, Tin-Yam, 2012, On The Taxonomy Of The Slipper Lobster Chelarctus Cultrifer (Ortmann, 1897) (Crustacea: Decapoda: Scyllaridae), With Description Of A New Species, Raffles Bulletin of Zoology 60 (2), pp. 449-460 : 454-458

publication ID	https://doi.org/ 10.5281/zenodo.5349972
persistent identifier	https://treatment.plazi.org/id/4150117D-7B06-B318-FF28-F95BFE3CB1C0
treatment provided by	Tatiana
scientific name	Chelarctus virgosus
status	sp. nov.

Treatment

Chelarctus virgosus View in CoL , new species

( Figs. 3 View Fig , 4B View Fig )

Arctus haanii – Ortmann, 1891: 42 (in part) [not Scyllarus Haani Berthold, 1845 View in CoL ]

Arctus cultrifer View in CoL – Ortmann, 1897: 272 (in part); Yokoya, 1933: 46 [not Ortmann, 1897]

Scyllarus cultrifer View in CoL – Balss, 1914: 80; Parisi, 1917: 9; Utinomi, 1956: 62, pl. 31, Fig. 5 View Fig ; Kubo, 1960: 98, pl. 49, Fig. 5 View Fig ; 1965: 627, Fig. 1023; Miyake, 1961: 9; 1972: 67, unnumbered fig.; 1975: 106, unnumbered fig.; 1982: 84, pl. 29, Fig. 1 View Fig ; Harada, 1962: 114, [?] Scyllarus cultrifer View in CoL – Wang et al., 1998: 446 [not Ortmann, 1897]

Chelarctus cultrifer View in CoL – Holthuis, 2002: 572 (in part), Fig. 26A, B; Humann & DeLoach, 2010: 153, unnumbered fig. [not Ortmann, 1897]

[?] Chelarctus cultrifer View in CoL – Zhang & Liu, 2006: 20, Figs. 1-4, 1-5, 1 View Fig View Fig View Fig View Fig View Fig -6, 4-6. [not Ortmann, 1897]

Material examined. — Holotype. Taiwan, Hepingdao fishing port, Keelung City, lobster gill net, 7 Jun.2000, ovigerous female 26.0 mm cl ( NTOU M01571 View Materials ).

Paratypes: Taiwan, Hepingdao fishing port, Keelung City, lobster gill net, Apr.1998, 2 females 26.9–27.2 mm cl ( NTOU M01293 View Materials ) ; 7 Jun.2000, 8 ovigerous females 26.3–31.6 mm cl, 1 female 26.4 mm cl ( NTOU M01294 View Materials ) . Dasi fishing port, Yilan County, commercial trawlers, 10 Apr.2000, 1 male 22.8 mm cl ( NTOU M01290 View Materials ) ; Jul.2004, 1 male 12.8 mm cl ( NTOU M01291 View Materials ) ; 29 Jun.2011, 1 female 10.9 mm cl ( NTOU M01292 View Materials ) . Su-ao fishing port, Yilan County, commercial trawler, 9 Dec.1992, 1 male 22.3 mm cl ( NTOU M01289 View Materials ) .

Non-type specimens: Madagascar, Majunga , 1 male 19.1 mm cl, 1 ovigerous female 21.0 mm cl (MNHN-IU-2011-5172) .

Description. — Rostrum rather broad, with large sharp rostral tooth. Pregastric tooth absent. Gastric tooth strong, highly elevated and followed posteriorly by 5 or 6 transverse rows of squamae ( Fig. 3A, C View Fig ). Anterior submedian carina composed of 2 or 3 large squamae. Cardiac tooth only slightly elevated but distinctly bifurcate, flanked with patch of 6 or 7 clustered squamae; cardiac tooth continuous posteriorly with 6 or 7 transverse rows of 2 or 3 flattened squamae; 4 or 5 intermediate tubercles present. Cervical groove weak but not very narrow; 2 large sharp teeth present on anterior branchial carina. Posterior branchial carina anteriorly terminating in acute tooth, followed posteriorly by double rows of 7 or 8 irregular squamiform tubercles. Postorbital carina distinct. Anterolateral, mediolateral and posterolateral teeth squmiform and flat except for anteriormost tooth. Posterior marginal groove narrow but deep. Posterior margin of carapace incised medially ( Fig. 3A View Fig ).

Abdomen with arborescent sculpture, without elevated median dorsal carina and only with median areas bluntly arched. Articulating surfaces of tergites II–V each with 1 or 2 often interrupted but rather simple transverse grooves. Arborescent sculpture on non-articulating surfaces of tergites I–V consisting of rather simple grooves, distinctly forked distally, particularly prominent on tergite I. Posterior margins of tergites I–III distinctly incised medially, that of tergite IV weakly (mostly) or not incised medially ( Fig. 3B View Fig ). Pleura II–IV acutely pointed posteroventrally. Calcified part of telson with 2 pairs of teeth along posterior margin.

Anterior margin of antennal segment VI with 6 or 7 teeth, including inner short tooth.Antennal segment IV with anterior margin bearing 2 large teeth, often accompanied with some small serrations; outer margin armed with 2 large teeth only; dorsal surface with 1 oblique carina. Anterior margin of fused antennal segments II and III with 2 teeth, outer tooth much larger and even larger than rostral tooth ( Fig. 3A View Fig ).

Pereiopod I robust and shorter than other pereiopods ( Fig. 3D View Fig ). Pereiopod II slender ( Fig. 3E View Fig ). Propodi of pereiopod III and IV with 2 parallel long setose grooves on outer surface, with large anteroventral tooth which act as subchela with dactylus. Propodus of pereiopod III very broad, subchela very prominent ( Fig. 3F View Fig ). Propodus of pereiopod IV rather slender but with subchela still quite distinct ( Fig. 3G View Fig ). Carpi of pereiopods III–V each with 1 setose groove on outer surface ( Fig. 3F–H View Fig ). Meri of pereiopods II–V each with 2 setose grooves ( Fig. 3E–H View Fig ).

Anterior part of thoracic sternum greatly produced anteriorly, anterior margin somewhat truncate, medial part deeply sunken and continuous posteriorly as median fissure extending to posterior end of thoracic sternite IV (pereiopod I); median sunken parts broad while non-sunken lateral parts rather narrow, with latter less than half as wide as former. Median parts of thoracic sternites V–VII rather deeply excavate and often with distinct median fissure (sometimes interrupted) on thoracic sternites V and VI. Lateral parts of thoracic sternum not ridged, without distinct tubercle ( Fig. 3I View Fig ). Thoracic sternite VIII without median tubercle, posterolateral angle with small tooth in males but unarmed in females.

Egg small and numerous, about 0.3 mm in diameter.

Colouration. — Carapace yellowish brown with some dark brown patches. Large teeth on carapace and antenna distally orangish brown with white tips. Eyes black brown. Pereiopods dull yellowish and with thick dark blue bands. Antennules also dull yellowish and with short brown bands, flagella somewhat orange. Abdomen generally brownish, articulating surface of abdominal tergite I somewhat with 3 large orange-brown spots. Abdominal somite VI to tail fan somewhat dull yellowish ( Fig. 4B View Fig ).

Distribution. — Known with certainty from Japan, Taiwan and Madagascar, probably also in East and South China Seas, Somalia and the Seychelles (see “Remarks”); 5– 146 m.

Etymology. — The Latin “ virgosus ” (meaning full of twigs) refers to the arborescent sculpture on the abdomen in this species has a clear branching pattern as compared to its congeners.

Remarks. — Although there are numerous reports over the last century of this species from Japan, mostly under the name “ Scyllarus cultrifer ” (see synonymy), the present study discovered that it is actually unnamed, following the valid lectotype selection of Arctus cultrifer Ortmann, 1897 by Holthuis (2002) using a Philippines female. Even though no specimen from Japan had been examined, the Taiwanese specimens almost certainly belong to the same species as the Japanese material as they are almost identical in both morphology and colouration based on the abundant Japanese literature.

The Taiwan-Japan form, now with the name C. virgosus , new species, can be readily separated from the true C. cultrifer by many obvious characters. The cardiac tooth is distinctly bifurcate in C. virgosus , new species ( Fig. 3A View Fig ), but either truncate or at most represented by two weak blunt tubercles (in 11 of the 36 specimens examined) in C. cultrifer ( Fig. 1A View Fig ). The outer tooth on the anterior margin of the fused antennal segments II and III is very large, being much larger than the inner tooth and even larger than the rostral tooth in C. virgosus , new species ( Fig. 3A View Fig ). In C. cultrifer , the outer tooth on the anterior margin of fused antennal segments II and III is smaller than the rostral tooth ( Fig. 1A View Fig ). The number of large teeth on anterior margin of the antenna segment IV is always two in C. virgosus , new species ( Fig. 3A View Fig ), but only one in C. cultrifer ( Figs. 1A View Fig , 2A View Fig ). The anteroventral tooth at the propodus of pereiopod IV is large in C. virgosus , new species ( Fig. 3G View Fig ), but small to minute in C. cultrifer ( Fig. 2C, E View Fig ). Thus, pereiopod IV is distinctly subchelate in C. virgosus , new species, but essentially not subchelate in C. cultrifer . The arborescent sculpture is simpler but with the branches distinctly forked in C. virgosus , new species, thus giving a general impression of irregular branching lines on the abdomen ( Fig. 3B View Fig ). The abdominal sculpture is more complex in C. cultrifer , with the longitudinal grooves rather parallel with each other and not distinctly branched. Therefore, the arborescent sculpture of C. cultrifer appeared to be composed of rows of large rectangular squamae ( Fig. 1B, C View Fig ). Such differences in sculpture pattern are more pronounced at the non-articulating surface of the abdominal tergite I. The thoracic sternum is generally more deeply excavated in C. virgosus , new species ( Fig. 3I View Fig ), than in C. cultrifer ( Fig. 1D, E View Fig ), and with the lateral regions of the anterior part of the thoracic sternum distinctly narrower in the new species (i.e., lateral part less than half as wide as median sunken part versus lateral part distinctly more than half as wide as median sunken part). Moreover, the median fissure extends from the median sunken area to at least the posterior end of thoracic sternite IV and sometimes to thoracic sternite V (in 8 of the 18 specimens examined) or even to the thoracic sternite VI (in 5 of the 18 specimens examined) in C. virgosus , new species ( Fig. 3I View Fig ). However, C. cultrifer often lacks a median fissure behind the median sunken area at the anterior part of the thoracic sternum ( Fig. 1D, E View Fig ). In the few specimens (i.e., 2 of the 37 specimens examined) with a distinct median fissure, it is restricted to thoracic sternite IV.

Of the four characters used by Holthuis (1960) to separate the material from Japan and the Philippines, the characters on the abdominal tergite I and the anterior part of the thoracic sternum is essentially the same as those discussed above. The other two characters on the postrostral carina and abdominal somite IV are rather variable. For example, in 2 of the 37 C. cultrifer specimens examined there is a minute median incision on the posterior margin of the abdominal tergite IV.

Comparison of the barcoding gene sequence COI shows 15.5–16.5% nucleotide divergence between C. virgosus , new species, and C. cultrifer (Table 2, Fig. 5 View Fig ). This difference is higher than the minimal divergence amongst the other species in the genus Chelarctus (i.e., 14.6%, between C. cultrifer and C. crosnieri , Table 2), and well accepted to represent specific differences in Scyllarinae ( Yang et al., 2008; Yang &Chan, 2010; Yang et al., 2011). Moreover, there are distinct difference in the colour pattern between C. virgosus , new species, and C. cultrifer , with the colouration of the latter being much duller ( Fig. 4 View Fig ). The generally appearance of C. virgosus , new species, is orangish brown with blue bands on the pereiopods and with blurred large spots on the articulate surface of the abdominal tergite I. However, the overall impression of C. cultrifer is dull brown with dull bands on the pereiopods and only longitudinal lines on the articulating surface of abdominal tergite I.

Amongst the southern material identified as “ C. cultrifer ” in the Muséum national d’Histoire naturelle, Paris, one lot and two specimens from Madagascar are morphologically identical with the Taiwanese material. Although these two Madagascan specimens were collected in 1912 and failed to generate genetic sequence for comparisons, there is little doubt that they are C. virgosus , new species, instead of the true C. cultrifer . Therefore, C. virgosus , new species, is not strictly a northern species, although it does range further north than C. cultrifer . On the other hand, C. virgosus , new species, is usually collected from less than 50 m deep in Taiwan and Japan (Chan & Yu, 1993; Minemizu et al., 2000) while the true C. cultrifer examined in this study were mostly from deeper than 150 m. This recalls a similar situation shown in Galearctus kitanoviriosus ( Harada, 1962) , which was recently found to contain two species that have different depth ranges ( Yang et al., 2011). The collection depth of the two Madagascan specimens identified here as C. virgosus , new species, is not known. However, another MNHN lot from Îles Glorieuses, which is adjacent to Madagascar, and collected from 250 m deep represents true C. cultrifer . Thus, the exact distribution of C. virgosus , new species, will need to be verified, particularly by re-examining those “ C. cultrifer ” specimens reported in Holthuis (2002) and from shallower depths (e.g., those from Somalia and Seychelles), as well as those Chinese records ( Wang et al., 1998, Zhang & Liu, 2006). The source of the Wang et al. (1998) South China Sea record is unknown as there is no specimen cited in the report. The East China Sea specimen reported in Zhang & Liu (2006) has the anteroventral tooth at the propodus of pereiopod IV smaller than usual but this maybe due to the specimen being a very small juvenile (see Zhang & Liu, 2006: Figs. 4 View Fig –6). The true identity of these two Chinese records probably will never be determined unless adult specimens can be collected from the East China Sea. It may also be useful to point out that the photograph in Humann & DeLoach (2010) under the name “ Chelarctus cultrifer ” without locality specified is the same photograph (but with image in reverse) used in Debelius (1999) for “ Scyllarus cultrifer ” taken in Japan. Thus, the photographs of both Humann & DeLoach (2010) and Debelius (1999) show the same Japanese specimen of C. virgosus , new species.