Argathona Stebbing, 1905

Bruce, Niel L., Wong, Helen P. - S. & Merrin, Kelly L., 2022, The genus Argathona Stebbing, 1905 (Crustacea: Isopoda: Corallanidae) in Singapore marine waters, with description of two new species, Raffles Bulletin of Zoology 70, pp. 492-510 : 493

Argathona Stebbing, 1905

Restricted synonymy. — Delaney, 1989: 16.

Type species: Argathona normani Stebbing, 1905 ; by original designation.

Remarks. Corallanid genera, keyed by Delaney (1989), are identified primarily by characters of the buccal appendages. Argathona has a 4-articled or 5-articled maxilliped palp with broad articles that have convex margins, a single lobed quadrate or sub-quadrate maxilla and the maxillula has only one prominent falcate robust seta at the apex with some smaller falcate robust setae at the base of the major seta; typically, the mandible molar is relatively larger and wider than in the other genera (see Delaney, 1989) and may be tridentate. Both Corallana Dana, 1853 and Excorallana Stebbing, 1904 have a slender maxilliped with sub-quadrate palp articles. In Alcirona Hansen, 1890 the maxillula has two terminal falcate robust setae, the maxilla is distally distinctly rounded and the dactylus of pereopods 1–3 has a series of prominent spines giving it a comb-like appearance. In Lanocira Hansen, 1890 , the maxillula is in the form of a large hook, while the maxilla is 2-articled and elongate ( Delaney, 1989; Bruce & Sidabalok, 2011) rather than a single quadrate or sub-quadrate article. Species of Argathona are frequently moderately to heavily setose over the dorsal body surfaces, often with stiff ‘hyaline’ setae, particularly on the pleotelson, a character shared with Alcirona and to a lesser degree Lanocira .

It is clear when reviewing the history of the genus that assigning species to a genus has often been problematic, and the identification of species also similarly difficult. At present, at least two species held in combination with Argathona are of doubtful generic placement, and one additional species is a likely junior synonym. The widely reported Argathona macronema ( Bleeker, 1857) contains at least two species under that name and the status of this species will need to be resolved. The species are discussed under the annotated list of Argathona species.

Sexual dimorphism. It is usually reported that ornamentation such as rostrum development or pereonal and pleonal nodules is less developed in females. In Argathona lineata new species, and A. trichota new species, the ovigerous females are far more strongly setose than males and non-ovigerous females, with some non-ovigerous specimens having a largely or totally smooth pereon and presenting a rather different appearance. Other diagnostic characters, such as the shape of the pleotelson, uropods, frontal lamina shape, and also the pattern and number of robust setae on the appendages, allows for identification of both males and females in those species where there is some sexual variation as outlined above.

Distribution. Argathona occurs throughout the Indo-West Pacific, primarily within the tropics, and to date has not been reported from the Atlantic or East Pacific ( Delaney, 1989).