Metacirolana Kussakin, 1979

Sidabalok, Conni M. & Bruce, Niel L., 2018, Two new species and a new record of Metacirolana Kussakin, 1979 (Crustacea: Isopoda: Cirolanidae) from Indonesia, Zootaxa 4370 (5), pp. 519-534 : 520

Genus Metacirolana Kussakin, 1979

Restricted synonymy. Sее Schоttе and Kеnslеу (2005).— Brucе, 1996: 157.— Mооrе and Brusca, 2003: 1331. Paracirolana .— Niеrstrasz 1931, p. 147.

Tуpе spеciеs. Metacirolana japonica ( Hansеn, 1890) ; subsеquеntlу dеsignatеd bу Kussakin (1979).

Diagnosis. Diagnoses has been given by Bruce (1981a, 1986), Schotte and Kensley (2005) and Brusca et al. (1995).

Remarks. Metacirolana can be distinguished from other cirolanids by its relatively small size (mostly 1.5–3.5 mm, with the largest species ca. 13 mm – deep sea species, e.g. Metacirolana neocaledonica Bruce, 1996 ), often with dark chromatophores, rostral point present and projecting anteriorly, not ventrally folded, not in contact with frontal lamina, the anteriorly dilated frontal lamina has a posteriorly narrow ‘stem’ that does not meet the anterior margin of the clypeus, the clypeus is usually a flat ventrally or anteroventrally projecting triangular blade, maxilliped endite with 1–2 coupling hooks, maxilliped article 5 always quadrate, proportionally wide body (LW 2.0–3.0), pleonite 1 visible in dorsal view, pleonite 5 posterolateral angles not overlapped by lateral margins of pleonite 4, the absence of molariform robust setae on merus of pereopod 1 and the presence of distinctive flat penial lobes. Males are dimorphic with sexually mature ‘swimming males’ developing a more elongate pleon, larger eyes and longer antennula and antenna.

The genus name was proposed by Nierstrasz (1931), but as he did not provide a type species so that name was nomen nudum. Kussakin (1979) later designated the type species, which then established Kussakin, 1979 as the authority for the genus.

Moore & Brusca (2003), in their review of the genus Colopisthus Richardson, 1902 , removed three species from Metacirolana placing them into their new genus Aphantolana Moore & Brusca, 2003 . They recognized differences in dorsal ornamentation, short antenna, ‘connate spines’ on pereopods 1–3, and the pleotelson with sinuate lateral margins with a narrowly rounded posterior margin among the key diagnostic characters.

Metacirolana species that occur on coral reefs largely belong to two groups of similar looking species. One group contains those species similar to Metacirolana serrata (Bruce, 1980a) , characterized by smooth body surfaces, lack of dorsal carinae and abundant chromatophores. There are 15 species known to date (see the annotated species list below). The second group contains three species of a generally similar body appearance to Aphantolana , with a rugose body, sometimes with carina on the pleotelson and usually lacking chromatophores. These species are more dorsoventrally flattened than M. serrata and related species. The ‘rugose’ species are Metacirolana rugosa (Bruce, 1980a) , M. costata Nunomura, 1999 and M. mbudya Bruce, 1981b ; there are further undescribed Pacific coral-reef species.