Cuthona scintillans, Miller, 2004

Miller, M. C., 2004, An appraisal of the identity of the New Zealand species of the aeolid nudibranch family Tergipedidae (Gastropoda: Opisthobranchia), Journal of Natural History 38, pp. 1183-1192 : 1188

as Cuthona scintillans sp. nov. in Miller (1977)

Additional material examined

Locality, site and date as for C. alpha (see above): three specimens (lengths five and six mm).

Additions to previous description Rhinophores nearly one-third length of body, bases close together.

Colour

Opaque white pigment on tail from hindmost cerata to near tip, pale yellow surface pigment crystalline, ceratal diverticula fawn and olive green, pale green and dark olive, or pale and dark green, darker pigment, granular, at ends and midway, thus forming two light and three dark zones (figure 2). These observations add just a little to the original characterisation.

Remarks

When re-describing the boreo-arctic species Cuthona viridis (Forbes, 1840) , Brown (1980) found it almost indistinguishable from three other ‘green’ species, one of them being C. scintillans . It is unfortunate that Bleakney (1996), on no additional evidence, actually united these species, a change not made by Brown (1980) nor by Thompson and Brown (1984). A comparison of all four species had been made when C. scintillans was first described, and separation of them maintained. At that time C. scintillans was considered closest to C. viridis , these two species being distinguished by differences in surface pigmentation, shape of the foot angles, length of the oral tentacles, and number of lateral denticles on the radular tooth (Miller, 1977)—these differences are clear still. As well as examining the specimens of C. scintillans collected recently (see above), I have referred to my notes, drawings and photographs of specimens of C. viridis collected from Manx waters in the 1950s and off Plymouth, England and the Isle of Cumbrae, Scotland during 1990. There are other distinctive characters: in C. scintillans the body is transparent colourless or very pale yellowish, oral veil large and elliptical, rhinophores taper from wide bases, cerata are long and linear and the colour of the diverticula distinctly zoned (dark granules aggregated), radular tooth has a wide blade and long limbs; in C. viridis the body is translucent almost opaque pale yellow or greenish yellow, oral veil small and almost angular, rhinophores short and only slightly tapered, cerata short, clavate and carried on low ridges and colour of the diverticula even (dark granules dispersed), radular tooth has a narrow blade and short limbs. When photographs of the two species are compared, it is immediately apparent that they are different—the ‘gestalt’ shows this difference much more clearly than a comparison of separate characters. This applies to the other two species, C. signifera Baba, 1961 and C. albocrusta (MacFarland, 1966) , which in individual characters are more easily distinguished from C. scintillans than C. viridis . When describing C. scintillans I overlooked two other known ‘green’ species. One of these is Cuthona viridiana (Burn, 1962) which differs from C. scintillans in having a yellowish green body, green rhinophores distally, dark green digestive diverticula, yellow cnidosacs, and a low-arched radular tooth (Burn, 1963, 1964). The other is C. virens (MacFarland, 1966) which is said to be an ‘extremely rare’ Californian species. Photographs of this species ( McDonald and Nybakken, 1980; Behrens, 1991) suggest close similarity to C. viridis . A comparison of C. virens and C. viridis , using the descriptions, reveals differences only in colour ( C. virens has a light yellow frontal margin, minute white dots, small flecks of orange or yellow on the cerata, and orange yellow cnidosacs). As a consequence of my review of our present knowledge of the species considered I maintain C. scintillans as a distinct species.