Cuthona yamasui
Hamatani, 1993

Order: NUDIBRANCHIA
Suborder: AEOLIDINA
Family: Tergipedidae

DISTRIBUTION

Tropical Indo-West Pacific.

PHOTO

UPPER: Wonga Beach, N. of Mossman, Queensland, Australia, January 1974. AM C94083. Photo: I. Loch.
LOWER LEFT: Broadhurst Reef, 12-15m, Townsville, Queensland, 18 Nov 1974, AM C96580. Photo: I. Loch.
LOWER RIGHT: SEM Photo of radula of Wonga Beach specimen. Photo: G. Avern.

This species seems to be quite variable in colour, in particular, the head, rhinophores and oral tentacles appear to range in colour from a translucent orange to a dark translucent blue-black. The second point of variation concerns the areas with opaque white pigementation. In some animals the translucent body wall has scattered patches of opaque white while in other specimens there is a solid colouring of white.

Hamatani's description was based on an animal from Okinawa in which the head was orange and the white pigmentation consisted of scattered, irregular shaped and sized white patches. He described it as having a ground colour which was translucent or colourless or light orange-yellow. The head, oral tentacles and rhinophores were orange red, and over the dorsal and lateral surfaces of the body behind the rhinophores there were many [irregular] opaque white patches. There was a prominent white [median] band on the head beween the rhinophores which extended anteriorly to the lower halves of the oral tentacles and laterally to the outer sides of the rhinophores. The tips of the oral tentacles and rhinophores were white. The upper portion of the cerata were tinged with reddish orange and there was a small white ring below the protruded tip of each ceras. The lower portion of the ceras was covered with clusters of opaque white dots. It was found feeding on the hydroid Aglaophenia cupressina.

The two animals illustrated here represent two extremes of the colour pattern. Other photos in messages from Erwin Koehler and Bernard Picton show other colour variations. The radular morphology illustrated here is identical to Hamatani's dscription.

Note: This species was previously named Cuthona sp. 1 on the Forum.

Reference:
• Hamatani, I (1993) A new cuthonid species (Nudibranchia, Aeolidacea), Cuthona yamasui n.sp., from Okinawa, Southwestern Japan. Venus, The Japanese Journal of Malacology, 52(2): 127-133. (Figs 1-3)

Authorship details
Rudman, W.B., 2002 (March 13) Cuthona yamasui Hamatani, 1993. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/cuthyama

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