Author: Gosliner, Gonzalez-Duart & Cervera, 2007

Order: Nudibranchia  Family: Babakinidae

Maximum Size: 18 mm

Sightings: Sunshine Coast

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Babakina indopacifica Gosliner, Gonzalez-Duart & Cervera, 2007

The aeolid nudibranchs of the Babakina genus are easily recognized by what has been called their “bushy” rhinophores. Closer examination however shows the rhinophores to be not so much bushy but rather to be quite large and bulbous with numerous lamellae. The other significant feature is that the rhinophores arise from a common base for half their length. The genus is occupied by four species three of which have a temperate distribution and a fourth, Babakina indopacifica, that by its name, describes its distribution – tropical Indo-Pacific. Babakina is the only genus of the Babakinidae family.

Babakina indopacifica has a body that is long and narrow with a short tapered tail, visible past the posterior-most cerata. Body colour varies in intensity from deep purple to light translucent pinkish-purple. The head carries a broad opaque white patch covering most of the region anterior to the rhinophores and often with a similar patch directly behind, and also over the pericardial region. The oral tentacles, although short, are longer than the rhinophores, smooth and tapered to a point. Their colouration can be variable but the basal half is usually pinkish-purple while the distal half may be opaque white or the white may be limited to a mid-length band only. The rhinophores are the most distinctive feature being large, bulbous, carrying approximately 30 lamellae each and arising via a common base for half their length. There is a short pointed apex. Reddish in colour, the lamella carry white pigment on their lateral and posterior edges but is lacking anteriorly. A small though distinctive eyespot is situated laterally on each side of the common stalk. The anterior foot corners are tentaculate, although this is not easily observed in situ as the animal tends to move with them folded back against the foot. These too are pinkish-purple in colour. The dorsum is densely covered in short, thick spindle-shaped cerata without the pericardial interruption usually observed in many aeolids, however the medial region posterior to the rhinophores and anterior to the pericardial region is bare. Gosliner et al report that the cerata are arranged in from 15 to 33 rows with 2 to 3 cerata in each row, the innermost being the largest. The cerata are opaque white with a translucent tip and a sub-apical pinkish band.

This genus was raised in 1972 and originally named Babaina and the family Babainidae in honour of Dr. Kikutaro Baba, a prolific opisthobranch taxonomist of Japanese waters. However it was soon realized that the name Babaina was previously occupied as a Chromodorididae genus, so Babakina and Babakinidae were substituted in 1973. (As for Babaina, it was later synonymized with Thorunna by Rudman in 1984.)

Prior to the Babakina indopacifica description in 2007, Rudman, on the Sea Slug Forum, had referred to this species as Babakina cf. festiva following communication from Gosliner about ongoing research into the group. Both these taxonomists originally felt that all the variations belonged to the one species, but kept an open mind until the phylogenetic work was done, that eventually separated them into four distinct species.

References:
– Roller, R. A. (1972). Three new species of eolid nudibranchs from the west coast of North America. Veliger, 14: 416–423.

– Roller, R. A. (1973). Babakina, new name for Babaina Roller, 1972, preoccupied. Veliger, 16: 117–118.

– Rudman, W. B. (1984). The Chromodorididae (Opisthobranchia: Mollusca) of the Indo-West Pacific: a review of the genera. Zoological Journal of the Linnean Society. 81(2): 115-273.

– Rudman, W. B., (1999) (September 10) Babakina cf. festiva (plus related messages) [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/babacffe

– Gosliner, T. M., Garcia-Duarte, M. M. & Cervera, J. L. (2007). Revision of the systematics of Babakina Roller, 1973 (Mollusca: Opisthobranchia) with the description of a new species and a phylogenetic analysis. Zoological Journal of the Linnean Society, 151: 671–689.

– Carmona, L., Gosliner, T. M., Pola, M. & Cervera, J. L. (2011). A molecular approach to the phylogenetic status of the aeolid genus Babakina Roller, 1973 (Nudibranchia). Journal of Molluscan Studies. 77(4): 417-422.

David A. Mullins – April 2020