Ceratodoris plana (Baba, 1960)

Description

A small goniodoridid, 7-8 mm in length. Very like a planarian in general aspect — body short and flattened, head forming a semicircular veil without paired oral tentacles. No marked pallial ridge. A single median papilla on the back; five claviform marginal papillae of varying length on each side; rhinophores typical; 8-11 simply pinnate gills arranged in a semicircle. The foot is broadly expanded. Body above plentifully sprinkled with minute spots of chocolate brown on the translucent whitish ground; rhinophores yellow on the upper half; gill plumes colourless; tips of all papillae densely whitish; sole colourless. The semicircular head-veil and the absence of a pallial ridge are the principal external diagnostic features.

Distribution

Type locality: Toba, Mie Pref., Japan. Additional records from Kada (Osaka Bay) and from near Mukaishima in the Seto Inland Sea, where the species occurs on Sargassum.

Etymology

The specific epithet plana is Latin "flat" (feminine), in reference to the short, flattened body form.

Remarks

Originally placed in Okenia and later transferred to Ceratodoris in a goniodoridid revision.

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References

• Okenia ( Okenia) plana BABA, n. sp. Hime-ibara-umiushi (n. n.), Baba K. (1960). THE GENERA OKENIA, GONIODORIDELLA AND GONIODORIS FROM JAPAN (NUDIBRANCHIA-GONIODORIDIDAE). Publications of the Seto Marine Biological Laboratory. 8(1): 79-83. https://doi.org/10.5134/174698
• Okenia plana Baba, 1960, Gosliner T. M. (2004). Phylogenetic Systematics of Okenia, Sakishmaia, Hopkinsiella and Hopkinsia (Nudibranchia: Goniodorididae) with descriptions of new species from the tropical Indo-Pacific". Proceedings of the California Academy of Sciences 55(5): 125-161.
• Valdés Á. & Fahey S.J. (2006) Dorid nudibranchs described by J.E. Gray in M.E. Gray, 1842-1857 (Mollusca Opisthobranchia). Records of the Western Australian Museum Supplement 69: 95-102.
• Okenia plana, Terrence Gosliner, Ángel Valdés and David Behrens. (2015). Nudibranch and Sea Slug Identification Indo-Pacific. New World Pubns Inc.
• PAZ-SEDANO S., COBB G., GOSLINER T.M. & POLA M. (2024). Filling gaps in the knowledge of Goniodorididae taxa (Mollusca, Gastropoda, Nudibranchia) with description of seven new species. Zootaxa. 5443(4): 523-547. https://doi.org/10.11646/zootaxa.5443.4.3