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Goniodoridella unidonta

Species Profile

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Goniodoridella unidonta

Author: Paz-sedano, Ekimova, Smirnoff, Gosliner & Pola, 2023

Order: Nudibranchia  Family: Goniodorididae

Maximum Size: 5 mm

Sightings: Sunshine Coast

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Goniodoridella unidonta Paz-sedano, Ekimova, Smirnoff, Gosliner & Pola, 2023

Recent molecular sequencing, Paz-Sedano, Ekimova, et al, 2023, has revealed that Goniodoridella savignyi is actually a clade of cryptic species. The paper identified three new species of Goniodoridella: G. geminae, G. unidonta and G. serrata cryptic with G. savignyi (Pruvot-Fol, 1933) and the previously described G. borealis Martynov, Sanamyan & Korshunova, 2015. 

Goniodoridella unidonta is a small species up to 5 mm in length. The body is elongate with a long and tapered tail. The body, mantle, foot and appendages are supported by a dense network of spicules. The mantle is wide, covering the body and foot, apart from the aforementioned tail. The notal edge of the mantle is well-developed and carries a series of small pointed tubercles supported by spicules, but not papillae. Small tubercles forming a midline dorsal crest are present on the mantle, extending from the rhinophores, posteriorly to the gill. The non-retractile rhinophores are smooth and slender. Anterior to each rhinophore is a distinctive, conical papilla of medium length on the anterior notal brim. The gill branches form a semicircle around the anus. There are normally four gill branches, the central anterior-most two sharing a common stalk. Posterior and lateral to the gill branches are two extrabranchial papillae that are large, pointed, very broad at their bases creating a triangular-like appearance. The mantle, body, foot, tail, rhinophores, gill branches, papillae and tubercles are covered in white pigment. The white pigment coverage is not solid nor is it translucent appearing more hyaline or glass-like. The rhinophores, anterior and posterior papillae, gill branches and tubercles on the midline crest and notal edge are all usually tipped in yellow, but exceptions do occur.  

Distribution is currently known from the Philippines and Sunshine Coast of Australia.

As with all the Goniodoridella, diet is thought to be bryozoans.

Differentiation
Although most of the external features of this cryptic clade are shared with their congeners they may be delineated from each other thus: G. geminae has gill branches and extrabranchial papillae that are all sausage-shaped and of equal size. G. savignyi has extrabranchial papillae that are much larger than the gill branches. G. borealis has three yellow longitudinal rows on the mantle. G. unidonta has extrabranchial papillae that are very broad at their bases giving them a somewhat triangular shape. G. serrata is essentially translucent white all over, with a mantle edge that is highly serrated and extrabranchial papillae that are short and pointed. 

David A. Mullins – December 2023

References:
– Pruvot-Fol, A. (1933). Mission Robert Ph. Dollfus en Egypte. Opisthobranchiata. Mem. l’Inst. d’Egypte, tom. 21.

– Paz-Sedano, S., Diaz-Agras, G., Gosliner, T. M. & Pola, M. (2021). Revealing morphological characteristics of Goniodorididae genera (Mollusca: Nudibranchia). Organisms Diversity & Evolution, 22: 93–116.

– Paz-Sedano, S., Ekimova, I., Smirnoff, D., Gosliner, T. M. and Pola, M. (2023). Shedding light on a species complex within the genus Goniodoridella Pruvot-Fol, 1933 (Nudibranchia: Goniodorididae), with the description of three new species. Journal of Molluscan Studies (2023) 89: eyad020.

– Paz-Sedano, S., Moles, J., Smirnoff, D., Gosliner, T. M. and Pola, M. (2023). A combined phylogenetic strategy illuminates the evolution of Goniodorididae nudibranchs (Mollusca, Gastropoda, Heterobranchia). Molecular Phylogenetics and Evolution 107990

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