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Goniodoridella savignyi

Species Profile

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Goniodoridella savignyi

Author: (Pruvot-Fol, 1933)

Order: Nudibranchia  Family: Goniodorididae

Maximum Size: 11 mm

Sightings: Sunshine Coast

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This species, Goniodoridella savignyi, the type species of the genus, has been long thought to have a wide distribution. Recent molecular sequencing, Paz-Sedano, Ekimova, et al, 2023, has revealed that it is actually a clade of cryptic species. To quote from the paper: “….because of the presence of a group of cryptic species, the known geographic range of G. savignyi may have been overestimated, while the species richness of the genus may be underestimated.” The paper identified three new species of Goniodoridella: G. geminae, G. unidonta and G. serrata cryptic with G. savignyi and the previously described G. borealis Martynov, Sanamyan & Korshunova, 2015. These five together with five species previously known as Okenia but through molecular sequencing (Paz-Sedano, Moles et al, 2023) now placed in Goniodoridella, increases the genus holding to ten species.

Using Table 2. and the differentiation remarks at the end of each description in the paper, Paz-Sedano, Ekimova, et al, 2023, plus the redescription of Goniobranchus savignyi in Paz-Sedano et al, 2021, there are a couple of external features upon which we can peg our photographic identifications. It should be borne in mind however, that both of these descriptions have relied upon material limited to a single site, the Mooloolah River on the Sunshine Coast of southern Queensland, Australia. Baba, 1960, in his redescription of G. savignyi has a mixture of both G. savignyi and G. borealis in his specimens.

Goniodoridella savignyi is a small species up to 11 mm in length but usually recorded half that size. 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 size on the anterior notal brim. The gill branches form a semicircle around the anus. There are normally six gill branches arranged in pairs, each pair sharing a common stalk. Posterior and lateral to the gill branches are two elongate and well-developed extrabranchial papillae that are considerably wider in thickness than the gill branches. These reach back to at least the mid-length of the tail. The mantle, body, foot, tail, rhinophores, gill branches, papillae and tubercles are covered in white pigment. The white pigment coverage is not solid but not translucent either and the word hyaline or glass-like is a term used in some descriptions. The rhinophores, anterior and posterior papillae, gill branches, tail tip and tubercles on the midline crest and notal edge are all usually tipped in yellow, but exceptions do occur.  

Distribution is considered to be widespread in the Indo-Pacific region.

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

Differentiation
Although most of the external features of Goniodoridella savignyi are shared with its congeners it may be delineated from G. geminae by the possession of extrabranchial papillae that are considerably wider than the gill branches that in G. geminae are all of relatively equal thickness. 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.

Originally described from a specimen collected in the Gulf of Suez, northern Red Sea, and named Goniodoris (Goniodoridella) savignyi. The portion of the name in parenthesis was explained as a new sub-genus but that form of a name is not accepted. The subgenus was eventually recognized to be sufficiently distinct to be a separate genus in its own right.

David A. Mullins – December 2023

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

– Baba, K. (1960). The genera Okenia, Goniodoridella and Goniodoris from Japan (Nudibranchia-Goniodorididae). Publications of the Seto Marine Biological Laboratory, 8(1), 79–83.

– Marshall, J.G., Willan, R.C. (1999). Nudibranchs of Heron Island, Great Barrier Reef: A survey of the Opisthobranchia (sea slugs) of Heron and Wistari Reefs; Backhuys: Leiden, The Netherlands, 1999.

– 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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