Rhodope veranii

Rhodope veranii Kölliker, 1847

Rhodope veranii 6mm @ Rovinj, Croatia 1985 by Maria Mizzarro-Wimmer

Taxonomic note: Initially, due to its worm-like appearance, Rhodope veranii was misclassified as a turbellarian. Over time, its classification has been debated, but it is now recognized as a gastropod within the subclass Heterobranchia. The type species of the genus Rhodope (Rhodope veranii) was initially described with a transverse bar of dark red colour between the first and the second third of its body (Kölliker 1847). Subsequent studies, however, have observed a variation in the colouration of this bar across specimens, ranging from brick red to orange hues (Salvini-Plawen, 1991; Haszprunar and Heß, 2005; Wilson et al., 2017). What seems to be the diagnostic character of this species is the length of the transverse bar, occupying one-third of the body. The shape of the coloured patch was described by Kölliker as a conspicuous “T”, but a certain variability in uniformity across the dorsum has been noted, with some specimens exhibiting a more uniformly transverse shape (Wilson et al. 2017; Fernández-Simón et al.,2025).

Description
It has a worm-like, elongated, and flattened body, typically measuring up to 6 mm in length when fully extended. The head region is slightly distinct and narrower compared to the rest of the body. Notably, this species lacks several features common to other gastropods, such as a foot, jaws, radula, gills, and heart. The eyes are deeply embedded in the head region, and the body contains elongated, slightly curved spicules ranging from 70 to 170 μm in length. The coloration is generally light yellowish to white, adorned with a transverse bar of dark red colour between the first and the second third of its body, which is characteristic for this species.

Biology
Rhodope veranii is known to feed on sponge larvae and exhibits slow movement compared to turbellarians. It is typically found on algae, particularly Ulva (Riedl, 1983), although specimens found by Fernández-Simón et al.(2025) were associated with Codium and occasionally crawling on sand grains. It lays between 6-30 relatively large eggs which have direct development. At present, species are distinguished by their colour pattern.

Similar Species
Whereas the principal colour (white body with orange pattern) is shared with several other Rhodope species, Rh.veranii differs from all other in the distinct orange pattern. Haszprunar & Heß (2005) presented an overview of all named species of Rhodope (and some unnamed), with a schematic drawing of the orange pattern in order to facilitate future identifications.

Etymology

• Rhodope. From ancient Greek “Ῥοδόπη” ‎(Rhodópē), one of the 3,000 Oceanids, water-nymphs daughters of the Titans Oceanus and his sister-wife Tethys.
• Veranii. In honor of Chevalier Jean Baptiste Vérany, (1800-1865), French pharmacist, who in 1846 became one of the two founders of a Natural History Museum in Nice, France.

Distribution
To date it is only found in the Mediterranean Sea: Sicily, Italy (type locality, Kölliker 1847); Croatia (Salvini-Plawen 1991; Haszprunar and Heß 2005; Wilson et al. 2017), in NE Spain (Fernández-Simón et al., 2025) and the last report in southern Spain (Granada) on september 2025.

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Bibliography

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Bibliography based on the works by Steve Long, 2006. Bibliography of Opisthobranchia 1554-2000 and Gary McDonald, 2009. Bibliographia Nudibranchia, with later updates from other resources.

Further reading

• Biodiversity Heritage Library
• Flickr pictures
• Interim Register of Marine and Nonmarine Genera
• NCBI GenBank
• OBIS - Search by Taxon
• OBIS - Search by Taxon
• World Register of Marine Species

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