| Acteonoidea | |
|---|---|
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| LiveHydatina physis | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Gastropoda |
| Subterclass: | Acteonimorpha |
| Superfamily: | Acteonoidea d'Orbigny, 1843 |
| Diversity[1] | |
| about 150 species | |
Acteonoidea is asuperfamily ofsea snails, or bubble snails,marinegastropodmollusks.
In thetaxonomy of Bouchet & Rocroi (2005), the superfamily Acteonoidea has been included into the informal group "Lower Heterobranchia" (Heterostrophasensu Ponder & Warén, 1988), also known as the Allogastropoda.[2]
Only one of analyses by Jörger et al. (2010)[3] indicates the Acteonoidea sister toNudipleura.[3] This clade that had resulted repeatedly in molecular studies with still limited "lower heterobranch" taxon sampling, either in a derived position or as a basal offshoot within Euthyneura.[3] A recent molecular phylogeny on Acteonoidea suggest a common origin with lower heterobranchRissoelloidea and a sister group relationship to Nudipleura.[1][3] While the basal position of Acteonoidea was commonly accepted, some authors doubted the basal position of Nudipleura, which was originally considered as a highly derived taxon, and suspect rate heterogeneity and deviant base composition as causing this unnatural grouping.[3] Based on potentialsynapomorphies in thereproductive system (presence of a ciliary stripe within the ampulla, androdiaulic or triaulic pallial gonoduct), Ghiselin already suggested a relationship between Acteonoidea and Nudipleura.[3] However, Acteonoidea form a well-supported "lower heterobranch" clade with Rissoelloidea, confirming results by Aktipis et al. and Dinapoli and Klussmann-Kolb.[3] The latter authors also recovered Nudipleura as the first offshoot of Euthyneura, which is confirmed by Jörger et al. (2010) study. Salvini-Plawen and Steiner grouped Umbraculoidea with Nudipleura, but none of the recent molecular or morphological studies support such a relationship.[3]
The following fivefamilies have been recognized inthe taxonomy of Bouchet & Rocroi (2005):[2]
All acteonoids have ashell that resembles that of manyprosobranchs. Some of the members are able to withdraw completely into the shell and to close the shell with anoperculum, e.g.Acteon tornatilis.[4]
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No defensive strategies are known from these animals although histological investigations show a highly glandular area in themantle cavity and the mantle rim. The mantle rim glands, for example, are very conspicuous. These comprise largeepithelial cells that are filled with a non-stainingvacuole. The glandular area is highly folded. The cells appear to lie subepithelially due to their size. They alternate with smallciliated cells. The hypobranchial gland in the roof of the mantle cavity is small and consists of violet-staining epithelial cells indicating acidmucopolysaccharides.[4]
Acteonidae and Aplustridae are carnivorous and mainly feed onpolychaetes.[4]
This article incorporatesCC-BY-2.0 text from references.[3][4]