Acteonoidea
Encyclopedia
Acteonoidea is a superfamily
of sea snail
s, or bubble snails, marine
gastropod mollusks.
(2005), the superfamily Acteonoidea has been included into the informal group "Lower Heterobranchia
" (Heterostropha sensu Ponder & Warén, 1988), also known as the Allogastropoda.
Only one of analyses by Jörger et al. (2010) indicates the Acteonoidea sister to Nudipleura
. 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. A recent molecular phylogeny on Acteonoidea suggest a common origin with lower heterobranch Rissoelloidea and a sister group relationship to Nudipleura. 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. Based on potential synapomorphies in the reproductive system
(presence of a ciliary stripe within the ampulla, androdiaulic or triaulic pallial gonoduct), Ghiselin already suggested a relationship between Acteonoidea and Nudipleura. However, Acteonoidea form a well-supported "lower heterobranch" clade with Rissoelloidea, confirming results by Aktipis et al. and Dinapoli and Klussmann-Kolb. The latter authors also recovered Nudipleura as the first offshoot of Euthyneura, which is confirmed by our study. Salvini-Plawen and Steiner grouped Umbraculoidea with Nudipleura, but none of the recent molecular or morphological studies support such a relationship.
have been recognized in the taxonomy of Bouchet & Rocroi (2005)
:
that resembles that of many prosobranchs. Some of the members are able to withdraw completely into the shell and to close the shell with an operculum
, e.g. Acteon tornatilis.
cavity and the mantle rim. The mantle rim glands, for example, are very conspicuous. These comprise large epithelial cells that are filled with a non-staining vacuole
. The glandular area is highly folded. The cells appear to lie subepithelially due to their size. They alternate with small ciliated cell
s. The hypobranchial gland in the roof of the mantle cavity is small and consists of violet-staining epithelial cells indicating acid mucopolysaccharides.
Taxonomic rank
In biological classification, rank is the level in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, and class. Each rank subsumes under it a number of less general categories...
of sea snail
Snail
Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...
s, or bubble snails, marine
Marine (ocean)
Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...
gastropod mollusks.
Taxonomy
In the taxonomy of Bouchet & RocroiTaxonomy of the Gastropoda (Bouchet & Rocroi, 2005)
The taxonomy of the Gastropoda as it was revised by Philippe Bouchet and Jean-Pierre Rocroi is currently the most up-to-date overall system for classifying gastropod mollusks...
(2005), the superfamily Acteonoidea has been included into the informal group "Lower Heterobranchia
Lower Heterobranchia
Lower Heterobranchia, also known as the Allogastropoda, is a group of rather specialized, highly-evolved sea slugs and sea snails, within the clade Heterobranchia...
" (Heterostropha sensu Ponder & Warén, 1988), also known as the Allogastropoda.
Only one of analyses by Jörger et al. (2010) indicates the Acteonoidea sister to Nudipleura
Nudipleura
Nudipleura are a clade of sea snails and sea slugs, marine gastropod mollusks within the large clade Heterobranchia.- 2005 taxonomy :In the taxonomy of Bouchet & Rocroi , the clade Nudipleura is arranged as follows:*Clade Nudipleura...
. 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. A recent molecular phylogeny on Acteonoidea suggest a common origin with lower heterobranch Rissoelloidea and a sister group relationship to Nudipleura. 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. Based on potential synapomorphies in the reproductive system
Reproductive system of gastropods
The reproductive system of gastropods varies greatly from one group to another within this very large and diverse taxonomic class of animals...
(presence of a ciliary stripe within the ampulla, androdiaulic or triaulic pallial gonoduct), Ghiselin already suggested a relationship between Acteonoidea and Nudipleura. However, Acteonoidea form a well-supported "lower heterobranch" clade with Rissoelloidea, confirming results by Aktipis et al. and Dinapoli and Klussmann-Kolb. The latter authors also recovered Nudipleura as the first offshoot of Euthyneura, which is confirmed by our study. Salvini-Plawen and Steiner grouped Umbraculoidea with Nudipleura, but none of the recent molecular or morphological studies support such a relationship.
Families
The following five familiesFamily (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
have been recognized in the taxonomy of Bouchet & Rocroi (2005)
Taxonomy of the Gastropoda (Bouchet & Rocroi, 2005)
The taxonomy of the Gastropoda as it was revised by Philippe Bouchet and Jean-Pierre Rocroi is currently the most up-to-date overall system for classifying gastropod mollusks...
:
- family ActeonidaeActeonidaeActeonidae, common name the "barrel bubble snails", is a family of small sea snails, marine gastropod mollusks of the informal group Lower Heterobranchia.-Shell description:The shell is usually smaller than 25 mm...
d' Orbigny, 1843 - † family ActeonellidaeActeonellidaeActeonellidae is an extinct family of gastropods in the informal group Lower Heterobranchia .- Taxonomy :* Acteonellinae** Acteonella d'Orbigny, 1843 - type genus...
Gill, 1871 - family Aplustridae Gray, 1847 - former name Hydatinidae has been declared invalid
- family BullinidaeBullinidaeBullinidae is a taxonomic family of small sea snails or bubble snails, marine gastropod mollusks in the superfamily Acteonoidea.Synonyms for this family are Nonacteoninidae Bandel, 1994 and Sulcoactaeonidae Gründel, 1997....
Gray, 1850 - † family ZardinellidaeZardinellidaeThe Zardinellidae is an extinct taxonomic family of sea snails, marine gastropod mollusks in the informal group Lower Heterobranchia.- References :*...
Bandel, 1994
Description
All acteonoids have a shellGastropod shell
The gastropod shell is a shell which is part of the body of a gastropod or snail, one kind of mollusc. The gastropod shell is an external skeleton or exoskeleton, which serves not only for muscle attachment, but also for protection from predators and from mechanical damage...
that resembles that of many prosobranchs. Some of the members are able to withdraw completely into the shell and to close the shell with an operculum
Operculum (gastropod)
The operculum, meaning little lid, is a corneous or calcareous anatomical structure which exists in many groups of sea snails and freshwater snails, and also in a few groups of land snails...
, e.g. Acteon tornatilis.
Anatomy
No defensive strategies are known from these animals although histological investigations show a highly glandular area in the mantleMantle (mollusc)
The mantle is a significant part of the anatomy of molluscs: it is the dorsal body wall which covers the visceral mass and usually protrudes in the form of flaps well beyond the visceral mass itself.In many, but by no means all, species of molluscs, the epidermis of the mantle secretes...
cavity and the mantle rim. The mantle rim glands, for example, are very conspicuous. These comprise large epithelial cells that are filled with a non-staining vacuole
Vacuole
A vacuole is a membrane-bound organelle which is present in all plant and fungal cells and some protist, animal and bacterial cells. Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic molecules including enzymes in solution, though in certain...
. The glandular area is highly folded. The cells appear to lie subepithelially due to their size. They alternate with small ciliated cell
Cilium
A cilium is an organelle found in eukaryotic cells. Cilia are slender protuberances that project from the much larger cell body....
s. The hypobranchial gland in the roof of the mantle cavity is small and consists of violet-staining epithelial cells indicating acid mucopolysaccharides.