Heterobranchia

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Heterobranchia
Heterobranchia composite 03.jpg
Some examples of Heterobranchia
Scientific classification
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
(unranked): clade Heterobranchia
Taxonomic subcategories

informal group Lower Heterobranchia
clade Nudipleura
clade Euopisthobranchia
clade Panpulmonata

Heterobranchia, the heterobranchs (meaning "different-gilled snails"), is a taxonomic clade of snails and slugs, which includes marine, aquatic and terrestrial gastropod mollusks.

Heterobranchia is one of the main clades of gastropods. Currently Heterobranchia comprises three informal groups: the Lower Heterobranchia, the Opisthobranchia and the Pulmonata, also known as the lower heterobranchs, the opisthobranchs and the pulmonates.[1]

A shell of the marine species Bulla quoyii, which is an opisthobranch.

Diversity[edit]

The three subdivisions of this large clade are quite diverse:

  • Opisthobranchia are almost all marine species, some shelled and some not. The internal organs of the opisthobranchs have undergone detorsion (unwinding of the viscera that were twisted during torsion).
  • The Pulmonata includes the majority of land snails and slugs, many freshwater snails, and a small number of marine species. The mantle cavity of the Pulmonata is modified into an air-breathing organ. They are also characterized by detorsion and a symmetrically-arranged nervous system. The pulmonates almost always lack an operculum and are hermaphroditic.

Taxonomy[edit]

Older taxonomy[edit]

The families currently included in Heterobranchia have historically been placed in many different parts of the taxonomic class of gastropods. Earlier authors (such as J.E. Gray, 1840) considered Heterobranchia to consist of only marine gastropods, and conceptualized it as a borderline category, intermediate between the Opisthobranchia & Pulmonata, and all the other gastropods.[2]

The (sometimes recognized) category Heterostropha within the Heterobranchia, which includes such families as Architectonicidae, the sundial or staircase snails, is primarily characterized by a shell which has a heterostrophic protoconch, in other words the apical whorls are coiled in the opposite plane to the adult whorls. The classification of this group was revised by Ponder & Warén in 1988.[3]

According to the older taxonomy of the Gastropoda (Ponder & Lindberg, 1997) the Heterobranchia were ranked as a superorder.

2005 taxonomy[edit]

The graph of neighbor-joining phylogenetic tree shows that there is no clade-supporting pattern for the monophyly of Opisthobranchia (green) or of Pulmonata (yellow) based on datasets by Jörger et al. (2010).[4]

Heterobranchia is currently one of the main clades of gastropods. For a detailed taxonomy, see Taxonomy of the Gastropoda (Bouchet & Rocroi, 2005)#Clade Heterobranchia.

2010 taxonomy[edit]

Jörger et al. (2010)[4] have redefined major groups within the Heterobranchia: they created the new clades Euopisthobranchia and Panpulmonata.[4]

A cladogram showing phylogenic relations of Heterobranchia as proposed by Jörger et al. (2010):[4]

Heterobranchia

Lower Heterobranchia (including Acteonoidea) - Lower Heterobranchia does not form a clade in the study by Jörger et al. (2010)[4]


Euthyneura

Nudipleura



Euopisthobranchia

Umbraculoidea





Runcinacea




Anaspidea



Pteropoda





Cephalaspidea s.s.




Panpulmonata


Siphonarioidea



Sacoglossa






Glacidorboidea




Amphiboloidea



Pyramidelloidea






Hygrophila




Acochlidiacea


Eupulmonata

Stylommatophora




Systellommatophora




Ellobioidea




Otinoidea



Trimusculoidea













References[edit]

  1. ^ Bouchet P. & Rocroi J.-P. (Ed.); Frýda J., Hausdorf B., Ponder W., Valdes A. & Warén A. 2005. Classification and nomenclator of gastropod families. Malacologia: International Journal of Malacology, 47(1-2). ConchBooks: Hackenheim, Germany. ISBN 3-925919-72-4. Issn = 0076-2997. 397 pp. http://www.vliz.be/Vmdcdata/imis2/ref.php?refid=78278
  2. ^ Haszprunar G. (1985). "The Heterobranchia ― a new concept of the phylogeny of the higher Gastropoda". Zeitschrift für zoologische Systematik und Evolutionsforschung 23 (1): 15–37.  ISSN 0044-3808
  3. ^ Ponder, W. F. & Warén, A. (1988). "Classification of the Caenogastropoda and Heterostropha- A list of family-group names and higher taxa". Malacological review supplement 4: 288–317. 
  4. ^ a b c d e Jörger K. M., Stöger I., Kano Y., Fukuda H., Knebelsberger T., Schrödl M. (2010). "On the origin of Acochlidia and other enigmatic euthyneuran gastropods, with implications for the systematics of Heterobranchia". BMC Evolutionary Biology 10: 323. doi:10.1186/1471-2148-10-323. PMC 3087543. PMID 20973994. 

Further reading[edit]

  • Dinapoli A. (2009). Phylogeny and Evolution of the Heterobranchia (Mollusca, Gastropoda). Thesis, Frankfurt am Main, 176 pp. PDF.
  • Dinapoli A., Klussmann-Kolb A. (2010). "The long way to diversity – Phylogeny and evolution of the Heterobranchia (Mollusca: Gastropoda)".". Molecular Phylogenetics and Evolution 55 (1): 60–76. doi:10.1016/j.ympev.2009.09.019.