Euthyneura
| Euthyneura Temporal range:
| |
|---|---|
| Various euthyneurans (left to right, top to bottom): Aplustrum amplustre (an acteonoid sea snail), Glaucus atlanticus (a nudibranch sea slug), Pneumodermopsis canephora (a sea angel), Costasiella kuroshimae (a sacoglossan sea slug), Physella acuta (a hygrophilan freshwater snail), Cepaea sp. (a stylommatophoran land snail) | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Gastropoda |
| Subclass: | Heterobranchia |
| Infraclass: | Euthyneura Johann Wilhelm Spengel, 1881[1] |
| Subgroups | |
| |
| Diversity[2] | |
| Over 30000 species | |
Euthyneura is a taxonomic infraclass of snails and slugs, which includes species exclusively from marine, aquatic and terrestrial gastropod mollusks in the clade Heterobranchia. Euthyneurans are a diverse group, containing about 40% of the known species of gastropods,[3] including the major land snail and slug clade Stylommatophora, which contains over 20,000 species, various sea slug lineages such as nudibranchs, the parasitic sea snail family Pyramidellidae, one of the most diverse families of gastropods with over 6,000 species, and several other lineages of snails and slugs from a variety of habitats.[4]
Historically, euthyneurans were considered to be divided into two groups, the predominantly marine Opisthobranchia, which contained most sea slugs, and the air-breathing Pulmonata. Phylogenetic analyses have since revealed that opisthobranchs are a paraphyletic group, with some lineages more closely related to traditional pulmonates than to other opisthobranchs, and that the non-pulmonate acochlidians and pyramidellids belong among pulmonates. A monophyletic core of Opisthobranchia, named Euopisthobranchia, remains, while pulmonates, acochlidians, pyramidellids, and the closely-related "opisthobranch" group Sacoglossa form the clade Panpulmonata and nudibranchs and their close relatives form an earlier-diverging group.[5][3][4]
Euthyneura are characterised by several autapomorphies, but are named for euthyneury, the loss of the torsion that characterizes other groups of gastropods. Euthyneurans can be distinguished from other gastropods by having two distinct pairs of head tentacles, the anterior and posterior tentacles. The anterior pair is specialized for contact chemoreception ("taste"), while the posterior pair is specialized for distance chemoreception ("smell") and detection of currents, and modified into eyestalks in stylommatophoran land snails and slugs.[3] They are considered to be the most successful and diverse group of Gastropoda. Within this taxon, the Gastropoda have reached their peak in species richness and ecological diversity. This obvious evolutionary success can probably be attributed to several factors. Marine Opisthobranchia, e.g., have evolved several clades specialised on less used food resources such as sponges or cnidarians. A key innovation in the evolution of Pulmonata was the colonization of freshwater and terrestrial habitats.[6] The increased sensory capability provided by the specialized tentacles may have also contributed to euthyneuran success.[3]
The superfamily Cylindrobullinoidea have been considered probable euthyneuran predecessors and have a fossil record dating back to the Triassic, around 245 million years ago.[3][7] They may have arisen from the Carboniferous to Permian allogastropod family Streptacididae.[7] Molecular clock analyses have suggested that euthyneurans began to diversify in the Carboniferous or Permian periods, with an average age estimate of 296 million years.[3]
The closest relatives of euthyneurans are the mesoneurans, a small group of largely enigmatic marine gastropods with characteristics intermediate between euthyneurans and lower heterobranchs.[3]
Taxonomy
Various phylogenetic studies focused on Euthyneura: Dayrat et al. (2001),[8] Dayrat & Tillier (2002)[9] and Grande et al. (2004).[10] Morphological analyses by Dayrat and Tillier (2002)[9] demonstrated the need to explore new datasets in order to critically analyse the phylogeny of this controversial group of gastropods. Klussmann-Kolb et al. (2008) traced an evolutionary scenario regarding colonisation of different habitats based on phylogenetic hypothesis and they showed that traditional classification of Euthyneura needs to be reconsidered.[6]
2010 taxonomy
Jörger et al. (2010)[11] have redefined major groups within the Heterobranchia and a cladogram showing phylogenic relations of Euthyneura is as follows:[11]
| Heterobranchia |
| ||||||
2014 taxonomy
Cladogram showing phylogenic relations of Euthyneura sensu Wägele et al. (2014):[12][2]
2016 taxonomy
Kano et al. (2016) proposed a new taxon Ringipleura and classified Ringiculoidea as sister group to Nudipleura:[2]
| Heterobranchia |
| ||||||
References
This article incorporates CC-BY-2.0 text from the reference[6]
- ^ Johann Wilhelm Spengel (1881). "Die Geruchsorgane und des Nervensystem der Mollusken". Zeitschrift für wissenschaftliche Zoologie 35(3): 333-383.
- ^ a b c Kano, Yasunori; Brenzinger, Bastian; Nützel, Alexander; Wilson, Nerida G.; Schrödl, Michael (2016-08-08). "Ringiculid bubble snails recovered as the sister group to sea slugs (Nudipleura)". Scientific Reports. 6 30908. Bibcode:2016NatSR...630908K. doi:10.1038/srep30908. ISSN 2045-2322. PMC 4976385. PMID 27498754.
- ^ a b c d e f g Brenzinger, Bastian; Schrödl, Michael; Kano, Yasunori (2021-10-25). "Origin and significance of two pairs of head tentacles in the radiation of euthyneuran sea slugs and land snails". Scientific Reports. 11 (1): 21016. doi:10.1038/s41598-021-99172-5. ISSN 2045-2322.
- ^ a b Krug, Patrick J.; Caplins, Serena A.; Algoso, Krisha; Thomas, Kanique; Valdés, Ángel A.; Wade, Rachael; Wong, Nur Leena W. S.; Eernisse, Douglas J.; Kocot, Kevin M. (2022-04-13). "Phylogenomic resolution of the root of Panpulmonata, a hyperdiverse radiation of gastropods: new insight into the evolution of air breathing". Proceedings of the Royal Society B: Biological Sciences. 289 (1972) 20211855. doi:10.1098/rspb.2021.1855. eISSN 1471-2954. ISSN 0962-8452.
- ^ Wägele, Heike; Klussmann-Kolb, Annette; Verbeek, Eva; Schrödl, Michael (2014). "Flashback and foreshadowing—a review of the taxon Opisthobranchia". Organisms Diversity & Evolution. 14 (1): 133–149. doi:10.1007/s13127-013-0151-5. eISSN 1618-1077. ISSN 1439-6092.
- ^ a b c Klussmann-Kolb A., Dinapoli A., Kuhn K., Streit B. & Albrecht C. (2008). "From sea to land and beyond – New insights into the evolution of euthyneuran Gastropoda (Mollusca)". BMC Evolutionary Biology 2008, 8: 57. doi:10.1186/1471-2148-8-57.
- ^ a b Pan, Hua-Zhang; Erwin, D. H.; Nützel, A.; Zhu, Xiang-Shui (2003). "Jiangxispira, a new gastropod genus from the early Triassic of China with remarks on the phylogeny of the Heterostropha at the Permian/Triassic boundary". Journal of Paleontology. 77 (1): 44–49. doi:10.1666/0022-3360(2003)077<0044:JANGGF>2.0.CO;2. ISSN 0022-3360.
- ^ Dayrat B., Tillier A., Lecointre G. & Tillier S. (2001). "New clades of euthyneuran Gastropods (Mollusca) from 28S rRNA sequences". Molecular Phylogenetics and Evolution 19(2): 225-235. doi:10.1006/mpev.2001.0926.
- ^ a b Dayrat B. & Tillier S. (2002). "Evolutionary relationships of euthyneuran gastropods (Mollusca): a cladistic re-evaluation of morphological characters". Zoological Journal of the Linnean Society 135(4): 403-470. doi:10.1046/j.1096-3642.2002.00018.x
- ^ Grande C., Templado J., Cervera J. L. & Zardoya R. (2004). "Molecular Phylogeny of Euthyneura (Mollusca: Gastropoda)". Molecular Biology and Evolution 21(2): 303-313. doi:10.1093/molbev/msh016.
- ^ a b c 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.
- ^ Wägele H., Klussmann-Kolb A., Verbeek E. & Schrödl M. (2014). "Flashback and foreshadowing—a review of the taxon Opisthobranchia". Organisms Diversity & Evolution 14(1): 133–149. doi:10.1007/s13127-013-0151-5