Solenogastres

{{Short description|Class of molluscs}} {{Automatic taxobox | image = Dondersia_annulata,_Nudi_Falls_imported_from_iNaturalist_photo_95332364.jpg | image_caption = An individual of the species ''Dondersia annulata'' observed in Suli Falls, Indonesia | taxon = Solenogastres | authority = | subdivision_ranks = Orders | subdivision = * Neomeniamorpha * Pholidoskepia * Sterrofustia }}

The '''Solenogastres''' (less often referred to as '''Neomeniomorpha'''), commonly known as '''solenogasters''', are a class of small, worm-like, shell-less molluscs (Aplacophora), the other class being the Caudofoveata (Chaetodermomorpha).<ref name="WoRMS">MolluscaBase eds. (2021). MolluscaBase. Solenogastres. Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=2094 on 2021-04-14</ref>

Some recent literature and recent molecular evidence,{{when?|date=January 2025}} indicates that the Aplacophora may be polyphyletic, and therefore some taxonomists may divide Solenogastres and Caudofoveata into separate classes.<ref>e.g. {{cite book| author=Todt, C.| author2=Okusu, A.| author3=Schander, C.| author4=Schwabe, E.| name-list-style=amp|chapter= Solenogastres, Caudofoveata and Polyplacophora. |editor=Ponder, W. |editor2=Lindberg D. |title=Phylogeny and Evolution of the Mollusca. |publisher=University of California Press |year=2008|isbn =978-0-520-25092-5}} </ref>

==Morphology== In contrast to many other mollusc classes, aplacophorans have no shell, and are instead covered by aragonitic sclerites (calcareous spicules), which can be solid or hollow. These spicules can be arranged perpendicular to one another within the cuticle to form a skeleton, stick up to form a palisade, or can lie flat against the cuticle.<ref name=" Scheltema">{{Cite journal | last1 = Scheltema | first1 = A. H. | title = Two solenogaster molluscs, ''Ocheyoherpia trachia'' n.sp. From Macquarie Island and ''Tegulaherpia tasmanica'' Salvini-Plawen from Bass Strait (Aplacophora: Neomeniomorpha) | journal = Records of the Australian Museum | volume = 51 | pages = 23–31 | year = 1999 | doi = 10.3853/j.0067-1975.51.1999.1266| doi-access = free }}</ref>

80% of solenogaster species have a radula, while in others it is secondarily lost. The radula may bear one or more teeth per row; where there is more than one tooth, there is no central radular tooth.<ref name=" Scheltema" /> The radula grows by dividing existing teeth in two, or by adding a new tooth at the center of the radular row.<ref name=" Scheltema" /> The salivary glands are very elaborate, and are an important characteristic for taxonomy. Next to the mouth they have a unique sense organ, the vestibulum.

Solenogastres do not have true ctenidia, though their gill-like structures may resemble them.<ref>{{The Mollusca|volume=10|chapter=2. Early evolution and the Primitive Groups}}</ref>

==Development== During development, many Solenogastres are covered by a spiny scleritome comprising spines or scale-like plates. This has been likened to the halwaxiid scleritome.<ref name="Todt2010">{{Cite journal | last1 = Todt | first1 = C. | last2 = Wanninger | first2 = A. | doi = 10.1186/1742-9994-7-6 | title = Of tests, trochs, shells, and spicules: Development of the basal mollusk ''Wirenia argentea'' (Solenogastres) and its bearing on the evolution of trochozoan larval key features | journal = Frontiers in Zoology | volume = 7 | issue = 1 | page = 6 | year = 2010 | pmid = 20181015| pmc =2828982 | doi-access = free }}</ref>

Sclerites of ''Epimenia'' start out solid before developing a hollow stem that subsequently solidifies.<ref name="Okusu2002">{{Cite journal | last1 = Okusu | first1 = A. | title = Embryogenesis and development of ''Epimenia babai'' (Mollusca: Neomeniomorpha) | journal = The Biological Bulletin | volume = 203 | issue = 1 | pages = 87–103 | year = 2002 | pmid = 12200259 | doi=10.2307/1543461 | jstor = 1543461 | s2cid = 39411465 | url = https://www.biodiversitylibrary.org/part/36017 }}</ref>

Solenogastres can be found in a diverse range of habitats across the world, from the coast to the deep ocean.<ref>{{Cite journal |last1=Vortsepneva |first1=Elena |last2=Chevaldonné |first2=Pierre |last3=Klyukina |first3=Alexandra |last4=Naduvaeva |first4=Elizaveta |last5=Todt |first5=Christiane |last6=Zhadan |first6=Anna |last7=Tzetlin |first7=Alexander |last8=Kublanov |first8=Ilya |date=2021-12-15 |title=Microbial associations of shallow-water Mediterranean marine cave Solenogastres (Mollusca) |journal=PeerJ |language=en |volume=9 |article-number=e12655 |doi=10.7717/peerj.12655 |issn=2167-8359 |pmc=8684320 |pmid=35003936 |doi-access=free }}</ref>

==Ecology==

===Diet=== Solenogastres feed on cnidaria and ctenophores, either sucking their bodily fluids or eating their tissue.<ref name="Guralnick1999">{{Cite journal | doi = 10.1002/(SICI)1097-4687(199908)241:2<175::AID-JMOR7>3.0.CO;2-0 | last1 = Guralnick | first1 = R. | last2 = Smith | first2 = K. | title = Historical and biomechanical analysis of integration and dissociation in molluscan feeding, with special emphasis on the true limpets (Patellogastropoda: Gastropoda) | journal = Journal of Morphology | volume = 241 | issue = 2 | pages = 175–195 | year = 1999 | pmid = 10420163 | s2cid = 14497120 }}</ref> They do not use their radulae to rasp prey, as some other molluscs do.<ref name="Scheltema1994">{{Cite journal | last1 = Scheltema | first1 = A. H. | last2 = Jebb | first2 = M. | title = Natural history of a solenogaster mollusc from Papua New Guinea,Epimenia australis(Thiele) (Aplacophora: Neomeniomorpha) | journal = Journal of Natural History | volume = 28 | issue = 6 | page = 1297 | year = 1994 | doi = 10.1080/00222939400770661| bibcode = 1994JNatH..28.1297S }}</ref>

==Phylogeny== There is some uncertainty regarding the phylogenetic position of the Solenogastres. Traditionally considered to be the most basal molluscan group and the sister group to the Caudofoveata, alternatives to both of these statements have been proposed.<ref name="Todt2010" /> Some molecular datasets plot Solenogastres as an outgroup to Mollusca.<ref>{{Cite journal| doi = 10.1016/j.ympev.2009.07.028| pmid = 19647088| year = 2010| last1 = Wilson | first1 = N.| last2 = Rouse | first2 = G.| last3 = Giribet | first3 = G.| title = Assessing the molluscan hypothesis Serialia (Monoplacophora+Polyplacophora) using novel molecular data.| volume = 54| issue = 1| pages = 187–193| journal = Molecular Phylogenetics & Evolution }}</ref> However, there are cryptic species which are hard to delineate due to there being a lack of multiple morphological characteristics.<ref>{{Cite journal |last1=Bergmeier |first1=Franziska S. |last2=Haszprunar |first2=Gerhard |last3=Todt |first3=Christiane |last4=Jörger |first4=Katharina M. |date=September 2016 |title=Lost in a taxonomic Bermuda Triangle: comparative 3D-microanatomy of cryptic mesopsammic Solenogastres (Mollusca) |url=http://link.springer.com/10.1007/s13127-016-0266-6 |journal=Organisms Diversity & Evolution |language=en |volume=16 |issue=3 |pages=613–639 |doi=10.1007/s13127-016-0266-6 |bibcode=2016ODivE..16..613B |s2cid=256005322 |issn=1439-6092|url-access=subscription }}</ref>

==Families== * Acanthomeniidae Salvini-Plawen, 1978 * Amphimeniidae Salvini-Plawen, 1972 * Apodomeniidae Kocot, Todt, N. T. Mikkelsen & Halanych, 2019 * Dondersiidae Simroth, 1893 * Drepanomeniidae Salvini-Plawen, 1978 * Epimeniidae Salvini-Plawen, 1978 * Gymnomeniidae Odhner, 1920 * Hemimeniidae Salvini-Plawen, 1978 * Heteroherpiidae Salvini-Plawen, 1978 * Imeroherpiidae Salvini-Plawen, 1978 * Lepidomeniidae Pruvot, 1902 * Macellomeniidae Salvini-Plawen, 1978 * Meiomeniidae Salvini-Plawen, 1985 * Neomeniidae Ihering, 1876 * Notomeniidae Salvini-Plawen, 2004 * Phyllomeniidae Salvini-Plawen, 1978 * Proneomeniidae Mitchell, 1892 * Pruvotinidae Heath, 1911 * Rhipidoherpiidae Salvini-Plawen, 1978 * Rhopalomeniidae Salvini-Plawen, 1978 * Sandalomeniidae Salvini-Plawen, 1978 * Simrothiellidae Salvini-Plawen, 1978 * Strophomeniidae Salvini-Plawen, 1978 * Syngenoherpiidae Salvini-Plawen, 1978 ;Unassigned in Solenogastres * ''Pholidoherpia'' Salvini-Plawen, 1978 * ''Rhabdoherpia'' Salvini-Plawen, 1978 ;Synonyms: * Superorder Aplotegmentaria (not monophyletic) ** Myzomeniidae Thiele, 1894: synonym of Dondersiidae Simroth, 1893 * Superorder Pachytegmentaria (not monophyletic) ** Parameniidae Simroth, 1893: synonym of Pruvotinidae Heath, 1911 (invalid: type genus a junior homonym) ** Pararrhopaliidae Salvini-Plawen, 1972: synonym of Pruvotinidae Heath, 1911 ** Perimeniidae Nierstrasz, 1908: synonym of Pruvotinidae Heath, 1911 ** Proneomenidae Mitchell, 1892: synonym of Proneomeniidae Mitchell, 1892 ** Pruvotiniidae Heath, 1911: synonym of Pruvotinidae Heath, 1911 (incorrect original spelling) ** Solenopodidae Koren & Danielssen, 1877: synonym of Neomeniidae Ihering, 1876 ** Wireniidae Salvini-Plawen, 1978: synonym of Gymnomeniidae Odhner, 1920

==References== {{Reflist}}

==Further reading== {{Commons category}} * {{cite journal|doi=10.1186/1471-2148-10-70|pmid=20214780|pmc=2841657|title=Fast evolving 18S rRNA sequences from Solenogastres (Mollusca) resist standard PCR amplification and give new insights into mollusk substitution rate heterogeneity|journal=BMC Evolutionary Biology|volume=10|page=70|year=2010|last1=Meyer|first1=Achim|last2=Todt|first2=Christiane|last3=Mikkelsen|first3=Nina T.|last4=Lieb|first4=Bernhard |issue=1 |doi-access=free |bibcode=2010BMCEE..10...70M }}

Category:Solenogastres Category:Mollusc classes