The Solenogastres (less often referred to as Neomeniomorpha),

common name In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often contra ...

the solenogasters, are one class of small, worm-like, shell-less molluscs (Aplacophora), the other class being the

Caudofoveata Caudofoveata is a small class within the phylum Mollusca, also known as Chaetodermomorpha. The class is often combined with Solenogastres and termed Aplacophora, but some studies have cast doubt on the monophyly of this group. Anatomy Caudofov ...

( Chaetodermomorpha). 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 Some recent literature, and recent molecular evidence, indicates that the Aplacophora may be

polyphyletic A polyphyletic group is an assemblage of organisms or other evolving elements that is of mixed evolutionary origin. The term is often applied to groups that share similar features known as homoplasies, which are explained as a result of conver ...

, and therefore these taxonomists divide Solenogastres and Caudofoveata into separate classes.

Morphology

In contrast to all other molluscan classes, the Aplacophora have no shell, and are instead covered by

aragonitic Aragonite is a carbonate mineral, one of the three most common naturally occurring crystal forms of calcium carbonate, (the other forms being the minerals calcite and vaterite). It is formed by biological and physical processes, including p ...

sclerites A sclerite (Greek , ', meaning " hard") is a hardened body part. In various branches of biology the term is applied to various structures, but not as a rule to vertebrate anatomical features such as bones and teeth. Instead it refers most commonly ...

(

calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines. In zoology ''Calcareous'' is used as an a ...

spicule Spicules are any of various small needle-like anatomical structures occurring in organisms Spicule may also refer to: * Spicule (sponge), small skeletal elements of sea sponges *Spicule (nematode), reproductive structures found in male nematodes ...

s), which can be solid or hollow. These spicules can be arranged perpendicular to one another within the cuticle to form a skeleton, or can stick up to form a palisade, or can lie flat against the cuticle. 80% of solenogaster

species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...

have a

radula The radula (, ; plural radulae or radulas) is an anatomical structure used by molluscs for feeding, sometimes compared to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food ...

, 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. The radula grows by dividing existing teeth in two, or by adding a new tooth at the centre of the radular row. The

salivary gland The salivary glands in mammals are exocrine glands that produce saliva through a system of ducts. Humans have three paired major salivary glands ( parotid, submandibular, and sublingual), as well as hundreds of minor salivary glands. Salivar ...

s are very elaborate, and are an important character for taxonomy. Next to the mouth they have a unique sense organ, the vestibulum. The solenogastres do not have true ctenidia, although their gill-like structures resemble them.

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.

Sclerite A sclerite ( Greek , ', meaning " hard") is a hardened body part. In various branches of biology the term is applied to various structures, but not as a rule to vertebrate anatomical features such as bones and teeth. Instead it refers most commonl ...

s of '' Epimenia'' start out solid before developing a hollow stem that subsequently solidifies.

Ecology

Diet

Solenogasters feed on

cnidaria Cnidaria () is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in Fresh water, freshwater and Marine habitats, marine environments, predominantly the latter. Their distinguishing feature is cnidocyt ...

and

ctenophores Ctenophora (; ctenophore ; ) comprise a phylum of marine invertebrates, commonly known as comb jellies, that inhabit sea waters worldwide. They are notable for the groups of cilia they use for swimming (commonly referred to as "combs"), and ...

, either sucking their bodily fluids or eating their tissue. They do not use their radulae to rasp prey, as other molluscs do.

Phylogeny

There is some uncertainty regarding the phylogenetic position of the solenogasters. 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 on various lines of evidence. Indeed, some molecular datasets plot Solenogastres as an outgroup to Mollusca.

Families

Acanthomeniidae Acanthomeniidae is a family of solenogaster, a shell-less worm-like mollusk.MolluscaBase eds. (2021). MolluscaBase. Acanthomeniidae Salvini-Plawen, 1978. Accessed through: World Register of Marine Species at: http://marinespecies.org/aphia.php?p= ...

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 Imeroherpiidae is a family of solenogaster, comprising the sole genus ''Imeroherpia''. Sterrofustia {{solenogaster-stub ...

Salvini-Plawen, 1978 * Lepidomeniidae Pruvot, 1902 *

Macellomeniidae Macellomenia is a genus of solenogaster The Solenogastres (less often referred to as Neomeniomorpha), common name the solenogasters, are one class of small, worm-like, shell-less molluscs (Aplacophora), the other class being the Caudofoveata ( ...

Salvini-Plawen, 1978 *

Meiomeniidae Meiomeniidae is a family of molluscs belonging to the order Pholidoskepia. Genera: * ''Meioherpia'' Salvini-Plawen, 1985 * ''Meiomenia ''Meiomenia'' is a genus of pholidoskepian solenogasters, shell-less, worm-like, marinemollusk Mollus ...

Salvini-Plawen, 1985 * Neomeniidae Ihering, 1876 * Notomeniidae Salvini-Plawen, 2004 *

Phyllomeniidae Phyllomeniidae is a family of molluscs belonging to the order Sterrofustia The Sterrofustia are one of the three orders of solenogaster. The status of this order is uncertain, as it is deemed not monophyletic In cladistics for a group o ...

Salvini-Plawen, 1978 *

Proneomeniidae Proneomeniidae is a family of uncommon molluscs in the class Solenogastres The Solenogastres (less often referred to as Neomeniomorpha), common name the solenogasters, are one class of small, worm-like, shell-less molluscs (Aplacophora), the o ...

Mitchell, 1892 * Pruvotinidae Heath, 1911 *

Rhipidoherpiidae Rhipidoherpiidae is a family of solenogaster, a kind of shell-less, worm-like, marine mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). ...

Salvini-Plawen, 1978 *

Rhopalomeniidae Rhopalomeniidae is a family of solenogaster, , a kind of shell-less, worm-like, marine mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks () ...

Salvini-Plawen, 1978 *

Sandalomeniidae Sandalomenia is a genus of solenogaster The Solenogastres (less often referred to as Neomeniomorpha), common name the solenogasters, are one class of small, worm-like, shell-less molluscs (Aplacophora), the other class being the Caudofoveata ( ...

Salvini-Plawen, 1978 *

Simrothiellidae ''Kruppomenia'' is a family of solenogaster, a kind of shell-less, worm-like, marine mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). ...

Salvini-Plawen, 1978 *

Strophomeniidae Strophomeniidae is a family of solenogaster, a kind of shell-less, worm-like, marine (ocean), marine mollusk.MolluscaBase eds. (2021). MolluscaBase. Strophomeniidae Salvini-Plawen, 1978. Accessed through: World Register of Marine Species at: http ...

Salvini-Plawen, 1978 *

Syngenoherpiidae Syngenoherpiidae is a family of solenogaster The Solenogastres (less often referred to as Neomeniomorpha), common name the solenogasters, are one class of small, worm-like, shell-less molluscs (Aplacophora), the other class being the Caudofove ...

Salvini-Plawen, 1978 ;Unassigned in Solenogastres * '' Pholidoherpia'' Salvini-Plawen, 1978 * ''

Rhabdoherpia ''Rhabdoherpia'' is a genus of solenogaster of uncertain relationship within the order Sterrofustia The Sterrofustia are one of the three orders of solenogaster. The status of this order is uncertain, as it is deemed not monophyletic ...

'' 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

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

Morphology

Development

Ecology

Diet

Phylogeny

Families

References

Further reading