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 contrast ...

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 Caudofo ...

(

Chaetodermomorpha 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 ...

). 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 converg ...

, 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 pre ...

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 adje ...

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 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 the appropriate s ...

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. Salivary gla ...

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 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 ...

comprising spines or scale-like plates; this has been likened to the

halwaxiid Halwaxiida or halwaxiids is a proposed clade equivalent to the older orders Sachitida He 1980 and Thambetolepidea Jell 1981, loosely uniting scale-bearing Cambrian animals, which may lie in the stem group to molluscs or lophotrochozoa. Some palae ...

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 commonly ...

s of ''

Epimenia ''Epimenia'' is a genus of cavibelonian solenogasters, a kind of shell-less, worm-like mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks () ...

'' 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 freshwater and marine environments, predominantly the latter. Their distinguishing feature is cnidocytes, specialized cells that th ...

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"), a ...

, 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 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 Caudofovea ...

Salvini-Plawen, 1978 *

Amphimeniidae Amphimeniidae is a family of solenogaster, a shell-less worm-like mollusk. MolluscaBase eds. (2021). MolluscaBase. Amphimeniidae Salvini-Plawen, 1972. Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p ...

Salvini-Plawen, 1972 * Apodomeniidae Kocot, Todt, N. T. Mikkelsen & Halanych, 2019 *

Dondersiidae Dondersiidae is a family of molluscs belonging to the order Pholidoskepia The Pholidoskepia are one of the three orders of solenogaster. It is considered an alternate representation for the class Solenogastres. MolluscaBase eds. (2021). Mollus ...

Simroth, 1893 *

Drepanomeniidae Drepanomeniidae 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 *

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

Salvini-Plawen, 1978 *

Gymnomeniidae Gymnomeniidae is a family of molluscs Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognize ...

Odhner, 1920 *

Hemimeniidae Hemimeniidae is a family of molluscs belonging to the order Neomeniamorpha The Neomeniamorpha are one of the three taxonomic orders of solenogasters, shell-less, worm-like, marine mollusks. It is considered an alternate representation for the ...

Salvini-Plawen, 1978 *

Heteroherpiidae ''Heteroherpia'' 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 Caudofovea ...

Salvini-Plawen, 1978 *

Imeroherpiidae Imeroherpiidae 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 Caudofoveat ...

Salvini-Plawen, 1978 *

Lepidomeniidae Lepidomeniidae is a family of molluscs belonging to the order Pholidoskepia. Genera: * '' Lepidomenia'' Kowalevsky, 1883 * '' Nierstrassia'' Heath, 1918 * '' Tegulaherpia'' Salvini-Plawen, 1983 References {{Taxonbar, from=Q20735729 Pholido ...

Pruvot, 1902 * Macellomeniidae Salvini-Plawen, 1978 * Meiomeniidae Salvini-Plawen, 1985 * Neomeniidae Ihering, 1876 *

Notomeniidae Notomeniidae 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 (). Ar ...

Salvini-Plawen, 2004 * Phyllomeniidae Salvini-Plawen, 1978 * Proneomeniidae Mitchell, 1892 *

Pruvotinidae ''Pruvotinidae'' is a diverse taxonomic family of cavibelonian solenogasters, 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 ...

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

Simroth, 1893 * Superorder Pachytegmentaria (not monophyletic) ** Parameniidae Simroth, 1893: synonym of

Heath, 1911 (invalid: type genus a junior homonym) ** Pararrhopaliidae Salvini-Plawen, 1972: synonym of

Heath, 1911 ** Perimeniidae Nierstrasz, 1908: synonym of

Heath, 1911 ** Proneomenidae Mitchell, 1892: synonym of Proneomeniidae Mitchell, 1892 ** Pruvotiniidae Heath, 1911: synonym of

Heath, 1911 (incorrect original spelling) ** Solenopodidae Koren & Danielssen, 1877: synonym of Neomeniidae Ihering, 1876 ** Wireniidae Salvini-Plawen, 1978: synonym of

Odhner, 1920

Morphology

Development

Ecology

Diet

Phylogeny

Families

References

Further reading