Acochlidiacea, common name acochlidians, are a

taxonomic 280px, Generalized scheme of taxonomy Taxonomy is a practice and science concerned with classification or categorization. Typically, there are two parts to it: the development of an underlying scheme of classes (a taxonomy) and the allocation ...

clade of very unusual

sea snail Sea snails are slow-moving marine (ocean), marine gastropod Mollusca, molluscs, usually with visible external shells, such as whelk or abalone. They share the Taxonomic classification, taxonomic class Gastropoda with slugs, which are distinguishe ...

s and sea and freshwater

slug Slug, or land slug, is a common name for any apparently shell-less Terrestrial mollusc, terrestrial gastropod mollusc. The word ''slug'' is also often used as part of the common name of any gastropod mollusc that has no shell, a very reduced ...

aquatic Aquatic means relating to water; living in or near water or taking place in water; does not include groundwater, as "aquatic" implies an environment where plants and animals live. Aquatic(s) may also refer to: * Aquatic animal, either vertebrate ...

gastropod Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and fro ...

mollusk Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The ...

s within the large clade

Heterobranchia Heterobranchia, the heterobranchs (meaning "different gill"), is a taxonomic clade of snails and slugs, which includes marine, aquatic, and terrestrial gastropod molluscs. Heterobranchia is one of the main clades of gastropods. Currently Het ...

. Acochlidia is a variant spelling. Pseudunela cornuta svg hariadhi

Description

These are mostly very small animals, without a

shell Shell may refer to: Architecture and design * Shell (structure), a thin structure ** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses Science Biology * Seashell, a hard outer layer of a marine ani ...

gill A gill () is a respiration organ, respiratory organ that many aquatic ecosystem, aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow r ...

s, distinguished by the

viscera In a multicellular organism, an organ is a collection of tissues joined in a structural unit to serve a common function. In the hierarchy of life, an organ lies between tissue and an organ system. Tissues are formed from same type cells to a ...

l mass being sharply set off from the rest of the body. Being a small group with only 47 species worldwide known in 2023,MolluscaBase eds. (2021)
MolluscaBase. Acochlidiimorpha.
Accessed on 2023-02-13. this group has been the subject of active research since 2010, by which date only 32 species were named. These slugs are morphologically and biologically highly aberrant and diverse, comprising a series of unusual characters (e.g. secondary

gonochorism In biology, gonochorism is a sexual system where there are two Sex, sexes and each individual organism is either male or female. The term gonochorism is usually applied in animal species, the vast majority of which are gonochoric. Gonochorism con ...

, lack of copulatory organs, asymmetric

radula The radula (; : radulae or radulas) is an anatomical structure used by mollusks 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 enters ...

e). Most acochlidians live interstitially in marine sands, while some have conquered limnic systems (uniquely within opisthobranch gastropods).

Taxonomy

Nils Hjalmar Odhner Nils Hjalmar Odhner (6 December 1884 – 12 June 1973) was a Swedish zoologist who studied mollusks, a malacologist. He was professor of invertebrate zoology at the Swedish Museum of Natural History, Stockholm, and a member of the Royal Swedish Ac ...

established this taxon as a family in 1937, when he created the families

Microhedylidae Parhedylidae are a taxonomic family of sea slugs, marine gastropod mollusks in the superfamily Parhedyloidea.MolluscaBase eds. (2021). MolluscaBase. Parhedylidae Thiele, 1931. Accessed through: World Register of Marine Species at: http://www. ...

and

Acochlidiidae Acochlidiidae are a taxonomic family of shell-less freshwater gastropods (one of them '' Palliohedyle weberi'' lives in brackish water),Schrödl M. & Neusser T. P. (2010). "Towards a phylogeny and evolution of Acochlidia (Mollusca: Gastropoda: ...

. In 1939, he treated this taxon as an order. Rankin (1979)Rankin J. J. (1979). "A freshwater shell-less mollusc from the Caribbean: structure, biotics, and contribution to a new understanding of the Acochlidioidea". ''

Royal Ontario Museum The Royal Ontario Museum (ROM) is a museum of art, world culture and natural history in Toronto, Ontario, Canada. It is one of the largest museums in North America and the largest in Canada. It attracts more than one million visitors every year ...

, Life Sciences Contributions'' 116: 123 pp., page 83. treated this taxon as an order, the order Acochlidioidea. Salvini-Plawen (1983) wrote this taxon as Acochlidiomorpha. Anderson (1992) treated this taxon as the order Acochlidiida. Burn in Beesley et al. (1998), wrote this taxon as the order Acochlidea. Wawra (1987) and various authors (2007–2010)Schrödl M. & Neusser T. P. (2010). "Towards a phylogeny and evolution of Acochlidia (Mollusca: Gastropoda: Opisthobranchia)". ''

Zoological Journal of the Linnean Society The ''Zoological Journal of the Linnean Society'' is a monthly peer-reviewed scientific journal covering zoology published by Oxford University Press on behalf of the Linnean Society. The editor-in-chief is Maarten Christenhusz (Linnean Society) ...

'' 158: 124–154. . spelled this taxon as Acochlidia. Three families (

Hedylopsidae Hedylopsis is a genus of sea slugs, marine gastropod mollusks within the clade Acochlidiacea. Taxonomy Hedylopsidae has been classified within the superfamily Hedylopsoidea in the taxonomy of Bouchet & Rocroi (2005). Sensu Schrödl & Neuss ...

and

) are classically recognized. Two controversial classifications (Rankin 1979,

Starobogatov Yaroslav Igorevich Starobogatov (; 13 July 1932 – 3 December 2004) was a Russian zoologist, professor and chief scientist at the Zoological Institute of the Russian Academy of Sciences. His research was on invertebrate zoology, particularly on ...

1983) Starobogatov Ya. I. (1983). "Sistema otriada Acochlidiiformes ystem of the order Acochlidiiformes" ''Vsesoiuznoe soveshchanie po izucheniiu molliuskov'', Leningrad, 7: 30–32. have been proposed recently, but they have not been evaluated since. An alternative classification by Burn (in Beesley et al., 1998) for the Australian species recognizes 2 superfamilies and 5 families. Pseudunela cornuta 2

The Acochlidia, a traditional "order" of the Opisthobranchia since their establishment by Odhner have formed one of the unsolved mysteries within

Euthyneura Euthyneura is a taxonomic infraclass of snails and slugs, which includes species exclusively from marine, aquatic and terrestrial gastropod mollusks in the clade Heterobranchia. Euthyneura are characterised by several autapomorphies, bu ...

. Their

monophyly In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent comm ...

is widely accepted especially since a proposed sister group relationship of the acochlidian family

Ganitidae Parhedylidae are a taxonomic family of sea slugs, marine gastropod mollusks in the superfamily Parhedyloidea.MolluscaBase eds. (2021). MolluscaBase. Parhedylidae Thiele, 1931. Accessed through: World Register of Marine Species at: http://www. ...

with

Sacoglossa Sacoglossa are a superorder of small sea slugs and sea snails, marine gastropod mollusks that belong to the clade Heterobranchia known as sacoglossans. There are 284 valid species recognized within this superorder. Sacoglossans live by ingestin ...

(based on the dagger-shaped radula teeth) could be rejected based on a comprehensive

parsimony analysis In phylogenetics and computational phylogenetics, maximum parsimony is an optimality criterion under which the phylogenetic tree that minimizes the total number of character-state changes (or minimizes the cost of differentially weighted charact ...

of morphological characters. During the last years a series of studies have redescribed key acochlidian taxa in great detail, including

3D reconstruction In computer vision and computer graphics, 3D reconstruction is the process of capturing the shape and appearance of real objects. This process can be accomplished either by active or passive methods. If the model is allowed to change its shape i ...

s, and added considerably to the morphological and biological knowledge of this previously little understood group. Most recent morphological analyses suggested a common origin with either the equally enigmatic Rhodopemorpha, the diaphanid cephalaspidean '' Toledonia'', or with runcinid or philinoid

cephalaspidea The order Cephalaspidea, also known as the headshield slugs and bubble snails, is a major taxon of sea slugs and bubble snails, marine (ocean), marine gastropod mollusks within the larger clade Euopisthobranchia. Bubble shells is another commo ...

ns. Molecular markers independent from direct ecological pressures suggested an unresolved basal opisthobranch origin for Acochlidia (based on nuclear 18S rRNA and 28S rRNA) (Vonnemann et al. 2005). A first combined multi-gene dataset led to the surprising result of Acochlidia clustering in a pulmonate relationship, united in a clade with

Pyramidelloidea Pyramidelloidea is a superfamily of mostly very small sea snails, marine gastropod mollusks and micromollusks within the clade Panpulmonata. This is a voluminous taxon: above the species level close to 400 named taxa are referred to this gastr ...

Amphiboloidea Amphiboloidea is a taxonomic superfamily of air-breathing land snails. Distribution Amphibolids are found in Indo-Pacific intertidal mangrove, saltmarsh and estuarine mudflat habitats. Taxonomy 2005 taxonomy According to the taxonomy o ...

and

Eupulmonata Eupulmonata is a taxonomic clade of air-breathing gastropod molluscs. The great majority of this group are land snails and slugs, but some are intertidal or inhabit coastal saltmarshes and mangroves. Possible synapomorphy of the group are gl ...

. However, only three derived acochlids were included into analysis prior to 2010, with partially missing data.

2005 taxonomy

The taxonomy of Bouchet & Rocroi (2005) tentatively follows Starobogatov (1983), but they have downgraded his taxonomic ranks (suborders to superfamilies, superfamilies to families). The group Acochlidiacea is arranged as follows: *Superfamily

Acochlidioidea Acochlidiidae are a taxonomic family of shell-less freshwater gastropods (one of them '' Palliohedyle weberi'' lives in brackish water),Schrödl M. & Neusser T. P. (2010). "Towards a phylogeny and evolution of Acochlidia (Mollusca: Gastropoda: O ...

**Family

*Superfamily

Hedylopsoidea Hedylopsoidea was defined as a taxonomic superfamily of sea slugs, mostly marine gastropod mollusks within the informal group Opisthobranchia according to the taxonomy of Bouchet & Rocroi (2005). Schrödl & Neusser (2010)Schrödl M. & Neusser ...

**Family

Livorniellidae Parhedylidae are a taxonomic family of sea slugs, marine gastropod mollusks in the superfamily Parhedyloidea.MolluscaBase eds. (2021). MolluscaBase. Parhedylidae Thiele, 1931. Accessed through: World Register of Marine Species at: http://www.m ...

**Family

Minicheviellidae ''Asperspina'' is a genus of sea slugs, marine gastropod mollusks within the clade Acochlidiacea. Taxonomy Asperspinidae has been listed as a synonym of Parhedylidae in the taxonomy of Bouchet & Rocroi (2005). Sensu Schrödl & Neusser (201 ...

**Family

Parhedylidae Parhedylidae are a taxonomic family of sea slugs, marine gastropod mollusks in the superfamily Parhedyloidea.MolluscaBase eds. (2021). MolluscaBase. Parhedylidae Thiele, 1931. Accessed through: World Register of Marine Species at: http://www.m ...

**Family

Tantulidae ''Tantulum elegans'' is a species of freshwater slug, an aquatic shell-less gastropod mollusk within the clade Acochlidiacea. This species has no shell. The maximum recorded length is 2 mm.Welch J. J. (2010). "The "Island Rule" and Deep-Sea ...

*Superfamily

Palliohedyloidea Acochlidiidae are a taxonomic family of shell-less freshwater gastropods (one of them '' Palliohedyle weberi'' lives in brackish water),Schrödl M. & Neusser T. P. (2010). "Towards a phylogeny and evolution of Acochlidia (Mollusca: Gastropoda: O ...

**Family

Palliohedylidae Acochlidiidae are a taxonomic family of shell-less freshwater gastropods (one of them '' Palliohedyle weberi'' lives in brackish water),Schrödl M. & Neusser T. P. (2010). "Towards a phylogeny and evolution of Acochlidia (Mollusca: Gastropoda: ...

*Superfamily

Strubellioidea According to the taxonomy of Bouchet & Rocroi (2005), Strubellioidea was a taxonomic superfamily of sea slugs, mostly marine gastropod mollusks within the informal group Opisthobranchia. However, Schrödl & Neusser (2010)Schrödl M. & Neusser ...

**Family

Strubelliidae ''Strubellia paradoxa'' is a species of freshwater slug, a shell-less freshwater gastropod,Strong E. E., Gargominy O., Ponder W. F. & Bouchet P. (2008). "Global Diversity of Gastropods (Gastropoda; Mollusca) in Freshwater". ''Hydrobiologia'' 595 ...

**Family

Pseudunelidae ''Pseudunela'' is a genus of minute sea slugs, acochlidians, shell-less marine or temporary brackish or brackish gastropod mollusks in the clade Acochlidiacea. ''Pseudunela'' is the only genus in the family Pseudunelidae. ''Pseudunela'' is the ...

2010 taxonomy

A first comprehensive

cladistic analysis Cladistics ( ; from Ancient Greek 'branch') is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is ...

of their

phylogeny A phylogenetic tree or phylogeny is a graphical representation which shows the evolutionary history between a set of species or Taxon, taxa during a specific time.Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, M ...

has been established by Schrödl & Neusser (2010), but the identity of their sister group remained uncertain. Morphology-based analyses by Schrödl & Neusser, demonstrated that Acochlidia usually group with other mesopsammic (they live in interstitial spaces of marine sands) taxa, if any were included (i.e. with the sacoglossan '' Platyhedyle'', the rhodopemorph ''

Rhodope Rhodope may refer to: * Rhodope (mythology), several figures of Greek mythology * Rhodope Mountains, in Bulgaria and Greece * Rhodope (regional unit), of Greece * Rhodope (province), a Roman and Byzantine province * 166 Rhodope, an asteroid * Rhodop ...

'' or the cephalaspideans '' Philinoglossa'' or '' Philine exigua''). Thus, it is likely that convergent adaptations to the interstitial habitat mask the truly phylogenetic signals. Schrödl & Neusser (2010) split Acochlidiacea into two (unranked) taxa and into six families like this:

Hedylopsacea

Hedylopsacean Acochlidiacea, whose evolution involves several habitat shifts from marine interstitial to amphibious or freshwater benthic habitats, possess complex

excretory Excretion is elimination of metabolic waste, which is an essential process in all organisms. In vertebrates, this is primarily carried out by the lungs, kidneys, and skin. This is in contrast with secretion, where the substance may have specific ...

and reproductive systems. (unranked) Hedylopsacea has no superfamilies defined: *

: '' Acochlidium'', ''

Palliohedyle ''Palliohedyle'' is a genus of gastropods belonging to the family Acochlidiidae. Species: *''Palliohedyle sutteri ''Palliohedyle sutteri'' is a species of gastropods belonging to the family Acochlidiidae Acochlidiidae are a taxonomic fam ...

'', including ''

Strubellia ''Strubellia paradoxa'' is a species of freshwater slug, a shell-less freshwater gastropod,Strong E. E., Gargominy O., Ponder W. F. & Bouchet P. (2008). "Global Diversity of Gastropods (Gastropoda; Mollusca) in Freshwater". ''Hydrobiologia'' 595 ...

'' *

: with the only genus '' Pseudunela'' *

: with the only genus ''

Hedylopsis Hedylopsis is a genus of sea slugs, marine gastropod mollusks within the clade Acochlidiacea. Taxonomy Hedylopsidae has been classified within the superfamily Hedylopsoidea in the taxonomy of Bouchet & Rocroi (2005). Sensu Schrödl & Neusse ...

'' *

: with the only species '' Tantulum elegans''

Microhedylacea

Microhedylacean Acochlidiacea are exclusively found in interstitial spaces in sediment, and show a tendency toward reduction of complexity in major organ systems. (unranked) Microhedylacea has no superfamilies defined: *

Asperspinidae ''Asperspina'' is a genus of sea slugs, marine gastropod mollusks within the clade Acochlidiacea. Taxonomy Asperspinidae has been listed as a synonym of Parhedylidae in the taxonomy of Bouchet & Rocroi (2005). Sensu Schrödl & Neusser (201 ...

: with the only genus '' Asperspina'' – junior synonym:

s.l.: ''

Pontohedyle ''Pontohedyle'' is a genus of sea slugs, acochlidians, shell-less marine gastropod mollusks in the family Parhedylidae. Sea slugs in this genus are highly simplified and uniform. Distribution The genus ''Pontohedyle'' shows a circumtropical di ...

'', '' Parhedyle'', '' Microhedyle'' – including

: '' Ganitus'' and '' Paraganitus''. Inclusion of Ganitidae within Microhedylidae requires further research and higher statistical support. A multi-locus molecular study by Jörger et al. (2010), included six out of seven acochlidian families. It confirmed Acochlidiacea in a pulmonate relationship, as sister to Eupulmonata. Euthyneura, Opisthobranchia and Pulmonata as traditionally defined were found non-monophyletic. The enigmatic amphibious and insectivorous

Aitengidae ''Aiteng'' is a genus comprising three species of sea slug, ''A. ater'' and ''A. mysticus'' being found in intertidal zones while ''A. marefugitus'' is fully terrestrial. ''Aiteng'' is the only genus in the family Aitengidae. The name of a biolog ...

clusters within Acochlidiacea, as sister to

meiofauna Meiobenthos, also called meiofauna, are small benthic invertebrates that live in marine or freshwater environments, or both. The term ''meiofauna'' loosely defines a group of organisms by their sizelarger than microfauna but smaller than macrof ...

l and brackish Pseudunelidae and limnic Acochlidiidae. Inclusion of this small acochlidian group resulted in redefinition of major groups within

, that has led to creation of the new clades

Euopisthobranchia Euopisthobranchia is a taxonomic clade of snails and slugs in the clade Heterobranchia within the clade Euthyneura. This clade was established as a new taxon by Jörger et al. in October 2010. Euopisthobranchia is a monophyletic portion of the ...

and

Panpulmonata Panpulmonata is a taxonomic clade of snails and slugs in the clade Heterobranchia within the clade Euthyneura. Panpulmonata was established as a new taxon by Jörger et al. in October 2010. The older name "Pulmonata" referred to a group of euth ...

2016 taxonomy

Two more families were established. Both include slugs that are unusual among acochlidians for their anatomy and habitat (amphibious, terrestrial, or benthic in deeper waters): *

Swennen & Buatip, 2009 * Bathyhedylidae Neusser, Jörger, Lodde-Bensch, Strong & Schrödl, 2016Neusser T. P., Jörger K. M., Lodde-Bensch E., Strong E. E. & Schrödl M. (2016). "The unique deep sea - land connection: Interactive 3D visualization and molecular phylogeny of ''Bathyhedyle boucheti'' n. sp. (Bathyhedylidae n. fam.) - the first panpulmonate slug from bathyal zones". ''PeerJ'' 4: e2738. .

Phylogeny

There is no fossil record of Acochlidiacea. Application of a

molecular clock The molecular clock is a figurative term for a technique that uses the mutation rate of biomolecules to deduce the time in prehistory when two or more life forms diverged. The biomolecular data used for such calculations are usually nucleot ...

allowed estimation of divergence times for these groups. The split between

and Acochlidiacea took place in the

Mesozoic The Mesozoic Era is the Era (geology), era of Earth's Geologic time scale, geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Period (geology), Periods. It is characterized by the dominance of archosaurian r ...

, between the Triassic and Jurassic periods. The diversification of Acochlidia is estimated to have happened in the Jurassic with the split between

Hedylopsacea Acochlidiacea, common name acochlidians, are a taxonomic clade of very unusual sea snails and sea and freshwater slugs, aquatic gastropod mollusks within the large clade Heterobranchia. Acochlidia is a variant spelling. Description These a ...

and

Microhedylacea Acochlidiacea, common name acochlidians, are a Taxonomy (biology), taxonomic clade of very unusual sea snails and sea and freshwater slugs, aquatic animal, aquatic gastropod mollusks within the large clade Heterobranchia. Acochlidia is a variant ...

Cladogram

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

showing phylogenetic relations of some genera and species within Acochlidiacea:

Ecology

The life cycle of Acochlidiacea is poorly known. With a typically low reproductive output in Acochlidiacea (max. of 40 eggs in ''

Pontohedyle milaschewitchii ''Pontohedyle milaschewitchii'' is a species of sea slug, an acochlidian, a shell-less marine gastropod mollusk in the family Parhedylidae.Jörger K. M., Norenburg J. L., Wilson N. G. & Schrödl M. (2012). "Barcoding against a paradox? Combine ...

''), free

veliger A veliger is the planktonic larva of many kinds of sea snails and freshwater snails, as well as most bivalve molluscs (clams) and tusk shells. Description The veliger is the characteristic larva of the gastropod, bivalve and scaphopod taxono ...

larvae are assumed to stay in the interstices of the sand grains rather than entering the water column thereby avoiding long distance dispersal. Fertilized eggs are attached to sand grains and might promote dispersal via current driven sediment transport along shorelines.

Overview of species

# '' Hedylopsis spiculifera'' (Kowalevsky, 1901) (Hedylopsidae) – marine # '' Hedylopsis ballantinei'' Sommerfeldt & Schrödl, 2005 (Hedylopsidae) – marine # ''

Pseudunela cornuta ''Pseudunela cornuta'' is a species of small sea slug, an acochlidian, a shell-less marine (ocean), marine and temporarily brackishNeusser T. P., Jörger K. M. & Schrödl M. (2011). "Cryptic Species in Tropic Sands – Interactive 3D Anatomy ...

'' (Challis, 1970) (Pseudunelidae) – marine and temporary brackish # ''

Pseudunela eirene ''Pseudunela'' is a genus of minute sea slugs, acochlidians, shell-less marine or temporary brackish or brackish gastropod mollusks in the clade Acochlidiacea. ''Pseudunela'' is the only genus in the family Pseudunelidae. ''Pseudunela'' is the ...

'' Wawra, 1988 (Pseudunelidae) – marine # ''

Pseudunela espiritusanta ''Pseudunela espiritusanta'' is a species of sea slug, an acochlidian, a shell-less marine gastropod mollusk in the family Pseudunelidae. Its specific name is a reference to Espiritu Santo Island in Vanuatu, where it was found. This species, ...

'' Neusser & Schrödl, 2009 (Pseudunelidae) – in brackish water # ''

Pseudunela marteli ''Pseudunela marteli'' is a species of sea slug, an acochlidian, a shell-less marine gastropod mollusk in the family Pseudunelidae. The specific name ''marteli'' is in honour of author's "big-hearted friend and colleague" biologist Martin “M ...

'' Neusser, Jörger & Schrödl, 2011 (Pseudunelidae) – marine # ''

Pseudunela viatoris ''Pseudunela viatoris'' is a species of sea slug, an acochlidian, a shell-less marine gastropod mollusk in the family Pseudunelidae. The specific name ''viatoris'' is after the Latin word “viator” (engl. pilgrim/voyager) according to its su ...

'' Neusser, Jörger & Schrödl, 2011 (Pseudunelidae) – marineNeusser T. P., Jörger K. M. & Schrödl M. (2011). "Cryptic Species in Tropic Sands - Interactive 3D Anatomy, Molecular Phylogeny and Evolution of Meiofaunal Pseudunelidae (Gastropoda, Acochlidia)". '' PLoS ONE'' 6(8): e23313. . # ''

Aiteng ater ''Aiteng ater'' is a species of sea slug, a marine gastropod mollusc in the family Aitengidae. The specific name ''ater'' is from the Latin language and means black, in reference to the appearance of the slug on the mud. ''Aiteng ater'' was cho ...

'' Swennen & Buatip, 2009 (Aitengidae) – marine (and brackish) # ''

Aiteng marefugitus ''Aiteng marefugitus'' is a species of fully terrestrial sea slug found only on the Ulong Island of Palau. The species name is derived from Latin, meaning "fled from the sea". Description ''A. marefugitus'' is a very small slug, reaching onl ...

'' Kano, Neusser, Fukumori, Jörger & Schrödl, 2015 (Aitengidae) – marine # ''

Aiteng mysticus ''Aiteng mysticus'' is a species of sea slug in the family Aitengidae, found around Hisamatsu, Miyako-jima, Okinawa, Japan. Morphologically it clearly belongs to the Aitengidae, but it shows differences to ''Aiteng ater'' at genus or species lev ...

'' Neusser, Fukuda, Jörger, Kano & Schrödl, 2011 (Aitengidae) – from Japan # ''

Bathyhedyle boucheti ''Bathyhedyle boucheti'' is a species of Panpulmonata, panpulmonate slug, a deep-sea dwelling gastropod native to the continental slope off the coast of Mozambique. It is the first ever such panpulmonate slug to be discovered at such depths. It ...

'' Neusser, Jörger, Lodde-Bensch, Strong & Schrödl, 2016 (Bathyhedylidae) - marine # ''

Strubellia paradoxa ''Strubellia paradoxa'' is a species of freshwater slug, a shell-less freshwater gastropod,Strong E. E., Gargominy O., Ponder W. F. & Bouchet P. (2008). "Global Diversity of Gastropods (Gastropoda; Mollusca) in Freshwater". ''Hydrobiologia'' 595 ...

'' (Strubell, 1892) (Acochlidiidae) – freshwater # ''

Strubellia wawrai ''Strubellia paradoxa'' is a species of freshwater slug, a shell-less freshwater snail, freshwater gastropod,Strong E. E., Gargominy O., Winston Ponder, Ponder W. F. & Bouchet P. (2008). "Global Diversity of Gastropods (Gastropoda; Mollusca) in F ...

'' Brenzinger, Neusser, Jörger & Schrödl, 2011 (Acochlidiidae) – freshwater # ''

Acochlidium amboinense ''Acochlidium amboinense'' is a species of freshwater gastropod, an aquatic gastropod mollusc within the family Acochlidiidae. References Acochlidiidae Gastropods described in 1892 {{Heterobranchia-stub ...

'' (Strubell, 1892) (Acochlidiidae) – freshwater # ''

Acochlidium bayerfehlmanni ''Acochlidium bayerfehlmanni'' is a species of freshwater gastropod, an aquatic gastropod mollusc within the family Acochlidiidae. The specific name ''bayerfehlmanni'' is in honour of Frederick Merkle Bayer and of Herman Adair Fehlmann, who ma ...

'' Wawra, 1980 (Acochlidiidae) – freshwater # ''

Acochlidium fijiiensis ''Acochlidium fijiiensis'' is a species of freshwater slug, an aquatic gastropod mollusc within the family Acochlidiidae. This species lives in two rivers on Fiji.Rudman W. B. (23 March 2010). "''Acochlidium fijiiensis'' Haynes & Kenchington, 19 ...

'' Haynes & Kenchington, 1991Haynes A. & Kenchington W. (1991). "''Acochlidium fijiiensis'' sp. nov. (Gastropoda: Opisthobranchia: Acochlidiacea) from Fiji". ''The Veliger'' 34(2): 166–171. (Acochlidiidae) – freshwater # ''

Palliohedyle sutteri ''Palliohedyle sutteri'' is a species of gastropods belonging to the family Acochlidiidae Acochlidiidae are a taxonomic family of shell-less freshwater gastropods (one of them '' Palliohedyle weberi'' lives in brackish water),Schrödl M. & N ...

'' (Wawra, 1979) (Acochlidiidae) – freshwater # '' Palliohedyle weberi'' (Bergh, 1895) (Acochlidiidae) – in brackish waters # '' Tantulum elegans'' Rankin, 1979 (Tantulidae) – freshwater # ''

Asperspina brambelli ''Asperspina'' is a genus of sea slugs, marine gastropod mollusks within the clade Acochlidiacea. Taxonomy Asperspinidae has been listed as a synonym of Parhedylidae in the taxonomy of Bouchet & Rocroi (2005). Sensu Schrödl & Neusser (201 ...

'' (Swedmark, 1968) (Asperspinidae) # ''

Asperspina loricata ''Asperspina'' is a genus of sea slugs, marine gastropod mollusks within the clade Acochlidiacea. Taxonomy Asperspinidae has been listed as a synonym of Parhedylidae in the taxonomy of Bouchet & Rocroi (2005). Sensu Schrödl & Neusser (201 ...

'' (Swedmark, 1968) (Asperspinidae) # ''

Asperspina murmanica ''Asperspina'' is a genus of sea slugs, marine gastropod mollusks within the clade Acochlidiacea. Taxonomy Asperspinidae has been listed as a synonym of Parhedylidae in the taxonomy of Bouchet & Rocroi (2005). Sensu Schrödl & Neusser (201 ...

'' (Kudinskaya & Minichev, 1978) (Asperspinidae) # ''

Asperspina rhopalotecta ''Asperspina'' is a genus of sea slugs, marine gastropod mollusks within the clade Acochlidiacea. Taxonomy Asperspinidae has been listed as a synonym of Parhedylidae in the taxonomy of Bouchet & Rocroi (2005). Sensu Schrödl & Neusser (201 ...

'' Salvini-Plawen, 1973 (Asperspinidae) # ''

Asperspina riseri ''Asperspina'' is a genus of sea slugs, marine gastropod mollusks within the clade Acochlidiacea. Taxonomy Asperspinidae has been listed as a synonym of Parhedylidae in the taxonomy of Bouchet & Rocroi (2005). Sensu Schrödl & Neusser (201 ...

'' (Morse, 1976) (Asperspinidae) # '' Microhedyle gerlachi'' Marcus & Marcus, 1959 - synonym: ''

Parhedyle gerlachi ''Parhedyle'' is a genus of gastropods Gastropods (), commonly known as slugs and snails, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from salt ...

'' (Ev. Marcus & Er. Marcus, 1959) (Microhedylidae) # '' Microhedyle glandulifera'' (Kowalevsky, 1901) (Microhedylidae) # '' Microhedyle nahantensis'' (Doe, 1974) (Microhedylidae) # '' Microhedyle remanei'' (Er. Marcus, 1953) (Microhedylidae) # '' Ganitus evelinae'' Marcus, 1953 (Microhedylidae s.l. / Ganitidae) # '' Paraganitus ellynnae'' Challis, 1968 (Microhedylidae s.l. / Ganitidae) # '' Parhedyle cryptophthalma'' (Westheide & Wawra, 1974) (Microhedylidae) # '' Parhedyle odhneri'' (Ev. Marcus & Er. Marcus, 1955) - synonym: '' Microhedyle odhneri'' (Ev. Marcus & Er. Marcus, 1955) (Microhedylidae) # ''

Parhedyle tyrtowii ''Parhedyle'' is a genus of gastropods Gastropods (), commonly known as slugs and snails, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from salt ...

'' (Kowalevsky, 1900) (Microhedylidae) # ''

Pontohedyle brasilensis ''Pontohedyle'' is a genus of sea slugs, acochlidians, shell-less marine gastropod mollusks in the family Parhedylidae. Sea slugs in this genus are highly simplified and uniform. Distribution The genus ''Pontohedyle'' shows a circumtropical di ...

'' (Rankin, 1979) (Microhedylidae) # '' Pontohedyle joni'' Jörger & Schrödl, 2013 # ''

Pontohedyle kepii ''Pontohedyle'' is a genus of sea slugs, acochlidians, shell-less marine (ocean), marine gastropod mollusks in the family Parhedylidae. Sea slugs in this genus are highly simplified and uniform. Distribution The genus ''Pontohedyle'' shows a cir ...

'' Jörger & Schrödl, 2013 # '' Pontohedyle liliae'' Jörger & Schrödl, 2013 # '' Pontohedyle martynovi'' Jörger & Schrödl, 2013 # ''

'' (Kowalevsky, 1901) (Microhedylidae) # '' Pontohedyle neridae'' Jörger & Schrödl, 2013 # '' Pontohedyle peteryalli'' Jörger & Schrödl, 2013 # ''

Pontohedyle verrucosa ''Pontohedyle verrucosa'' is a species of sea slug, an acochlidian, a shell-less marine gastropod mollusc in the family Parhedylidae.Jörger K. M., Norenburg J. L., Wilson N. G. & Schrödl M. (2012). "Barcoding against a paradox? Combined molec ...

'' (Challis, 1970) (Microhedylidae) # '' Pontohedyle wenzli'' Jörger & Schrödl, 2013 # '' Pontohedyle wiggi'' Jörger & Schrödl, 2013 # ''

Pontohedyle yurihookeri ''Pontohedyle'' is a genus of sea slugs, acochlidians, shell-less marine gastropod mollusks in the family Parhedylidae. Sea slugs in this genus are highly simplified and uniform. Distribution The genus ''Pontohedyle'' shows a circumtropical di ...

'' Jörger & Schrödl, 2013 # '' Helicohedyle dikiki'' Drainas, Carlson, Jörger, Schrödl & Neusser, 2017 (unassigned to family) – marine

References

This article incorporates CC-BY-2.0 text from referencesJörger 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 ''BMC Ecology and Evolution'' (since January 2021), previously ''BMC Evolutionary Biology'' (2001–2020), is a peer-reviewed open access scientific journal covering all fields of evolutionary biology, including phylogenetics and palaeontology ...

'' 10: 323. .Jörger K. M., Norenburg J. L., Wilson N. G. & Schrödl M. (2012). "Barcoding against a paradox? Combined molecular species delineations reveal multiple cryptic lineages in elusive meiofaunal sea slugs". ''

'' 12: 245. . and CC-BY-SA-3.0 text from the reference.Gofas, S. (2010). Acochlidiacea. In: Bouchet, P.; Gofas, S.; Rosenberg, G. (2010) World Marine Mollusca database. Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=411937 on 2010-11-30

External links

Acochlidea on Sea Slug Forum
{{Taxonbar, from=Q1054947 Panpulmonata