Melayonchis

{{Short description|Genus of air-breathing marine slugs}} {{Automatic taxobox | image = | image_caption = | taxon = Melayonchis | authority = Dayrat & Goulding, 2017 | type_species = ''Melayonchis eloisae'' | type_species_authority = Dayrat, 2017 }}

'''''Melayonchis''''' is a genus of air-breathing, shell-less marine gastropods in the family Onchidiidae.<ref name="Dayrat2017">{{cite journal |last1=Dayrat |first1=Benoît |last2=Goulding |first2=Tricia C. |last3=Apte |first3=Deepak |last4=Bhave |first4=Vishal |last5=Ngô Xuân |first5=Quảng |title=A new genus and four new species of onchidiid slugs from South-East Asia (Mollusca: Gastropoda: Pulmonata: Onchidiidae) |journal=Journal of Natural History |date=2017 |volume=51 |issue=31–32 |pages=1851–1897 |doi=10.1080/00222933.2017.1347297}}</ref>Members of the genus are mangrove-associated slugs found in the intertidal zone of coastal Southeast Asia, where they live on tree trunks, stilt roots, dead logs, and other hard surfaces rather than on open mudflats.<ref name="Dayrat2017" /> The genus was first described in 2017 and currently contains six recognised species.<ref name="Dayrat2017" /><ref name="Dayrat2019">{{cite journal |last1=Dayrat |first1=Benoît |last2=Goulding |first2=Tricia C. |last3=Bourke |first3=Alan J. |last4=Khalil |first4=Mohd |last5=Tan |first5=Siong Kiat |title=New species and new records of ''Melayonchis'' slugs (Gastropoda: Euthyneura: Pulmonata: Onchidiidae) |journal=Raffles Bulletin of Zoology |date=2019 |volume=67 |pages=557–585 |doi=10.26107/RBZ-2019-0043}}</ref>

==Description== Members of ''Melayonchis'' are medium-sized onchidiid slugs with an elongated body and a dorsal notum covered in conical papillae, some of which bear dorsal eyes.<ref name="Dayrat2017" /> Like other onchidiids, they lack an external shell and breathe air using a lung rather than gills.<ref name="Dayrat2017" />

The genus can be distinguished from other onchidiids by internal anatomical characters, especially a distinctive protuberance on the inner lateral margin of the lateral teeth in the radula, a feature reported as unique within the family in the original description.<ref name="Dayrat2017" /> Species of ''Melayonchis'' also lack dorsal gills and marginal glands.<ref name="Dayrat2017" />

Species within the genus show varied defensive behaviour. For example, ''Melayonchis eloisae'' has been observed rolling into a tight ball when disturbed, while ''Melayonchis siongkiati'' secretes abundant oily mucus from the dorsal notum.<ref name="Dayrat2017" /> These behavioural traits have been noted as useful for field identification.<ref name="Dayrat2017" />

==Etymology== The generic name ''Melayonchis'' is derived from ''Melayu'', the Malay word for "Malay", combined with ''Onchis'', a historical name element used in onchidiid taxonomy.<ref name="Dayrat2017" /> The name refers to the Malay-region core of the genus's known distribution, particularly Peninsular Malaysia, Singapore, and coastal Borneo.<ref name="Dayrat2017" />

==Taxonomy== ''Melayonchis'' was first described in 2017 during a systematic revision of the family Onchidiidae.<ref name="Dayrat2017" /> The genus was erected for a distinct clade of onchidiid slugs for which no previously available generic name was considered applicable.<ref name="Dayrat2017" /> The type species is ''Melayonchis eloisae''.<ref name="Dayrat2017" />

The genus was originally described with four species from Southeast Asia.<ref name="Dayrat2017" /> Two additional species were described in 2019, bringing the total number of recognised species to six.<ref name="Dayrat2019" />

===Species=== ''Melayonchis'' contains the following species:<ref name="Dayrat2017" /><ref name="Dayrat2019" />

* ''Melayonchis aileenae'' Dayrat & Goulding, 2017 * ''Melayonchis annae'' Dayrat, 2017 * ''Melayonchis eberlyi'' Dayrat & Goulding, 2019 * ''Melayonchis eloisae'' Dayrat, 2017 * ''Melayonchis siongkiati'' Dayrat & Goulding, 2017 * ''Melayonchis tillieri'' Dayrat, 2019

==Distribution and habitat== thumb|right| Mangrove forest habitats typical of ''Melayonchis'' species in Southeast Asia ''Melayonchis'' is distributed from the Andaman Islands and the Andaman Sea eastward through the Strait of Malacca to the South China Sea.<ref name="Dayrat2017" /> The original description recorded species from the Andaman Islands, Peninsular Malaysia, Singapore, Brunei, and Vietnam.<ref name="Dayrat2017" /> Subsequent records expanded the known range to eastern Sumatra and the Northern Territory of Australia.<ref name="Dayrat2019" />

Species of ''Melayonchis'' are strictly associated with mangrove habitats in the upper intertidal zone.<ref name="Dayrat2017" /> They are typically found on the stilt roots and bark of ''Rhizophora'' trees, on decaying logs, and occasionally on artificial hard surfaces such as concrete drainage channels near the high-tide line.<ref name="Dayrat2017" /> They are generally absent from exposed mudflats.<ref name="Dayrat2017" />

==Ecology== Like other members of the Onchidiidae, ''Melayonchis'' species are marine slugs that breathe air and are active when exposed during low tide.<ref name="Dayrat2017" /> Their larvae develop in the sea, but adults are associated with emergent mangrove substrates and cannot remain submerged for prolonged periods.<ref name="Dayrat2017" />

The dorsal surface is often coated with a thin layer of muddy mucus, which may provide camouflage against bark and woody mangrove substrates.<ref name="Dayrat2017" /> This cryptic covering, together with their preference for mangrove roots and logs, makes living individuals difficult to detect in the field.<ref name="Dayrat2017" />

==References== {{Reflist}}

==External links== * [https://www.inaturalist.org/taxa/710838-Melayonchis ''Melayonchis''] on iNaturalist

Category:Onchidiidae Category:Gastropod genera