Melayonchis
Genus of air-breathing marine slugs
From Wikipedia, the free encyclopedia
Melayonchis is a genus of air-breathing, shell-less marine gastropods in the family Onchidiidae.[1]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.[1] The genus was first described in 2017 and currently contains six recognised species.[1][2]
| Melayonchis | |
|---|---|
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Gastropoda |
| Order: | Systellommatophora |
| Family: | Onchidiidae |
| Subfamily: | Onchidiinae |
| Genus: | Melayonchis Dayrat & Goulding, 2017 |
| Type species | |
| Melayonchis eloisae Dayrat, 2017 | |
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.[1] Like other onchidiids, they lack an external shell and breathe air using a lung rather than gills.[1]
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.[1] Species of Melayonchis also lack dorsal gills and marginal glands.[1]
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.[1] These behavioural traits have been noted as useful for field identification.[1]
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.[1] The name refers to the Malay-region core of the genus's known distribution, particularly Peninsular Malaysia, Singapore, and coastal Borneo.[1]
Taxonomy
Melayonchis was first described in 2017 during a systematic revision of the family Onchidiidae.[1] The genus was erected for a distinct clade of onchidiid slugs for which no previously available generic name was considered applicable.[1] The type species is Melayonchis eloisae.[1]
The genus was originally described with four species from Southeast Asia.[1] Two additional species were described in 2019, bringing the total number of recognised species to six.[2]
Species
Melayonchis contains the following species:[1][2]
- 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
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Melayonchis is distributed from the Andaman Islands and the Andaman Sea eastward through the Strait of Malacca to the South China Sea.[1] The original description recorded species from the Andaman Islands, Peninsular Malaysia, Singapore, Brunei, and Vietnam.[1] Subsequent records expanded the known range to eastern Sumatra and the Northern Territory of Australia.[2]
Species of Melayonchis are strictly associated with mangrove habitats in the upper intertidal zone.[1] 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.[1] They are generally absent from exposed mudflats.[1]
Ecology
Like other members of the Onchidiidae, Melayonchis species are marine slugs that breathe air and are active when exposed during low tide.[1] Their larvae develop in the sea, but adults are associated with emergent mangrove substrates and cannot remain submerged for prolonged periods.[1]
The dorsal surface is often coated with a thin layer of muddy mucus, which may provide camouflage against bark and woody mangrove substrates.[1] This cryptic covering, together with their preference for mangrove roots and logs, makes living individuals difficult to detect in the field.[1]