Sunday 2 September 2018

Alionchis jailoloensis: A new species of Onchidiid Slug from the Mangroves of Halmahera, eastern Indonesia.

Onchidiid Slugs are shell-less Gastropods found almost exclusively in Mangroves and intertidal zones (though two species are found at high altitudes in Montane Rianforests in Borneo and the Philippines). Remarkably, unlike all other marine Gastropods, they are air-breathing Pulmonates, closely related to terrestrial Slugs and Snails, and cannot survive below the low-tide line, as if they are not periodically exposed to the air they will drown. Onchidiids reach their maximum diversity in Southeast Asia and Indonesia, but are found around the world, reaching as far north as Scotland and Alaska.

In a paper published in the journal Raffles Bulletin of Zoology on 21 May 2018, Tricia Goulding of the Department of Biology at Pennsylvania State University, and the Bernice Pauahi Bishop Museum, Munawar Khalil of the Department of Marine Science at Universitas Malikussaleh, Shau Hwai Tan of the Marine Science Laboratory and Centre for Marine and Coastal Studies at Universiti Sains Malaysia, and BenoƮt Dayrat, also of the Department of Biology at Pennsylvania State University, describe a new species of Onchidiid Slug from Halmahera Island in Indonesia.

The new species is named Alionchis jailoloensis, where 'Alionchis' honours Ali, an assistant of Alfred Russel Wallace during his travels in the Malay Archipelago, originally hired as a cook, but who went on to make a significant contribution to the study of Ornithology in the region, and 'jailoloensis' means 'from Jailolo', a small port on Halmahera, near where the species was discovered, and the  former name of the entire island. Alionchis jailoloensis is flattened with thick eyestalks and additional eyes on its dorsal surface, it is muddy brown in colour and reaches about 65 mm in length. 

Live specimens, Alionchis jailoloensis, Indonesia, Halmahera. (A) Dorsal view, 63 mm long; (B) Dorsal view, 48 mm long; (C) Dorsal view, holotype, 43 mm long); (D) Dorsal view, 64 mm long; (E) Dorsal view (the arrow points to the pneumostome), same as (A); (F) Dorsal view, 51 mm long); (G) Dorsal view, 61 mm long; (H) Lateral view, 69 mm long; (I) Ventral view, 33 mm long; (J) Ventral view, 45 mm long. Goulding et al. (2018).

Alionchis jailoloensis was found living on mudflats between trees in open Mangrove Forest. It appears to be endemic to the island of Halmahera (i.e. not found anywhere else), which is unusual for a Onchidiid Slug, as most species have quite wide distributions.

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