Sciency Thoughts: Ayeyarwaddy River Basin

Showing posts with label Ayeyarwaddy River Basin. Show all posts

Saturday, 30 December 2023

Trimeresurus ayeyarwadyensis: A new species of Mangrove Pit Viper from the Ayeyarwady and Yangon regions in Myanmar.

The taxonomy of the Asian Pit Viper genus Trimeresurus have proved difficult to unravel, as species tend to be both similar to one-another and morphologically variable. The Mangrove Pit Vipers, Trimeresurus purpureomaculatus and Trimeresurus erythrurus are considered to form a species complex, with Trimeresurus purpureomaculatus being an obligate Mangrove-inhabitant with variable colouration and dark blotches on its back, found in southern Thailand, Peninsula Malaysia, and on the island of Sumatra, while Trimeresurus erythrurus is a green Snake lacking markings, found in but not restricted to Mangroves, found in northern Myanmar, and eastern Bangladesh and India. Between these, in southern Myanmar, is a population of Snakes which show a mixture of traits seen in the other two groups, which have been assumed to represent a zone of hybridization. However, a recent study of genetic structures within the group has suggested that this southern Myanmar population is actually a separate species, which forms a sister taxon to Trimeresurus purpureomaculatus, although this species does show signs of hybridizing with Trimeresurus erythrurus.

In a paper published in the journal ZooKeys on 13 December 2023, Kin Onn Chan of the Lee Kong Chian Natural History Museum at the National University of Singapore, and the School of Biological Sciences at the Universiti Sains Malaysia, Shahrul Anuar, also of the School of Biological Sciences at the Universiti Sains Malaysia, Ananthanarayanan Sankar of the Herpetological Society of Singapore, and the Department of Biological Sciences at the National University of Singapore, Ingg Thong Law and Ing Sind Law, also of the Herpetological Society of Singapore, Rasu Shivaram, also of the Lee Kong Chian Natural History Museum at the National University of Singapore, and of the Herpetological Society of Singapore, Ching Christian, again of the Herpetological Society of Singapore, and of the Department of Life Sciences at the Natural History Museum, Daniel Mulcahy of the Museum für Naturkunde at the Leibniz Institute for Evolution and Biodiversity Science, and Anita Malhotra of the School of Natural Sciences at Bangor University, formally describe the southern Myanmar Trimeresurus population as a new species.

The new species is named Trimeresurus ayeyarwadyensis, meaning 'from Ayeyarwady'; the species is known from the Ayeyarwady and Yangon regions on the Ayeyarwady delta in southern Myanmar. The species has partially fused first infralabial and nasal scales, a condition not seen in any other member of the genus Trimeresurus, but otherwise shows a mosaic of traits seen in other species.

An unvouchered, live specimen of Trimeresurus ayeyarwadyensis from the Yangon Region, Myanmar. Wolfgang Wüster in Chan et al. (2023).

Unhybridized populations of Trimeresurus ayeyarwadyensis were found in Mangrove forests in the Pyapon and Myaungmya districts of the Ayeyarwady Region, as well as in a forest surrounding a lake unconnected to any Mangrove system in the Hlawga Park in the Yangon Region. In the Pathein District of the Ayeyarwady Region a population of Trimeresurus ayeyarwadyensis hybridized with Trimeresurus erythrurus was found living alongside an unhybridized population of Trimeresurus erythrurus. Trimeresurus purpureomaculatus is known from the Dawei District in the Tanintharyi Region of Myanmar, and could potentially have a contact zone with Trimeresurus ayeyarwadyensis in Mon State, where no members of the genus Trimeresurus have been recorded, but this is thought likely to be due to a lack of searching rather than an absence of Snakes.

Tuesday, 7 February 2017

Devario fangae & Devario myitkyinae: Two new species of Striped Devario from northern Myanmar.

Devarios, Devario spp., are small freshwater Cyprinid Fish found in hillstreams across South and Southeast Asia. There are currently about 38 described species from Bhutan, India, Myanmar, Nepal, Pakistan, Sri Lanka, southern China, Cambodia, Laos, Malaysia, Vietnam, and Thailand, which can be divided into two groups, Barred and Striped Devarios, based upon their markings, though this probably does not reflect the true diversity of the group. There are currently six species listed from Myanmar, though one of these, Devario aequipinnatus, is almost certainly a misidentification.

In a paper published in the journal Zootaxa on 3 February 2017, Sven Kullander of the Department of Zoology at the Swedish Museum of Natural History describes two new species of Striped Devario from the Ayeyarwaddy River Basin in northern Myanmar.

The first new species is named Devario fangae, in honour of the late ichthyologist Fang Fang Kullander (wife of Sven Kullander), who first identified the new species, but sadly passed away before she was able to formally describe it. The species was found in hillstreams around Putao in Kachin State in March 1998, and is 43-61 mm in length. The specimens from which the species is described are pale creamish brown in colour with darker stripes, though they have been kept in preservative for over a decade and their original colour is unclear.

Devario fangae. (a) Male, 47.9 mm; (b) male 58.5 mm; (c) female, 49.2 mm. All from Kachin State, Putao, Ayeyarwaddy River drainage, Nan Hto Chaung. Kullander (2017).

The second new species is named Devario myitkyinae, in reference to the city of Myitkyina in Kachin State, near which it was discovered close to. The species is described from specimens collected from Hpa Lap stream in the upper Ayeyarwaddy River Basin by Fang Fang Kullander in 1997. These are 42.8-68.7 mm in length, and pale brown with a yellowish white belly and darker stripes in preservative, the original colour is unknown.

Devario myitkyinae. (a) Male , 65.8 mm; (b) male, 61.8 mm; (c) female, 56.7 mm. All from Myanmar: Kachin State, Ayeyarwaddy River drainage, Hpa Lap Chaung near Myitkyina. Kullander (2017).