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| เต่านาอีสาน | Malayemys isan |
Abstract
We describe a snail-eating turtle, Malayemys isan sp. nov., from the Mekong River Basin in northeastern Thailand (Nong Bua Lamphu, Nong Khai and Udon Thani provinces) and the adjacent Vientiane area in Laos. The new species is readily distinguishable from M. subtrijuga by its two (vs. six to nine) nasal stripes, and from both M. subtrijuga and M. macrocephala by its thin, often discontinuous, infraorbital stripe that never reaches the loreal seam. This geographically-restricted new species is sold in several food markets throughout the species' distribution and is in urgent need of conservation measures.
Keywords: Aquatic ecosystems, biodiversity, herpetofauna, Mekong, snail-eating turtle
Diagnosis: The new species is a medium-sized Malayemys species reaching a maximum carapace length of at least 152 mm in males and 206 mm in females, characterized by the consistent combination of (1) only two nasal stripes, (2) a thin, often discontinuous, infraorbital stripe that never reaches the loreal seam, (3) an uninterrupted supraorbital stripe, and (4) the absence of stripes or light spots between the infra- and supraorbital stripes.
การจำแนกชนิด: มีขีดสีขาวที่จมูก 2 ขีด แต่ละเส้นมักไม่ชนริมฝีปาก เส้นสีขาวที่ผ่านแนวใต้ตาโค้งขึ้นเล็กน้อยถึงระดับหลังจมูก ไม่ชนเส้นขาวที่ผ่านขอบบนของหัว ไม่มีเส้น/ขีดสีขาวระหว่างเส้นสีขาวที่ผ่านเหนือตาและใต้ตาในส่วนที่อยู่หลังตา ส่วนท้ายของกระหม่อมเป็นเส้นโค้งไปทางท้ายทอยชัดเจนและไม่เป็นมุมป้านยื่นไป สีท้องโดยรวมมีพื้นที่สีดำเข้มมากกว่าเต่านาชนิดอื่นๆ โดยเฉพาะเต่านาวัยเด็ก
การจำแนกชนิด: มีขีดสีขาวที่จมูก 2 ขีด แต่ละเส้นมักไม่ชนริมฝีปาก เส้นสีขาวที่ผ่านแนวใต้ตาโค้งขึ้นเล็กน้อยถึงระดับหลังจมูก ไม่ชนเส้นขาวที่ผ่านขอบบนของหัว ไม่มีเส้น/ขีดสีขาวระหว่างเส้นสีขาวที่ผ่านเหนือตาและใต้ตาในส่วนที่อยู่หลังตา ส่วนท้ายของกระหม่อมเป็นเส้นโค้งไปทางท้ายทอยชัดเจนและไม่เป็นมุมป้านยื่นไป สีท้องโดยรวมมีพื้นที่สีดำเข้มมากกว่าเต่านาชนิดอื่นๆ โดยเฉพาะเต่านาวัยเด็ก
Etymology: “Isan” is a Thai word designating the northeastern region of Thailand, where the type locality of the new species lies. It is here used as a noun in apposition, invariable.
We suggest the following common names: เต่านาอีสาน, Tao na Isan (Thai), Isan Snail-eating Turtle (English), Isan-Schneckenfresser (German), and Malayémyde d’Isan (French).
We suggest the following common names: เต่านาอีสาน, Tao na Isan (Thai), Isan Snail-eating Turtle (English), Isan-Schneckenfresser (German), and Malayémyde d’Isan (French).
Distribution and natural history: The species is nocturnal, aquatic and lives in shallow, stagnant or slow-moving freshwater bodies. The type series was collected in the Lampaniang River, which is part of the Nam Phong River system. The river has its source near Ban Na Klang and runs N-NE along Regional Roads 2097-2098-2020 towards Tha Bo District in Nong Khai Province where it flows into the Mekong marking the boundary between Thailand and Laos. The Malayemys macrocephala-morphotype from northeastern Thailand, mentioned without further details by Claude & Naksri (2014), is probably referrable to Malayemys isan sp. nov. We also refer the individual illustrated by Stuart & Platt (2004: 135: fig. 18), from Vientiane Municipality, Laos and identified by them as a M. subtrijuga, to the new taxon based on its lateral head color pattern showing a thin infraorbital stripe ending below the loreal seam. Kubota et al. (2015: 23) illustrated (under the name M. subtrijuga) a group of Malayemys isan sp. nov. on sale among snails in Thong Khan Kham market in Vientiane. Tha Bo is about 15 airline km south of Vientiane, and about 65 airline km from the type locality of Malayemys isan sp. nov. One can expect that the new species occurs in the entire river between Na Klang and Tha Bo districts. Typical Malayemys macrocephala and M. subtrijuga were also found on sale in the food markets of the Vientiane area by Suzuki et al. (2015). These authors suggested two possibilities for the occurrence of M. macrocephala in Vientiane markets: that individuals were imported from Thailand or Malaysia, or that the species occurs in Laos. In any case, the individual Suzuki et al. (2015) illustrated in their figure 2C is indeed a M. macrocephala, showing four nasal stripes and an infraorbital stripe reaching the loreal seam. There is a possibility that the live individual illustrated by Stuart & Platt (2004) was an escapee from a market. However, it was caught in the wild while crossing a road near a culvert in May 1999 (i.e. a typical habitat for Malayemys) and, zoogeographically speaking, Vientiane is immediately adjacent to the distributional area of Malayemys isan sp. nov. in Thailand. In addition to the series from Ban Na Klang, we observed individuals in ditches in Nong Bua Lamphu, Muang District, Nong Bua Lamphu Province and in Udon Thani, Muang District, Udon Thani Province. In Nong Bua Lamphu, the turtles were found in a muddy field flooded with shallow, transparent water, in strict syntopy with the freshwater snakes Homalopsis nigroventralis Deuve, 1970 and Hypsiscopus plumbeus (Boie, 1827) (Homalopsidae) (see Figs. 4, 8, 9A). The broad and flat triturating surface of the upper jaw is an indication that, similar to the other members of this genus, the new species is a specialized snail-eater. In fact, some individuals we kept in captivity readily consumed the indigenous freshwater snail Filopaludina martensi (Frauenfeld, 1864) (Gastropoda: Viviparidae) and exotic freshwater snails of the genus Pomacea Perry, 1810 (Gastropoda: Ampullariidae). This new turtle species is sold in large numbers in the food markets of Ban Na Klang, Nong Bua Lamphu and Udon Thani (MS, pers. obs.; Figs. 9, 10).
.Montri Sumontha, Timothy R. Brophy, Kirati Kunya, Suthep Wiboonatthapol and Olivier S. G. Pauwels. 2016. A New Snail-eating Turtle of the Genus Malayemys Lindholm, 1931 (Geoemydidae) from Thailand and Laos. TAPROBANICA. 8(1); 1–9.