Hyriopsis bialata (Simpson, 1900)

Ng, Ting Hui, Jeratthitikul, Ekgachai, Sutcharit, Chirasak, Chhuoy, Samol, Pin, Kakada, Pholyotha, Arthit, Siriwut, Warut, Srisonchai, Ruttapon, Hogan, Zeb S. & Ngor, Peng Bun, 2020, Annotated checklist of freshwater molluscs from the largest freshwater lake in Southeast Asia, ZooKeys 958, pp. 107-141 : 107

Hyriopsis bialata (Simpson, 1900) Fig. 3E

Unio delphinus Gruner, 1841: 276, pl. 9, fig. 1a-c. (non Spengler, 1793) Type locality: "sungi flumine, Malaccae".

Hyriopsis bialatus Simpson, 1900: 579. (new replacement name for Unio delphinus ).

Hyriopsis (Hyriopsis) bialatus : Brandt 1974: 272-273, pl.21, fig. 36.

Material examined.

CIFI.MOL.007, CIFI.MOL.008, CIFI.MOL.009, MUMNH.UNI.2618, MUMNH.UNI.2622, MUMNH.UNI.2627, MUMNH.UNI.2630, MUMNH.UNI.2635, MUMNH.UNI.2650, MUMNH.UNI.2652, MUMNH.UNI.2658, MUMNH.UNI.2662, ZRC.MOL.015644.

Distribution and habitat.

Tonle Sap River in Kampong Chhnang Province and Tonle Sap Lake at Kampong Chhnang and Siem Reap Provinces, Sen River in Kampong Thom Province, Sangkae River, Battambang Province (locality no. 8, 11, 16, 23, 27, 36, 37, 38 and 40); in soft muddy substrate.

Remarks.

Not sold for food, collected as by-catch of Corbicula and Mekongia harvests, and were often observed to be discarded along with other large unionids. At some parts of the Tonle Sap Lake, shells of Hyriopsis bialata were often covered in mats of Limnoperna fortunei and Sinomytilus harmandi . Hyriopsis bialata is widespread in Indochina, from Thailand to Peninsular Malaysia, and along the middle Mekong basin to the Mekong Delta in southern Vietnam ( Brandt 1974). Recent molecular analyses have revealed cryptic divergence in Hyriopsis bialata based on specimens from peninsular Malaysia and the Chao Phraya and Mekong basins ( Zieritz et al. 2016). Pending systematic revision of this species complex, the name Hyriopsis bialata is herein used for the species in Cambodia.

Figures

Figure 3. Freshwater bivalves of the Tonle Sap basin, Cambodia (Pharidae and Unionidae) A Novaculina siamensis B Bineurus mouhotii C Contradens contradens D Ensidens ingallsianus E Hyriopsis bialata F Hyriopsis delaportei G Monodontina cambodjensis H Physunio micropterus I Pilsbryoconcha linguaeformis J Pilsbryoconcha lemeslei and K Scabies mandarinus. Scale bars: 10 mm, unless stated otherwise. Photographs by K Macharoenboon.