The freshwater mussel fauna of Borneo is highly endemic, with at least 11 species being unique to that island. Most of these species have not been recorded for at least 50 years owing to a lack of sampling effort and large-scale habitat destruction and degradation. Surveys conducted in 2016 across much of Malaysian Borneo failed to locate four out of five native species historically recorded in the study area. The present study aimed to determine the diversity and distribution of freshwater mussels of Brunei and adjacent Limbang Division, Malaysia. In 2018, we conducted interviews with locals, recorded environmental data and surveyed mussels at 43 sites, and conducted interviews at a further 38 sites. Only one population of native mussels, i.e. Ctenodesma borneensis, was found in a small tributary of the Limbang River situated in a patch of intact rainforest, representing the first record of this Bornean endemic genus since 1962. In addition, Sinanodonta lauta was found in a pond in Lawas district, representing the first record of this species outside its native East Asian distribution. Our data suggest that C. borneensis can sustain populations in relatively undisturbed habitats and is likely to have suffered population losses across northern Borneo. The first molecular phylogenetic analysis (COI + 28S) including an endemic Bornean freshwater mussel genus revealed that Ctenodesma is phylogenetically divergent from all other previously sampled lineages, rendering it a particularly valuable conservation target.

婆罗洲的淡水贻贝动物区系高度流行，该岛至少有11种独特。由于缺乏采样工作以及大规模的栖息地破坏和退化，至少有50年没有记录这些物种。2016年对马来西亚婆罗洲大部分地区进行的调查未能找到研究区域历史记录的五分之四的本地物种。本研究旨在确定文莱和马来西亚邻邻林邦省的淡水贻贝的多样性和分布。2018年，我们在43个地点对当地人进行了采访，记录了环境数据并调查了贻贝，并在另外38个地点进行了采访。贻贝只有一种种群，即伯氏梭状芽胞杆菌在一片完整的雨林中的林邦河的一条小支流中发现了该菌，这是该婆罗洲特有属自1962年以来的首次记录。该物种不在其本地东亚分布范围内。我们的数据表明，山楂衣原体可以维持相对未受干扰的生境中的种群，并有可能在婆罗洲北部遭受人口损失。包括特有的婆罗洲淡水贻贝属在内的首次分子系统发育分析（COI + 28S）表明，Ctenodesma与以前所有其他采样谱系在系统发育上均存在差异，使其成为特别有价值的保护目标。