Rumen flukes in the genus Fischoederius are neglected foodborne parasites of cattle in Asia. Fischoederius elongatus, first described in 1883 from a sample collected in Indonesia is the type-species of the genus and is found from South to East Asia. In this study Fischoederius spp were collected from cattle in Thailand. The flukes resembled F. elongatus and images of 48 specimens were taken and their DNA was isolated. The mtDNA sequence of the cytochrome c oxidase subunit I (COX1) gene was amplified by PCR and used for restriction analysis with MseI. Nine restriction patterns (A–I) were observed and the COX1 mtDNA sequence for each pattern was determined. Phylogenetic analysis clustered the nine COX1 sequences into five groups with 4.6–9.6 % sequence differences between the groups. This is beyond intragenic variation observed for the COX1 gene in other organisms and suggested that the analyzed specimens represented several species. A comparative transcriptome analysis of specimens with COX1 MseI patterns A, C, E supported this finding. The observed median base differences, both absolute and relative, in the protein coding sequences of 999 orthologs were similar to those between distinct fruit fly species. It is proposed that the genus Fischoederius contains undescribed species that follow the classic description of F. elongatus.

Fischoederius属的瘤胃吸虫是亚洲被忽视的牛食源性寄生虫。Fischoederius elongatus于 1883 年从印度尼西亚采集的样本中首次描述，是该属的典型种，分布于南亚至东亚。在这项研究中， Fischoederius spp 是从泰国的牛身上采集的。吸虫类似于F. elongatus并拍摄了 48 个样本的图像并分离了它们的 DNA。细胞色素 c 氧化酶亚基 I ( COX1 ) 的 mtDNA 序列) 基因通过 PCR 扩增并用于 MseI 限制性分析。观察到九种限制模式（A-I），并确定了每种模式的 COX1 mtDNA 序列。系统发育分析将九个 COX1 序列分为五组，组间序列差异为 4.6-9.6%。这超出了在其他生物体中观察到的COX1基因的基因内变异，并表明分析的标本代表了几个物种。对具有 COX1 MseI 模式 A、C、E 的标本进行的比较转录组分析支持了这一发现。在 999 个直系同源物的蛋白质编码序列中观察到的绝对和相对中值碱基差异与不同果蝇物种之间的碱基差异相似。建议Fischoederius属包含遵循F. elongatus经典描述的未描述物种。