Air-breathing fish species of the genus Trichopsis have been reported in Cambodia, Lao PDR, Indonesia, Malaysia, Singapore, Thailand and Vietnam. It is only in Thailand that all three recognized species (Trichopsis vittata, Trichopsis schalleri and Trichopsis pumila), as judged by distinct external features, are found. Cambodia and Lao PDR harbor two species each. The present work involves first-time DNA sequencing and analysis based on mitochondrial (COI) and nuclear (RAG1) DNA of numerous specimens of these species and specimens of a controversial Phetchaburi (Thailand) fish population with a mixed outward appearance. In addition to confirming the morphologically clear-cut taxonomic division of the three fish species, our DNA results show that whereas the T. pumila populations form one single species, there are cryptic species in the T. vittata and T. schalleri populations and possibly a new one in the latter. Members of the putative Phetchaburi fish population have been proven to be hybrids between T. pumila and T. vittata. In addition, a new the phylogenetic tree indicating ancestral relationships is also presented. This study should generate further research to find new/cryptic species of the genus Trichopsis in all countries harboring the fish.
Tilapia lake virus (TiLV) is an emerging pathogen in aquaculture, reportedly affecting farmed tilapia in 16 countries across multiple continents. Following an early warning in 2017 that TiLV might be widespread, we executed a surveillance programme on tilapia grow-out farms and hatcheries from 10 districts of Bangladesh in 2017 and 2019. Among farms experiencing unusual mortality, eight out of 11 farms tested positive for TiLV in 2017, and two out of seven tested positive in 2019. Investigation of asymptomatic broodstock collected from 16 tilapia hatcheries revealed that six hatcheries tested positive for TiLV. Representative samples subjected to histopathology confirmed pathognomonic lesions of syncytial hepatitis. We recovered three complete genomes of TiLV from infected fish, one from 2017 and two from 2019. Phylogenetic analyses based on both the concatenated coding sequences of 10 segments and only segment 1 consistently revealed that Bangladeshi TiLV isolates formed a unique cluster within Thai clade, suggesting a close genetic relation. In summary, this study revealed the circulation of TiLV in 10 farms and six hatcheries located in eight districts of Bangladesh. We recommend continuing TiLV-targeted surveillance efforts to identify contaminated sources to minimize the countrywide spread and severity of TiLV infection.