Integration of Morphology and the Mitochondrial Cox1 Gene to Identify Killifishes, Aplocheilus Species, in the Attanagalu River, Sri Lanka

Aplocheilus species, often known as killifishes, are popular in the aquarium trade and are used as biological control agents for mosquito larvae. They are endemic to Madagascar, Seychelles, and South-East Asia. Aplocheilus species were collected from the Attanagalu River in Sri Lanka, identified using morphological and meristic characters and subjected to truss analysis. The genomic DNA of fresh muscle tissues of 10 fish with different morphological features was amplified by targeting the Cox1 gene with FishF1 and FishR1 primers. The amplicons were sequenced and subjected to DNA homology search and phylogenetic analysis. According to morphological identification, A. dayi and A. parvus were identified, but the truss analysis did not differentiate between the two species. According to a homology search, out of eight sequences, two were best matched with A. werneri and the rest with A. blockii and phylogenetic analysis formed two separate clusters for two species. We propose that the two individuals showed a closer genetic relationship with A. werneri as A. dayi and those who showed a closer genetic relationship with A. blockii as A. parvus. Sequence diversity observed within the proposed two species revealed that intraspecies genetic variation exists in the two populations in the Attanagalu River. The present study suggests the presence of A. dayi and A. parvus in the Attanagalu River basin, along with the intraspecies genetic variations among individuals within species regarding the mitochondrial Cox1 gene.