ABSTRACT
Thai medaka (Oryzias minutillus) are alternatively known as Thai rice-fish or dwarf medaka, and they widely inhabit natural freshwater environments in all regions of Thailand. In this study, we aimed to investigate the molecular genetics of the Thai medaka population in Thailand inferred from the mitochondrial control region (D-loop) and the cytochrome c oxidase subunit 1 (coxI) sequences. Furthermore, we examined RNA sequencing (RNA-seq) of adult males and females was performed with next-generation sequencing. Together, the combination of the D-loop and coxI sequences clearly distinguished the Thai medaka populations into 2 groups, such as group 1, which generally included samples from the central, northern, western, and eastern regions of the northeastern region. In this group, the fish populations seem to be a little monophyly in which the first subpopulation comprised the main samples from the northern and central regions. The second subpopulation commonly contained fish from the eastern region and specimens from the southern part of the central region near the Gulf of Thailand. Although these subgroups related to geographical distribution, bootstrap values were low in branch considered significant for both subgroups. Group 2 consisted of almost all samples from the southern population and those from the central and southern part of the northeastern region. Group 2 was found that it was made of samples from the northeastern region and samples from the southern population. A total of 73551 unigenes were identified after gene annotation. Signal transduction was the predominant protein classification among the Thai medaka orthologous groups. A differentially expressed gene (DEG) analysis identified 6 subclusters between both sexes that were composed of 257, 131, 364, 386, 114 and 108 genes. Phototransduction was the most enriched pathway and was highly expressed in males, while viral carcinogenesis, oocyte genesis, and the complement and coagulation cascades were highly expressed in females. Further details of these DEGs are discussed below. These results suggest that Thai medaka may genetically exhibit independent populations in the geographic habitats of Thailand. Moreover, these fish also reveal the genes that are conserved in other organisms and those that may be specific to this species.
ABSTRACT
Redclaw crayfish (Cherax quadricarinatus) is a decapod species originating from Australian freshwater. For more than two decades, these crayfish have been re-distributing to environments in many countries, including Thailand. Moreover, they can carry endosymbionts and/or ectosymbionts into new environments. The aim of this study was to introduce a morphological description of Pseudolevinseniella anenteron as a metacercaria of the endoparasites of redclaw crayfish collected from natural water sources in Thailand. The occurrence of two ectosymbiotic temnocephalans (Diceratocephala boschmai and Temnosewellia sp.) in C. quadricarinatus was also reported. The internal morphology of P. anenteron, D. boschmai and Temnosewellia were described and discussed. The surface ultrastructure of the multidentate spines on the body and the metacercarial cyst wall of P. anenteron was investigated by scanning electron microscopy (SEM). By performing a search of the GenBank nucleotide database of partial sequences of 18S, 28S rDNA and cytochrome c oxidase subunit I (cox1), P. anenteron was found to be related to Maritrema, and Temnosewellia was found to be related to T. fasciata. However, according to the cox1 gene, Temnosewellia was found to be similar to T. minor. These results reveal that redclaw crayfish that inhabit natural freshwaters in Thailand may harbour endoparasites and ecto- and endosymbionts. Furthermore, these findings may be able to monitor invasive or non-invasive species in an ecosystem.
