Parames Laosinchai

Phylogenetic Analysis of Parasitic Trematodes of the Genus Euclinostomum Found in Trichopsis and Betta Fish

Abstract:  Many species of fish in the world are infected with digenean trematodes belonging to the genera Clinostomum and Euclinostomum. In this study, metacercariae, identified as Euclinostomum sp. on the basis of morphological characteristics and molecular data, were taken from 3 osphronemid fish—Trichopsis vittata, Trichopsis schalleri, and Betta imbellis, in Thailand. Phylogenetic analysis based on a mitochondrial gene (cytochrome c oxidase subunit I) and 2 nuclear genes (18S rDNA and ITS—internal transcribed spacer) of these Euclinostomum parasites indicated a clear distinction from those belonging to the Clinostomum genus. These are the first records of partial mitochondrial and nuclear DNA sequences of an Euclinostomum sp.

Southeast Asian mouth-brooding Betta fighting fish (Teleostei: Perciformes) species and their phylogenetic relationships based on mitochondrial COI and nuclear ITS1 DNA sequences and analyses.

Fighting fish species in the genus Betta are found in several Southeast Asian countries. Depending on the mode of paternal care for fertilized eggs and hatchlings, various species of the betta fish are classified as mouth brooders or nest builders whose members in turn have been grouped according to their similarities mainly in morphology. The mouth brooders as well as some nest builders involved in the present study include fishes discovered and identified subsequent to previous reports on species groupings and their positions on phylogenetic trees based on DNA sequences that differ from those used by us in this study. From the mitochondrial COI gene and nuclear ITS1 gene sequences and more accurate analyses we conclude that the following members of the mouth-brooding pairs, named differently previously, are virtually identical, viz the Betta prima–Betta pallida pair and Betta ferox–Betta apollon pair. The Betta simplex, hitherto believed to be one species, could possibly be genetically split into 2 distinct species. In addition, several other established type-locality fishes could harbor cryptic species as judged by genetic differences. Assignments of fish species to groups reported earlier may have to be altered somewhat by the present genetic findings. We propose here a new Betta fish phylogenetic tree which, albeit being similar to the previous ones, is clearly different from them. Our gene-based evidence also leads to assignments of some fishes to new species groups and alters the positions of some species on the new phylogenetic tree, thus implying different ancestral relationships.

Mitochondrial COI and nuclear RAG1 DNA sequences and analyses of specimens of the three morphologically established species in the genus Trichopsis (Perciformes: Osphronemidae) reveal new/cryptic species

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.

A Demonstration Setup to Simulate Detection of Planets outside the Solar System.

We constructed a simple demonstration setup to simulate an extrasolar planet and its star revolving around the systems centre of mass. Periodic dimming of light from the star by the transiting planet and the stars orbital revolution simulate the two major ways of deducing the presence of an exoplanet near a distant star. Apart from being a visual aid for those needing help, the setup also elicited unexpected questions and suggestions from students, who achieved a fairly good level of understanding of the basis for the transit and radial velocity methods.

Morphology and molecular phylogeny of Macrobrachium suphanense sp. nov. (Decapoda: Palaemonidae) from Thailand

A small freshwater prawn in Thailand has been found to be a new species and is named Macrobrachium suphanense (Decapoda: Palaemonidae). Fully grown male M. suphanense appeared very different from the most closely related male of M. sintangense: size smaller, second pereiopod smaller and less robust, rostrum form different and, in females, fewer eggs. Less closely related, fully grown M. dolatum has sharper distal cutting edge on fixed finger and M. hungi has longer rostrum than M. suphanense. DNA analyses put M. suphanense, M. sintangense and M. nipponense in the same clade with M. nipponense sister to the other two. Two more clades consist of M. dienbienphuense and M. niphanae on the one hand and M. lanchesteri and M. rosenbergii on the other. The relationship among the three clades is not clearly resolved.