Real-time multiplex PCR for simultaneous detection of multiple species from environmental DNA: an application on two Japanese medaka species.

Information about species distribution is crucial to ecological studies. Environmental DNA (eDNA) analysis has recently been used to estimate the distribution of aquatic organisms. Several analytical methods including metabarcoding and species-specific PCR are being used for eDNA analysis.

Differences in the behavior and ecology of wild type medaka (Oryzias latipes complex) and an orange commercial variety (himedaka).

Genetic disturbance in wild populations of medaka (Oryzias latipes complex) has been mainly caused by the introduction of the orange-red commercial variety medaka (himedaka) in Japan. To examine whether survival, reproduction, and species recognition would be influenced by this difference in body coloration, we conducted three laboratory experiments (predatory pressure, mate choice, schooling behavior) using wild type medaka and himedaka. In the predation experiment using dark chub (Candidia temminckii) as a predator, himedaka were predated upon more often than wild type medaka.

FAK-mediated extracellular signals are essential for interkinetic nuclear migration and planar divisions in the neuroepithelium.

During the development of the vertebrate nervous system, mitosis of neural progenitor cells takes place near the lumen, the apical side of the neural tube, through a characteristic movement of nuclei known as interkinetic nuclear migration (INM). Furthermore, during the proliferative period, neural progenitor cells exhibit planar cell divisions to produce equivalent daughter cells. Here, we examine the potential role of extracellular signals in INM and planar divisions using the medaka mutant tacobo (tab).

Phenotypic analysis of a novel chordin mutant in medaka.

We have isolated and characterized a ventralized mutant in medaka (the Japanese killifish; Oryzias latipes), which turned out to have a mutation in the chordin gene. The mutant exhibits ventralization of the body axis, malformation of axial bones, over-bifurcation of yolk sac blood vessels, and laterality defects in internal organs. The mutant exhibits variability of phenotypes, depending on the culture temperature, from embryos with a slightly ventralized phenotype to those without any head and trunk structures.

Right-elevated expression of charon is regulated by fluid flow in medaka Kupffer's vesicle.

Recent studies have revealed that a cilium-generated liquid flow in the node has a crucial role in the establishment of the left-right (LR) axis in the mouse. In fish, Kupffer's vesicle (KV), a teleost-specific spherical organ attached to the tail region, is known to have an equivalent role to the mouse node during LR axis formation. However, at present, there has been no report of an asymmetric gene expressed in KV under the control of fluid flow.

Mutant analyses reveal different functions of fgfr1 in medaka and zebrafish despite conserved ligand-receptor relationships.

Medaka (Oryzias latipes) is a small freshwater teleost that provides an excellent developmental genetic model complementary to zebrafish. Our recent mutagenesis screening using medaka identified headfish (hdf) which is characterized by the absence of trunk and tail structures with nearly normal head including the midbrain-hindbrain boundary (MHB). Positional-candidate cloning revealed that the hdf mutation causes a functionally null form of Fgfr1.

Genetic structure of a Japanese allotetraploid loach of the genus Cobitis (Osteichthyes, Cobitidae).

The Japanese allotetraploid spined loach of the genus Cobitis "yamato complex" sensu SAITOH et al. (2000), distributed in Western Japan, originated from hybridization between C. biwae on the maternal side and C.

Genetic differentiation of piscivorous chub (genus Opsariichthys) in Japan, Korea and Russia.

A comparison of allozyme variation, restriction fragment length polymorphisms in the mitochondrial DNA and partial sequences of the ND II gene (496 bp) was made among two lacustrine populations of the piscivorous chub (Opsariichthys uncirostris uncirostris) in Japan, four fluvial populations in Korea, one lacustrine population in Russia and one specimen from the Amur River (O. u. amurensis).