Akihiro Takemura

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Corals perform simultaneous mass spawning around the full moon. Most Acropora species release gamete bundles, which are a complex of eggs and sperm, into the seawater. Then, gamete bundles are separated into eggs and sperm. Eggs are fertilized when sperm and eggs come in contact with each other. However, it is still unclear how sperm meet the eggs of the(More)
Rabbitfishes are known to spawn synchronously around the species-specific lunar phase. It is considered that they perceive and utilize cues from the moon in order to be synchronized gonadal development and spawning with the lunar cycle. Using the golden rabbitfish, Siganus guttatus, which spawns synchronously around the first quarter moon during the(More)
Currently, a large number of endovascular interventions are performed for treatment of intracranial aneurysms. For these treatments, correct positioning of microcatheter tips, microguide wire tips, or coils is essential. Techniques to detect such devices may facilitate endovascular interventions. In this paper, we describe an algorithm for tracking of(More)
Demembranated euryhaline tilapia Oreochromis mossambicus sperm were reactivated in the presence of concentrations in excess of 10(-6) M Ca(2+). Motility features changed when Ca(2+) concentrations were increased from 10(-6) to 10(-5) M. Although the beat frequency did not increase, the shear angle and wave amplitude of flagellar beating increased,(More)
To improve the accuracy and robustness of 2D/3D registration of digital subtraction angiography images and magnetic resonance angiography (MRA) data, we have developed an automatic method for anatomical labeling of the cerebral arteries in MRA data. The anatomical labeling method is a location-based method which segments an artery tree to branches and(More)
Wrasse species exhibit a definite daily rhythm in locomotor activity and bury themselves in the sand at the bottom of the ocean at night. It remains unclear how their behavior in locomotor activity is endogenously regulated. The aim of the present study was to clarify the involvement of melatonin and clock genes (Per1, Per2, Bmal1, and Cry1) in daily and(More)
Lunar cycle-associated physiology has been found in a wide variety of organisms. Recent study has revealed that mRNA levels of Cryptochrome (Cry), one of the circadian clock genes, were significantly higher on a full moon night than on a new moon night in coral, implying the involvement of a photoreception system in the lunar-synchronized spawning. To(More)
Ovarian development of the sapphire devil, Chrysiptera cyanea, exhibits photoperiodism and is stimulated under long-day conditions. Previous studies suggest that red light is more effective than green and blue lights for inducing ovarian development. In addition, the extra-retinal photoreception involved in the ovarian development is suggested in this(More)
Sequence variation of the mitochondrial DNA was analyzed to examine the genetic structure and demographic history of the goldlined spinefoot Siganus guttatus in the northwestern Pacific. In total, 451 nucleotide sequences spanning from the tRNAThr gene to the middle of the control region were determined from 254 specimens collected from five localities;(More)
Many tropical wrasses show a daily pattern of spawning with gamete release typically near daytime high tide. The environmental cues the fish obtains from day-night and tidal cycles to ensure spawning synchrony and how those cues are transduced, however, are not fully understood. To gain insight into these issues, the involvement of monoamines in mediating(More)