Lunar cycles of coho salmon, Oncorhynchus kisutch. II. Scale amino acid uptake, nucleic acids, metabolic reserves and plasma thyroid hormones.
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[14C]glycine uptake by scales in vitro was measured in coho salmon (Oncorhynchus kisutch Walbaum) smolts at different times during several semi-lunar cycles. There was a clear cyclical pattern of glycine uptake during the semi-lunar period. Evidence for semi-lunar cycles of liver and muscle RNA:DNA ratios, carcass water content, haematocrit, and plasma triglyceride, glucose and cholesterol levels was also found in coho salmon parrs. Plasma L-thyroxine (T4) levels exhibited a cyclical pattern during the semi-lunar cycle in parrs sampled in March when plasma T4 levels tended to be low, but no such pattern was seen in parrs sampled in January when the plasma T4 levels were relatively high (1.39-1.88 micrograms dl-1 in January compared with 0.38-0.83 micrograms dl-1 in March). There were no apparent semi-lunar cycles in liver mass:body mass ratios and plasma triiodo-L-thyronine (T3) levels. Changes in growth parameters (nucleic acid levels and glycine uptake by scales) and the content of nutrient reserves are discussed in relation to the semi-lunar patterns of growth in length, growth in mass, and food intake in this species. (+info)
Lunar cycles of coho salmon, Oncorhynchus kisutch. I. Growth and feeding.
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Coho salmon (Oncorhynchus kisutch Walbaum) parrs and smolts, maintained in a laboratory under a fixed artificial 12 h light:12 h dark photoperiod from the time of hatching, exhibited a pattern of alternating periods of rapid and slow growth in body mass; the peaks and troughs in growth rate were significantly different from one another. The alternating growth rate changes were rhythmic in nature, of approximately 14 to 15 days in length. Evidence for cyclic patterns of growth in relative length and in food consumption was also found in coho salmon parr. Peak food intake appeared to occur 2-4 days after each peak of growth in relative mass. Although the pattern of growth in relative length was less clear, there was evidence to suggest that growth in length might be out of phase with growth in mass. There was no pattern of cycling growth rates in coho salmon parr subsampled from a common stock. The significance of this is discussed. The data suggest that the lunar cycle acts as a Zeitgeber for synchronization of the growth rate rhythms. (+info)
X-ray and molecular emission from the nearest region of recent star formation.
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The isolated, young, sunlike star TW Hya and four other young stars in its vicinity are strong x-ray sources. Their similar x-ray and optical properties indicate that the stars make up a physical association that is on the order of 20 million years old and that lies between about 40 and 60 parsecs (between about 130 and 200 light years) from Earth. TW Hya itself displays circumstellar CO, HCN, CN, and HCO+ emission. These molecules probably orbit the star in a solar-system-sized disk viewed more or less face-on, whereas the star is likely viewed pole-on. Being at least three times closer to Earth than any well-studied region of star formation, the TW Hya Association serves as a test-bed for the study of x-ray emission from young stars and the formation of planetary systems around sunlike stars. (+info)