Some aspects of the biology of sea stars Asterias vulgaris Verrill and Leptasterias polaris (Muller and Troschel) in Newfoundland waters

Kao, Ming-hsiung (1979) Some aspects of the biology of sea stars Asterias vulgaris Verrill and Leptasterias polaris (Muller and Troschel) in Newfoundland waters. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

The comparative respiratory metabolism of Asterias vulgaris and Leptasterias polaris was determined by oxygen consumption measurements in both whole organisms and excised tissues under different temperatures. Oxygen consumption was measured by using Winkler' s method for whole organisms and by the Warburg technique for excised tissues. Various levels of some important environmental factors influencing the oxygen consumption of whole sea stars were evaluated. Statistical analyses were applied to estimate and compare the effect of these factors on respiration in both species of sea stars. – The relation between the body weight of sea stars and oxygen consumption was expressed as a logarithmic linear regression. Regression lines of oxygen consumption of whole sea stars rise from 0°C to 5°C. The mean slope of the regression line was 0.72-0.89 for A. vulgaris and 0-75-0.92 for L. polaris. There is no significant difference in oxygen consumption of whole sea stars between the sexes within a species. L. polaris has a lower oxygen consumption than A. vulgaris except in the larger L. polaris at 15°C. The oxygen consumption rate of sea stars is dependent on the ambient oxygen content in the sea water. The relationship showed a curvilinear instead of simple linear correlation as general oxyconformer invertebrates do. The oxygen consumption rate decreases as the pH value in sea water is changed from normal sea water. The oxygen consumption rate of sea stars decreased more sharply with pH values above that of normal sea water (toward basic) compared to pH value below that of normal sea water. A. vulgaris is more sensitive than L. polaris to the pH effect. Salinity changes above or below the salinity of normal sea water also reduced oxygen consumption rate. Short-term food deprivation does not affect the oxygen consumption of sea stars. The oxygen consumption rate of various tissues in sea stars showed a tendency similar to that of whole sea stars, but the slopes varied greatly for different tissues. Some regression lines are not significant at the 5% level. It may be due to the different relative weights of various organs. Coelomic fluid exhibited the lowest oxygen uptake because there are few living cells in the fluid. The mature gonad of male sea stars indicate positive correlation between body weights and the oxygen consumption rate. This is as expected because the mature and full grown sea star would more likely possess active sperm. -- The moving speed of A. vulgaris is faster than that of L. ,polaris and is more sensitive to temperature change. The moving speed of sea stars is not related to body weight, but righting response time is a function of body weight. The smaller sea stars require less time to right themselves. When both species employed the same righting method, there was no significant difference between them. However, most larger sizes of L. Polaris quite often applied the tulip method which consumes more time than the rest. Temperature does affect the uptake of amino acids. A. vulgaris appears to have better absorption capacity at high temperature. On the other hand, L. polaris exhibits better ability at low temperature. A. vulgaris is distributed from Southern Labrador to Cape Hatteras. This species can be found in shallow water in Northern North America, but south of Long Island Sound, it is not found along the shore. Temperature limits their distribution to deeper and cooler water in more southern regions. Therefore, it is classified as a boreal species. On the other hand, L. Polaris occurs from the high Arctic region to Nova Scotia and can be recognized as an Arctic species.

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