. Bulletin of the United States Fish Commission. Fisheries -- United States; Fish-culture -- United States. EXPERIMENTAL STUDY OF THE OYSTER GILL ss shell open during a day is 17 hours 7 minutes; the median is 18 hours 5 minutes. In a preliminary paper published in 1926 (Galtsoff, 1926) it was stated that the average period of time the shells of an oyster arc open during a day is 20 hours. Nelson (1921), analyzing the records of 3 oysters kept under observation for 21 days, also states that on the average the oysters were open for 20 hours. The present investi- gation, based on more numerous o
. Bulletin of the United States Fish Commission. Fisheries -- United States; Fish-culture -- United States. EXPERIMENTAL STUDY OF THE OYSTER GILL ss shell open during a day is 17 hours 7 minutes; the median is 18 hours 5 minutes. In a preliminary paper published in 1926 (Galtsoff, 1926) it was stated that the average period of time the shells of an oyster arc open during a day is 20 hours. Nelson (1921), analyzing the records of 3 oysters kept under observation for 21 days, also states that on the average the oysters were open for 20 hours. The present investi- gation, based on more numerous observations, shows that the average period of time when the shells are open is smaller. The decrease of the average from 20 to 17 hoiu-s and 7 minutes is due to a few instances where the oysters failed to open during the 24-hour period. â An analysis of the records shows that when the shells are open the adductor mus- cle contracts and relaxes periodically. The contraction is often so shght that it does not result in a complete closing of the shell (fig. 11) and is of brief duration, the muscle beginning to relax immediately after the maximum contraction is reached. It has been shown by several investigators that by periodical contractions the NI6HTâ7. Fig. 11.âPart of the record of shell movements of two oysters made at 16° C. the pens when shells are closed Dotted lines indicate the position of oysters cleanse themselves and discharge the material that had accumulated in the paUial cavity. Although by this reaction the organism is able to get rid of the material accumulated by the gills, the inference that every contraction of the muscle is an ejection reaction is incorrect. Nelson (1921, p. 343) states that from observa- tion of the extent and frequency of the down strokes made by the oysters on the recording apparatus and representing the contraction of the adductor muscle, together with a knowledge of the turbidity of the water, it is possible to determin
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