-- a j - 7
VICTOIC L. LOOSANOFI.’ A N D IIAHRY C . DAVIS
chemical agents, or by improving the methods of stripping w e n better
results may 1~ obtained.
Finitlly. tlicixl ucre scvcrnl qwcit~s of’ I)ivalvcs wliic.11 W P ooulti
ncitlirr spawn artificidly nor c w l l w t t I i c h i r normally tlisc~lmrgcd eggs.
Moreowr, eggs strippcd from somc. of thew: forms coultl not bc. ftirtiliacd
regardless of various prtxparatory measures, which includcd the
chemical treatment described above.
Fecundity of many lamellibranchs, especially those of commercial
importance, has been speculated upon for a long time. Brooks (1880)
estimated that C. virginica could produce between 18 750 000 and
125 000 000 eggs. He based his estimate upon volume of material
removed from the ripe female, but stated that this figure should be
reduced by approximately 50% because of other matter that was
measured together with eggs. Churchill (1920) stated that a large
oyster may discharge 60 million eggs, while Galtsoff (1930) estimated
that the number of eggs released in a single spawning may range
between 15 and 115 million. He concluded that the maximum
number of eggs that can be released by a single female during the
entire spawning season is approximately half a billion. Burkenroad
(1947), without offering any experimental observations of his own,
suggested that Galtsoff’s estimate was approximately ten times too
high. Belding (1912) estimated that M . mercenaria, 2 $ in long, produces
an average of 2 million eggs, a figure not substantiated by experimental
studies.
Since reliable informat,ion on the fecundity of even the most commonly studied pelecypods was unavailable, experiments were undertaken by Davis and Chanley (1956h) to determine total numbers of
eggs actually produced by individual oysters, C. virginica, and clams,
M . mercenaria, under natural and artificial conditions.
The first series of observations was made on seventy-five oysters,
measuring from 39 to 4q in long, and on the same number of clams
approximately 3 to 4 in long.
The experiments were conducted in the laboratory during the winter, a most convenient period for proper conditioning of both clams
and oysters. Each bivalve was individually numbered and a complete
record was kept of its behavior during the entire experiment. The first
group of oysters composed of twenty-five individuals was spawned at
3-day intervals, the second group at 5-day intervals and the third
at 7-day intervals. In clams, which were also divided into three groups
of twenty-five individuals each, spawning was induced a t 3-, 7- and
14-day intervals. Spawning of these groups of clams and oysters was
continued a t the specified intervals for more than 2 months.
VICTOIC L. LOOSANOFI.’ A N D IIAHRY C . DAVIS
chemical agents, or by improving the methods of stripping w e n better
results may 1~ obtained.
Finitlly. tlicixl ucre scvcrnl qwcit~s of’ I)ivalvcs wliic.11 W P ooulti
ncitlirr spawn artificidly nor c w l l w t t I i c h i r normally tlisc~lmrgcd eggs.
Moreowr, eggs strippcd from somc. of thew: forms coultl not bc. ftirtiliacd
regardless of various prtxparatory measures, which includcd the
chemical treatment described above.
Fecundity of many lamellibranchs, especially those of commercial
importance, has been speculated upon for a long time. Brooks (1880)
estimated that C. virginica could produce between 18 750 000 and
125 000 000 eggs. He based his estimate upon volume of material
removed from the ripe female, but stated that this figure should be
reduced by approximately 50% because of other matter that was
measured together with eggs. Churchill (1920) stated that a large
oyster may discharge 60 million eggs, while Galtsoff (1930) estimated
that the number of eggs released in a single spawning may range
between 15 and 115 million. He concluded that the maximum
number of eggs that can be released by a single female during the
entire spawning season is approximately half a billion. Burkenroad
(1947), without offering any experimental observations of his own,
suggested that Galtsoff’s estimate was approximately ten times too
high. Belding (1912) estimated that M . mercenaria, 2 $ in long, produces
an average of 2 million eggs, a figure not substantiated by experimental
studies.
Since reliable informat,ion on the fecundity of even the most commonly studied pelecypods was unavailable, experiments were undertaken by Davis and Chanley (1956h) to determine total numbers of
eggs actually produced by individual oysters, C. virginica, and clams,
M . mercenaria, under natural and artificial conditions.
The first series of observations was made on seventy-five oysters,
measuring from 39 to 4q in long, and on the same number of clams
approximately 3 to 4 in long.
The experiments were conducted in the laboratory during the winter, a most convenient period for proper conditioning of both clams
and oysters. Each bivalve was individually numbered and a complete
record was kept of its behavior during the entire experiment. The first
group of oysters composed of twenty-five individuals was spawned at
3-day intervals, the second group at 5-day intervals and the third
at 7-day intervals. In clams, which were also divided into three groups
of twenty-five individuals each, spawning was induced a t 3-, 7- and
14-day intervals. Spawning of these groups of clams and oysters was
continued a t the specified intervals for more than 2 months.