REARING O F BIVALVE MOLLUSKS
71
Still another experiment showed that eggs and larvae of M . m,ercenaria can develop under even much more crowded conditions than we
have indicated thus far. In thiR expcrimcnt cultiirerr werc begun by
placing in rearing v e s d s 2b0, fj00, 7b0, 1000 rind 3000 ~ g g s pvr ml of
water. The cultures wcre incu t)ntctl r h t R tcrnpcmtirre of ahout 24'C
and examined st the end of 48 hr. 'I'hc majority of eggs rcarccl a t a
density of 'LBO per ml developed into normal straight-hinge larvae
(Fig. 25), while in cultures that were begun with 3000 eggs per ml,
most of the eggs failed to develop past morula stage and those few
that managed to develop to shelled stage were abnormal. In intermediate concentrations of BOO, 750 and 1000 larvae per ml some eggs
managed to dcvolop into normal straight-hitigo larvae Init thc' w numhcrs clecreasctl proportionally with each iricroase in the initial concentration of eggs.
Experiments on effects of crowding on growth of larvae of the
American oyster, C. virginica, were described by Davis (1953). He
used 640, 2 785, 18 518 and 32 918 48-hr-old larvae per liter and gave
all of these cultures the same quantity of food, namely, 50000 cells
of Chlorella per ml of water. A t the end of 14 days larvae from all
cultures werc! examined and measured. Rceults showed that there
was an invc:rst. relationship bctwcen conccntrations and rates of growth
of larvae. Thus, observations on Inrvac! of (1. viryinica were in agrccment with similar observations on clam Iarvac.
On the basis of our results we can conclude that the danger from
overcrowding larvae in well-maintained cultures may not be as acute
as believed. Nevertheless, crowding is undesirable because it decreases
rate of growth of larvae and, ot)viously, overcrowded larva(. are more
susceptible to diseases than are larvao in IPHS ~ P I I H P I Y ~ ~ ) p i i I ~ t C ! d
cultures.
71
Still another experiment showed that eggs and larvae of M . m,ercenaria can develop under even much more crowded conditions than we
have indicated thus far. In thiR expcrimcnt cultiirerr werc begun by
placing in rearing v e s d s 2b0, fj00, 7b0, 1000 rind 3000 ~ g g s pvr ml of
water. The cultures wcre incu t)ntctl r h t R tcrnpcmtirre of ahout 24'C
and examined st the end of 48 hr. 'I'hc majority of eggs rcarccl a t a
density of 'LBO per ml developed into normal straight-hinge larvae
(Fig. 25), while in cultures that were begun with 3000 eggs per ml,
most of the eggs failed to develop past morula stage and those few
that managed to develop to shelled stage were abnormal. In intermediate concentrations of BOO, 750 and 1000 larvae per ml some eggs
managed to dcvolop into normal straight-hitigo larvae Init thc' w numhcrs clecreasctl proportionally with each iricroase in the initial concentration of eggs.
Experiments on effects of crowding on growth of larvae of the
American oyster, C. virginica, were described by Davis (1953). He
used 640, 2 785, 18 518 and 32 918 48-hr-old larvae per liter and gave
all of these cultures the same quantity of food, namely, 50000 cells
of Chlorella per ml of water. A t the end of 14 days larvae from all
cultures werc! examined and measured. Rceults showed that there
was an invc:rst. relationship bctwcen conccntrations and rates of growth
of larvae. Thus, observations on Inrvac! of (1. viryinica were in agrccment with similar observations on clam Iarvac.
On the basis of our results we can conclude that the danger from
overcrowding larvae in well-maintained cultures may not be as acute
as believed. Nevertheless, crowding is undesirable because it decreases
rate of growth of larvae and, ot)viously, overcrowded larva(. are more
susceptible to diseases than are larvao in IPHS ~ P I I H P I Y ~ ~ ) p i i I ~ t C ! d
cultures.