54
used in his experiments were the Same as those enxplogfh(l i)y horanoff
and Tominers (1948) in their st1ltljc.s 0 1 1 behavior of atfillt O.yst(’rs.
Thry wwc fine silt collected frorii t j(jjtl f{ats, kmliii (alr~mitriurn silicatcb),
powdered chalk and Fuller’s cart h.
Davis showed that silt was considerably more harmful to eggs of
oysters, C. cirginica, than t o those of clams, M , mmenaria. For
example, in concentrations of 0-25 g/l of silt only 737& of oyster eggs
survived, while more than 95% of clam eggs developed to straighthinge stage. Practically all clam eggs developed to straight-hinge stage
in concentrations of 0.5 g/l of silt, while only 31% of oyster eggs
survived.
I n a suspension of kaolin and Fuller’s earth, on the other hand,
clam eggs showed much higher mortality than eggs of oysters. Thus,
in concentrations of 1 g of these substances per liter of sea water,
practically all oyster eggs developed to straight-hinge stage, while
only 31% and 57% of clam eggs Survived.
Strangely enough, of the materials which were tested in these
experiments, silt, a natural substance, was more harmful to oyster
eggs than either kaolin or Fuller’s wrth. While practically none of the
eggs exposed to 1 g/l of silt rcachtd straight-hinge stage, some eggu
developed normally even iri conccntrations as heavy as 4 g/l of kaolin
or Fuller’s earth.
As in the case of eggs of thcsc: t w o specieB, silt was more harmful to
oyster larvae than to clam larvae. At a concentration of 0.75 g/1 of
silt growth of oyster larvae was markedly decreased while, a4 a striking
contrast, clam larvae grew normally even in 1 g/l of silt. Moreover,
the majority of the clam larvae survived for 12 days and even showed
lome growth in 3 and 4 g/l although it is doubtful that they could
reach metamorphosis under these conditions.
Kaolin and Fuller’s earth were considerably more harmful to clam
larvae than to oyster larvae. Concentrations of 0.5 g/l of kaolin
caused about 5076 mortality of clam larvae in 12 days and, while
Practically no clam larvae survived in concentrations of 1 g/1 of either
kaolin 01‘ Fuller’s earth, growth of oyster larvae was not appreciably
affected by 1 g/l of kaolin. Davis also found that some oyster larvaR
may live as long as 14 days in concentrations of 2 g/l of silt and up
to ‘ d1 Of either kaolin or Fuller’s earth. These observations demonstrated an unusual ability of larvae of C. virginica to withstand highly
Of rivers where natural oyster be& arc found.
Creating IUdXrials were added to Water containing straj&-hjnge larvae
VICTOR L. LOOSANOFF ANI) HARRY c . D A V I S
turbid water, a situation often exifiting summer at o r near mouths
In several exPeriments, where small quantities of turbidity-
used in his experiments were the Same as those enxplogfh(l i)y horanoff
and Tominers (1948) in their st1ltljc.s 0 1 1 behavior of atfillt O.yst(’rs.
Thry wwc fine silt collected frorii t j(jjtl f{ats, kmliii (alr~mitriurn silicatcb),
powdered chalk and Fuller’s cart h.
Davis showed that silt was considerably more harmful to eggs of
oysters, C. cirginica, than t o those of clams, M , mmenaria. For
example, in concentrations of 0-25 g/l of silt only 737& of oyster eggs
survived, while more than 95% of clam eggs developed to straighthinge stage. Practically all clam eggs developed to straight-hinge stage
in concentrations of 0.5 g/l of silt, while only 31% of oyster eggs
survived.
I n a suspension of kaolin and Fuller’s earth, on the other hand,
clam eggs showed much higher mortality than eggs of oysters. Thus,
in concentrations of 1 g of these substances per liter of sea water,
practically all oyster eggs developed to straight-hinge stage, while
only 31% and 57% of clam eggs Survived.
Strangely enough, of the materials which were tested in these
experiments, silt, a natural substance, was more harmful to oyster
eggs than either kaolin or Fuller’s wrth. While practically none of the
eggs exposed to 1 g/l of silt rcachtd straight-hinge stage, some eggu
developed normally even iri conccntrations as heavy as 4 g/l of kaolin
or Fuller’s earth.
As in the case of eggs of thcsc: t w o specieB, silt was more harmful to
oyster larvae than to clam larvae. At a concentration of 0.75 g/1 of
silt growth of oyster larvae was markedly decreased while, a4 a striking
contrast, clam larvae grew normally even in 1 g/l of silt. Moreover,
the majority of the clam larvae survived for 12 days and even showed
lome growth in 3 and 4 g/l although it is doubtful that they could
reach metamorphosis under these conditions.
Kaolin and Fuller’s earth were considerably more harmful to clam
larvae than to oyster larvae. Concentrations of 0.5 g/l of kaolin
caused about 5076 mortality of clam larvae in 12 days and, while
Practically no clam larvae survived in concentrations of 1 g/1 of either
kaolin 01‘ Fuller’s earth, growth of oyster larvae was not appreciably
affected by 1 g/l of kaolin. Davis also found that some oyster larvaR
may live as long as 14 days in concentrations of 2 g/l of silt and up
to ‘ d1 Of either kaolin or Fuller’s earth. These observations demonstrated an unusual ability of larvae of C. virginica to withstand highly
Of rivers where natural oyster be& arc found.
Creating IUdXrials were added to Water containing straj&-hjnge larvae
VICTOR L. LOOSANOFF ANI) HARRY c . D A V I S
turbid water, a situation often exifiting summer at o r near mouths
In several exPeriments, where small quantities of turbidity-