46
VICTOR, L. LOOSANOB’E’ A N D HARRY C . DAVIS
still not certain whethcr it is the presence of deleterious materials
or absence of growth-promoting siibstances in sea water that, slows
growth or prevents normal development of larvae.
W’e have observed that somc substances which interfere with
normal development of larvae may originate from sources to which
we have previously paid little attention. Under certain conditions
these substances may be released mechanically from bottom soil. This
was noticed during a winter when a deep channel was dredged in
Milford Harbor, from which our laboratory obtains its water. During
that period the water acquired certain properties whch strongly
interfered with normal development of eggs and larvae. These substances were apparently in solution or in fine colloidal suspension
because they were still present in the water after it was filtered.
Neither aeration nor ageing appreciably improved the quality of the
water.
Sensitivity of eggs and larvae to different substances dissolved in
sea water was further demonstrated by Davis and Chanley (1956b) in
a series of experiments which showed that, while low concentrations
of antibiotics may increase rate of’ growth of larvae, even a slight
excess of them reduces rate of growth. Progressively increasing concentrations of these substances corrrspondingly decrease rate of growth
of larvae and eventually cause their mortality. This mattcr will be
discussed in greater detail in the section devoted to larval diseases
and their treatment.
Recently. extensive studies on effects of r~umerous insecticides,
weedicides, oils, organic solvents and detergents on mollusks have been
undertaken at Milford Laboratory. While these studies are still in
progress, it has already been found (Davis, 1961) that within each
group of these compounds there are great differences in toxicity of
individual chemicals to eggs and larvae of bivalves. For example,
DDT was found to be one of the most toxic of the commonly used
insecticides because even at a concentration of 0.05 parts per million
it caused almost total mortality of oyster larvae. On the other hand,
another common insecticide, Lindane ( 1 , 2 , 3, 4, 5. 6 hexachlorocyclohexane), even at a concentration of 10 ppm, which is essentially a
saturated solution in sea water, caused no appreciable mortality of
larvae. On the contrary, growth of clam larvae in 5 ppm of Lindane
was somewhat faster than that of larvae in control cultures.
Certain concentrations of phenol, chloramphcnicol and Dowicide
“A”, among the antibiotic, bactericide and disinf‘cctant compounds
a180 appreciably improved rate of growth of bivalvc: larvae. Thiu iu
attributed to the action of these compounds which inhibits growth of
VICTOR, L. LOOSANOB’E’ A N D HARRY C . DAVIS
still not certain whethcr it is the presence of deleterious materials
or absence of growth-promoting siibstances in sea water that, slows
growth or prevents normal development of larvae.
W’e have observed that somc substances which interfere with
normal development of larvae may originate from sources to which
we have previously paid little attention. Under certain conditions
these substances may be released mechanically from bottom soil. This
was noticed during a winter when a deep channel was dredged in
Milford Harbor, from which our laboratory obtains its water. During
that period the water acquired certain properties whch strongly
interfered with normal development of eggs and larvae. These substances were apparently in solution or in fine colloidal suspension
because they were still present in the water after it was filtered.
Neither aeration nor ageing appreciably improved the quality of the
water.
Sensitivity of eggs and larvae to different substances dissolved in
sea water was further demonstrated by Davis and Chanley (1956b) in
a series of experiments which showed that, while low concentrations
of antibiotics may increase rate of’ growth of larvae, even a slight
excess of them reduces rate of growth. Progressively increasing concentrations of these substances corrrspondingly decrease rate of growth
of larvae and eventually cause their mortality. This mattcr will be
discussed in greater detail in the section devoted to larval diseases
and their treatment.
Recently. extensive studies on effects of r~umerous insecticides,
weedicides, oils, organic solvents and detergents on mollusks have been
undertaken at Milford Laboratory. While these studies are still in
progress, it has already been found (Davis, 1961) that within each
group of these compounds there are great differences in toxicity of
individual chemicals to eggs and larvae of bivalves. For example,
DDT was found to be one of the most toxic of the commonly used
insecticides because even at a concentration of 0.05 parts per million
it caused almost total mortality of oyster larvae. On the other hand,
another common insecticide, Lindane ( 1 , 2 , 3, 4, 5. 6 hexachlorocyclohexane), even at a concentration of 10 ppm, which is essentially a
saturated solution in sea water, caused no appreciable mortality of
larvae. On the contrary, growth of clam larvae in 5 ppm of Lindane
was somewhat faster than that of larvae in control cultures.
Certain concentrations of phenol, chloramphcnicol and Dowicide
“A”, among the antibiotic, bactericide and disinf‘cctant compounds
a180 appreciably improved rate of growth of bivalvc: larvae. Thiu iu
attributed to the action of these compounds which inhibits growth of