34
VICTOR L. LOOSANOFF AND HARRY C. DAVIS
of larvae of M . mercenaria receiving Chlamydomonm sp. displayed
this abnormality, while the remaining 50% fed and grew at a normal
rate, as did all of the sibling larvae in other cultures receiving other
foods. A similar phenomenon was observed in American oyster larvae
fed Phaeodactylum tricornutum (Davis and Guillard, 1958).
While some anatomical abnormalities may interfere with the
ability of larvae to gather or ingest food, resulting in poor growth
and eventually death, other abnormalities, such as badly deformed
shells, may still permit larvae to feed and grow. Sometimes, as they
grow, such larvae gradually become more normal in appearance, but
usually remain distinguishable even when they are nearing metamorphosis.
Experimeiits on tolerance of eggs and larvae of bivalves to such
factors as turbidity and salinity, and to chemicals, such as pesticides,
antibiotics, and bacteriostatic compounds, have also shown that if
any one of these falls outside of the tolerated limits, embryonic development becomes affected, resulting either in death of the zygotes or in
abnormal larvae. These matters will be discussed in more detail later
in the article.
Some of the larvae, particularly those of the clam, M . mercenaria,
that are abnormal because of overcrowding, exposure to low temperatures or high turbidity during early stages of development often grow
t o metamorphosis if returned to favorable conditions and given good
food.
We
have frequently observed, during blooms of dinoflagellates in Milford
Harbor, that in our laboratory cultrire~ only a Rmall prrc:rlntag:e of
clam or oyster eggh d ~ ~ e 1 0 j ~ t : d
inho rrormal ntmigtit tiirigc! Isrvrrc~.
Eggs placed in, water from which dgae w m : rt$movcvl hy Millipor(!
filters showed only a slightly higher rate of normal d~:vc:loj)rnr:nt ttiari
eggs grown in unfiltered water containing dinoflagc:Il~~t~:~. Egg8 from
the same spawning8 but cultured in sea water co1lectr:d prior h the
bloom gave considerably higher percentages of normal IltrvrLc: ( IJavin
and Chanley, 1956b).
It may IJC addod that plrtnkt,ori sarriplm co1l~ctc:tl i r i I ~ ) t i l r ; l h n d
Sound t l u r i r i K o r iniawtliata~ly followitlg Iicvtvy dgnl t ) I o o r n H aro usiitLlly
rliuructcrixcd I b y tho nciwiby or wcm complete abwnce of early straighthinge stagex of bivalve larvae (hosanoff, 1958a). We believe that
reduction in numbers of normally developing bivalve eggs and larvae
ill t h a h v v iiistaiiccs is primarily caused by highly toxic metabolites
of algno thst may pcrsist for several days after the blooms have ended.
It is possible, however, that this phenomenon is due, at least in part,
Dense algal blooms may also cause abnormal development.
VICTOR L. LOOSANOFF AND HARRY C. DAVIS
of larvae of M . mercenaria receiving Chlamydomonm sp. displayed
this abnormality, while the remaining 50% fed and grew at a normal
rate, as did all of the sibling larvae in other cultures receiving other
foods. A similar phenomenon was observed in American oyster larvae
fed Phaeodactylum tricornutum (Davis and Guillard, 1958).
While some anatomical abnormalities may interfere with the
ability of larvae to gather or ingest food, resulting in poor growth
and eventually death, other abnormalities, such as badly deformed
shells, may still permit larvae to feed and grow. Sometimes, as they
grow, such larvae gradually become more normal in appearance, but
usually remain distinguishable even when they are nearing metamorphosis.
Experimeiits on tolerance of eggs and larvae of bivalves to such
factors as turbidity and salinity, and to chemicals, such as pesticides,
antibiotics, and bacteriostatic compounds, have also shown that if
any one of these falls outside of the tolerated limits, embryonic development becomes affected, resulting either in death of the zygotes or in
abnormal larvae. These matters will be discussed in more detail later
in the article.
Some of the larvae, particularly those of the clam, M . mercenaria,
that are abnormal because of overcrowding, exposure to low temperatures or high turbidity during early stages of development often grow
t o metamorphosis if returned to favorable conditions and given good
food.
We
have frequently observed, during blooms of dinoflagellates in Milford
Harbor, that in our laboratory cultrire~ only a Rmall prrc:rlntag:e of
clam or oyster eggh d ~ ~ e 1 0 j ~ t : d
inho rrormal ntmigtit tiirigc! Isrvrrc~.
Eggs placed in, water from which dgae w m : rt$movcvl hy Millipor(!
filters showed only a slightly higher rate of normal d~:vc:loj)rnr:nt ttiari
eggs grown in unfiltered water containing dinoflagc:Il~~t~:~. Egg8 from
the same spawning8 but cultured in sea water co1lectr:d prior h the
bloom gave considerably higher percentages of normal IltrvrLc: ( IJavin
and Chanley, 1956b).
It may IJC addod that plrtnkt,ori sarriplm co1l~ctc:tl i r i I ~ ) t i l r ; l h n d
Sound t l u r i r i K o r iniawtliata~ly followitlg Iicvtvy dgnl t ) I o o r n H aro usiitLlly
rliuructcrixcd I b y tho nciwiby or wcm complete abwnce of early straighthinge stagex of bivalve larvae (hosanoff, 1958a). We believe that
reduction in numbers of normally developing bivalve eggs and larvae
ill t h a h v v iiistaiiccs is primarily caused by highly toxic metabolites
of algno thst may pcrsist for several days after the blooms have ended.
It is possible, however, that this phenomenon is due, at least in part,
Dense algal blooms may also cause abnormal development.