16
VICTOR L. LOOSANOFF AND HARRY C. DAVIS
M . mercemria, and oysters, C . virginica, are taken from Long Island
Sound early in the season, usually late in May, long before the beginning
of their natural spawning, and transplanted to the waters of Maino,
where the summer temperature averages about 7" lower than in our
waters. This temperature, while permitting slow development of
gonads, is, nevertheless, low enough to prevent spawning. Thus, when
oysters and clams in Long Island Sound are already spent, those
transplanted to Maine still retain their spawn. In the fall, small groups
of these mollusks are routinely shipped back to our laboratory, where
they are easily induced to spawn, providing normal gametes which are
unobtainable locally during that time of the year.
By using the above method spawning of C. virgiiticu can be postponed only for 6 or 8 weeks after oysters of Long Island Sound are
completely spent. After that period the oysters, even if they are still
kept in the waters of Maine, begin to resorb undischarged gonad
material and, thereafter, become useless as spawners. We overcame
this difficulty by developing another useful method, which postpones
early gonad resorption. It consists of conditioning oysters early in the
spring and spawning them at Milford by early June. After that they
are transferred to the colder waters of Maine. Oysters treated in this
manner must resorb old gonads and build up glycogen before developing
new gonads. Because they are compelled to go through these processes,
these oysters reach ripeness much later in the season than those that
are planted in Maine without spring conditioning and spawning and,
aa a result, they do not begin to resorb gonad material aa early as do
unspawned oysters transferred to Maine at the same time. Taking
advantage of this Rituation we have: h n obtaining normal larvaa from
I3conu.rc~ M. mrrcenaria d o o H not, rtrnorh untlinchargod gonad material
in tho fall, an oynterH do, tranuforritig them to the coldor wtltern of Maino
in tlw xpritlg p v o d to he n highly HatiAfactory method of delaying
spawning. Under thea: conditions the clams retain sperm or eggs
throughout the summer imd, a8 a reuult, can be induced to spawn
throughout the next fall, winter and even during the following spring,
always producing gametes which develop into normal larvae.
We have a160 delayed spawning of clams and oysters by taking
these mollusks early in the summer from their natural habitat and
keeping them in insulated boxeH through which mochttriic~ll,y-oooled
sea water flowed. U~ually, only a uomparativcly Hrrinll numhor of
adult mollusks could be convenicn tly kept urrt1r:r ttieru: cc~rirlitior~
and, as a rule, bivalves so treated wcre in much jworcr conditiorr t h n
those kept under natural surroundings in the waters of Maine. More0Ck)tMtr .IfLflll&r,J' fr0m HpfbWrl Of OyHtA'rH HO !Jcl&h%l.
VICTOR L. LOOSANOFF AND HARRY C. DAVIS
M . mercemria, and oysters, C . virginica, are taken from Long Island
Sound early in the season, usually late in May, long before the beginning
of their natural spawning, and transplanted to the waters of Maino,
where the summer temperature averages about 7" lower than in our
waters. This temperature, while permitting slow development of
gonads, is, nevertheless, low enough to prevent spawning. Thus, when
oysters and clams in Long Island Sound are already spent, those
transplanted to Maine still retain their spawn. In the fall, small groups
of these mollusks are routinely shipped back to our laboratory, where
they are easily induced to spawn, providing normal gametes which are
unobtainable locally during that time of the year.
By using the above method spawning of C. virgiiticu can be postponed only for 6 or 8 weeks after oysters of Long Island Sound are
completely spent. After that period the oysters, even if they are still
kept in the waters of Maine, begin to resorb undischarged gonad
material and, thereafter, become useless as spawners. We overcame
this difficulty by developing another useful method, which postpones
early gonad resorption. It consists of conditioning oysters early in the
spring and spawning them at Milford by early June. After that they
are transferred to the colder waters of Maine. Oysters treated in this
manner must resorb old gonads and build up glycogen before developing
new gonads. Because they are compelled to go through these processes,
these oysters reach ripeness much later in the season than those that
are planted in Maine without spring conditioning and spawning and,
aa a result, they do not begin to resorb gonad material aa early as do
unspawned oysters transferred to Maine at the same time. Taking
advantage of this Rituation we have: h n obtaining normal larvaa from
I3conu.rc~ M. mrrcenaria d o o H not, rtrnorh untlinchargod gonad material
in tho fall, an oynterH do, tranuforritig them to the coldor wtltern of Maino
in tlw xpritlg p v o d to he n highly HatiAfactory method of delaying
spawning. Under thea: conditions the clams retain sperm or eggs
throughout the summer imd, a8 a reuult, can be induced to spawn
throughout the next fall, winter and even during the following spring,
always producing gametes which develop into normal larvae.
We have a160 delayed spawning of clams and oysters by taking
these mollusks early in the summer from their natural habitat and
keeping them in insulated boxeH through which mochttriic~ll,y-oooled
sea water flowed. U~ually, only a uomparativcly Hrrinll numhor of
adult mollusks could be convenicn tly kept urrt1r:r ttieru: cc~rirlitior~
and, as a rule, bivalves so treated wcre in much jworcr conditiorr t h n
those kept under natural surroundings in the waters of Maine. More0Ck)tMtr .IfLflll&r,J' fr0m HpfbWrl Of OyHtA'rH HO !Jcl&h%l.