66
VICTOR L. LOOSANOFF AND HARRY C. DAVIS
especially I. gaBana and M. Eutheri, are the best foods for larvae of
this oyster.
Imai et al. (1953) mentioned in several articles the successful use
of the colorless naked flagellate, Monas sp., as a food for oyster larvae.
Through the kindness of Dr. Imai we received a sample of a culture of
this organism and grew i t on a large scale. However, we have consistently been unable to raise larvae on a diet of this flagellate alone. I n
our controlled experiments larvae of M. mercenaria and C. virginica
grew and survived better in unfed controls than when given 4 000 cells
of M o w sp. per ml of water in culture vessels. Use of the same
flagellate by oyster biologists of the State of Washington (Lindsay,
personal communication), who also obtained these flagellates from
Dr. Imai, always resulted in failure. Our conclusion that colorless
flagellates are not a good food for bivalve larvae is also supported by
recent observations of Walne (1956), who could not raise larvae of
0. edulis by using another colorless flagellate, B& sp.
Growing of algal food for larval or juvenile mollusks, even if these
cultures do not need to be kept unialgal and bacteria-free, presents a
number of difficulties and, naturally, an easier method of producing
food for bivalves, including adults, is desirable. Our experience, in the
late 'thirties, in attempting to increase the glycogen content of adult
oysters by feeding them pulverized dried algae, such as different
species of Ulva and Laminaria, led us to try the same approach in
feeding larvae with dried algae. In the initial experiments dried and
pulverized Ulva, which we preserved and kept in a glass jar for over
20 years, was used. Surprisingly enough, many cultures of larvae of
M. mercenaria, given this food, grew to metamorphosis. However,
several problems were encountered in connection with this method.
First, it was found difficult to grind these algae into particles small
enough to be ingested by larvae. Secondly, the material quickly
settled on the bottom, thus becoming unavailable to swimming larvae.
Finally, because of rapid decomposition of unconsumed algae, the
larval cultures became fouled and the bacterial flora in them quickly
increased.
Fortunately, we have been able to overcome these difficultiea.
Through the courtesy of Dr. Hiroshi Tamiya of The Tokugawa Institute
for Biological Research in Tokyo, Japan, and Dr. Hiroshi Nakamura
of the Japanese Nutrition Association, we received samples of dried
Scenedamus sp. and ChloreUa sp. Because the average size of the
individual cells of both of these algae is small, they can be easily
ingested by larvae. By feeding proper quantities of dried, ground
Scenedesmus in larval cultures, which are continuouely agitated by
VICTOR L. LOOSANOFF AND HARRY C. DAVIS
especially I. gaBana and M. Eutheri, are the best foods for larvae of
this oyster.
Imai et al. (1953) mentioned in several articles the successful use
of the colorless naked flagellate, Monas sp., as a food for oyster larvae.
Through the kindness of Dr. Imai we received a sample of a culture of
this organism and grew i t on a large scale. However, we have consistently been unable to raise larvae on a diet of this flagellate alone. I n
our controlled experiments larvae of M. mercenaria and C. virginica
grew and survived better in unfed controls than when given 4 000 cells
of M o w sp. per ml of water in culture vessels. Use of the same
flagellate by oyster biologists of the State of Washington (Lindsay,
personal communication), who also obtained these flagellates from
Dr. Imai, always resulted in failure. Our conclusion that colorless
flagellates are not a good food for bivalve larvae is also supported by
recent observations of Walne (1956), who could not raise larvae of
0. edulis by using another colorless flagellate, B& sp.
Growing of algal food for larval or juvenile mollusks, even if these
cultures do not need to be kept unialgal and bacteria-free, presents a
number of difficulties and, naturally, an easier method of producing
food for bivalves, including adults, is desirable. Our experience, in the
late 'thirties, in attempting to increase the glycogen content of adult
oysters by feeding them pulverized dried algae, such as different
species of Ulva and Laminaria, led us to try the same approach in
feeding larvae with dried algae. In the initial experiments dried and
pulverized Ulva, which we preserved and kept in a glass jar for over
20 years, was used. Surprisingly enough, many cultures of larvae of
M. mercenaria, given this food, grew to metamorphosis. However,
several problems were encountered in connection with this method.
First, it was found difficult to grind these algae into particles small
enough to be ingested by larvae. Secondly, the material quickly
settled on the bottom, thus becoming unavailable to swimming larvae.
Finally, because of rapid decomposition of unconsumed algae, the
larval cultures became fouled and the bacterial flora in them quickly
increased.
Fortunately, we have been able to overcome these difficultiea.
Through the courtesy of Dr. Hiroshi Tamiya of The Tokugawa Institute
for Biological Research in Tokyo, Japan, and Dr. Hiroshi Nakamura
of the Japanese Nutrition Association, we received samples of dried
Scenedamus sp. and ChloreUa sp. Because the average size of the
individual cells of both of these algae is small, they can be easily
ingested by larvae. By feeding proper quantities of dried, ground
Scenedesmus in larval cultures, which are continuouely agitated by