REARING O F BIVALVE MOLLUSKS
95
larvae were already metamorphosing and the mean length was 181 p,
but some larvae only 128 p long were still present.
This experiment demonstrated, as we have pointed out on many
occasions, that it is obviously incorrect to relate the size of larvae to
their age because variations in size, even among larvae that originate
from the same parents, are of considerable magnitude. In cultures
that are grown at different temperatures and fed different foods these
differences are usually even more striking.
Some workers explain variations in size of larval fish originating
from eggs produced by the same female as dependent upon development of these eggs while still in the ovaries, including proximity of an
egg to large blood vessels which provide the best feeding conditions for
a single egg. Others explain the different rates of survival and growth
of fin fish larvae as dependent upon quantities of yolk in different eggs.
Possibly, the same considerations hold true and, in part, explain
variations in rate of growth of bivalve larvae that originate from eggs
discharged by the same female in the same spawning.
As is usually the case with larvae of most bivalves, their color varies
greatly in accordance with the color of the food microorganisms that
they are able to obtain from water. Larvae of M . edulis given heavy
doses of purple bacteria rapidly acquired a pinkish color, which was
most pronounced in the area of their digestive organs. If these larvae
were later fed green Chlorellu, their coloration changed to a greenish
tint and the livers became dark green. Contrary to Sullivan’s (1948)
contentions, no purple tint was observed around the shoulders of the
shell, even in advanced larval stages.
F. Anomia simplex D’Orbigny
A . simplex is a common bivalve of Long Island Sound, where it
propagates at approximately the same time as C . virginica. Because
of its more rapid growth immediately after setting, however, this
mollusk is a dangerous competitor, since it overgrows and completely
covers large numbers of recently set oysters (Loosanoff and Engle,
1941).
Descriptions of larvae of several species of Anomia are given by
students working in widely separated parts of the world. Stafford
(1912) gave a description of A . acubata; Miyazaki (1935) described
the larvae of the Japanese species, A . Zischkei, and Lebour (1938),
as well as Jmgensen (1946), described those of A . sqwlmula. More
recently, Sullivan (1948) also described larvae of A . aculeata, while
Rees (1950) made a brief reference to three species of Anomia. One
95
larvae were already metamorphosing and the mean length was 181 p,
but some larvae only 128 p long were still present.
This experiment demonstrated, as we have pointed out on many
occasions, that it is obviously incorrect to relate the size of larvae to
their age because variations in size, even among larvae that originate
from the same parents, are of considerable magnitude. In cultures
that are grown at different temperatures and fed different foods these
differences are usually even more striking.
Some workers explain variations in size of larval fish originating
from eggs produced by the same female as dependent upon development of these eggs while still in the ovaries, including proximity of an
egg to large blood vessels which provide the best feeding conditions for
a single egg. Others explain the different rates of survival and growth
of fin fish larvae as dependent upon quantities of yolk in different eggs.
Possibly, the same considerations hold true and, in part, explain
variations in rate of growth of bivalve larvae that originate from eggs
discharged by the same female in the same spawning.
As is usually the case with larvae of most bivalves, their color varies
greatly in accordance with the color of the food microorganisms that
they are able to obtain from water. Larvae of M . edulis given heavy
doses of purple bacteria rapidly acquired a pinkish color, which was
most pronounced in the area of their digestive organs. If these larvae
were later fed green Chlorellu, their coloration changed to a greenish
tint and the livers became dark green. Contrary to Sullivan’s (1948)
contentions, no purple tint was observed around the shoulders of the
shell, even in advanced larval stages.
F. Anomia simplex D’Orbigny
A . simplex is a common bivalve of Long Island Sound, where it
propagates at approximately the same time as C . virginica. Because
of its more rapid growth immediately after setting, however, this
mollusk is a dangerous competitor, since it overgrows and completely
covers large numbers of recently set oysters (Loosanoff and Engle,
1941).
Descriptions of larvae of several species of Anomia are given by
students working in widely separated parts of the world. Stafford
(1912) gave a description of A . acubata; Miyazaki (1935) described
the larvae of the Japanese species, A . Zischkei, and Lebour (1938),
as well as Jmgensen (1946), described those of A . sqwlmula. More
recently, Sullivan (1948) also described larvae of A . aculeata, while
Rees (1950) made a brief reference to three species of Anomia. One