THE BIOLOGY OF WOOD-BORING TEREDINID MOLLUSUS
407
D. Food of the larvae
Exact knowledge of the food of larvae is of great impoi tance if they
are to be cultured. Most bivalve larvae need to feed during their free
swimming stages and the provision of an adequate food is of utmost
importance (Walne, 1964). Failure to raise larvae of bivalves by earlier
investigators has been chiefly due to poor culture methods and want of
suitable food. Diseases have also been responsible for such failures
(Loosanoff and Davis, 1963). Yonge (1924) who reared the larvae of T.
norvegica (Spengler) in Plymouth found that the larvae lived on their
reserve food supply for as long a period as 14 days. Feeding on algae
(diatoms) was also observed from the tenth day. Many bivalve larvae
thrive on a diet of unicellular algae, sufficiently small to be swallowed
and having a suitable nutritive value. Using a culture of the nonpigmented flagellate, Monas, Imai and Hatanaka (1949) and Imai,
Hatanaka and Sat0 (1 950) successfully raised teredo larvae. However,
Loosanoff and Davis, (1963) who give instructions about larvae rearing,
and Walne (1956) consider that colourless flagellates are not good food
for bivalve larvae.
The activities of the larvae of T. bartschi Clapp previous to attachment to wood appear to rely mainly on glycogen stored in the oocytes
and perhaps also obtained later from the maternal gill. During the
first 24 h of free existence there is an increase in the rate of oxygen consumption (Lane and Greenfield, 1952)) probably owing to increased
ciliary activity or to the operation of glycogenic enzyme systems which
allow the completion of oxidative glycolysis. Then oxygen consumption
decreases rapidly up to 72 h, and more slowly until the larvae die after
about 300 h if they do not attain a suitable substrate (Lane et al., 1954).
The large endowment of glycogen with which the zygote begins its
existence is largely expended by the time the larva has penetrated
wood (Lane and Greenfield, 1952). Apart from utilizing the stored
glycogen, the larvae also feed on micro-organisms. Karande et al.
(1968) on the other hand found that the larvae of T. furcifera need no
food prior to settlement since larvae deprived of food by maintenance
in sterilized filtered sea water have successfully bored into timber even
after 4-5 days. The source of energy for the larvae has been attributed
to the stored glycogen only (Lane, 1955).
E. Settlement
Larvae are attracted to wood, at least in the sense that, should they
chance to encounter it, they remain upon it and there metamorphose.
This was established by Harrington (1922) who further suggested that
malic acid was the active constituent responsible for this. Yonge (see
407
D. Food of the larvae
Exact knowledge of the food of larvae is of great impoi tance if they
are to be cultured. Most bivalve larvae need to feed during their free
swimming stages and the provision of an adequate food is of utmost
importance (Walne, 1964). Failure to raise larvae of bivalves by earlier
investigators has been chiefly due to poor culture methods and want of
suitable food. Diseases have also been responsible for such failures
(Loosanoff and Davis, 1963). Yonge (1924) who reared the larvae of T.
norvegica (Spengler) in Plymouth found that the larvae lived on their
reserve food supply for as long a period as 14 days. Feeding on algae
(diatoms) was also observed from the tenth day. Many bivalve larvae
thrive on a diet of unicellular algae, sufficiently small to be swallowed
and having a suitable nutritive value. Using a culture of the nonpigmented flagellate, Monas, Imai and Hatanaka (1949) and Imai,
Hatanaka and Sat0 (1 950) successfully raised teredo larvae. However,
Loosanoff and Davis, (1963) who give instructions about larvae rearing,
and Walne (1956) consider that colourless flagellates are not good food
for bivalve larvae.
The activities of the larvae of T. bartschi Clapp previous to attachment to wood appear to rely mainly on glycogen stored in the oocytes
and perhaps also obtained later from the maternal gill. During the
first 24 h of free existence there is an increase in the rate of oxygen consumption (Lane and Greenfield, 1952)) probably owing to increased
ciliary activity or to the operation of glycogenic enzyme systems which
allow the completion of oxidative glycolysis. Then oxygen consumption
decreases rapidly up to 72 h, and more slowly until the larvae die after
about 300 h if they do not attain a suitable substrate (Lane et al., 1954).
The large endowment of glycogen with which the zygote begins its
existence is largely expended by the time the larva has penetrated
wood (Lane and Greenfield, 1952). Apart from utilizing the stored
glycogen, the larvae also feed on micro-organisms. Karande et al.
(1968) on the other hand found that the larvae of T. furcifera need no
food prior to settlement since larvae deprived of food by maintenance
in sterilized filtered sea water have successfully bored into timber even
after 4-5 days. The source of energy for the larvae has been attributed
to the stored glycogen only (Lane, 1955).
E. Settlement
Larvae are attracted to wood, at least in the sense that, should they
chance to encounter it, they remain upon it and there metamorphose.
This was established by Harrington (1922) who further suggested that
malic acid was the active constituent responsible for this. Yonge (see