THE BIOLOUY O F WOOD-BORING TEREDINID MOLLUSCS
431
ful penetration of the wood before a species can become an established
member of any local fauna (Turner, 1966).
XV. PHYSIOLOGICAL STUDIES
That the shipworms have not been favourite objects of physiological
work is evident from the fact that the recent review " Physiology of
Mollusca ) ) edited by Wilbur and Yonge (1964, 1966) contains only few
references t o them. The physiological studies carried out so far have
been based on observations on very few species and are concerned
chiefly with factors affecting settlement, reactions to changes in certain
physical and chemical features of the environment, digestion of cellulose, respiration, glycogen metabolism and the mechanism of boring.
The chemical composition of a number of marine organisms has
been studied and a comprehensive literature exists (see Vinagradov,
1953). For the Tcredinidae information is confined to the observations
of Lane et al. (1952) on the distribution of glycogen in Teredo (Lyrodus)
pedicellata, of Lasker and Lane (1953) on the origin and distribution of
nitrogen in T . bartschi and of Greenfield (1953) on the nitrogen and
glycogen content of T . (Lyrodus) pedicellata. The importance of such
studies lies in the fact that the gonad is the locus of intensive biochemical synthesis a t the time gametes are being formed (Giese, 1959).
It is known that in the male large amounts of nucleic acids are needed
for the sperm heads and in the female lipids and protein are mobilized
to be stored in the eggs. These aspects have been studied by us (Saraswathy and Nair, 1969a) since we felt that Nausitora hedleyi with its
peculiar restricted breeding habits can be expected t o undergo variations in its biochemical composition during the yearly cycle. This is
all the more probable since the gonad may form about 45% or more of
the entire wet weight of the animal during the breeding season, and
may fall to as low a level as 2.97% during the non-breeding period.
Annual reproductive cycle analyses were carried out in the hope that
correlations might emerge to serve as a basis for a clearer interpretation
of the annual reproductive cycle.
In these biochemical studies detailed comparisons and generalizations are rather difficult owing to the difference in the collection of
material and in the methods adopted for estimation by the various
authors. Our estimations have been made on entire animals collected
from Cochin backwaters for a period of 12 months. All biochemical
estimations were made on material dried to constant weight. Water
content, ash content, glycogen, protein, total nitrogen and non-protein
nitrogen, lipids, calcium, phosphorus and chloride content were
estimated. Glycogen estimation was done according to the method of
431
ful penetration of the wood before a species can become an established
member of any local fauna (Turner, 1966).
XV. PHYSIOLOGICAL STUDIES
That the shipworms have not been favourite objects of physiological
work is evident from the fact that the recent review " Physiology of
Mollusca ) ) edited by Wilbur and Yonge (1964, 1966) contains only few
references t o them. The physiological studies carried out so far have
been based on observations on very few species and are concerned
chiefly with factors affecting settlement, reactions to changes in certain
physical and chemical features of the environment, digestion of cellulose, respiration, glycogen metabolism and the mechanism of boring.
The chemical composition of a number of marine organisms has
been studied and a comprehensive literature exists (see Vinagradov,
1953). For the Tcredinidae information is confined to the observations
of Lane et al. (1952) on the distribution of glycogen in Teredo (Lyrodus)
pedicellata, of Lasker and Lane (1953) on the origin and distribution of
nitrogen in T . bartschi and of Greenfield (1953) on the nitrogen and
glycogen content of T . (Lyrodus) pedicellata. The importance of such
studies lies in the fact that the gonad is the locus of intensive biochemical synthesis a t the time gametes are being formed (Giese, 1959).
It is known that in the male large amounts of nucleic acids are needed
for the sperm heads and in the female lipids and protein are mobilized
to be stored in the eggs. These aspects have been studied by us (Saraswathy and Nair, 1969a) since we felt that Nausitora hedleyi with its
peculiar restricted breeding habits can be expected t o undergo variations in its biochemical composition during the yearly cycle. This is
all the more probable since the gonad may form about 45% or more of
the entire wet weight of the animal during the breeding season, and
may fall to as low a level as 2.97% during the non-breeding period.
Annual reproductive cycle analyses were carried out in the hope that
correlations might emerge to serve as a basis for a clearer interpretation
of the annual reproductive cycle.
In these biochemical studies detailed comparisons and generalizations are rather difficult owing to the difference in the collection of
material and in the methods adopted for estimation by the various
authors. Our estimations have been made on entire animals collected
from Cochin backwaters for a period of 12 months. All biochemical
estimations were made on material dried to constant weight. Water
content, ash content, glycogen, protein, total nitrogen and non-protein
nitrogen, lipids, calcium, phosphorus and chloride content were
estimated. Glycogen estimation was done according to the method of