438
N. BALAKRISHNAN NAIR AND M. SARASWATHY
may be stored in the mantle which accounts for the comparatively high
values during that time. On the onset of breeding season the stored
reserves may be utilized for sperm formation. The only explanation,
therefore, for its apparent fall on the onset of breeding season is the loss
of this material through spawning. However, a clear picture of these
cycles can be obtained only through a detailed analysis of the different
organs separately.
To find the relationship in N . hedleyi of glycogen, protein and total
nitrogen content to dry weight, specimens were grouped with a weight
difference of 50 mg irrespective of sex, time of collection or length. The
average glycogen content of animals below 50 mg was about 23.17%
and the values showed a steady increase to reach more than 50% of the
weight of the animal, in specimens above 400 mg. I n this estuarine
species glycogen in terms of per cent dry weight is higher than in other
wood borers such as Teredo pedicellata and Martesia striata or in
oysters. The protein content of animals in the weight group 0-50 mg
was found to be the highest (23.51%) and this constituent continued to
be high (18%) even in specimens of the weight group 250-300 mg. But
in higher weight groups the protein content was found to be very low
( 10.5y0) indicating an inverse relationship between glycogen and protein content. The total nitrogen content had a similar trend to that of
protein with high values in smaller animals.
The lipid content expressed in terms of percentage of dry weight
varied from 3.46 in June to 8.34 in November and was low during April
and May. Correlation between lipid content and breeding period was
not evident. I n N . hedleyi lipids constitute only a small percentage of
the dry weight, unlike chitons (Giese and Araki, 1962) where this reaches
levels of 29% in some organs. A marked seasonal variation in the fat
content was not noticed in Martesia striata (Nagabhushanam, 1961).
The lipid content does not significantly vary throughout the year.
Glycogen is the most important storage material in N . hedleyi. The
percentage of salts (chloride as sodium chloride) expressed as percentage of dry tissues showed a distinct fall on the onset of the breeding
season which in this case coincided with a fall in salinity. During the
highly saline period of February, March and April the salt content of
the body was curiously low. The ash content expressed as percentage
of dry weight varied from 11.45 in June to 4.68 in July, i.e. there is a
noticeable fall of the ash content soon after the onset of breeding. On
average the amount of ash in this species is about 8.12% of the dry
tissue, thus falling within the usual range in mature molluscs. The
calcium content (Fig. 45) of the species expressed as percentage of the
ash content fluctuated between 7.1 in November and 22-48 in August.
N. BALAKRISHNAN NAIR AND M. SARASWATHY
may be stored in the mantle which accounts for the comparatively high
values during that time. On the onset of breeding season the stored
reserves may be utilized for sperm formation. The only explanation,
therefore, for its apparent fall on the onset of breeding season is the loss
of this material through spawning. However, a clear picture of these
cycles can be obtained only through a detailed analysis of the different
organs separately.
To find the relationship in N . hedleyi of glycogen, protein and total
nitrogen content to dry weight, specimens were grouped with a weight
difference of 50 mg irrespective of sex, time of collection or length. The
average glycogen content of animals below 50 mg was about 23.17%
and the values showed a steady increase to reach more than 50% of the
weight of the animal, in specimens above 400 mg. I n this estuarine
species glycogen in terms of per cent dry weight is higher than in other
wood borers such as Teredo pedicellata and Martesia striata or in
oysters. The protein content of animals in the weight group 0-50 mg
was found to be the highest (23.51%) and this constituent continued to
be high (18%) even in specimens of the weight group 250-300 mg. But
in higher weight groups the protein content was found to be very low
( 10.5y0) indicating an inverse relationship between glycogen and protein content. The total nitrogen content had a similar trend to that of
protein with high values in smaller animals.
The lipid content expressed in terms of percentage of dry weight
varied from 3.46 in June to 8.34 in November and was low during April
and May. Correlation between lipid content and breeding period was
not evident. I n N . hedleyi lipids constitute only a small percentage of
the dry weight, unlike chitons (Giese and Araki, 1962) where this reaches
levels of 29% in some organs. A marked seasonal variation in the fat
content was not noticed in Martesia striata (Nagabhushanam, 1961).
The lipid content does not significantly vary throughout the year.
Glycogen is the most important storage material in N . hedleyi. The
percentage of salts (chloride as sodium chloride) expressed as percentage of dry tissues showed a distinct fall on the onset of the breeding
season which in this case coincided with a fall in salinity. During the
highly saline period of February, March and April the salt content of
the body was curiously low. The ash content expressed as percentage
of dry weight varied from 11.45 in June to 4.68 in July, i.e. there is a
noticeable fall of the ash content soon after the onset of breeding. On
average the amount of ash in this species is about 8.12% of the dry
tissue, thus falling within the usual range in mature molluscs. The
calcium content (Fig. 45) of the species expressed as percentage of the
ash content fluctuated between 7.1 in November and 22-48 in August.