450
N. BALAKRISHNAN NAIK. AND M. YARASWATHY
T . navalis and T . pedicellata of the British Isles exceeded in size those
found along the coast of Spain and Sicily. Sigerfoos (1896) states that
Xylotrya Jimbriata (= Bankia gouldi Bartsch) at Beaufort, N. Carolina
grew to a length of 100 mm in 36 days. Orton (1914) found Teredo
nccvalis growing to a length of 19.8 cm in 31 weeks. Potts (1921) made
preliminary observations on the comparative growth rates of certain
marine organisms of temperate and tropical seas and noted a faster
growth rate for Teredo from the tropics. Nair (1962) noted that there
was a retardation in the growth of T . megotara in western Norway with
the onset of cold conditions. For this species Kramp (1927)’ noted at
Hirtshals, a growth of 15 cm in 6 months and 26 cm in 1 year. Nair
(1962) obtained a maximum length of 28.6 cm for a period of about
5 months for this species at Espegrend, W. Norway while Dons (1940)
observed at Trondheim, one of 37 cm in 6 months and of 52 cm in 1
year. Needler and Needler (1940) noted a correlation between maximum growth rates in shipworms and highest temperature. Even though
in the warm tropical waters Nair (1960) was not able to notice any
correlation between growth rates and hydrographic conditions for
Bankia indica (=B. carinutu) at Madras, Nagabhushanam (1961) was
able to record maximum growth for Teredo furcillatus (=T. furcifera)
in May coinciding with the highest temperature for the year at Visakhapatanam. Studies by Potts (1921) on Teredo sp. showed that this
attained sexual maturity and produced larvae in 24 days and in less
than 1 month infected wood was riddled by its burrows.
In many shipworms, the spawning activity is stimulated by rising
temperature. Thus Nelson (1928) has shown that T . nawalis spawns
when the temperature reaches 15-16°C and this spawning temperature
has been cited as a factor which has facilitated the spread of this
species to most parts of the world. I n Onagawa Bay, Japan, according to Imai et al. (1950) it spawns from early summer (temp. 18°C) to
late fall. T . navalis at Milford were conditioned to spawn by Loosanoff
and Davis (1963) in sea water maintained at a temperature between
15-20°C. Spawning occurred at temperatures of 14°C and higher, and
larvae were released at temperatures ranging from about 16-20°C.
Grave ( 1 928) reported that this species spawned when the water temperature reached 11-12°C. Imai et al. (1950) found that spawning begins when the water temperature reaches 18°C. Sullivan’s data (1948)
closely agree with those of Loosanoff and Davis ( 1 963), spawning occurring at approximately 15°C.
At Ladysmith harbour, British Columbia, Ba.rLkia sdacea spawns
when the water temperature reaches 10°C (Quayle, 1959a), and at
Puget Sound for the same species between 7-12OC (Johnson and Miller,
N. BALAKRISHNAN NAIK. AND M. YARASWATHY
T . navalis and T . pedicellata of the British Isles exceeded in size those
found along the coast of Spain and Sicily. Sigerfoos (1896) states that
Xylotrya Jimbriata (= Bankia gouldi Bartsch) at Beaufort, N. Carolina
grew to a length of 100 mm in 36 days. Orton (1914) found Teredo
nccvalis growing to a length of 19.8 cm in 31 weeks. Potts (1921) made
preliminary observations on the comparative growth rates of certain
marine organisms of temperate and tropical seas and noted a faster
growth rate for Teredo from the tropics. Nair (1962) noted that there
was a retardation in the growth of T . megotara in western Norway with
the onset of cold conditions. For this species Kramp (1927)’ noted at
Hirtshals, a growth of 15 cm in 6 months and 26 cm in 1 year. Nair
(1962) obtained a maximum length of 28.6 cm for a period of about
5 months for this species at Espegrend, W. Norway while Dons (1940)
observed at Trondheim, one of 37 cm in 6 months and of 52 cm in 1
year. Needler and Needler (1940) noted a correlation between maximum growth rates in shipworms and highest temperature. Even though
in the warm tropical waters Nair (1960) was not able to notice any
correlation between growth rates and hydrographic conditions for
Bankia indica (=B. carinutu) at Madras, Nagabhushanam (1961) was
able to record maximum growth for Teredo furcillatus (=T. furcifera)
in May coinciding with the highest temperature for the year at Visakhapatanam. Studies by Potts (1921) on Teredo sp. showed that this
attained sexual maturity and produced larvae in 24 days and in less
than 1 month infected wood was riddled by its burrows.
In many shipworms, the spawning activity is stimulated by rising
temperature. Thus Nelson (1928) has shown that T . nawalis spawns
when the temperature reaches 15-16°C and this spawning temperature
has been cited as a factor which has facilitated the spread of this
species to most parts of the world. I n Onagawa Bay, Japan, according to Imai et al. (1950) it spawns from early summer (temp. 18°C) to
late fall. T . navalis at Milford were conditioned to spawn by Loosanoff
and Davis (1963) in sea water maintained at a temperature between
15-20°C. Spawning occurred at temperatures of 14°C and higher, and
larvae were released at temperatures ranging from about 16-20°C.
Grave ( 1 928) reported that this species spawned when the water temperature reached 11-12°C. Imai et al. (1950) found that spawning begins when the water temperature reaches 18°C. Sullivan’s data (1948)
closely agree with those of Loosanoff and Davis ( 1 963), spawning occurring at approximately 15°C.
At Ladysmith harbour, British Columbia, Ba.rLkia sdacea spawns
when the water temperature reaches 10°C (Quayle, 1959a), and at
Puget Sound for the same species between 7-12OC (Johnson and Miller,