42 6
N. BALAKRISRNAN NAIR AND M. SARASWATHY
3 9 cm long from a block which had been immersed from September to
January, while from British Columbia, Quayle (1959) reported a mean
monthly increase of 12.2 cm in one specimen which attained a length of
61.0 cm in about 5 months. I n Woods Hole, Grave (1928) noted growth
in length of Teredo navalis as follows : 0-35-0.5 mm in 18 days, 8-10 mm
in 33 days, 100-120 mm in 72 days to reach a length of 250-400 mm in
one year. Miller (1922) observed in T . navalis that the rate of growth
as measured by the addition of ridges is extremely rapid during the
first month (9.3) after which it stops suddenly remaining nearly constant during the next 2 months (3.8-3.6) followed by a further decrease
during the fourth month (2.6). He suggested that the decrease is due
either t o the lowering of temperature or t o the effects of crowding,
limiting further growth. According t o Richards (1943) the growth rate
in N. Carolina for T . navalis is 10-30mm and for Lyrodus bipartita
10-15 mm during the period May-January. Sigerfoos (1908) observed in
Bankia gouldi from N. Carolina a growth of 3 mm in 12 days, 6 mm in
16 days, 11 mm in 20 days, 63 mm in 30 days and 100 mm in 36 days.
This represents a higher growth rate than what Richards and Clapp
(1944) reported for the same species from Florida waters and a little less
than that reported by Richards (1943) from Wilmington, N. Carolina
(35-125 mm). For Teredo megotara, & (1927) noted at Hirtshals a
growth of 15 cm for 6 months and 26 cm for 1 year. However, Dons
(1940) obtained a t Trondheim, Norway, different values namely 37 cm
in 6 months and 52 cm in 1 year and Nair (1962) observed a maximum
length of 28.6 cm for a period of about 5 months for this species at
Espegrend in western Norway. For Bankia australis Ralph and Hurley
(1952) recorded growth in length of about 45 cm in 1 year. They
obtained an ordinary growth curve which showed a deceleration of
growth rate in September and again in November, i.e. in winter and
in spring. This feature has been noticed by Isham et al. (1951)
in Teredo pedicellata at Florida. While in T . pedicellata this was
attributed to the effect of overcrowding, in Bankia australis the deviation of the curve was interpreted as due t o individual variation.
According to Lane (1959), the average life span of Teredo in Miami is
about 10 weeks during which time it grows to a length of 100-125 mm
and a diameter of 0.25 mm. Johnson et al. (1936) noted a diameter of
& i n at the end of 3 months growth for 3 Australian species. As
early as 1923, Bartsch proposed a new term " stenomorph " for shipworms that are dwarfed as a result of overcrowding and consequent
lack of sufficient space for normal growth. Despite this stunted growth,
he observed that these dwarfs attain sexual maturity. Clapp (1925)
also recorded such stenomorphs and pointed out that while these may
N. BALAKRISRNAN NAIR AND M. SARASWATHY
3 9 cm long from a block which had been immersed from September to
January, while from British Columbia, Quayle (1959) reported a mean
monthly increase of 12.2 cm in one specimen which attained a length of
61.0 cm in about 5 months. I n Woods Hole, Grave (1928) noted growth
in length of Teredo navalis as follows : 0-35-0.5 mm in 18 days, 8-10 mm
in 33 days, 100-120 mm in 72 days to reach a length of 250-400 mm in
one year. Miller (1922) observed in T . navalis that the rate of growth
as measured by the addition of ridges is extremely rapid during the
first month (9.3) after which it stops suddenly remaining nearly constant during the next 2 months (3.8-3.6) followed by a further decrease
during the fourth month (2.6). He suggested that the decrease is due
either t o the lowering of temperature or t o the effects of crowding,
limiting further growth. According t o Richards (1943) the growth rate
in N. Carolina for T . navalis is 10-30mm and for Lyrodus bipartita
10-15 mm during the period May-January. Sigerfoos (1908) observed in
Bankia gouldi from N. Carolina a growth of 3 mm in 12 days, 6 mm in
16 days, 11 mm in 20 days, 63 mm in 30 days and 100 mm in 36 days.
This represents a higher growth rate than what Richards and Clapp
(1944) reported for the same species from Florida waters and a little less
than that reported by Richards (1943) from Wilmington, N. Carolina
(35-125 mm). For Teredo megotara, & (1927) noted at Hirtshals a
growth of 15 cm for 6 months and 26 cm for 1 year. However, Dons
(1940) obtained a t Trondheim, Norway, different values namely 37 cm
in 6 months and 52 cm in 1 year and Nair (1962) observed a maximum
length of 28.6 cm for a period of about 5 months for this species at
Espegrend in western Norway. For Bankia australis Ralph and Hurley
(1952) recorded growth in length of about 45 cm in 1 year. They
obtained an ordinary growth curve which showed a deceleration of
growth rate in September and again in November, i.e. in winter and
in spring. This feature has been noticed by Isham et al. (1951)
in Teredo pedicellata at Florida. While in T . pedicellata this was
attributed to the effect of overcrowding, in Bankia australis the deviation of the curve was interpreted as due t o individual variation.
According to Lane (1959), the average life span of Teredo in Miami is
about 10 weeks during which time it grows to a length of 100-125 mm
and a diameter of 0.25 mm. Johnson et al. (1936) noted a diameter of
& i n at the end of 3 months growth for 3 Australian species. As
early as 1923, Bartsch proposed a new term " stenomorph " for shipworms that are dwarfed as a result of overcrowding and consequent
lack of sufficient space for normal growth. Despite this stunted growth,
he observed that these dwarfs attain sexual maturity. Clapp (1925)
also recorded such stenomorphs and pointed out that while these may