THE BIOLOGY OF WOOD-BORING TEREDINID MOLLUSCS
453
The importance of salinity as a limiting factor for the existence and
distribution of shipworms has been known as early as 1733. Sellius
(1733), Baumhauer (1860) and Harting (1862) noted a correlation between increased activity of shipworms and increase in the salinity of
the water. A review of the more important references about shipworms
in relation to salinity endurances brings forth the following facts.
Bankia setacea, according to Barrows (1917) was very sensitive to a
lowering of the salinity in San Francisco Bay. Its lower limit has been
determined at 20%, in California (Kofoid, 1921), IS%, at San Francisco
Bay (Miller, 1926) and 7-5-13-7%, at the Strait of Georgia (White, 1929).
It was also noted (White, 1929) that the species is killed within 1 h at
salinities less than 7-5%,, within 6 h at lo%, and within 12 h at 13*7%,.
White (1929a) further noticed that this species has two seasonal peaks
of breeding corresponding with low temperature and high salinity.
During the very low salinities (15-8%,) of winter no breeding was observed. In British Columbia, Black and Elsey (1948) observed that a
salinity range between 9 and 23%, was optimum for B. setacea. The
lowest salinity for normal activity of B. gouldi at Beaufort was found
to be la%, (Allen and Carter, 1924). Scheltema and Truitt (1954) record
B. gouldi in waters with a mean salinity of approximately 9.3%, (range
3.3-15.6%,) at Annapolis, Maryland. According to Nagabhushanam
(1961) B. campanellata in Visakhapatnam occurs in areas where the
salinity is between 21 and 34%,. The magnitude of the strike decreased
with decreasing salinity. Roch (1940) found minimum salinity for
normal activity of B. minima to be 32%, and still higher in the Adriatic.
B. huwaiiensis lived in fresh water for 2 days and in a mixture of equal
parts of normal sea water and fresh water for as long a period as 12 days
(Edmondson, 1942). These records give the impression that the genus
Bankia is capable of tolerating a fairly wide range of salinities.
Teredo navalis (if the determination of the species is correct in all
cases) is reported as showing a wide salinity tolerance. M’Gonigle (1926)
noted that the boring activity of T . navalis was affected at IS%, and
suspended at lo%, in Nova Scotia and a similar result was obtained by
Imai et al. (1950) in Onagawa Bay, Japan. Blum (1922) in his classical
experiments at San Francisco Bay showed that normal activities were
carried on until salinity fell to 9%, but a fall below 6%, was lethal.
Individuals living for long periods exposed to low salinities were usually
malformed. Miller (1926) noticed that T . navalis in the same locality
could tolerate a range of salinity from normal sea water to 9%, and
observed that 4%, was lethal in 2 months. Kofoid et al. (1927) fixed the
lethal salinity at 5%,. Barrows (1917) found that salinity is an important factor in the distribution of T. diegensis in San Francisco Bay
453
The importance of salinity as a limiting factor for the existence and
distribution of shipworms has been known as early as 1733. Sellius
(1733), Baumhauer (1860) and Harting (1862) noted a correlation between increased activity of shipworms and increase in the salinity of
the water. A review of the more important references about shipworms
in relation to salinity endurances brings forth the following facts.
Bankia setacea, according to Barrows (1917) was very sensitive to a
lowering of the salinity in San Francisco Bay. Its lower limit has been
determined at 20%, in California (Kofoid, 1921), IS%, at San Francisco
Bay (Miller, 1926) and 7-5-13-7%, at the Strait of Georgia (White, 1929).
It was also noted (White, 1929) that the species is killed within 1 h at
salinities less than 7-5%,, within 6 h at lo%, and within 12 h at 13*7%,.
White (1929a) further noticed that this species has two seasonal peaks
of breeding corresponding with low temperature and high salinity.
During the very low salinities (15-8%,) of winter no breeding was observed. In British Columbia, Black and Elsey (1948) observed that a
salinity range between 9 and 23%, was optimum for B. setacea. The
lowest salinity for normal activity of B. gouldi at Beaufort was found
to be la%, (Allen and Carter, 1924). Scheltema and Truitt (1954) record
B. gouldi in waters with a mean salinity of approximately 9.3%, (range
3.3-15.6%,) at Annapolis, Maryland. According to Nagabhushanam
(1961) B. campanellata in Visakhapatnam occurs in areas where the
salinity is between 21 and 34%,. The magnitude of the strike decreased
with decreasing salinity. Roch (1940) found minimum salinity for
normal activity of B. minima to be 32%, and still higher in the Adriatic.
B. huwaiiensis lived in fresh water for 2 days and in a mixture of equal
parts of normal sea water and fresh water for as long a period as 12 days
(Edmondson, 1942). These records give the impression that the genus
Bankia is capable of tolerating a fairly wide range of salinities.
Teredo navalis (if the determination of the species is correct in all
cases) is reported as showing a wide salinity tolerance. M’Gonigle (1926)
noted that the boring activity of T . navalis was affected at IS%, and
suspended at lo%, in Nova Scotia and a similar result was obtained by
Imai et al. (1950) in Onagawa Bay, Japan. Blum (1922) in his classical
experiments at San Francisco Bay showed that normal activities were
carried on until salinity fell to 9%, but a fall below 6%, was lethal.
Individuals living for long periods exposed to low salinities were usually
malformed. Miller (1926) noticed that T . navalis in the same locality
could tolerate a range of salinity from normal sea water to 9%, and
observed that 4%, was lethal in 2 months. Kofoid et al. (1927) fixed the
lethal salinity at 5%,. Barrows (1917) found that salinity is an important factor in the distribution of T. diegensis in San Francisco Bay