454
N. BALAKRISHNAN NAIRAND M. SARASWATHY
and that at least lo%, was required for normal activity. Studies by
Edmondson (1942) proved that T . milleri, T . diegensis, T . bartschi and
T . trulliformis survived in wood for 12 days in normal sea water diluted
with fresh water and that 60 h is about an average period of resistance
of various species of Hawaiian shipworms to fresh water. Roch (1940)
found the lethal salinity for T . utriculus to be about 28%, and for T .
pedicellata 20%, in the Adriatic.
On the other end of the scale is the genus Nausitora which is
generally confined to brackish water, though some species have occasionally been taken from marine habitats (Nagabhushanam, 1960 ;
Nair, 1954). In N . hedleyi a majority of the adults are typically euryhaline, capable of enduring the whole range of salinities present
(0-65-33.68%,) in the environment but with breeding apparently restricted to the low saline period (Saraswathy, 1967).
The first record of this genus was by Wright (1864) who obtained
specimens of N . hedleyi from fresh water (salinity neither determined
nor given), 150 miles above the mouth of the Ganges. Recently Rajagopalaiengar (1964) reported N . lanceolata from Sajnakhali, 24 Parganas
District of West Bengal. Hedley (1901) collected N . jluviatilis in the
rivers Rewa and Nauva, Fiji and a specimen has been recorded from
the Zambezi River in Africa (see Edmondson, 1942). Bartsch (1922)
lists four records of Namitora, N . excolpa from the Gulf of California,
N . dryas from Peru, N . braziliensis from Brazil and N . fusticula probably from the tropical western Atlantic. From the general locality of
Port Jackson, Hedley collected specimens of Nausitora and others were
later recorded from Cattai Creek in the Hawkesbury river by Iredale
et al. (1932). Watson et al. (1936) reported heavy attacks from a species
of Nausitora in the Brisbane river where the salinity is less than lo%,
and noticed reduced activity of the shipworm in salinities above 15%,.
Populations of N . dunlopei and Teredo poculifer shift up and down the
Brisbane River with seasonal changes in salinity. From the same
locality Johnson et al. (1936) recorded Nausitora in salinities not higher
than lo%, and in the upper George River where the salinity was found
to be as low as 1 ~ 5 % ~ .
N . oahuensis is known from one locality about
Oahu where sea water is diluted by fresh water. N . hedleyi has recently
been reported from the low saline waters of Pulicat Lake on the east
coast of India (Nair, 1963). These records show that this genus is
sensitive to higher salinities and so restricted to estuarine areas. N .
hedleyi can apparently withstand wider changes of salinity than allied
species like N . dunbpei and is capable of tolerating much lower
salinities than typical marine species. Great damage can be expected
from species of this genus in the low saline localities of river mouths etc.
N. BALAKRISHNAN NAIRAND M. SARASWATHY
and that at least lo%, was required for normal activity. Studies by
Edmondson (1942) proved that T . milleri, T . diegensis, T . bartschi and
T . trulliformis survived in wood for 12 days in normal sea water diluted
with fresh water and that 60 h is about an average period of resistance
of various species of Hawaiian shipworms to fresh water. Roch (1940)
found the lethal salinity for T . utriculus to be about 28%, and for T .
pedicellata 20%, in the Adriatic.
On the other end of the scale is the genus Nausitora which is
generally confined to brackish water, though some species have occasionally been taken from marine habitats (Nagabhushanam, 1960 ;
Nair, 1954). In N . hedleyi a majority of the adults are typically euryhaline, capable of enduring the whole range of salinities present
(0-65-33.68%,) in the environment but with breeding apparently restricted to the low saline period (Saraswathy, 1967).
The first record of this genus was by Wright (1864) who obtained
specimens of N . hedleyi from fresh water (salinity neither determined
nor given), 150 miles above the mouth of the Ganges. Recently Rajagopalaiengar (1964) reported N . lanceolata from Sajnakhali, 24 Parganas
District of West Bengal. Hedley (1901) collected N . jluviatilis in the
rivers Rewa and Nauva, Fiji and a specimen has been recorded from
the Zambezi River in Africa (see Edmondson, 1942). Bartsch (1922)
lists four records of Namitora, N . excolpa from the Gulf of California,
N . dryas from Peru, N . braziliensis from Brazil and N . fusticula probably from the tropical western Atlantic. From the general locality of
Port Jackson, Hedley collected specimens of Nausitora and others were
later recorded from Cattai Creek in the Hawkesbury river by Iredale
et al. (1932). Watson et al. (1936) reported heavy attacks from a species
of Nausitora in the Brisbane river where the salinity is less than lo%,
and noticed reduced activity of the shipworm in salinities above 15%,.
Populations of N . dunlopei and Teredo poculifer shift up and down the
Brisbane River with seasonal changes in salinity. From the same
locality Johnson et al. (1936) recorded Nausitora in salinities not higher
than lo%, and in the upper George River where the salinity was found
to be as low as 1 ~ 5 % ~ .
N . oahuensis is known from one locality about
Oahu where sea water is diluted by fresh water. N . hedleyi has recently
been reported from the low saline waters of Pulicat Lake on the east
coast of India (Nair, 1963). These records show that this genus is
sensitive to higher salinities and so restricted to estuarine areas. N .
hedleyi can apparently withstand wider changes of salinity than allied
species like N . dunbpei and is capable of tolerating much lower
salinities than typical marine species. Great damage can be expected
from species of this genus in the low saline localities of river mouths etc.