THE BIOLOGY OF WOOD-BORING TEREDINID MOLLUSCS
41 1
competition with Bankia campanellata whose intensity was greatest
during the winter months.
Erlanson (1936) only found Teredo in the test blocks she used at
Cochin harbour in spite of the fact that the period of her tests coincided
with the breeding period of Nausitora hedleyi in the area. Since her
tests were confined chiefly to the monsoon and post-monsoon periods
(May-November), a period of very low salinity in the harbour when
the breeding period of Martesia and Teredo was nearing completion,
and since her test blocks were not attacked by Nausitora hedleyi she
could not get a full picture of the magnitude of destruction by shipworms at Cochin harbour even though local people were fully aware of
it. Erlanson (p. 731) concluded ‘‘ Contrary to local opinion the activity
of molluscan borers in Cochin harbour and vicinity is less than
elsewhere.”
I
1
No
160140 -
120100 -
80 -
60 -
40 -
20 -
I
- 32
’ 28
. 2 4
- 2 0
’ 16
12
8
4
FIG. 35. Histograms representing the nature of settlement of Nuusitoru hedleyi on test
panels. Short-term (shaded) and long-term (blank) during the different months at
the pier of the Oceanographic Laboratory, Cochin. The graph presents the average
gonad indices for the respective months.