THE BIOLOGY OF WOOD-BORING TEREDINID MOUUSCS
421
VII) will suggest probable causes for the differences in the pattern of
vertical distribution. During the monsoon period distinctly greater
numbers settled over the bottom panels. During the post-monsoon
period the nature of settlement was different with the sub-tidal panels
giving evidence of a greater strike than the bottom panels. This
naturally suggests a shift in the nature of settlement owing to the overriding influence of some ecological factor, most probably salinity. The
trend is almost the same in the long-term panels also and serves to
ctonfirm the results obtained from the short-term panels.
In Table VIII and in Fig. 40 are presented the results of a conTABLE VIII. Naueitora hedleyi, THE NATURE OF THE VERTICAL
DISTRIBUTION DURINQ THE MONSOON AND THE POST-MONSOON PERIODS
Position of panel
Number of
above mud line
epecimens on
Date of
Date of
immersion
colleotion
i n cm
Panel
20.6.1965
20.6.1966
20.6.1965
20.6.1966
20.6.1965
20.6.1965
15.10.1965
15.10.1965
16.10.1965
15.10.1966
16.10.1965
15.10.1965
5.10.1965
6.10.1965
5.10.1966
5.10.1965
5.10.1966
5.10.1965
3.1.1966
3.1.1966
3.1.1966
3.1.1966
3.1.1966
3.1.1966
270
230
180
130
80
30
270
230
180
130
80
30
14
15
37
19
38
72
210
536
472
494
417
219
h a t o r y test carried out with a view t o checking the details of the
difference noticed in the short-term and long-term series. The pattern
of settlement is different during the low salinity period of the monsoon
(A) and during the post-monsoon period (B) when salinity shows an
upward trend. While the pattern during the first test (June-October)
is suggestive of an apparent increase in larval strike towards the bottom
Qhis is not so for the second test (OctoberJanuary). Here maximum
mttlement is towards the upper levels and minimum numbers occur in
both the bottom and topmost panels. The apparent change in the
pattern of settlement suggests that vertical distribution is not based on
a set behavioural pattern but depends also on such factors as the distribution of salinity in the surrounding water. It was not evident from
these tests whether the larvae were distributed equally throughout the
421
VII) will suggest probable causes for the differences in the pattern of
vertical distribution. During the monsoon period distinctly greater
numbers settled over the bottom panels. During the post-monsoon
period the nature of settlement was different with the sub-tidal panels
giving evidence of a greater strike than the bottom panels. This
naturally suggests a shift in the nature of settlement owing to the overriding influence of some ecological factor, most probably salinity. The
trend is almost the same in the long-term panels also and serves to
ctonfirm the results obtained from the short-term panels.
In Table VIII and in Fig. 40 are presented the results of a conTABLE VIII. Naueitora hedleyi, THE NATURE OF THE VERTICAL
DISTRIBUTION DURINQ THE MONSOON AND THE POST-MONSOON PERIODS
Position of panel
Number of
above mud line
epecimens on
Date of
Date of
immersion
colleotion
i n cm
Panel
20.6.1965
20.6.1966
20.6.1965
20.6.1966
20.6.1965
20.6.1965
15.10.1965
15.10.1965
16.10.1965
15.10.1966
16.10.1965
15.10.1965
5.10.1965
6.10.1965
5.10.1966
5.10.1965
5.10.1966
5.10.1965
3.1.1966
3.1.1966
3.1.1966
3.1.1966
3.1.1966
3.1.1966
270
230
180
130
80
30
270
230
180
130
80
30
14
15
37
19
38
72
210
536
472
494
417
219
h a t o r y test carried out with a view t o checking the details of the
difference noticed in the short-term and long-term series. The pattern
of settlement is different during the low salinity period of the monsoon
(A) and during the post-monsoon period (B) when salinity shows an
upward trend. While the pattern during the first test (June-October)
is suggestive of an apparent increase in larval strike towards the bottom
Qhis is not so for the second test (OctoberJanuary). Here maximum
mttlement is towards the upper levels and minimum numbers occur in
both the bottom and topmost panels. The apparent change in the
pattern of settlement suggests that vertical distribution is not based on
a set behavioural pattern but depends also on such factors as the distribution of salinity in the surrounding water. It was not evident from
these tests whether the larvae were distributed equally throughout the