THE BIOLOGY O F WOOD-BORING TEREDINID MOLLUSCS
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canal in Thailand (Bartsch, 1927), Upper Passaic river, New Jersey, in
the Sacramento river, California, in the Apalachicola river, north-west
Florida and north of New Orleans (Von Schrenk, 1935), and Mira Flores
Lake, Panama canal zone (Smith, 1944).
D. Illumination
Experiments on settlement of Teredo pedicellata and Bankia
Jimbriatula on test surfaces under various conditions of illumination
have shown that the attack is greatest at an intensity of 166 foot
candles (Isham et al., 1951). These authors also tested the locomotor
reactions of the larvae of Teredo pedicellata to various intensities of
diffuse and unidirectional light and noted that only the free-swimming
larvae are affected by light and not the crawling ones. General conclusions regarding the probable behaviour of larvae under natural conditions were (1) at night the larvae are likely to concentrate at the
water surface but tend to remain in deeper water during the day,
(2) attachment to timber may be expected to be greatest at an illumination of 160 foot candles which in fact represents deep shade. The
latter conclusion has been confirmed by the observations of Owen
(1953) at Loch Ryan in Scotland, where horizontally placed timbers
were attacked more heavily on the shaded under surface than on the
vertical surfaces, obliquely driven piles showing heaviest attack at the
sharp angle above the mud line.
E. Settlement in relation to light and gravity
The effects of light and gravity upon the intensity of attack by
Teredo furcillatus ( = T . furcifera) and Bankia campanellata have been
investigated at Visakhapatnam harbour (Nagabhushanam, 1959b).
The larvae of Teredo furcillatus settled in any range of light intensity
except under conditions approximating to total darkness. In contrast,
Bankia campanellata settled most abundantly on the least illuminated
panels. The study of settlement of the larvae upon wooden surfaces
held at different angles showed that the greatest intensity of settlement
occurred on the underside of the horizontal surface and that the intensity of attack decreased as the angle of the surface increased.
F. Role of primary jilm
Nagabhushanam (1959~) observed that in 30 days, 124 larvae of
Martesia striata settled on filmed blocks and 2 on clean ones while in
the case of Teredo furcillatus 161 settled on the former as a,gainst 32
on the latter. Moreover a greater number of larvae metamorphosed
on the filmed blocks. These experiments suggest that the primary film
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canal in Thailand (Bartsch, 1927), Upper Passaic river, New Jersey, in
the Sacramento river, California, in the Apalachicola river, north-west
Florida and north of New Orleans (Von Schrenk, 1935), and Mira Flores
Lake, Panama canal zone (Smith, 1944).
D. Illumination
Experiments on settlement of Teredo pedicellata and Bankia
Jimbriatula on test surfaces under various conditions of illumination
have shown that the attack is greatest at an intensity of 166 foot
candles (Isham et al., 1951). These authors also tested the locomotor
reactions of the larvae of Teredo pedicellata to various intensities of
diffuse and unidirectional light and noted that only the free-swimming
larvae are affected by light and not the crawling ones. General conclusions regarding the probable behaviour of larvae under natural conditions were (1) at night the larvae are likely to concentrate at the
water surface but tend to remain in deeper water during the day,
(2) attachment to timber may be expected to be greatest at an illumination of 160 foot candles which in fact represents deep shade. The
latter conclusion has been confirmed by the observations of Owen
(1953) at Loch Ryan in Scotland, where horizontally placed timbers
were attacked more heavily on the shaded under surface than on the
vertical surfaces, obliquely driven piles showing heaviest attack at the
sharp angle above the mud line.
E. Settlement in relation to light and gravity
The effects of light and gravity upon the intensity of attack by
Teredo furcillatus ( = T . furcifera) and Bankia campanellata have been
investigated at Visakhapatnam harbour (Nagabhushanam, 1959b).
The larvae of Teredo furcillatus settled in any range of light intensity
except under conditions approximating to total darkness. In contrast,
Bankia campanellata settled most abundantly on the least illuminated
panels. The study of settlement of the larvae upon wooden surfaces
held at different angles showed that the greatest intensity of settlement
occurred on the underside of the horizontal surface and that the intensity of attack decreased as the angle of the surface increased.
F. Role of primary jilm
Nagabhushanam (1959~) observed that in 30 days, 124 larvae of
Martesia striata settled on filmed blocks and 2 on clean ones while in
the case of Teredo furcillatus 161 settled on the former as a,gainst 32
on the latter. Moreover a greater number of larvae metamorphosed
on the filmed blocks. These experiments suggest that the primary film