THE BIOLOGY O F WOOD-BORING TEREDINID MOLLUSCS
479
exposed in sea water. Borer resistance has thus been linked with certain
inherent physical or chemical properties of timbers.
As early as 1495 Theophrastus stated that olive escapes the attack
of Teredo because of its bitter taste. The bitter components present in
the wood has been cited as an effective repellent against the marine
borers and the application of these bitter extracts to non-resistant wood
was suggested even in early literature (Anon, 1666 ; Montanus, 1671).
Sellius in his monograph has mentioned timbers that are particularly
deeply coloured, bitter and resinous which appear to be immune to
Teredo attack.
The apparent indemnity from shipworm destruction of the famous
Jarrah (Eucalyptus marginata) of Australia has generally been attributed to its large content of resinous materials (Anon, 1862). This
deterrent substance, however, is not present in decayed Jarrah timber
(Du Cane, 1864). Oleoresins, chiefly between bark and sapwood, are
present in turpentine, Xyncarpia laurifolia (Fitzsimons and Brooks, 1920),
and resinous tylosus in the famous Greenheart, Nectandra rodioei
(Baldwin, 1938). Resinous substances have also been reported from such
timbers as Yellow pine (Cram, 1873), and Teak (Rivera, 1922).
The Demerara Greenheart (Nectandra rodioei) of British Guiana has
long been well known for its great resistance, though not for absolute
immunity, to shipworm attack. This resistance is ascribed to the
presence of poisonous alkaloids particularly the alcohol soluble bebeerine or nectandrine in considerable quantities (Barger, 1922, 1924 ;
Kooy, 1922; Record and Mell, 1924; Bianchi, 1933; Iterson, 1934;
Baldwin, 1938; Spoon and Loosjes, 1946; Moll, 1948a). This timber is
widely used in Europe and is highly resistant to borers in the harbours
of Holland (Thoorn, 1887 ; Kooy, 1922), at Lowestoft, England (Barger,
1924), Liverpool and the piers in the Tyne, England (Baldwin, 1938).
Light attack has occurred only after the protective poisonous properties
of this alkaloid have been leached out owing to long immersion in salt
water (Loppens, 1905; Reyne, 1922; Anon, 1937, 1942). The superficial
layer, which alone is attacked, has been shown to contain only 1.6%
of alkaloid while the deeper wood contained 5.2% (Anon, 1942). While
this timber resists shipworm attack in the cold European waters, its
protective qualities are not very effective in the warm tropical waters,
probably due to accelerated leaching of the poison. Teredo reyne
attacks this timber in the brackish waters of Saramacca Canal in Dutch
Guiana (Reyne, 1922; Record and Mell, 1924). Reports from Panama
and Guyana (Anon, 1937), also indicate that it is unable to resist attack
by Bankia xetaki and Teredo mirajlora in these waters. That accelerated
leaching is probably the reason is substantiated by the fact that even
479
exposed in sea water. Borer resistance has thus been linked with certain
inherent physical or chemical properties of timbers.
As early as 1495 Theophrastus stated that olive escapes the attack
of Teredo because of its bitter taste. The bitter components present in
the wood has been cited as an effective repellent against the marine
borers and the application of these bitter extracts to non-resistant wood
was suggested even in early literature (Anon, 1666 ; Montanus, 1671).
Sellius in his monograph has mentioned timbers that are particularly
deeply coloured, bitter and resinous which appear to be immune to
Teredo attack.
The apparent indemnity from shipworm destruction of the famous
Jarrah (Eucalyptus marginata) of Australia has generally been attributed to its large content of resinous materials (Anon, 1862). This
deterrent substance, however, is not present in decayed Jarrah timber
(Du Cane, 1864). Oleoresins, chiefly between bark and sapwood, are
present in turpentine, Xyncarpia laurifolia (Fitzsimons and Brooks, 1920),
and resinous tylosus in the famous Greenheart, Nectandra rodioei
(Baldwin, 1938). Resinous substances have also been reported from such
timbers as Yellow pine (Cram, 1873), and Teak (Rivera, 1922).
The Demerara Greenheart (Nectandra rodioei) of British Guiana has
long been well known for its great resistance, though not for absolute
immunity, to shipworm attack. This resistance is ascribed to the
presence of poisonous alkaloids particularly the alcohol soluble bebeerine or nectandrine in considerable quantities (Barger, 1922, 1924 ;
Kooy, 1922; Record and Mell, 1924; Bianchi, 1933; Iterson, 1934;
Baldwin, 1938; Spoon and Loosjes, 1946; Moll, 1948a). This timber is
widely used in Europe and is highly resistant to borers in the harbours
of Holland (Thoorn, 1887 ; Kooy, 1922), at Lowestoft, England (Barger,
1924), Liverpool and the piers in the Tyne, England (Baldwin, 1938).
Light attack has occurred only after the protective poisonous properties
of this alkaloid have been leached out owing to long immersion in salt
water (Loppens, 1905; Reyne, 1922; Anon, 1937, 1942). The superficial
layer, which alone is attacked, has been shown to contain only 1.6%
of alkaloid while the deeper wood contained 5.2% (Anon, 1942). While
this timber resists shipworm attack in the cold European waters, its
protective qualities are not very effective in the warm tropical waters,
probably due to accelerated leaching of the poison. Teredo reyne
attacks this timber in the brackish waters of Saramacca Canal in Dutch
Guiana (Reyne, 1922; Record and Mell, 1924). Reports from Panama
and Guyana (Anon, 1937), also indicate that it is unable to resist attack
by Bankia xetaki and Teredo mirajlora in these waters. That accelerated
leaching is probably the reason is substantiated by the fact that even