336
N. BALAKRISHNAN NAIR AND M. SARASWATHY
F. Role of Primary Film
. . . . .. .. .. .. 467
C . Marine Fungi and Shipworm Attack
.. .. .. . . 468
H. The Effects of Water Currents Upon the Rate of Attack of Shipworms .. . . . . . . . . .. .. .. . . 469
I. Oxygen Content of the Water
.. .. .. .. . . 469
J. Hydrogen-ion Concentration . . .. .. .. .. . . 460
K. The Effects of Turbidity
. . .. .. .. .. . . 460
L. The Effects of Pollution
. . .. .. .. .. . . 460
M. The Effects of Marine Fouling
. . .. .. .. . . 462
N. Relation to other Borers
. . .. .. .. .. .. 466
0. Parasites and Associates
. . .. .. .. .. . . 467
XVIII. Objects Attacked
. . .. .. .. .. .. .. . . 474
XIX. Detection and Prevention of Shipworm Attack . . . . .. . . 476
XX. Timbers of Unusual Durability Against Shipworms
. . .. .. 478
XXI. Acknowledgements . . .. . . . . .. .. .. . . 482
A. The Role of Silica
. . .. .. .. . . .. .. 480
B. Bark of Trees . . .. .. .. .. .. .. . . 481
XXII. References
.. .. .. .. .. .. .. .. 482
I. INTRODUCTION
A ubiquitous pest of all manner of timber in the sea, t e r e d o t h e
shipworm-causes damage worth millions of pounds every year all over
the world. Hidden protectively within the ‘‘ heart ” of both fixed and
floating timber, and hardly visible from the outside, these borers work
silently and reduce t o soft sawdust even the most resistent timber.
Rasping with their shells mechanically, these living drills draw a major
part of their nourishment from the hard cellulose. Known to Pliny,
Ovid and Aristophanes, shipworms are mentioned even by Homer.
The accounts of the voyages of Dampier, Cook and Drake reveal that
these early navigators dreaded shipworms. Columbus lost all the ships
of his fourth voyage as a result of their ravages. Thus, unaware of the
danger that lurked beneath them, ancient mariners were shipwrecked
in mid-ocean through the rapacity of these wood borers. Even the
safety of a nation was threatened owing to the ravages of the shipworms on the wooden dykes of Holland. Despite the care and constant
surveillance of harbour engineers, teredo successfully invaded San
Francisco Bay in about 1921. Unseen even by experts, this exotic
menace converted solid pillars and piers into weak and fragile “ honeycombs ”. Along the entire seafront, bridges collapsed, piers crashed and
boat hulls and wharf-piling crumbled. Like an unseen typhoon, it
swept up the coast leaving a trail of destruction along its path. The
first few waves of attack cost the United States several million dollars.
I n a second serious outbreak in the same locality property worth
21 million dollars was destroyed. Though present in all seas, shipworms
are particularly destructive in the tropical waters where they eat in-
N. BALAKRISHNAN NAIR AND M. SARASWATHY
F. Role of Primary Film
. . . . .. .. .. .. 467
C . Marine Fungi and Shipworm Attack
.. .. .. . . 468
H. The Effects of Water Currents Upon the Rate of Attack of Shipworms .. . . . . . . . . .. .. .. . . 469
I. Oxygen Content of the Water
.. .. .. .. . . 469
J. Hydrogen-ion Concentration . . .. .. .. .. . . 460
K. The Effects of Turbidity
. . .. .. .. .. . . 460
L. The Effects of Pollution
. . .. .. .. .. . . 460
M. The Effects of Marine Fouling
. . .. .. .. . . 462
N. Relation to other Borers
. . .. .. .. .. .. 466
0. Parasites and Associates
. . .. .. .. .. . . 467
XVIII. Objects Attacked
. . .. .. .. .. .. .. . . 474
XIX. Detection and Prevention of Shipworm Attack . . . . .. . . 476
XX. Timbers of Unusual Durability Against Shipworms
. . .. .. 478
XXI. Acknowledgements . . .. . . . . .. .. .. . . 482
A. The Role of Silica
. . .. .. .. . . .. .. 480
B. Bark of Trees . . .. .. .. .. .. .. . . 481
XXII. References
.. .. .. .. .. .. .. .. 482
I. INTRODUCTION
A ubiquitous pest of all manner of timber in the sea, t e r e d o t h e
shipworm-causes damage worth millions of pounds every year all over
the world. Hidden protectively within the ‘‘ heart ” of both fixed and
floating timber, and hardly visible from the outside, these borers work
silently and reduce t o soft sawdust even the most resistent timber.
Rasping with their shells mechanically, these living drills draw a major
part of their nourishment from the hard cellulose. Known to Pliny,
Ovid and Aristophanes, shipworms are mentioned even by Homer.
The accounts of the voyages of Dampier, Cook and Drake reveal that
these early navigators dreaded shipworms. Columbus lost all the ships
of his fourth voyage as a result of their ravages. Thus, unaware of the
danger that lurked beneath them, ancient mariners were shipwrecked
in mid-ocean through the rapacity of these wood borers. Even the
safety of a nation was threatened owing to the ravages of the shipworms on the wooden dykes of Holland. Despite the care and constant
surveillance of harbour engineers, teredo successfully invaded San
Francisco Bay in about 1921. Unseen even by experts, this exotic
menace converted solid pillars and piers into weak and fragile “ honeycombs ”. Along the entire seafront, bridges collapsed, piers crashed and
boat hulls and wharf-piling crumbled. Like an unseen typhoon, it
swept up the coast leaving a trail of destruction along its path. The
first few waves of attack cost the United States several million dollars.
I n a second serious outbreak in the same locality property worth
21 million dollars was destroyed. Though present in all seas, shipworms
are particularly destructive in the tropical waters where they eat in-