NATURAL HISTORY OF SHIPWORM, TEREDO NAVALIS, AT WOODS HOLE, MASSACHUSETTS

¹ WABASH COLLEGE

Teredo navalis occurs in abundance at Woods Hole and vicinity and has been known there for many years.

The breeding season extends from about May 10 to October 10. Spawning begins in the spring when the water reaches a temperature between 11° and 12° C. Spawning by each female occurs several times during the season. No lunar periodicity in spawning occurs and there are no broods caused by synchronous spawning.

The eggs are retained in the gills of the mother during cleavage and early larval development.

The time required for the fertilized egg to complete larval development to metamorphosis is approximately five weeks at Woods Hole. About half of this time is passed in the brood pouch and half as a free swimming veliger.

When eggs and early embryos are removed from the gills they do not develop normally.

The trochophore of Teredo is non-motile, having either a feebly developed protroch or none.

Teredo navalis reaches sexual maturity in six weeks or two months after metamorphosis when it measures four or five centimeters in length. It reaches adult size in on year, and dies during the second year. The largest specimen collected in four years measured forty centimeters in length and one centimeter in greatest diameter.

The rate of growth during the summer months and also during the winter was determined and tabulated. Certain habits of shipworms were also observed and recorded.