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

Abstract

T. navalis occurs in abundance at Woods Hole and vicinity and has been known there for many years. The breeding season extends from about May 10th to Oct. 10th. Spawning begins in the spring when the water reaches a temp. between 11[degree] and 12[degree] C. Spawing by each $ occurs several times during the season. No lunar periodicity in spawning occurs and no 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 5 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 prototroch or none. T. navalis reaches sexual maturity in 6 weeks or 2 months after metamorphosis, when it measures 4-5 cm. in length. It reaches adult size in 1 year and dies during the 2nd yr. The largest specimen collected in 4 yrs. measured 40 cm. in length and 1 cm. in greatest diam. 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.