The shipworm normally attacks permanent wooden structures, such as wharf piles; it is therefore difficult to obtain large numbers of these animals without making advance preparations. Turner (1947) recommends the use of a laminated collecting board. It is made of six or more layers of soft, straight-grained wood 12' x 6" x 1/2", with brass or galvanized iron washers separating the layers to produce cracks large enough so that the animals will not cross from one layer to the next. The borers form long straight tubes and, as the wood is very thin, may be easily extracted. The board should be suspended vertically in the region of most severe attack, which is usually near the mud-line, and weighted so that it will remain in place. If this is done in July or August, the boards will be infested with shipworms by the following summer. Another device for collection is described by Lasker and Lane (1953); it is somewhat less cumbersome than that recommended by Turner.

The animal is abundant at Woods Hole, Mass.

In the adult, the sexes are separate and cannot be distinguished externally. Young animals, however, are potentially hermaphroditic and pass through alternating und-sexual phases during their development. Details of this may be found in papers by Coe (1936, 1941) and Grave (1942). The species is viviparous, releasing larvae at an advanced veliger stage; certain other related species of shipworms (T. dilitata and Bankia (Xylotria) gouldii), not found in the Woods Hole region, are oviparous.

These animals breed at Woods Hole from the first or second week of May until mid-October. Spawning begins when the water temperature rises above 11 to 12û C. (Grave, 1928).

A. Care of Adults: The animals should be left in the collecting board and supplied with running sea water until required for study or experimentation, at which time they may be dissected out with ease.

B. Procuring Gametes: Active sperm are expelled by sexually mature males when they are removed from their burrows. However, eggs of this species which are artificially inseminated will not develop beyond the third or fourth cleavage.

C. Preparation of Cultures: Various developmental stages can be obtained by dissecting open the gill chamber of a ripe female. (Sigerfoos, 1908, presents a diagram showing the anatomy of the adult, and the location of this brood chamber.) The tightly packed embryos are arranged in two parallel rows on either side of the elongate body. Three developmental stages are usually present in each mature female; the oldest, which are grey in color, are located in the most anterior region (Hatschek, 1880). The eggs and younger stages are white in color; they will not live for more than a very short period outside the gill chamber. However, late trochophores and veligers can readily be cultured in fingerbowls of sea water. The veligers are very hardy and may be kept for about three weeks with a minimum of care, provided they are fed regularly with diatoms (Grave, 1937).

A. The Unfertilized Ovum: The egg is small, measuring 55 to 60 microns in diameter. It is surrounded by a delicate membrane and contains a large germinal vesicle. The animal pole is distinguishable from the darker vegetal pole, even in the unfertilized condition. The ovum is white in color.

B. Fertilization and Cleavage: There is apparently no observation recorded concerning the state of the ovum at fertilization. Cleavage is markedly unequal and undoubtedly spiral. Gastrulation is by epiboly and invagination. The embryo is about 250 microns in diameter when it is released from the maternal gill (Lane et al., 1954).

C. Rate of Development: Since the eggs of this species cannot be reared outside the parent, the developmental rate has been estimated, only, using indirect methods. Grave (1928) suggested that the entire developmental period from insemination to metamorphosis lasts about five weeks, with at least half this time spent within the gill chamber of the mother. Lane et al. (1954) state that the normal free-swimming period does not exceed four days. The young animal reaches sexual maturity about six weeks after metamorphosis.

D. Later Stages of Development and Metamorphosis: The early trochophore is top-shaped and measures 59 by 60 microns. Although the alimentary tract appears solid and dark, a recognizable stomodeum is present. The prototroch is either very poorly developed or absent. In older trochophores the cilia, which previously covered the entire body surface, are limited to the region of the velum. The appearance of the shell gland coincides with, or slightly precedes, velum formation. The newly-formed shell is single, but it soon becomes bivalved. Older veligers are actively motile, even within the branchial chambers. The velum in these larvae is well developed and the pre-trochal hemisphere is tipped with an apical tuft of cilia. The complex digestive tract consists of stomach, intestine and liver, and has mouth and anal openings. Traces of kidney and muscles are also present. Diagrams of the stages developing in the brood chambers can be found in a paper by Hatschek (1880).

During the free-swimming period, the larva develops siphons, gills and a well marked foot with byssus threads. The nervous and muscular systems continue to differentiate. As it grows older, the color of the larva changes from grey to yellow-green, and finally to olive green. After attachment, the young Teredo undergoes a remarkably rapid metamorphosis, during the course of which the velum is cast off and eaten. For details of metamorphosis and diagrams of the young attachment stages, see the paper by Sigerfoos (1908).

COE, W. R., 1933. Sexual phases in Teredo. Biol. Bull., 65: 283 303.

COE, W. R., 1934. Sexual rhythm in the pelecypod mollusk Teredo. Science, 80: 192.

COE, W. R., 1936. Sequence of functional sexual phases in Teredo. Biol. Bull., 71: 122-132. (Also in Coll. Pap., Osborn Zool. Lab., Yale Univ., vol. 18.)

COE, W. R., 1941. Sexual phases in wood-boring mollusks. Biol. Bull., 81: 168-176.

GRAVE, B. H., 1928. Natural history of shipworm, Teredo navalis, at Woods Hole, Massachusetts. Biol. Bull., 55: 260-282.

GRAVE, B. H., 1933. Rate of growth, age at sexual maturity, and duration of life of certain sessile organisms, at Woods Hole, Massachusetts. Biol. Bull., 65: 375-386.

GRAVE, B. H., 1937. Rearing Teredo navalis. In: Culture Methods for Invertebrate Animals, edit. by Galtsoff et al., Comstock, Ithaca, pp. 545-546.

GRAVE, B. H., 1942. The sexual cycle of the shipworm, Teredo navalis. Biol. Bull., 82: 438445.

GRAVE, B. H., AND J. SMITH, 1936. Sex inversion in Teredo navalis and its relation to sex ratios. Biol. Bull., 70: 332-343.

HATSCHEK, B., 1880. Ueber Entwicklungsgeschichte von Teredo. Arb. Zool. Inst., Wien, 3: 1-44.

LANE, C. E., J. Q. TIERNEY AND R. E. HENNACY, 1954. The respiration of normal larvae of Teredo bartschi Clapp. Biol. Bull., 106: 323-327.

LASKER, R., AND C. E. LANE, 1953. The origin and distribution of nitrogen in Teredo bartschi Clapp. Biol. Bull., 105: 316-319.

SIGERFOOS, C. P., 1908. Natural history, organization, and late development of the Teredinidae, or ship-worms. Bull. U. 5. Burl Fish., 27: 191-231.

TURNER, R., 1947. Collecting ship-worms. Spec. Publ. Limnological Soc. of Amer., no. 19.