Teredinidae 545 



1928. The vitality of the gametes of Citmingia tellinoides. Ibid. S4-35 1 ■ 



Morgan, T. H. 1910. A cytological study of centrifuged eggs. J. Exper. Zool. 



9:593- 



Family teredinidae 



REARING TEREDO NAVALIS 



Benjamin H. Grave, De Pauw University 



THE shipworm, Teredo navalis, is abundant at many places on the 

 coast of the United States. Its activities are serious everywhere 

 but it is most destructive in the warmer waters of the south. At Woods 

 Hole its breeding season extends from the first or second week in May 

 to the middle of October. The first larvae of the season metamorphose 

 and begin to burrow into exposed wooden structures about June 20. 

 They become fully mature worms in one year and die before the end of 

 the second summer at an age of 12 to 15 months. The largest specimens 

 collected measure about 16 inches in length and nearly % incri m widest 

 diameter. The average size attained, when grown in large timbers, is 

 12 to 14 inches in length but when grown in small strips of wood they 

 often do not exceed 2% inches in length at the end of a year's growth. 



METHODS OF STUDY 



It is difficult to get large numbers of Teredo for study without adopt- 

 ing special methods because they live normally in permanent wooden 

 structures such as the piles of wharves. It is therefore necessary to 

 raise them by putting out suitable timbers one summer to be studied the 

 next. Lobster pots or cages made of lath put out early in August 

 are found to contain sexually mature shipworms by the beginning of the 

 breeding season the following June. For growing Teredo 2x4 stakes 

 are excellent, and they may be put out as early as June or July without 

 being completely destroyed within a year by the infesting worms. By 

 adopting this method it is possible to obtain thousands of breeding 

 shipworms with the expenditure of very little effort. They attack the 

 wood at the mud-line and not to any great extent at the surface of the 

 water. 



METHODS OF EMBRYOLOGICAL STUDY 



The eggs when spawned are retained in the supra-branchial chamber 

 of the gills and during cleavage and early larval stages they will not 

 develop normally outside the gills. In order to secure embryos of all 

 ages it is therefore necessary to remove them from the gills of a large 



