Prionodesmacea 539 



I93 5. Physiology of ovulation and ejaculation in the oyster. Collecting 



Net 10:261. 



Galtsoff, P. S. and Smith, R. O. 1932. Stimulation of spawning and cross fer- 

 tilization between American and Japanese oysters. Science 76:371. 



Hopkins, A. E. 1931. Factors influencing the spawning and setting of oysters in 

 Galveston Bay, Texas. Bull. U. S. Bur. Fish. 47: 57. 



THE CULTIVATION OF LAMELLIBRANCH LARVAE 



Herbert F. Prytherch, U. S. Bureau of Fisheries 



LARVAL stages of many common lamellibranchs (Ostrea, Mya, Pecten, 

 _j Mytilus, Venus, Teredo, etc.) may be obtained from plankton 

 collections made in inshore coastal waters during the spring, summer, 

 and fall months. Plankton samples may be' collected with a tow net 

 or by means of a hand or power driven pump from which the seawater is 

 passed through a net of No. 10 or No. 14 bolting silk for retention of 

 only the larger and nearly full grown larvae or through No. 20 for all 

 stages. The larvae are usually more abundant in surface samples col- 

 lected at low slack water in proximity to the spawning beds of the 

 desired species. 



The separation of bivalve larvae from other marine forms is greatly 

 simplified by washing the plankton sample from the net into a fish 

 hatching jar or any tall, straight-sided glass container with funnel- 

 shaped bottom, into the center of which the heavier, shelled forms soon 

 collect. These are siphoned off with a glass tube, placed in Syracuse 

 glasses, and forms other than those desired removed under the binocular 

 by means of a fine pipette. The larvae are then placed in small piles 

 with dissecting needles, segregated as to size and species, and may be 

 transferred easily to other aquaria by employing a dilution pipette with 

 10-inch rubber tubing and mouthpiece. For identification of several 

 representative species see Stafford (1909). 



The maintenance and rearing of cultures may best be carried out in 

 cylindrical glass vessels having a hemispherical or funnel-shaped bottom. 

 Ordinary glass bottles, 1 to 5 gallon capacity, may be used in an 

 inverted position provided a tube is inserted in the stopper so that air 

 may be withdrawn from above the surface of the water. At the lowest 

 point in the jar or bottle a very small stream of air is introduced con- 

 tinually, preferably through porous plugs of wood or "filtros," in order 

 to aerate and circulate the water and stimulate the swimming (feeding) 

 activities of the larvae. The cultures should contain not more than 

 200 to 500 larvae per liter as the seawater is renewed only once or twice 

 daily and must be of sufficient quantity to provide an adequate food 

 supply. The larvae feed on microplankton and minute particles of 

 detritus and suspended matter, an ample supply of which may be ob- 

 tained from seawater that has been passed through coarse filter paper 



