CULTURE OF FRESH-WATER MUSSELS. 73 



Young mussels of various sizes from one-half inch up placed in tanks and aquaria 

 indoors at various times have shown a negligible amount of growth. Likewise, nega- 

 tive results have been secured in plants of young mussels made in the following types 

 of aquaria indoors supplied with flowing river water which was unmodified so far as 

 known: Wooden tanks or troughs, tanks and troughs lined with galvanized iron painted 

 and unpainted, and cement tanks and troughs. Two systems of water supply have been 

 tried. In one the river water was pumped direct, in the other it was pumped first into 

 a reservoir, from which it was distributed by gravity flow. Later results seemed to 

 indicate a difference to be discussed below under cement ponds. 



In order to eliminate the destructive turbellarians and other predacious forms that 

 might be introduced with the water, balanced aquaria, large and small, filled with filtered 

 river water were tried. Here, too, the mussels survived for only a short lime. 



More recent experiments in rearing young mussels in a type of container of com- 

 paratively small dimensions have been conducted with considerable success, first by 

 F. H. Reuling (1920) at Fairport and later by the author and others. The conditions 

 were so different from those of the experiments just described that they should throw 

 light on controlling factors in the development of juveniles. Their convenient size 

 made them admirably suited for experimental pi r] OSes where a considerable number 

 of units are required. The equipment consisted of galvanized-iron troughs 14 by 8 

 inches by 8 feet, painted with asphaltum. The troughs were protected from the sun 

 by a shed roof of wood; otherwise they were uninclosed. (See center background of 

 fig. 61.) 



The water supply was derived from the surface of a pond containing vegetation. 

 This arrangement yielded water of comparative clarity even when the river supplying 

 the pond was turbid. The point of intake at the surface probably insured a minimum 

 of animal enemies, such as Turbellaria, which might prey on the mussels. Additional 

 precautions were taken against enemies by further straining through ordinary cloth and 

 later close-meshed metal fabric. 



Broods of Lamps-Ms lulcola and some one-half dozen L. liganu niina, the river 

 mucket, were reared in these troughs the first summer. In 1919 successful results 

 were secured with three species approximately as follows: Yellow sand shells, L. ano- 

 dontoides, 2,000; Lake Pepin mucket, L. lutcola, 3,000; the river mucket, L. ligamentina, 

 .500. 



The dwarfing effect observed in aquaria and tanks indoors is a condition the causes 

 of which have not been entirely determined. There is reason to suppose that reduced 

 light and excessive precipitation of silt are possible factors, assuming that the water 

 supply is the same as that of the river, ponds, or out-of-door troughs. Any such 

 assumption is unwarranted, however, until comparative determinations of water condi- 

 tions and contents have been made. Lack of growth suggests that the plankton, sup- 

 posedly the principal food of the mussels, or other elements are for some reason wanting. 

 The following evidence indicates the nature of some of these constituents which con- 

 ceivably may be lost in part from water standing in reservoirs. 



Detritus, including dead organic matter, forms a considerable proportion of the 

 food of mussels, according to A. F. Shira and Franz Schrader. (Coker, Shira, Clark, and 

 Howard, 1921, pp. 88 and 93.) Wilson and Clark (19 12), in the examination of the 

 stomach contents of river mussels, find a proportionally small amount of plankton 



