FRESH-WATER MUSSELS. 



93 



mud, with rarely an occasional diatom. A young L. anodonioides from Smiths Creek bar 

 in the Mississippi contained fragments of diatom shells indicating that it had been feeding 

 on them to an unusual extent. Although Pleurosigma covered the mud of that region, 

 forming an almost unbroken brown scum, it is noteworthy that it was only rarely found in 

 the stomachs of the young mussels, it being apparently too large to enter the mouth. 



As regards the entire subject of mussel food and feeding there are some general 

 observations it may be pertinent to make at this point. 



At one time it was thought that extremely dense beds of mussels in the bottom of 

 lakes might act as reducers of an excessive accumulation of plankton. They might 

 indeed take care of many sunken and decaying plankton organisms, but under favor- 

 able conditions plankton can develop more rapidly than anything can eat it. 



The finding of what appears to be bacteria in the stomachs of mussels of the Auglaize 

 River and the observation made in tanks at the Biological Station at Fairport — that 

 turbid water in which there were mussels cleared up rapidly, the mussels collecting the 

 silt and other materials in suspension — raise the question as to whether mussel beds are 

 not or can not be of use in the purification and sanitation of rivers. If oysters grown 

 in polluted waters may harbor typhoid bacilli and so communicate the disease to those 

 who eat them, there seems to be no good reason why mussels, which are not eaten, may 

 not serve to arrest and devour those as well as other pathogenic organisms. 



Since mussels are very inactive animals, the rate of metabolism may be expected 

 to be low and the food requirements correspondingly small. The problem of obtaining 

 nourishment for mussels is then one of the least of our troubles. Doubtless younger, 

 more active mussels require a richer diet, and the first problem of mussel propagation, 

 that of finding a suitable host, is fundamentally one of finding suitable nutrition for a 

 creature remarkable for its fastidiousness in this regard. It may be that a critical 

 problem is the finding of suitable nourishment for the first month or so of free life, but 

 beyond this the only problem, so far as food supply is concerned, appears to be the 

 avoidance of actually poisonous or harmful substances. 



OBSERVATIONS OF A. F. SHIRA ON FOOD OF JUVENILE MUSSELS. 



The following table (i) embodies a record of the stomach contents of 60 juvenile 

 mussels, distributed among 6 species, taken in Lake Pepin during 1914. The material 

 was studied with the use of a rafter counting cell, but since only a very small quantity 

 of food could be obtained from each mussel the calculation of percentages can be only 

 approximate. 



Table i. — Food op Six Species op Juvenile Musseis Taken in Lake Pepin, September, October, 



AND November, 1914. 



Juveniles exaxniiied. 



Length of juveniles (milli- 

 meters). 



Percentage of food . 



Species. 



Number. 



Mini- 

 mum. 



Maxi- 

 mum. 



Average. 



Organic 

 remams 

 (princi- 

 pally 

 vege- 

 table 

 matter). 



In- 

 organic 

 remains 



(silt. 



etc.). 



Unicel- 

 lular 

 green 

 algae. 



Diatoms. 



Lampsilis luteola 



Lampsilis ventricosa 



Lampsilis alata 



Lampsilis gracilis 



Quadrula plicata 



Anodonta imbecilUs 



75412°— 22 7 



s. o 

 4.8 



8.2 



6.5 

 6.4 

 6.3 



15.^ 

 13- 



9.5 



8.8 

 13-7 

 13-5 



7.4 

 13.7 



Trace. 



