REPORT OF COMMISSIONERS OF IXLAXD FISHERIES. 207 



XM. The Ixfluexce of Parasites. 



One other factor which is able, not only to modify the rate of 

 growth of Homarus in the early stages, but even in some cases to 

 cause a tremendous mortality, is the growth of diatoms, algte. and 

 protozoa. This is particularly true in the earlier stages, and of 

 lobsters raised under artificial conditions. It is probable that this 

 pest is of little harm to young lobsters under natural conditions of 

 environment. The lobsters so attacked are designated as "fuzzy" 

 lobsters, for their appearance is characterized by a heavy fringe of 

 growth on all parts of the body, impeding their activities in both 

 swimming and feeding; and, unless the molting period comes quickly 

 enough, ultimately causing the death of the young lobsters. 



Although the question is so often one of life or death to the loljsters 

 attacked, the condition described has a marked effect upon the rate 

 of development of those which do not succumb. The molting periods 

 are delayed and the amount of increase in length for these lobsters 

 is correspondingly small. This diminution in the rate of growth is 

 probably, in this case, directly dependent upon the question of ade- 

 quate food supply, the possibility of which is so often cut off by 

 the excessive growth of protozoa, diatoms, and algie. This growth 

 is, in turn, partially dependent upon the conditions of light which 

 surround the individuals. At the Wickford Hatchery it was dis- 

 tinctly observable that, of three groups of lobsters which were placed 

 in dark cars, wire cylinders, and a shallow open box, respectively, the 

 most profuse growth of diatoms and protozoa was upon those which 

 were kept in the brightest light, while those confined in the dark 

 were quite free.* 



In the former case, the rate of growth was very slow, and though a 



*Regarding the influence of light upon the abundance of growths on the lobsters, William- 

 son ('04) mentions an interesting fact. In each of two large concrete tanks were placed two 

 female lobsters. In one tank a board shelf afforded protection from the sun so that only the 

 antennae of the lobsters were exposed to its rays. In the other tank there was no protection 

 from the sun whatsoever. In the first case, after the summer season, the lobsters themselves 

 were free from growth of all sorts, but the antenna were covered. The bodies and appendages 

 of the lobsters which were confined in the exposed tank were, however, quite hidden bj- the pro- 

 lific growth of seaweeds, Lammaria sp., young mussels, etc. 



