NATURAL HISTORY OP AMERICAN LOBSTER. 349 



FOOD AND CAUSES OF DEATH IN ARTIFICIALLY REARED LOBSTERS. 



The yolk of hard-boiled eggs, crushed crab, boiled liver, minced fish, beef, lobster's 

 liver, the soft parts of clams, and menhaden have all been tried as food for young lobsters 

 by different experimenters in America and Europe with varying degrees of success. 



Kmmel {93, a) in a series of experiments upon the rate of molting of 90 selected 

 lobsterlings which had reached the fourth stage on the same day, and which were 

 divided into lots and were fed on different foods, obtained the following results: Beef- 

 fed lobsters advanced to the fifth stage in an average period of 11.2 days; when fed on 

 minced muscle of soft-shelled clams, in 11.3 days; on shredded lobster muscle, in 11.5 

 days; on shredded fish, in 11. 7 days; on beef liver, in 12.3 days. While his tests 

 showed a slight advantage for the beef fed over those supplied with clams, the lot 

 which received no food other than the natural plankton of the water were twice as long 

 in passing to the fifth stage, or 24.6 days. 



In the experiments on the artificial rearing of the lobster conducted at Woods Hole, 

 Mass., by the United States Fish Commission in 1902, the flesh of the menhaden, which is 

 saturated with oil so that it does not readily sink, was found to answer admirably as a food 

 until many of the larvae began to sicken and die. The fish were shredded in a meat grind- 

 ing machine, and a teacup full of this finely triturated flesh taken twice daily was found to 

 meet the needs of about 5,000 larvae. The voracious young can hardly be fed too much, 

 provided the waste is not allowed to accumulate in the rearing tanks or bags, and as they 

 grow older their ration must be increased. In June it was noticed that many of the 

 menhaden-fed fry in the rearing bags were attacked by a fungus, which Gorham {121) 

 thought was attributable to the oily fish upon which the young had fed. According to 

 this observer, the mycelial filaments of this fungus spread from the point of infection 

 until all the animal's tissues were destroyed and the lobster's body was reduced to a 

 chitinous shell packed full of the mycelium. 



In 1893 I described a case in which a parasitic fungus, probably belonging to the 

 family Chrytridiaceae, had attacked the late egg embryos of the shrimp Alpheus, a relative 

 not far removed of the lobster. In this case the eggs were crammed full of the encysted 

 parasite." No internal egg parasites have yet been reported for the lobster. 



The chief causes of death in the artificially reared lobsters are organic sediments, 

 cannibalism, which is caused chiefly by overcrowding or a lack of proper food, and the 

 exceptional fungus growths under the conditions of feeding referred to above. The sedi- 

 ments cling to the hairs of the appendages, interfere with the locomotion of the larva, 

 and send it to the bottom, thus cutting off its supply of food. In this way it becomes 

 crippled, and, being too weak to molt, it usually starves to death. Various algae, bacteria, 

 stalked protozoa, and diatoms occur in these sediments, but the chief offenders are 

 diatoms. 



Gorham (J2i), who has made a careful investigation of the causes of death inarti- 

 cially hatched fry, names 24 species of diatoms which were found on lobsters reared at 



f^ For figures and description, see appendix n, ch. v, of The embryology and metamorphosis of the Macrura, Memoirs 

 National Academy of Sciences. Washington, 1893. 



