THE FLATWORM AS AN ENEMY OF FLORIDA OYSTERS. 
By Ernest DanauaDE, Formerly Field Assistant, U. S. Bureau of Fisheries. 
INTRODUCTION. 
During February, 1917, the Bureau of Fisheries and the Florida 
Shell Fish Commission made an investigation of a series of oyster 
areas on both the east and west coasts of Florida with regard to a 
reported destruction of oysters by a parasite, which later proved to 
be a polyclad turbellarian, or flatworm. As early as March, 1916, 
Dr. R. KE. Coker stated, in unpublished field notes, that a worm, 
known locally as the “leech,” was reported to occur occasionally on 
some of the oyster bars in the vicinity of Tampa, and sometimes to 
cause within a very short time an enormous mortality among the 
planted oysters, and that the fear of the pest served to deter the 
oyster ee from extending the cultivated areas. In the latter 
part of December of the same year T. R. Hodges, State shell fish 
commissioner of Florida, submitted to the Bureau a number of 
oysters, taken from the beds near Cedar Keys, affected with the so- 
called “leech.”” The oysters, which had been packed in ice, were 
alive when received in Washington, and contained from 2 to 3 flat- 
worms each; however, the worms were dead, probably having been 
frozen in transit. The attacks of this parasite on oysters in these 
two localities, Tampa and Cedar Keys, are the only ones that had 
ever come to the attention of the Bureau. 
The writer was informed by R. E. Gibson, an oyster dealer and 
lanter of Tampa, Fla., that the worms, or so-called ‘leeches,’ had 
Seias observed attacking the oysters on some of the oyster bars in the 
Tampa Bay region at more or less regular intervals during the past 
20 years, and particularly during the oyster season 10 years ago. 
The worms would disappear entirely from the beds for a period of 2 
or 3 years and then reappear, the reoccurrences apparently running 
in cycles. Compared with the attack of the season 1916-17, the 
previous infestations and mortality were said to have been less 
extensive and harmful. 
On the east coast of Florida a similar outbreak of the worms was 
observed 10 years ago at three or four points on Indian River. The 
rincipal infected localities in that bade of water were Indian River 
et, Bethel Creek, and Orchid. After a very serious and damaging 
attack, from which some oyster bars were practically depleted or 
greatly reduced in productivity, the fsoulble ceased and has not 
occurred there since. The oyster bars in the meantime have recov- 
ered their normal condition.* It is interesting to note that the de- 
struction of oysters by turbellarians was reported by David G. Stead 
@ This information was furnished by E. F. McDonald, a practical fisherman of Port Orange, Fla. 
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