Physid Snails Research Articles

The Effect of Toxaphene on the Benthos in a Thermally-Stratified Lake

Chaoborus larvae were the only profundal benthic organisms that were adversely affected by treatment of a dimictic lake with toxaphene to eradicate undesirable fish. The larvae were eliminated, and had not become reestablished 2 years after treatment. Subesquent to removal of the fish, an extremely large population of Chironomus larvae appeared, and when the lake was restocked with 7 species of fish, the population dropped to its former level. More than a year after treatment, a substantial population of Procladius larvae appeared, probably resulting from the removal of carp and the consequent reduction of turbidity, increased growth of rooted aquatic vegetation, and restoration of higher dissolved oxygen levels. The temporary absence of fish also favored an increase in the physid snail population.

Developmental Stages in the Digenea. I. Observations on the Hatchability and Infectivity of Ochetosomatid Eggs in Physid Snails

tion on the overall life-history pattern of the group dealt with, while many of the others have only indicated the probable pattern of the cycle. With the basic lifecycle pattern being well known, the elucidation of new life-cycles for the digenetic trematodes currently, then, is primarily a matter of determining the host species for the various developmental stages and of working out the time intervals. Perhaps one of the biggest stumbling blocks encountered in life-history investigations is the procurement of and the establishment of the infection in natural host animals which