Effects of Products Released by Aphanizomenon flos-aquae and Purified Saxitoxin on the Movements of Daphnia carinata Feeding Appendages

Experiments were run to determine the effect of filtrate from incubated Aphnizomenon flos-aquae on the thoracic appendage beat rate and frequency of postabdominal rejections by Daphnia carinata. Comparisons were made between the response to Aphanizomenon filtrate and to purified saxitoxin (STX). The short-term response pattern to the filtrate included an immediate 30-50% depression of thoracic appendage beat rate and elevation of postabdominal rejection rate followed by slowly decreasing thoracic appendage beat rate and increasing postabdominal rejection rate during the 10-min exposure. Animals recovered to pretreatment activity rates in