Copepods Cyclops

After first treatment, reduction within 1 week of 3 species of cladocerans (Daphnia laevis, Ceriodaphnia sp., Bosmina longirostus sp.), and 2 species of copepods (Cyclops sp., Diaptomus sp.). No recovery of Daphnia and Ceriodaphnia for 6 months, but Bosmina reappeared 11 weeks later. Diaptomus was depleted for 4 months, but Cyclops recovered in 6-7 weeks. The amphipod Hyallela azteca was eliminated within 4 weeks, and no recolonization was evident after 6 months. No adverse effects on oligochaetes, snails (Physa sp.), or ostracods (Cyprodopsis sp.). After second treatment, temporary reduction in Cyclops and Bosmina, and no significant effects on ostracods, snails, or worms... 

Table 8.4. Triaenophorus crassus growth of procercoids in adult males and females of the copepod Cyclops bicuspidatus thomasi. Comparison of mean length and width of 21- to 28-day old procercoids. (Data from Rosen Dick, 1983,)...

Although laboratory studies have value for specific purposes, it is in the natural ecosystem that we must determine the behavior of a pesticide and its possible effect. Studies of the cycling of radionuclide-labeled pesticides in natural ecosystems are limited, since introduction of radionuclides into the environment involves public-health and public-relations issues as well as possibly difficult technical considerations. However, an ecosystem study was conducted by spraying a 4-acre marsh in western Sandusky Bay, Ohio, with Cl-labeled DDT. One aspect of the study involved the incorporation of the pesticide in some invertebrates of this aquatic ecosystem as determined by autoradiography (Webster, 1967). An amount of the pesticide suitable for mosquito control was applied to the study area by helicopter. Samples of leeches (Erpobdella punctata), am-phipods (Hyallela sp.), and copepods (Cyclops bicuspidatus, Diaptomus orga-nensis) were collected, fixed, sectioned, and autoradiographed. It was observed that leeches contained the pesticide or a Cl-compound, but none was detected in amphipods or copepods. 

Although Cyclops is the most widespread copepod in lakes of this region (78), its diet is incompletely understood. Cyclops had the highest 15N content of all zooplankton, and in the fertilized side of the lake Cyclops was nearly one full trophic level enriched ( 3%>) above Daphnia. Thus Cyclops may function as an omnivore or a carnivore in this lake, and a second experiment was performed to address this question. Overall, these natural-abundance isotopic values are similar to the 815N values reported for zooplankton in other arctic lakes (49, 52). 

Measurement of susceptibility is further complicated by the fact that species of copepods which may readily be infected experimentally in the laboratory may only serve as poor hosts under natural conditions. For example, in the laboratory, Cyclops scutifer was found to be readily invaded by the coracidia of Triaenophorus nodulosus and yet in Lake Lergi, this species of copepod showed a prevalence of only 0.28% (849). This result may be due to the behaviour and/or the physiology of the coracidia or the host or both, being different under different environmental conditions. 

Copepoda A class of crustaceans occurring in marine and freshwater habitats. Copepods are usually 0.5-2 mm long and lack both a carapace and compound eyes. Copepods are important members of plankton some are free-living, feeding on microscopic organisms others are parasitic. A familiar freshwater genus is Cyclops, so named because the members have a single median eye. 

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