PARENT SESSION
Contributed Oral Session 167: Toxicology / Disease: Viruses, Fungi, and Contaminants
Friday, August 12, 8:00 AM - 11:30 AM, Meeting Room 524 A, Level 5, Palais des congrès de Montréal
Influence of metal contamination and predator density on morphological defenses and survival during predatory encounters in Daphnia pulex.
Mirza, Reehan*,1, Pyle, Gregory1, 1 Nipissing University, North Bay, ON, Canada
ABSTRACT- In this study, we examined the influence of copper (Cu) contamination on the production of morphological defenses in the water flea, Daphnia pulex. D. Pulex develops neck teeth, during the first to third instars, in response to chemical cues (kairomones) from gape-limited predators (e.g. aquatic fly larvae, Chaoborus americanus). These defenses are temporary and disappear once the prey outgrows the predator′s gape. Without these defenses we would predict that D. pulex survival should decrease in the presence of predators. However, behavioral responses may compensate for a lack of morphological defense. We exposed D. Pulex to chemical cues from C. americanus (fed either D. pulex or brine shrimp) at two different densities (1 predator/L or 50 predators/L) in the presence or absence of environmentally relevant levels of Cu (10 
g/L) and quantified neck tooth production in neonates. Subsequently, neonates were placed in staged encounters with Chaoborus larvae and we recorded survival. Our preliminary results suggest that under low predator densities the production of neck teeth is low compared to high predator densities. Moreover, Cu contamination inhibits neck tooth production at high predator densities, but at low predator densities affected the length of neck teeth produced. Subsequent staged encounters found that neonates from mothers reared under low predator densities and exposed to kairomones from predators fed Daphnia had higher survival compared to all other treatments. However, when mothers were reared under high predator densities neonates exhibited higher survival in both kairomone only treatments compared to Cu exposure and control water. Our results suggest that Cu at environmentally relevant levels can have strong influences on the survival of D. pulex which has important implications at the population and community levels.
Key words: copper, Daphnia pulex, neck teeth, kairomone