Scavenging Attraction of a Cyclopoid Copepod to Zooplankton Carcasses

Abstract

The detrital food chain plays a critical role in shaping community structure and sustaining ecosystem functioning. It is initiated by the consumption of dead organic matter through scavenging. However, scavengers in freshwater ecosystems remain poorly understood. In this study, we experimentally investigated whether Thermocyclops taihokuensis, a cyclopoid copepod widely distributed across East and Central Asia that has recently expanded its range into Europe, exhibits scavenging behavior and whether it uses chemical cues to locate and utilize carcasses of other organisms. Our results showed that T. taihokuensis approached and attacked experimentally presented cladoceran carcasses, suggesting that it recognized the carcasses as food. Indeed, T. taihokuensis was attracted to artificial baits infused with the odor of cladoceran carcasses but ignored identical baits lacking odor, suggesting that chemical cues serve as a primary mechanism for detecting them. These findings highlight that, although cyclopoid copepods are generally considered to be omnivorous, grazing on algae and preying on other organisms, T. taihokuensis appears to be a more versatile consumer than previously recognized and may also contribute to the detrital food chain by potentially scavenging.