Document: LAU-3-56-31

Understanding the interaction of crayfish and the Hine's Emerald Dragonfly larvae coexisting in crayfish burrows.

PINTOR, L.M.* ^1,2 and D.A.SOLUK ^1,2

University of Illinois, Urbana-Champaign, Champaign, IL 61820, USA ¹
Illinois Natural History Survey, Champaign, IL 61820, USA ²

Abstract:
Biotic interactions, such as predation, can have significant influences on population dynamics, community structure, and the behaviors of organisms. Odonates are a group of organisms in which predation has been a major factor shaping the observed life histories and behaviors. While most studies have focused on the effect of vertebrate fish predators and intraguild predation, crayfish are another predator present in many aquatic systems that can have an effect on larval Odonate populations. Habitat duration can also influence larval Odonate communities by limiting the species that can maintain populations in variable environments. It can also effect the strength of biotic interactions between those organisms that persist. The Hine's Emerald Dragonfly, Somatochlora hineana, inhabits small, ephemeral streamlets that experience seasonal drying; a situation intolerable for many larval Odonates. Field studies indicate that larvae use active crayfish burrows to survive through periods of drought. Crayfish are predators of dragonfly larvae, which raises the question of how these organisms coexist in burrows. To resist predation, S. hineana larvae may simply be distasteful or crayfish may fail to recognize them as prey. Lab experiments were conducted to establish whether a direct predator-prey relationship exists between S. hineana larvae and the crayfish, Cambarus diogenes. Results show that C. diogenes readily consume S. hineana and other dragonfly larvae, and are only limited by the size of the larvae relative to it's own size. To further investigate predation by crayfish inside burrows and whether larvae avoid active burrows, we conducted a field exclusion experiment manipulating the presence of crayfish in burrows. Preliminary results of a repeated-measures analysis shows no significant difference between treatments (p =0.87), indicating that the presence of crayfish has no effect on S. hineana larval densities within burrows. This suggests either that larvae may not be able to discriminate between burrows with crayfish present/absent, or that the cost may not be high, relative to the benefits attained by inhabiting the burrow. S. hineana larvae probably exhibit unique behaviors that allow them to avoid predation by crayfish within burrows.

Keywords: Predator-Prey Interactions, Dragonflies, Crayfish, Crayfish burrows

This abstract is being presented at: 9:00 AM in session:
Oral Session #7: Aquatic Ecology: Shellfish to Snails.