Feb 25, 2022

Public workspaceGeneral predation trial protocol

This document is a draft, published without a DOI.
  • 1National Centre for Immunisation Research and Surveillance;
  • 2University of Michigan - Ann Arbor
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Document Citation: Laura Lopez, Meghan Duffy 2022. General predation trial protocol. protocols.io https://protocols.io/view/general-predation-trial-protocol-b5m9q496
License: This is an open access document distributed under the terms of the Creative Commons Attribution License,  which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Created: February 25, 2022
Last Modified: February 25, 2022
Document Integer ID: 58785
Abstract
This is a protocol to quantify number of Daphnia that a Chaoborus will predate upon within a given time frame.
General Predation Trial Protocol- Duffy Lab

LK Lopez 11/11/2020

Materials:
1. 3rd or 4th instar Chaoborus larvae
2. Daphnia (at whatever age is appropriate for the experiment)
3. Pipettes
4. Filtered lake water
5. 150 mL beakers
6. Incubator
7. Beakers to rear Daphnia (size chosen based on experiment).

Methods for Maintaining Chaoborus
  • Chaoborus can be kept in the lab refrigerators for approximately 1-2 months. The low temperature prevents them from metamorphosing and reduces their energy requirements (less feeding is needed). However, the temperature change from the fridge to the incubator or lab can be stressful and result in high mortality. If keeping Chaoborus in the fridge, allow time to adjust to incubator conditions. Chaoborus do best if kept in beakers (in a covered tote in case they metamorphosise) in incubators at ~ 20 °C (same conditions as most Daphnia in the lab).
  • Chaoborus larvae need to be fed every 2-3 days, approximately 5 juvenile Daphnia per individual Chaoborus. Adult Daphnia can also be used for feeding, but depending on gape size, smaller 3rd instar Chaoborus may be unable to catch and eat them.
  • Water change 50-100% required weekly.

Predation Trial Methods
1. Starve Chaoborus 48 hours prior to trial
2. Place required density of Daphnia into beaker (e.g. 10 Daphnia aged 20 days into 150 mL beaker filled to 120 mL) filled with clean filtered lake water.
3. Add 1 Chaoborus
4. Leave beakers in incubator at 20 °C in the dark for 16 hours (can be longer than this but 16 is sufficient).
5. Remove beakers and count the remaining Daphnia alive.

Note: Gape size is an important predictor of predation success in ambush predators. Photograph and measure a subsample or Daphnia and the Chaoborus (their heads) to control for differences in size.
Note: The same Chaoborus can be reused if randomly allocated to across treatments.