A novel laboratory method to simulate climatic stress with successful application to experiments with medically relevant ticks

Sang Hyo Kim, Caleb Nielebeck, Lauren Dedmon, Mark Pangilinan, Jahred Quan, William Ota, Javier D. Monzón

Published: 2022-05-27 DOI: 10.17504/protocols.io.rm7vzyo8rlx1/v4

Abstract

This protocol details a novel method to isolate individual ticks and manipulate their environment. We successfully used this method to investigate how humidity affects survival and host-seeking (questing) behavior of three species of ticks: the lone star tick (Amblyomma americanum), American dog tick (Dermacentor variabilis), and black-legged tick (Ixodes scapularis). We placed 72 adult females of each species into individual plastic tubes and separated them into three experimental relative humidity (RH) treatments representing distinct climates: 32% RH, 58% RH, and 84% RH. For 30 days we assessed the survival and questing behavior of each tick.

Before start

We acquired adult female ticks from the Oklahoma State University Tick Rearing Facility and experimented with one temperature range and three relative humidities. This protocol can be modified for different species, life stages, temperatures, humidities, and other small organisms.

Steps

Set up

1.

Place a single tick with one wooden skewer in each tube and seal with a cap, labelling each tube with an individual identifier

PETG plastic tubes with wooden skewers prepared for ticks. Notice that we drilled holes in the caps to allow airflow between the tubes and the containers.

2.

Place six tubes in each airtight container along with a humidity pack, labelling each container

Airtight container with six tubes, humidity pack, and data logger. Example container of Dermacentor variabilis (purple) at 58% RH; every container was replicated four times for a sample size of n=24 per RH group.

2.1.

Confirm the humidity in one container of each RH level with the data logger

3.

Program the climate chamber

Note

Reference your chamber's user's manual

3.1.

To cycle between 20°C to 30°C, the temperature increments should be as follows:

3:00 - 25°C
6:00 - 27.5°C
9:00 - 30°C
12:00 - 27.5°C
15:00 - 25°C
18:00 - 22.5°C
21:00 - 20°C
24:00 - 22.5°C

3.2.

To create a 12:12 light:dark photoperiod, lighting increments should be as follows:

9:00 - Lights on
21:00 - Lights off

Data collection

4.

Place all of the airtight containers, filled with ticks and humidity packs, into the climate chamber and start the program

5.

Each day thereafter, during the 9:00 to 12:00 or 30°C increment, assess each tick for survivorship and questing behavior (see guidelines for qualifications of survivorship and questing)

Note

Only take one container out of the chamber at a time

Note

Collect a binary outcome for survivorship and questing, and measure the tick's height (to the nearest 0.5 cm) in the tube if it is found questing

5.1.

Periodically move the data logger to a new bin to confirm that no unexpected changes to the climate inside the containers has occurred

6.

Repeat steps 4 and 5 for 30 days or until all ticks have died

A novel laboratory method to simulate climatic stress with successful application to experiments with medically relevant ticks

Abstract

Before start

Steps

Set up

Data collection

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