Temperature Gradient Assay: A Method to Test Temperature Preference in Drosophila Larvae

Abstract

Source: Liu, J., et al. A Temperature Gradient Assay to Determine Thermal Preferences of Drosophila Larvae. J. Vis. Exp. (2018).

Drosophila fruit flies can distinguish small changes in temperature and therefore select environments with favorable thermal conditions. This video describes a behavioral assay that tests the temperature preference of Drosophila larvae on a linear thermal gradient.

Protocol

This protocol is an excerpt from Liu et al. A Temperature Gradient Assay to Determine Thermal Preferences of Drosophila Larvae, J. Vis. Exp. (2018).

1. Temperature Gradient Setup

1. Prepare single-directional gradient
   1. To create a humid ambient environment during the assays, place the two aluminum blocks connected to two water baths on wet paper towels, separated by 10 cm (Figure 1A).
   2. Turn on the two water baths ~2 h prior to initiating the assay to allow enough time for the temperature of the aluminum blocks to equilibrate.
      

Results

Figure 1: Single and bidirectional gradient assay setups. (A) Single-directional gradient setup with two aluminum assay plates on two aluminum blocks. The temperatures of the aluminum blocks are controlled by circulating water from two water baths.

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Gradient assay apparatus
PolyScience 9106, Refrigerated/Heated 6L Circulating Bath	Thomas Scientific	9106	This model is discontinued. Updated replacement models include: 1186R00 and 1197U04 for 120 V, 60 Hz, or 1184L08 and 1197U04 for 240 V, 50 Hz.
Aluminum assay plate (for single directional gradient)			Outer size: 14 x 10.1 x 0.9 cm, inner size: 12.9 x 8.7 x 0.8 cm, black anodized.
Aluminum plate (for bidirectional gradient)			25 x 22 x 0.2 cm, black anodized.
Aluminum block			Outer size: 25.5 x 5 x 1.4 cm, parameters of inner channels are shown in Figure 1D.
Connector for aluminum blocks and tubing	McMaster-Carr	91355K82
Tygon Sanitary Silicone Tubing	Tygon	57296	1/4" ID x 3/8" OD x 1/16" wall
Name	Company	Catalog Number	Comments
Items and reagents for assay
Pestle	USA Scientific	17361	Pestle for 1.5 mL microcentrifuge tubes
Thermometer	Fluke	51II
Thermocouple	Fluke	K type
Universal microplate lid	Corning	6980A77
35 mm dish	Corning	9380D40
Labeling tape (for bidirectional gradient)	Fisher Scientific	15-951	Fisherbrand labeling tape 2 in x 14 yds
Agarose	Invitrogen	16500500	Prepare 1% solution
Sucrose	Sigma	S0389-5KG	Prepare 18% solution right before starting assay
Paint brush	Fisher Scientific	11860
50 mL centrifuge tubes	Denville	C1062-P
Scoopula	Fisher Scientific	14-357Q
500 mL round wide-mouth bottle	Pyrex	1395-500
Cell strainer (300 mm pore)	PluriSelect	43-50300	Optional item for larvae washing
Cardboard box (vial tray)	Genesee Scientific	FS32-124