Maintaining Laboratory Cultures of Gryllus bimaculatus, a Versatile Orthopteran Model for Insect Agriculture and Invertebrate Physiology

Summary

This paper outlines basic methods to standardize important factors such as density, feed availability, hydration source, and environmental controls for the long-term rearing of laboratory cultures of the edible cricket, Gryllus bimaculatus.

Abstract

Gryllus bimaculatus (De Geer) is a large-bodied cricket distributed throughout Africa and Southern Eurasia where it is often wild-harvested as human food. Outside its native range, culturing G. bimaculatus is feasible due to its dietary plasticity, rapid reproductive cycle, lack of diapause requirement, tolerance for high-density rearing, and robustness against pathogens. Thus, G. bimaculatus can be a versatile model for studies of insect physiology, behavior, embryology, or genetics.

Cultural parameters, such as stocking density, within-cage refugia, photoperiod, temperature, relative humidity, and diet, all impact cricket growth, behavior, and gene expression and should be standardized. In the burgeoning literature on farming insects for human consumption, these crickets are frequently employed to evaluate candidate feed admixtures derived from crop residues, food-processing byproducts, and other low-cost waste streams.

To support ongoing experiments evaluating G. bimaculatus growth performance and nutritional quality in response to variable feed substrates, a comprehensive set of standard protocols for breeding, upkeep, handling, measurement, and euthanasia in the laboratory was developed and is presented here. An industry-standard cricket feed has proven nutritionally adequate and functionally appropriate for the long-term maintenance of cricket breeding stocks, as well as for use as an experimental control feed. Rearing these crickets at a density of 0.005 crickets/cm³ in screen-topped 29.3 L polyethylene cages at an average temperature of 27 °C on a 12 light (L)/12 dark (D) photoperiod, with moistened coconut coir serving both as hydration source and oviposition medium has successfully sustained healthy crickets over a 2-year span. Following these methods, crickets in a controlled experiment yielded an average mass of 0.724 g 0.190 g at harvest, with 89% survivorship and 68.2% sexual maturation between stocking (22 days) and harvest (65 days).

Introduction

As typified by the iconic insect, the fruit fly Drosophila melanogaster, the use of insects as laboratory model organisms provides distinct advantages for studies in genetics, toxicology, and physiology¹. The small size of insects reduces the space needed for cultures and the amount of feed and consumable materials required. Many insects reproduce quickly making them uniquely suited to the creation of specialized genetic lines and studies requiring the evaluation of multiple successive generations.

Many studies focus on holometabolous insects such as Drosophila, which exhibit complete metamorph....

Protocol

1. Preparing the oviposition substrate

NOTE: Coconut coir is an ideal oviposition substrate for G. bimaculatus. For detailed methods on how to separate coir from compressed coir brick and a note on respiratory safety, see Supplemental Materials step 1.1.

1. Wash hands with soap and water.
2. Tare a clean container on a balance and weigh a mass of dry coconut coir approximately the size of a human fist.
3. Place coir into a sealable, clean container, which can accommodate expansion up to 6x the original volume.
4. With clean hands, gently break up clumps of coir from th....

Results

Data demonstrating successful cricket rearing from hatching to 65 days old were collected during a September 2021 feed trial. Crickets were grown from eggs following steps 1.1.1-2.6.1 of these protocols, and six replicate cages were stocked with 24 random 22-day-old (third instar) crickets following step 2.7 above. Crickets were then reared in ambient room conditions; however, due to a malfunctioning facility air handling unit, the average room temperature was 25 ± 1 °C at 20% relative humidity rather than the .......

Discussion

The simplicity of this approach to cricket rearing can benefit a range of research areas and represents a generic template for successful cricket husbandry, easily adaptable to a variety of experimental needs. Compared to several other studies of G. bimaculatus, the individual body adult size is smaller and maturation is slower¹⁴, which we attribute to sub-optimal rearing temperature imposed on us by circumstance. The methods described above have been used and refined over the course of 2.......

Materials

Name	Company	Catalog Number	Comments
31-qt (29.3 L) Snap-lid tote bin with lid	HOMZ	3430CLBL	Used to house breeding stock
3-tier/12-tray Grow Light Stand	Fischer Scientific	NC1938548
50-gal (189.27L) tote bin with lid	Sterilite	#14796603	Used as secondary containment when handling crickets
50 mL polypropylene graduated cylinder	Fischer Scientific	S95171
7.5-qt (7.1 L) snap-lid tote bin with lid	HOMZ	3410CLBL	Used to house exprimental stock
Accuris 500 g x 0.01 g Balance	Manufactured by Accuris, a subsidieary of Benchmark Scientific	W3300-500	Purchased from Dot Scientific through University of Wisconsin system purchasing service "ShopUW+"
Ace Premier 1 Inch Flat Chip Brush	Ace Hardware	#1803261
Bel-Art SP Scienceware deionized water wash bottle	Fischer Scientific	03-421-160
Bright aluminum window screen	Phifer	UNSPSC# 11162108	Mesh size 18 x 16"
Clear Disposable Plastic Portion Cups 5.5 oz w/ lids	Wal-Mart	N/A
Deionized water
Diablo 4-4/8" x 13 TPI Ultra Fine Finish Bi-Metal Jigsaw Blade	Home Depot	#313114935
Egg Filler Flats-Paper, 12 x 12"	Uline	S-5189
Fisherbrand Petri Dishes with Clear Lid 100 x 15mm	Fischer Scientific	FB0875714
Fisherbrand Petri Dishes with Clear Lid 60 x 15mm	Fischer Scientific	FB0875713A
Georgia-Pacific Envision Brown Paper Towels	Home Depot	#205675843
Infinity Tough Guy high performance hot-melt glue sticks	Infinity Bond	Infinity IM-Tough-Guy-12
Mazuri Cricket Diet	Land O' Lakes International	SKU#  3002219-105
Stanley TimeIt Twin 2-outlet Grounded Mechanical 24 Hour Timer	Wal-Mart	N/A
Vermont Organics Reclamation Soil 11 lb Coir Block	Home Depot	#300679904