Cockroach cold preference: A behavioral strategy to defend fungal infection

Area of Science:

• * Integrated Pest Management
• * Insect Pathology
• * Behavioral Ecology

Background:

• * Entomopathogenic fungi offer sustainable alternatives to insecticides for controlling indoor pests.
• * Insect behavior, such as thermoregulation, can significantly influence pathogen efficacy.
• * Understanding host-pathogen interactions is crucial for developing effective biological control agents.

Purpose of the Study:

• * To investigate the impact of temperature on German cockroach susceptibility to *Metarhizium anisopliae*.
• * To elucidate the behavioral and physiological mechanisms underlying reduced fungal infection in cooler environments.
• * To assess the role of specific immune factors in low-temperature survival.

Main Methods:

• * Comparative toxicity assays and conidial adhesion tests at different temperatures (20°C vs. 28°C).
• * Histopathological analysis and fungal culturing to evaluate infection progression.
• * Gene expression analysis (RNAi) of immune effector defensin invertebrate_1 (DEFI_1).

Main Results:

• * Infected cockroaches exhibited a preference for colder temperatures (20°C).
• * Colder environments significantly increased the lethal time 50 (LT50) and reduced fungal conidial adhesion.
• * Cold exposure enhanced phenol oxidase activity, cell nodulation, and DEFI_1 expression, contributing to reduced mortality.

Conclusions:

• * Active cold-seeking behavior in infected cockroaches is a defense strategy against entomopathogenic fungi.
• * Low temperatures impair fungal infection efficiency by modulating host behavior and immune responses.
• * Findings support the development of fungal-based biocontrol agents, considering host behavioral thermoregulation.