Competitive growth, energy allocation, and host modification in the acanthocephalan Acanthocephalus dirus: field data

Area of Science:

• Ecology
• Parasitology
• Behavioral Ecology

Background:

• Acanthocephalus dirus, a parasite, alters intermediate host (isopod) physiology and behavior for transmission to definitive hosts (fish).
• Isopods often host multiple parasites, raising questions about the costs of host sharing and its impact on parasite-induced host modifications, specifically mating behavior.

Purpose of the Study:

• To investigate the costs of host sharing for Acanthocephalus dirus parasites.
• To determine if parasite energy content and body size influence host modification, particularly mating behavior suppression.

Main Methods:

• Field-based measurements of parasite energy content (glycogen, lipid) and body size (volume) in isopods.
• Analysis of relationships between host sharing, parasite characteristics, and host mating behavior.

Main Results:

• Host sharing was costly for parasites in terms of energy content but not body size.
• Parasite energy content and body size did not predict host behavior modification.
• Parasite intensity was the sole predictor of host behavior, with higher intensity correlating with less host modification (mating suppression).

Conclusions:

• Intraspecific competition among Acanthocephalus dirus likely influences parasite energy content.
• Competition costs appear to shape parasite growth and energy allocation strategies.
• These costs do not directly affect the modification of host mating behavior, with parasite intensity being the key factor.