Intra-population variation in behavior modification by the acanthocephalan Acanthocephalus dirus: are differences...

Area of Science:

• Parasitology
• Behavioral Ecology
• Invertebrate Zoology

Background:

• Acanthocephalus dirus is an acanthocephalan parasite with a life cycle involving freshwater isopods (Caecidotea intermedius) as intermediate hosts and fish as definitive hosts.
• Infection by A. dirus can reduce mating behavior in male C. intermedius, but significant variation exists within populations regarding this behavioral change.
• Previous research indicates host glycogen content predicts mating behavior in uninfected isopods.

Purpose of the Study:

• To investigate whether host glycogen content explains the intra-population variation in mating behavior of male C. intermedius infected with A. dirus.
• To determine the factors influencing mating behavior modification in infected male isopods.

Main Methods:

• A field-based experiment quantified mating behavior variation in male C. intermedius, observing 50% infected male responsiveness to females.
• Biochemical analysis assessed glycogen content in responsive and non-responsive infected and uninfected males.
• Parasite intensity was quantified in infected males.

Main Results:

• Glycogen content predicted mating behavior in uninfected males but not in infected males.
• For infected males, parasite intensity was a significant predictor of mating behavior.
• Males with higher Acanthocephalus dirus parasite loads were less likely to exhibit modified mating behavior.

Conclusions:

• Intra-population variation in mating behavior of infected C. intermedius is not mediated by host condition (glycogen levels).
• Parasite intensity, rather than host condition, influences the modification of mating behavior in infected male isopods.
• Acanthocephalus dirus infection impacts host behavior, with parasite load being a key factor in the extent of behavioral alteration.