Seasonal changes in host phenotype manipulation by an acanthocephalan: time to be transmitted?

• Published in: Parasitology 2009-02, Vol.136 (2), p.219-230
• Main Authors: BENESH, D. P., HASU, T., SEPPÄLÄ, O., VALTONEN, E. T.
• Format: Article
• Language: English
• Subjects: Acanthocephala; Acanthocephala - physiology; Acanthocephalus lucii; Aging; Analysis of Variance; Animals; Asellus aquaticus; Behavior, Animal - physiology; Biological and medical sciences; Environment; Environmental conditions; Fundamental and applied biological sciences. Psychology; General aspects; General aspects and techniques. Study of several systematic groups. Models; host manipulation; host pigmentation; host-parasite interaction; Host-Parasite Interactions; intermediate host; Invertebrates; Isopoda; Isopoda - parasitology; Isopoda - physiology; Light; Linear Models; Medically important nuisances and vectors, pests of stored products and materials: population survey and control; Parasites; Phenotype; plastic/flexible behaviour; seasonality; Seasons; Skin Pigmentation - physiology; Spring; Survival Rate; Temperature; trophic transmission; Vectors. Intermediate hosts
• ISSN: 0031-1820; 1469-8161
• DOI: 10.1017/S0031182008005271

Many complex life cycle parasites exhibit seasonal transmission between hosts. Expression of parasite traits related to transmission, such as the manipulation of host phenotype, may peak in seasons when transmission is optimal. The acanthocephalan Acanthocephalus lucii is primarily transmitted to its fish definitive host in spring. We assessed whether the parasitic alteration of 2 traits (hiding behaviour and coloration) in the isopod intermediate host was more pronounced at this time of year. Refuge use by infected isopods was lower, relative to uninfected isopods, in spring than in summer or fall. Infected isopods had darker abdomens than uninfected isopods, but this difference did not vary between seasons. The level of host alteration was unaffected by exposing isopods to different light and temperature regimes. In a group of infected isopods kept at 4°C, refuge use decreased from November to May, indicating that reduced hiding in spring develops during winter. Keeping isopods at 16°C instead of 4°C resulted in higher mortality but not accelerated changes in host behaviour. Our results suggest that changes in host and/or parasite age, not environmental conditions, underlie the seasonal alteration of host behaviour, but further work is necessary to determine if this is an adaptive parasite strategy to be transmitted in a particular season.