El parasitismo por profilicollis bullocki (acanthocephala: Polymorphidae) en emerita analoga (anomura: Hippidae) según condiciones contrastantes de abundancia de hospedadores definitivos en chile

Abstract

In Chile, the intermediate host of the acanthocephalan Profilicollis bullocki is the mole crab Emerita analoga, with seabirds as the definitive hosts, who arrive in mass during summer, enhancing the spread of acanthocephalan eggs to the environment. Thus, the magnitude of this parasitosis in E. analoga should attain higher values after the yearly arrival of seabirds. This study was performed in two periods contrasting in the abundance of marine birds, September-November 2008 (late winter-spring) and December 2008-January 2009 (summer), at 3 sandy beaches of the Biobío region, Chile. The abundance of birds was highest in summer, mainly due to the arrival of the Franklin's gull Larus pipixcan to the study sites. It was observed that the cephalotorax length (LCT) of E. analoga was much smaller in summer than in spring, and that the prevalence and abundance of P. bullocki increased with LCT. Although the prevalence of P. bullocki was higher before the arrival of birds, the slopes of the linear regressions between the abundance and intensity with LCT were higher after the arrival of the birds to the study sites. These results are partly explained by the comparatively large LCT of mole crabs before the arrival of seabirds, and by an intense recruitment pulse of small E. analoga after the arrival of seabirds, thus provoking a dilution effect on the prevalence.