Population structure of anisakis simplex (nematoda) in harbor porpoises phocoena phocoena off Denmark

• Main Authors: Herreras Belled, Maria Victoria, Balbuena, Juan Antonio, Aznar Avendaño, Francisco Javier, Kaarstad, S. E., Fernández, M., Raga Esteve, Juan Antonio
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2004
• Subjects: Anisakis Simplex; Phocoena; Denmark; UNESCO::CIENCIAS DE LA VIDA; UNESCO::CIENCIAS DE LA VIDA::Biología animal (Zoología) ::Parasitología animal; Diaz; Phocoena phocoena
• Online Access: http://hdl.handle.net/10550/16774

The population structure and habitat selection of Anisakis simplex in 35 harbor porpoises off Denmark are described. The nematodes were collected from the stomach and duodenal ampulla and were categorized as third-stage larvae, fourth-stage larvae, subadults, and adults. The porpoises harbored 8,043 specimens of A. simplex. The proportion of adults and subadults increased with infrapopulation size. The number of development stages across infrapopulations covaried significantly (Kendall's test of concordance). Concordance was higher in hosts with the highest intensities than in those with low and medium intensities. All stages occurred mainly in the forestomach, but this trend was stronger for the adults. Adult and subadult sex ratios did not depart significantly from 1:1. Our data suggested that recruitment and duration of each stage were the main factors accounting for infrapopulation structure. The preference of A. simplex for the forestomach conformed with previous studies, but the narrower distribution of adults relative to other stages might indicate a strategy to enhance mating opportunities. Information on sex ratios of A. simplex is scarce and contradictory. We suggest that the discrepancies might partly reflect differences in categorization criteria and statistical methods. Herreras Belled, Maria Victoria, [e-mail] Balbuena Diaz-Pines, Juan Antonio, [e-mail] Aznar Avendaño, Francisco Javier, [e-mail] Raga Esteve, Juan Antonio, [e-mail]