Recruitment, population structure, and habitat selection of Corynosoma australe (Acanthocephala) in South American fur seals, Arctocephalus australis, from Uruguay.

摘要

We analysed recruitment, population structure, and intestinal distribution of Corynosoma australe Johnston, 1937 in 27 South American fur seals, Arctocephalus australis (Zimmerman, 1783), collected in two Uruguayan localities during 1990 and 1991. Only heavy infections of C. australe were found in all intestines. High transmission rates might result from the massive concentration of fur seals in the study area and the ecological ubiquity of C. australe. Intestinal length (IL) accounted, through a cubic relationship, for most of the variation (74%) in parasite intensity. IL3 also predicted the percentage of juvenile females among hosts (an indicator of recruitment rate) better than intensity or host body size. Intestinal size might be a suitable surrogate of host metabolic rate, the potential factor influencing intensity. The percentages of females and gravid females significantly increased along the intestine, and the distribution of juvenile females, gravid females, and males significantly covaried after controlling for intensity effects. These patterns suggest that worms migrate towards the lower jejunum and ileum while they mature, copulate, and reproduce. Males and gravid females shifted their distribution anteriad, and gravid females expanded their distribution, with intensity. These patterns might result from recruitment dynamics, intraspecific competition, or both. We do not know why males, gravid females, and juvenile females respond differently to these factors.