Corynosoma cetaceum Johnston & Best, 1942 (Acanthocephala, Polymorphidae) in Arctocephalus australis Zimmermann, 1783 (Mammalia: Pinnipedia): Histopathology, parasitological indices, seasonality and host gender influences

The parasitological indices [Prevalence (P%), Mean Intensity (MI), Mean Abundance (MA) and the Range of Variation (Ax)] of Corynosoma cetaceum in Arctocephalus australis and the histopathology caused by this parasite are presented based on the necropsy of 32 specimens found stranded dead on the shore of Rio Grande do Sul, Brazil, from 2008 to 2010. Differences between the genders of the hosts as well as for their reproductive status [males (pups, prepubertals) and females (pups, reproductive-breeding)] were analyzed for P% (Chi-square test, X2) and MI (Bootstrap Confidence Interval, BCa , p < 0,05) and between genders of the hosts for season groups (Spring-Summer: S-S; Autumn-Winter: A-W). Abnormal tissue samplings of the stomachs (histopathology caused by the parasite) and the gonads (for analysis of the sexual maturity) of the hosts were submitted to the histological procedure of paraffin embedding and mounting of permanent slides in balsam. The infection occurred along the sampling period with low P%, MI and MA (respectively) for the genders of the hosts (males: 37.5, 2.83 and 1.5; females: 31.3, 3 and 1), for the reproductive status of the hosts (males pups: 25, 1.33 and 1; prepubertal males: 75, 4.33 and 5; female pups: 28.6, 2.5 and 1; reproductive-breeding females: 50. 5 and 5) and for season groups (S-S: 16.7, 4 and 0.67; A-W: 45, 2.78 and 1.25). Concerning to the hosts, there were no parasitological indices-related differences between genders and sexual maturation status. There were no season-related differences for P% and MI. The results suggest an accidental infection of C. cetaceum in A. australis despite the absence of severe inflammatory processes added with the parasite’s inadequate development.