Associations between fish reproductive cycle and the dynamics of metazoan parasite infection

Abstract

The parasite fauna of the stone loach (Barbatula barbatula) was investigated monthly from May to December 2001. Four parasite species were recorded: Gyrodactylus spp. (Monogenea), Tylodelphys clavata (Digenea), Proteocephalus sagittus (Cestoda), and Raphidascaris acus (Nematoda). The changes in the seasonal dynamics of parasite infection were investigated throughout the 8 months. The potential effect of the reproductive investment of the host, measured by gonad mass and gonado-somatic index (GSI), on the parasite infection was tested against the prediction that, during periods of high reproductive investment (beginning of the breeding period or forming gonads after breeding), the fish are more susceptible to parasite infection. Differences between parasite loads between genders were also hypothesized. Seasonal differences in infection were observed for all parasite species studied. The values of GSI showed a pattern of energy accumulation in the pre-reproductive period and at the beginning of breeding, a decrease during breeding, and an increase in the post-breeding period. A similar pattern was observed for parasite abundance, a strong or weak increase in spring and/or autumn and a decrease during summer (July and August). Positive correlations between the abundance of Gyrodactylus spp. and R. acus and both gonad mass and GSI were found in females after eliminating the effect of fish weight. Our results suggest that stone loach females are more susceptible to parasite infection in periods of higher reproductive investment. The main factor determining the infection of T. clavata was fish size. The abundance of P. sagittus was positively correlated with GSI in the total fish sample with no detectable effect of sex or fish weight. The increase in cestode infection in spring supports the hypothesis that the parasite life cycle could by synchronized with the beginning of host reproduction, probably induced by increasing fish hormone levels in the spring.

Frequency Distribution and Seasonal Dynamics of Intestinal Helminths in the Yellowhead Catfish Pelteobagrus fulvidraco from Liangzi Lake, China

“…This implies seasonal development of the tapeworm and infection with plerocercoids before summer. Similar results have been observed for the congeneric tapeworm Proteocephalus sagittus (Jarkovský et al, 2004;Š imková et al, 2005). Based on the present results, it is therefore presumed that the yellowhead catfish became infected with G. pseudobagri through digestion of copepods in the spring.…”

Ecology and Genetic Structure of Zoonotic Anisakis spp. from Adriatic Commercial Fish Species

“…We observed that the host sex had no statistically significant effect on the degree of infection in most studied species, except in hake and whiting, where females were more infected, probably related to the faster growth of females in these demersal species (54). Šimková et al (55) related the greater infection of the gill monogenean parasites in female fish to the greater investment of females in reproduction, which produces larger gametes than in males. The authors observed a positive correlation between parasite infection and gonad weight and the gonadosomatic index, although this does not fully explain the higher affinity of the parasite for female hosts.…”

Comunidad Parasitaria de Cabinza Isacia conceptionis (Cuvier & Valenciennes, 1830) (Perciformes: Haemulidae) en la Zona de Chorrillos, Lima, Perú

“…Simková et al (2005) encontraron un incremento de la parasitosis con el aumento del IGS con la abundancia de monogeneos, cestoda y digeneos en el pez Barbatula barbatula (Linnaeus, 1758) (Balitoridae), indicando que los peces son más susceptibles a la infección parasitaria en los periodos de mayor gasto reproductivo. Los índices de diversidad alfa (H I y J I ) de la parasitofauna de I. conceptionis mostraron valores relativamente altos y los índi-ces de dominancia (λ y I B-P ) tuvieron valores bajos.…”