Abstract
The degree of parasite aggregation is determined by a number of factors that are not well understood. In total, 3,746 fish from 73 species and their parasites were analyzed to determine associations between the degree of aggregation by taxon and specific characteristics of the fish. A multiple linear regression (95% confidence interval - CI) was used to show that in most taxa, the degree of parasite aggregation was significantly higher in freshwater fish and schooling fish but varied according to taxon in relation to gender, habitat and feeding habits. Parasite aggregations were also significantly increased in fish with a large number of parasitic larvae and greater body length in all evaluated taxa. Because the coefficients of determination of the models were lower than 60% for all taxa, other factors may be involved in parasite aggregation. Conversely, marked significance was observed for the tested variables in relation to taxon dependence, which indicates that additional studies should be performed for these factors using comprehensive databases with larger samples per parasite species.
Highlights
The aggregate spatial distribution pattern of parasites is a common characteristic among various types of hosts and metazoan parasites and is considered a law of parasite ecology (CROFTON, 1971; VON ZUBEN, 1997; POULIN, 2007a)
Because of the heterogeneous size of parasitic infrapopulations, parasite spacial distribution is significant in the epidemiology of parasitic diseases and is observed in two distribution patterns: homogeneous distribution, which is associated with the mortality and density of parasites and the mortality of hosts induced by the parasites; and aggregate distribution, which is associated with heterogeneous host susceptibility to infection, parasite reproduction in the host and different abilities of hosts to eliminate parasites through immune responses or other mechanisms (ANDERSON & GORDON, 1982)
The present study aimed to evaluate whether parasite aggregation in certain taxa of fish parasites is associated with characteristics of the host, such as gender, size, habitat, schooling, feeding habits, aquatic environment and parasite development stage
Summary
The aggregate spatial distribution pattern of parasites is a common characteristic among various types of hosts and metazoan parasites and is considered a law of parasite ecology (CROFTON, 1971; VON ZUBEN, 1997; POULIN, 2007a). This distribution pattern can be observed in practice, with many hosts harboring few or no parasites and few hosts harboring many parasites (SHAW & DOBSON, 1995; POULIN, 2007b). The author used a mixed-effects model to analyze the different degrees of aggregation between host samples, and the parasite species, host species and study of origin were included as random effect variables. The parasite taxon, developmental stages (larval/adult) and host size were variables included as fixed effects
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