Abstract
BackgroundThe patterns and processes linked to the host specificity of parasites represent one of the central themes in the study of host-parasite interactions. We investigated the evolution and determinants of host specificity in gill monogeneans of Cichlidogyrus and Scutogyrus species parasitizing African freshwater fish of Cichlidae.MethodsWe analyzed (1) the link between host specificity and parasite phylogeny, (2) potential morphometric correlates of host specificity (i.e. parasite body size and the morphometrics of the attachment apparatus), and (3) potential determinants of host specificity following the hypothesis of ecological specialization and the hypothesis of specialization on predictable resources (i.e. host body size and longevity were considered as measures of host predictability), and (4) the role of brooding behavior of cichlids in Cichlidogyrus and Scutogyrus diversification.ResultsNo significant relationships were found between host specificity and phylogeny of Cichlidogyrus and Scutogyrus species. The mapping of host specificity onto the parasite phylogenetic tree revealed that an intermediate specialist parasitizing congeneric cichlid hosts represents the ancestral state for the Cichlidogyrus/Scutogyrus group. Only a weak relationship was found between the morphometry of the parasites’ attachment apparatus and host specificity. Our study did not support the specialization on predictable resources or ecological specialization hypotheses. Nevertheless, host specificity was significantly related to fish phylogeny and form of parental care.ConclusionsOur results confirm that host specificity is not a derived condition for Cichlidogyrus/Scutogyrus parasites and may reflect other than historical constraints. Attachment apparatus morphometry reflects only partially (if at all) parasite adaptation to the host species, probably because of the morphological similarity of rapidly evolved cichlids (analyzed in our study). However, we showed that parental care behavior of cichlids may play an important role linked to host specificity of Cichlidogyrus/Scutogyrus parasites.
Highlights
The patterns and processes linked to the host specificity of parasites represent one of the central themes in the study of host-parasite interactions
We focused on (1) the morphometric correlates of host specificity, hypothesizing the role of haptor morphology in specialization and adaptation, (2) parasite abundance following the hypothesis of ecological specialization, and (3) the determinants of host specificity following the hypothesis of specialization on predictable resources and on the basis of the assumption that parental care behavior in cichlids represents an important factor linked to host specificity
Host specificity in species of the Cichlidogyrus/ Scutogyrus group At the global level of investigation, a total of 17 Cichlidogyrus and Scutogyrus species were identified as specialists; 11 parasite species were identified as generalists
Summary
The patterns and processes linked to the host specificity of parasites represent one of the central themes in the study of host-parasite interactions. The class Monogenea mainly includes ectoparasites with a direct life cycle, high morphological diversity, and high species richness. These parasites are highly host specific when compared to other groups of parasites [8,9,10]. For these reasons, the genera of Monogenea are often selected as suitable models for studying the patterns and processes connected with the evolution of parasite specialization, resulting in host specificity [1,11,12]. Host specificity may more likely describe current host-parasite relationships, which may or may not reflect macroevolutionary history [14]
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