Database of Anacanthorus spp.

Class Monogenoidea comprises flatworms belonging to Phylum Platyhelminthes, with representatives in freshwater, brackish and marine habitats. The majority of species are ectoparasitic and they all have a direct life cycle, i.e. without intermediate hosts. Although a number of species parasitize cephalopods, amphibians, reptiles and a single species of mammal, most of these platyhelminthes are fish parasites with a relatively high host specificity. Many fish species are supposed to harbour at least one unique monogenean species and this presumption can be used to estimate the total number of species present concerning the number of known fish species.

The majority of the monogenoideans are parasites on external surfaces of fish (skin, fins, gills, mouth cavity, nostrils) but a few species have reached the bladder and urinary ducts, the intestine and stomach and the cloaca as a microhabitat, adopting an endoparasitic life. 

In the natural environment, monogenoideans generally causes little damage to their fish hosts. However, under farming conditions, due to their direct reproduction (without intermediate hosts), monogenoidean populations can develop rapidly due to the low immunity that several factors can trigger in the hosts, culminating in high infestations, a fact that increases pathogenicity, also favored by the proximity of hosts of the same species.The pathogenesis caused by this group of parasites varies greatly, depending on the species and the site of attachment to the host. Gill parasites can cause cellular hyperplasia and mucus hypersecretion, which worsen as the parasite population increases at the site of infestation.

Monogenoidea are recognized as being highly host-specific, since most species infect one or very few host species. Analysis concerning the relationship between Monogenoidea and their hosts in the Neotropical Region showed a greater number of interactions between Dactylogyridae and Characiformes, followed by Siluriformes, including marine and freshwater fishes.

Monogenoidea parasites of freshwater fish belong mainly to two families: Dactylogyridae and Gyrodactylidae, which differ in reproductive strategies and in the mode of adhesion to the host. Dactylogyridae is the most abundant family in continental waters of South America comprising important parasites of fishes concerning fisheries and aquaculture.

Anacanthorus is the most specious genus of the family Dactylogyridae, reported from freshwater fishes and at present, 96 species are reported parasitizing families of Characformes: Serrasalmidae (41 spp.), Triportheidae (21 spp.),  Bryconidae (19 spp.) Erythrinidae (11 spp.) e Characidae (4 spp.), totaling more than 240 reports. Fishes from Serrasalmidae constitute the most common host group for Anacanthorus species and several species of this group are economically important commercially for aquaculture, especially in the Amazon region. 

Anacanthorus was proposed by Mizelle & Price (1965) to accommodate Anacanthorus Anacanthorus, parasite from a serrasalmid fish, Pygocentrus nattereri (=Serrasalmus nattereri). Species of the genus are mainly characterized by the absence of anchors and bars in the haptor and differentiation of the species are based on the morphology of the copulatory complex.  Studies on morphology of species of the genus have revealed that the phylogenetic relationships among Anacanthorus spp. and their hosts also seem to reflect the similarity in the morphology of the copulatory complex. 

Based on the evidence, it is possible to state that Anacanthorus spp. and its hosts provide a useful model for understanding host-parasite relationships and evolutionary processes in the Neotropics, supporting the hypothesis of phylogenetic congruence between Anacanthorus spp. and its hosts, which indicate a common evolutionary history of these organisms, based on morphological and molecular approaches.