Scolex Morphology of Proteocephalid Cestodes Parasites of Neotropical Freshwater Fishes

Abstract

The morphology of the scolices and metascolices of 29 proteocephalid species, parasites of freshwater fishes from Brazil was compared by using scanning electron microscope, light and laser microscopy. The following species were evaluated: Proteocephalus vazzolerae, P. piramutab, Robertiella paranaensis, Travassiella avitellina, Monticellia loyolai, M. spinulifera, M. belavistensis, Houssayela sudobim, Zygobothrium megacephalum, Gibsoniela mandube, Cangatiella arandasi, Nomimoscolex sudobim, N. lopesi, N. admonticellia, N. piraeeba, N. pirarara, Harriscolex kaparari, Crepidobothrium eirasi, Spatulifer rugosa, Megathylacus brooksi, Choanoscolex abscisus, Amphoteromorphus peniculus, A. piraeeba, Paramonticellia itaipuensis, Peltidocotyle rugosa, Othinoscolex lenha, Rudolphiella rugata, R. piranabu, Jauella glandicephalus.Some features as overall shape of scolex, suckers, apical sucker, frontal glands and several kinds of metascolex were analyzed. The taxonomic importance of scolex and metascolex is discussed.Key words : Cestoda Proteocephalidea -parasites of freshwater fishes -South American fish parasites Proteocephalid Cestodes are parasites of freshwater fishes, specially Siluriforms (catfishes), Amphibia and Reptilia. They are the most importante parasites in Siluriforms, considering the number of parasite species described within those hosts.The morphology of the scolex is one of the most important characteristics used for classification of proteocephalids at generic and subamily level (Scholz et al. 1998). However, morphological features of scolex/metascolex have been neglected in the definition of the subfamilies and families, particularly in the classification of South American proteocephalids. Woodland (1933Woodland ( -1935 and the following authors preferred to utilise the characteristics of reproductive organs, and their relationships with the internal longitudinal musculature to separate the taxa. Rego (1995) disagreed with this scheme of classification, and proposed the elimination of the Monticelliidae and its subfamilies, based in the fact that the actual classification is not suitable for the forms of proteocephalids recently described, which present intermediate characteristics, and others with inconspicuous longitudinal musculature, resulting the impossibility of the definition of the taxa they belong to. Rego et al. (1998) carried a cladistic analysis based on comparative morphology, to examine the subfamily-level relationships within the order Proteocephalidea. The study did not evaluate relationships at the generic level, particularly those within the Monticelliidae (sensu Rego 1994). It is fundamental to conduct a phylogenetic analyses of the genera, to the resolution of taxonomic problems of South American proteocephalids. In that paper, on considering the character metascolex, only two states were considered (presence versus absence). However, several types of metascolex have been recognized by the authors. The goal of the present paper is to contributes to a definition and to distinguish t...

Redescription of Houssayela sudobim (Woodland, 1935) (Cestoda: Proteocephalidea), a Parasite of Pseudoplatystoma Fasciatum (Pisces: Siluriformes) from the River Amazon

“…Together with the previous absence of any report of H. sudobim (see de Chambrier et al, 2006, for remarks on Rego's (1999) report of 'Houssayela sudobim'), this low prevalence indicates that this tapeworm may be a fairly rare parasite of P. fasciatum which is found only in the River Amazon in Brazil and Peru.…”

A new genus and species of proteocephalidean tapeworm (Cestoda), first parasite found in the driftwood catfish Tocantinsia piresi (Siluriformes: Auchenipteridae) from Brazil

“…-Freze 1965, Rego 1994, de Chambrier et al 2003. Many of these taxa possess a metascolex and the presence/ absence of this structure was considered to be the most important diagnostic character in classification of all proteocephalideans (Rego 1999). Even though molecular phylogenetic studies (de Chambrier et al 2004a, Hypša et al 2005, Scholz et al 2011) have demonstrated homoplastic character of this morphological structure, the presence of a metascolex, its form and structure are of taxonomic im- Gibsoniela mandube (Woodland, 1935) Ageneiosus inermis* A, PRB Woodland (1935), Rego (1984Rego ( , 1992 portance at least at the generic and species level (see, e.g.…”

Luciaella ivanovae n. g., n. sp. (Eucestoda: Proteocephalidea: Peltidocotylinae), a parasite of Ageneiosus inermis (L.) (Siluriformes: Auchenipteridae) in Argentina

“…Only Houssayela sudobim (Woodland, 1935) has paired cone-shaped (papilla-like) projections on the anterior margin of each unilocular sucker (de Chambrier & Scholz, 2005). The scolex of Harriscolex kaparari (Woodland, 1935) was described as having suckers with unguiculate protrusions (figures 13 and 14 of Rego, 1999), but these seem to be formed by an extension of the apical parenchyma and the musculature of the suckers (figure 62 of de Chambrier & Vaucher, 1999). Histological studies will be necessary to establish homologies between the projections described above.…”