The South American subcontinent supports one of the world's most diverse and commercially very important ichthyofauna. In this context, the study of South American fish parasites is of increased relevance in understanding their key roles in ecosystems, regulating the abundance or density of host populations, stabilizing food webs and structuring host communities. It is hard to estimate the number of fish parasites in South America. The number of fish species studied for parasites is still low (less than 10%), although the total number of host–parasite associations (HPAs) found in the present study was 3971. Monogeneans, with 835 species (1123 HPAs, 28.5%), and trematodes, with 662 species (1127 HPAs, 30.9%), are the more diverse groups. Data gathered from the literature are useful to roughly estimate species richness of helminths from South American fish, even though there are some associated problems: the reliability of information depends on accurate species identification; the lack of knowledge about life cycles; the increasing number of discoveries of cryptic species and the geographically biased number of studies. Therefore, the closest true estimations of species diversity and distribution will rely on further studies combining both molecular and morphological approaches with ecological data such as host specificity, geographical distribution and life-cycle data. Research on biodiversity of fish parasites in South America is influenced by problems such as funding, taxonomic impediments and dispersion of research groups. Increasing collaboration, interchange and research networks in the context of globalization will enable a promising future for fish parasitology in South America.

An exhaustive literature search supplemented by a critical examination of records made it possible to present an annotated checklist of tapeworms (Cestoda) that, as adults or larvae (metacestodes), parasitize freshwater, brackish water and marine fishes, i.e. cartilaginous and bony fishes, in South America. The current knowledge of their species diversity, host associations and geographical distribution is reviewed. Taxonomic problems are discussed based on a critical evaluation of the literature and information on DNA sequences of individual taxa is provided to facilitate future taxonomic and phylogenetic studies. As expected, the current knowledge is quite uneven regarding the number of taxa and host-associations reported from the principal river basins and marine ecoregions. These differences may not only reflect the actual cestode richness but may also be due to the research effort that has been devoted to unravelling the diversity of these endoparasitic helminths in individual countries. A total of 297 valid species, 61 taxa identified to the generic level, in addition to unidentified cestodes, were recorded from 401 species of fish hosts. Among the recognized cestode orders, 13 have been recorded in South America, with the Onchoproteocephalidea displaying the highest species richness, representing c. 50% of all species diversity. The majority of records include teleost fish hosts (79%) that harbour larval and adult stages of cestodes, whereas stingrays (Myliobatiformes) exhibit the highest proportion of records (39%) among the elasmobranch hosts. Fish cestodes are ubiquitous in South America, being mostly recorded from the Warm Temperate Southeastern Pacific (WTSP; 31%) for marine hosts and the Amazon River basin (45%) for freshwater ones. The following problems were detected during the compilation of literary data: (i) unreliability of many records; (ii) poor taxonomic resolution, i.e. identification made only to the genus or even family level; (iii) doubtful host identification; and (iv) the absence of voucher specimens that would enable us to verify identification. It is thus strongly recommended to always deposit representative specimens in any type of studies, including faunal surveys and ecological studies. An analysis of the proportion of three basic types of studies, i.e. surveys, taxonomic and ecological papers, has shown a considerable increase of ecological studies over the last decade.

Physaloptera tupinambae n. sp. (Nematoda: Physalopteridae) collected from the stomach of 1 Tupinambis merianae (Squamata: Teiidae) male lizard is described. Physaloptera tupinambae, which belongs to the didelphys group, is the only species in the genus that exhibits a bipartite internal tooth and in which the excretory pore is anterior to the deirids. The new species can be differentiated from the other congeners mainly based on the number and pattern of caudal papillae and the length and shape of spicules. Physaloptera murisbrasiliensis and Physaloptera clausa orientalis are the only physalopterids with the same number of caudal papillae as for P. tupinambae, but they differ from the new species mainly in length and shape of spicules. Based on morphological analysis, the speciation process among Physaloptera probably occurred via host capture, and P. tupinambae occupies an intermediate phylogenetic position in the genus. Most likely, the new parasite was acquired by the lizard through ingestion of an intermediate host. Finally, Physaloptera calotisi, Physaloptera funambuli, Physaloptera guptae, Physaloptera indica, Physaloptera johnsoni, Physaloptera kherai, and Physaloptera thaparus are moved to Abbreviata.

A Checklist of the Aspidogastrea (Platyhelminthes: Trematoda) of the World

Se proporciona una lista de verficación de todos los registros válidos publicados de los metazoos parásitos reportados en peces marinos y de agua dulce de Perú. Esta lista incluye los registros de 612 especies diferentes de metazoos parásitos (incluyendo parásitos no identificados) que pertenecen a los siguientes grupos: Platyhelminthes (430 total), incluyendo Monogenea (175), Cestoda (140), y Trematoda (115); Crustacea (99); Nematoda (49); Acanthocephala (16); Myxozoa (14) y Annelida (2). Estos parásitos fueron reportados de 207 especies de peces de Perú (174 teleósteos, 31 elasmobranquios y 2 especies de hospederos no determinados). Los registros de los parásitos no identificados a nivel de especie (182 de 612), representando el 30% de todas las especies, también fueron incluidos. Entre los parásitos de peces reportados de Perú, 391 fueron marinos, 217 de agua dulce y 4 especies se encontraron en ambos ambientes, para un total de 1015 asociaciones parásito-hospedero. Las especies de peces que albergaron el mayor número de parásitos fueron Merluccius gayi peruanus Ginsburg, 1954 (32), seguido de Paralonchurus peruanus (Steindachner, 1875) (31), Scomber japonicus Houttuyn, 1782 (31), Sciaena deliciosa (Tschudi, 1846) (29) y Stellifer minor (Tschudi, 1846) (28), todos ellos son peces marinos. Los parásitos con el mayor número de registros fueron las larvas del cestodo Adenocephalus pacificus Nybelin, 1931 (19), larvas del nematodo Anisakis sp. (18), larvas de Contracaecum sp. (17) y larvas y adultos de Lacistorhynchus tenuis (16), los cuales fueron recuperados de peces marinos, excepto las larvas de Contracaecum sp., las cuales fueron recuperados de ambos ambientes. La diversidad de parásitos en peces peruanos parece estar sesgado por el hospedero muestreado de acuerdo a los intereses del investigador, sino que también está relacionado con las características biológicas de los parásitos y de los hospederos.