Bull. Eur. Ass. Fish Pathol., 31(4) 2011, 161 NOTE About the biodiversity of parasites of freshwater fish from Brazil J. C. Eiras¹*, R. M. Takemoto², G. C. Pavanelli² and E. A. Adriano³ ¹ Departamento de Biologia, and CIIMAR, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre, s/n, Edifício FC4, 4169-007 Porto, Portugal; E-mail: [email protected]; ² Programa de Pós-graduação em Ecologia de Ambientes Aquáticos Continentais e Programa de Pós-graduação em Biologia Comparada, Universidade Estadual de Maringá, NUPELIA, Av. Colombo 5790, 87020-900 Maringá, PR, Brasil; E-mail: [email protected]; E-mail: [email protected]; ³ Departamento de Ciências Biológicas, Universidade Federal de São Paulo, Rua Professor Artur Riedel, 275, Jardim Eldorado, CEP 09972-270, Diadema, SP, Brasil; E-mail: [email protected] Abstract The authors analyze the biodiversity of parasites of freshwater fish from Brazil. It is concluded that the number of parasites described so far is low compared to the biodiversity of host species in the country, and that the number of parasites of the different taxa is very variable. An interpretation of these data is suggested, and several recommendations are suggested for the study of fish parasites in Brazil. Brazil is one of the largest countries in the world. Within this large amount of freshwater eco- It has a large number of rivers and some of them systems a great fish biodiversity can be found: are very long - the rivers Madeira, 3,250 km about 4,035 fish species representing approxi- long, São Francisco (3,160 km), Paraná (2,940 mately 31% of the world freshwater fish species km), Tocantins (2,640 km), Uruguai (1,770 km) (Levêque et al., 2008) distributed among 39 and Paraguai (1,500) km) are some examples. different families (Buckup et al., 2007). Besides, Brazil has the longest and largest river in the world, the Amazon River - the Amazon Due to the high biodiversity of freshwater fish River basin consists of the most extensive river in Brazil (as in other South-American countries) system on Earth, occupying a total area of about a large number of species are economically very 6,110,000 km2 and represents the largest amount important for several reasons. of liquid freshwater of the planet (Agência Na- cional de Águas, 2011). In general, a significant number of species are highly regarded as food source and reach very * Corresponding author’s email: [email protected] Bull. Eur. Ass. Fish Pathol., 31(4) 2011, 162 high prices in the market - the number of inland and Cohen, 1998; Cohen and Kohn, 2008); fishermen is of several thousands of people. nematodes (Moravec, 1998); copepods (Luque A great number of native species, as Piaractus and Tavares, 2007); cestodes (Rego, 2000) and mesopotamicus, Colossoma macropomum, Pseu- acanthocephalans (Santos et al., 2008). Thatcher doplatystoma spp., Leporinus spp. and Brycon (2006) reported the parasites of fish from the spp., among others, and some introduced ones, Amazonian region, and Takemoto et al. (2009) as Oreochromis niloticus, are farmed. The pro- described the diversity of fish parasites from the duction of farmed freshwater fish in Brazil in floodplain of the Upper Paraná River. 2009 was about 337.353 tons (Estatística MPA, 2008/2009), and the potential of new species Recently, Eiras et al. (2010a) produced a book for farming is being studied (Feijó et al., 2009). listing the parasites of all the taxa (and their In the last few years a large number of “fish respective hosts) infecting the freshwater fish and pay” farms to allow recreational fishing from the country. According to the results of to take place have been developed near small these authors a total of 1,034 nominal species and large cities with good exploitation results. of parasites were reported from freshwater fish Finally, an important resource is represented of Brazil (Table 1). The parasites were collected by the ornamental fish, especially the small from a total of 451 different host species. It is in- sized aquarium fish, whose capture is the main teresting to note that these hosts represent only economic activity of several small cities mainly 11.1 % of the species reported for the country, in the Amazonian region. but at the same time represents a considerable amount of different host species from a para- For these reasons the freshwater fish represent a sitological point of view. valuable resource and has justified, principally in the last years, the increasing interest of the These results, which have not been updated scientific community. As a result, the majority since July 2010 despite the description of a of scientific meetings have focused mainly on small number of new species since then pose aspects of the biology of these species, and the a number of interesting problems which deserve number of publications concerning fish biology some attention: in general increased significantly in the past two decades. However, the corresponding number Why is there such a low number of fish parasites of papers on the diseases and parasites of these described in so many fish species (an average hosts is generally low. number of 2.3 parasites species per host)? Why only 451 fish species were studied? How do The parasites of the freshwater fish from Brazil we explain the differences in the number of were studied by several researchers, and dif- species of the different taxa? Is the number of ferent checklists of parasites were produced parasitic species “real” or are there more or less for several taxa: trematodes (Viana, 1924; Tra- abundant synonyms? vassos et al., 1969; Thatcher 1993; Kohn et al., 2007); myxozoans (Gióia and Cordeiro, 1996; These are interesting questions which we try Eiras et al. 2008, 2010); monogeneans (Kohn to answer. We consider three main factors that Bull. Eur. Ass. Fish Pathol., 31(4) 2011, 163 might explain, at least partially, these figures: 1) species (35%) were described also in the same factors related to the research effort; 2) factors period. However, this does not necessarily related to the facility of detection of the para- mean an increase of researchers working in the sites, and 3) factors related to the type of the area. Concerning myxozoans, for instance, the host. number of people working in the field remained stable. However, the recent developments in the Table 1. Number of parasites species, per taxon, knowledge of these parasites and the utilization described for freshwater fish from Brazil (data of new tools, like molecular characterization reported to July, 2010). of the species, lead to a renewing of interest in the group, thus generating more studies and Number of Parasites taxon publications. species Amoebae 1 Considering the total number of fish species, Flagellata (sensu latum) 66 known fish parasites, and the number of host Apicomplexa 10 species, it has to be concluded that the number Ciliophora 15 of parasitic species is very low as indicated Myxozoa 79 above. The explanation for these pictures can Monogenea 312 be related to the fact that, most of the time, Digenea 148 the necropsy of the fish is done by researchers Cestoda 116 interested only in a particular kind of para- Nematoda 124 sites. For instance, a parasitologist interested Acanthocephala 133 in trypanosomes takes a blood sample only; Hirudinea 12 a researcher studying ectoparasites examines Crustacea 118 the body surface of the hosts; a myxozoan re- searcher only pays attention to those parasites. In any case, even if other parasites are present Research effort and observed, they are usually not sampled, In relation to some groups of parasites and, as a consequence, many parasites remain (Amoebae, Apicomplexa, Hirudinea) there is unreported. practically no research being conducted and the number of people studying these groups However, given the great diversity of fish found is very small. in the country, the very low number of research- ers studying fish parasites in Brazil seems to In other groups of parasites, an analysis of the be the most decisive factor responsible for the species descriptions in the last decades show low knowledge of the fish parasites fauna in that the majority or a significant proportion of the country. the species were described quite recently. For instance, from a total of 79 species of myxo- A search on the Lattes Platform (Cnpq) (Govern- zoans, 44 (55%) were described in the last 15 ment produced list of scientists curricula includ- years. Similarly, 109 out of 312 monogenean ing all the science subjects within the country) Bull. Eur. Ass. Fish Pathol., 31(4) 2011, 164 using the descriptors “fish parasites” indicates Host species about 200 different researchers. However, the in- The total number of different hosts examined so dividual examination of the curricula shows that far is about 451 species. Surprisingly, a detailed in fact only about 45 researchers work on fish analysis of the hosts demonstrates that most parasitology exclusively, including both marine of the parasitological studies are divided into and freshwater fish. This means that the number three groups of fish: farmed species (Colossoma of researchers working in this field is clearly macropomum, Piaractus mesopotamicus, Arapaima very low considering not only the population gigas, Pseudoplatystoma fasciatum, Oreochromis of the country (almost 200 million of people) niloticus, Tilapia rendalli, etc.); high economic but also the extremely high fish diversity. valuable species from natural environments (all the species cited above, plus a great number Facility of detection of the parasites of species as Prochilodus lineatus, Brycon spp., The facility of detecting the parasites obviously Hoplias malabaricus, Cichla spp., Plagyoscion sq- plays a role in the number of species described. uamosissimus, Salminus maxillosus, Pimelodus Ectoparasites, and parasites which have a mon- maculatus, Zungaro jahu, Leporinus spp., etc.); oxenous life cycle, are easier to detect and this ornamental fish species, mainly aquarium fish may explain why the most “abundant” para- (Xiphophorus maculatus, X.