INTRODUCTION
Parasite communities are playing an increasingly
important role as models for the study of
biodiversity and biogeography (Poulin & Morand,
2000). Given the integral roles played by parasites
in natural ecosystems, identifying hotspots of high
parasite diversity, as well as areas of relatively low
parasite diversity, is crucial for a complete
understanding of the functioning of the biosphere.
Currently, the biodiversity of marine and
freshwater ecosystems of Latin America is
threatened, mainly by environmental problems
resulting from the destruction and degradation of
the ecosystems. In this context, parasite
biodiversity can be very important because
parasitism plays key roles in ecosystems,
regulating the abundance or density of host
populations, stabilize food webs and structuring
animal communities (Luque & Poulin, 2007).
Takemoto et al. (2005) performed the first study
relating the different features of host species and
the parasite species richness in freshwater fishes
from Neotropical Region. In fish, for instance,
some previous studies have found that host body
size is a good predictor of parasite species richness
whereas others have found no effect of host size.
The same is true for a range of other host features. It
is therefore difficult to assess the relative
importance of different host traits for the evolution
of parasite diversity in general (Luque et al., 2004;
Luque & Poulin, 2008).
In the present study, we examine the relationship
between different features of host species and the
diversity of metazoan parasite communities across
species of fish hosts from Guandu River (Fig. 1) in
function of the strategic importance of this river,
which is the main source of potable water in Rio de
Janeiro, Brazil. The Guandu River supply water to
90% of population of City of Rio de Janeiro and
although be a very impacted environment (Bizerril
& Primo, 2001), it maintains an important level of
biodiversity of fishes, and consequently, fish
parasites (Azevedo et al., 2010). In addition, data
about population and community and quantitative
descriptors from the fish hosts are given herein.
Between April 2003 to September 2009 were
analyzed 786 specimens of fish, belonging to 21
species (Table 1) from the Guandu river, near the
dam of water treatment station (WTS) (22°48'32"S,
43°37'35"W). The taxonomy of the fishes follows
that of Reis et al. (2003). Parasites were collected
from the body surface, gills, and body cavities, and
viscera after examination under a stereoscopic
microscope. Washings from gills and gut lumen
were strained using a sieve (53 and 75 μm mesh
size) to retain even the smallest parasites.
Following Bush et al. (1997), prevalence, intensity
and abundance mean were calculated for parasites
of all fish species.
Pearson's correlation coefficient r was used to
analyze the possible correlation between the host's
total body length and the abundance of parasites,
with previous logarithmic transformation Log
(x+1) (Zar, 1999). The analysis included only
parasite species with prevalence greater than 10%
(Bush et al., 1990).
The following descriptors were calculated at the
parasites infracommunity level: total prevalence,
total intensity, total abundance, total species
richness, endoparasite and ectoparasite species
richness, Margalef's richness index (d), Brillouin's
diversity index (H) (log 10 based), Pielou's
evenness index (J`) and Berger-Parker dominance
index. In addition the Bray-Curtis similarity index
was calculated among infracommunities within
host fish species (Magurran, 2004). These
descriptors were used for all parasites with
exception of myxozoans. Statistical significance
level was established at P<0.05. All results were
presented in tabular form (Tables 2 and 3). The
relative abundance of metazoan parasites was
calculated at the level of infracommunities for all
species of fish that had more than three species of
parasites. The results were presented in graphical
form (Figs. 2 and 3).
For each fish species, the average taxonomic
distinctness (Δ+) and variance in taxonomic
distinctness (Λ+) of the parasite component
community were computed, following the
procedures and taxonomies used by Luque &
Poulin (2008). The effect of host length on
taxonomic distinctness, on variance and on total
richness were evaluated using the Pearson
correlation coefficient on logarithmic transformed
data. The Student`s t test or ANOVA test,
depending of the number of variables with previous
transformation, was used to verify the influence of
MATERIAL AND METHODS
186
Biodiversity of fish parasites from Guandu river
Azevedoet al.