Neotrop. Helminthol., 6(1), 2012

2012 Asociación Peruana de Helmintología e Invertebrados Afines (APHIA)

ISSN: 2218-6425 impreso / ISSN: 1995-1043 on line

ORIGINAL ARTICLE / ARTÍCULO ORIGINAL

1 2*

Elizângela Farias da Silva & Marcos Tavares-Dias

1Instituto de Saúde e Biotecnologia (ISB), Universidade Federal do Amazonas (UFAM). Coari, AM, Brazil.

2Laboratório de Aquicultura e Pesca, Embrapa Amapá, Rodovia Juscelino Kubitschek, km 5, N° 2600, 68903-419, Macapá,

AP, Brazil. e-mail: marcostavares@cpafap.embrapa.br; mtavaresdias @pq.cnpq.br

Suggested citation: Silva, EF & Tavares-Dias, M. 2012. Infection by helminthes in Mylossoma duriventre Cuvier, 1817, a

characid from the central Amazon, Brazil. Neotropical Helminthology, vol. 6, nº1, pp. 67 - 73.

Abstract

This study describes the parasitic fauna of Mylossoma duriventre caught at Lake Coari, a tributary of

the middle Solimões River, in the state of Amazonas (central Amazon, Brazil) and the relative

condition factor (Kn). Out of 70 necropsied specimens, 90% had the gills parasitized by the helminth

Anacanthorus paraspathulatus Kritsky, Boeger & Van Every, 1992 (Dactylogyridae:

Anacanthorinae) and the intestine by Eustrongylides Jägerskiöld 1909 (Nematoda:

Dioctophymatidae) larvae. A total of 19,763 specimens of A. paraspathulatus were collected, but the

infection by Eustrongylides sp. larvae seemed to be accidental, only three hosts were trophically

infected. However, there was no significant difference (p<0.05) in the Kn of parasitized and non-

parasitized fish, indicating that the intensity these parasites has not affected the health of the host. This

is the first report of parasitic infection rates for M. duriventre, as well of infections by Eustrongylides

sp. for this host.

Key words: Freshwater fish – Monogenoidea – Nematoda – Parasites.

Resumen

Palabras clave: Peces de agua dulce.Monogenoidea - Nematoda - Parásitos -

Este estudio describe la fauna parasitaria de Mylossoma duriventre colectada en el Lago Coari,

afluente medio del Río Solimões, estado del Amazonas (Amazonía Central, Brasil) y el factor de

condición relativo (Kn). De los 70 especímenes necropsiados, 90% estaban con las branquias

parasitadas por el helminto Anacanthorus paraspathulatus Kritsky, Boeger & Van Every, 1992

(Dactylogyridae: Anacanthorinae) y el intestino por larvas de Eustrongylides sp. Jägerskiöld, 1909

(Nematoda: Dioctophymatidae). Fueron colectados 19 763 especímenes de A. paraspathulatus, pero

la infección por larvas de Eustrongylides sp. parece accidental, debido a que solamente tres

hospederos fueron infectados por vía trófica. Sin embargo, no hubo diferencia significativa (p<0,05)

en el Kn de peces parasitados y no parasitados, indicando que la intensidad de parásitos no afecta la

salud del hospedero. Este es el primer registro sobre tasas de infección parasitaria para M. duriventre y

de infección por Eustrongylides sp.

INFECTION BY HELMINTHS IN MYLOSSOMA DURIVENTRE CUVIER, 1817, A CHARACID

FROM THE CENTRAL AMAZON, BRAZIL

INFECCIÓN POR HELMINTOS EN MYLOSSOMA DURIVENTRE CUVIER, 1817, UN

CHARÁCIDO DE LA AMAZONÍA CENTRAL, BRASIL

Silva & Tavares-Dias

Helminthes in Mylossoma duriventre

The Solimões-Amazonas basin is a typical large

river system with large adjacent plains that are

influenced by a predictable hydrological cycle

with annual flooding resulting from a lateral

overflow of water from the main channel of the

river towards the plain. At the peak of the flood,

much of the area is inundated and almost all the

lakes become connected with each other and with

the river. In this ecosystem, there are different

species of fish widely adapted with different

strategies and lifestyles. In lakes, Mylossoma

duriventre Cuvier, 1817 (Characidae) adults are

caught in open water and in flooded forest, while

juveniles are caught only in the flooded forest

(Soares et al., 2007).

The M. duriventre is distributed throughout the

Amazon Basin, its main nutrient-rich tributaries

and also in the Tocantins and Araguaia rivers

(Araújo-Lima & Rufino, 2003). A pelagic fish with

omnivorous feeding habits, M. duriventre shows

ontogenetic variations in its diet. Adults feed

mainly on leaves, fruit and seeds from the flooded

lowland forests and small terrestrial and aquatic

invertebrates (Claro-Júnior et al., 2004, Soares et

al., 2007). Juveniles show a preference for grass

and small mollusks. This fish is diurnal and

migratory, thus, during the period of ebb tide, it

migrates upstream to spawn in the confluence of

rivers. It has total spawning and external

fertilization. Females begin the sexual maturation

process with 15.5 cm and males with 14.8 cm. Its

reproduction period is long, covering periods of

drought (November) and flood (May), with a more

intense spawning between the months of

December and February (Soares et al., 2007).

This characid is medium sized, reaching up to 25

cm of total length and 500 g of weight. It is greatly

appreciated by the riverside population and also by

the urban population, therefore its has great

importance in extractive fishery and it is one of the

main species sold at fairs and markets of the

Amazon (Soares et al., 2007). In 2007, the

production of the extractive fishery of Mylossoma

spp. was 6543.0 tons, which generated US$ 16.358

millions for the local economy (Ibama, 2007).

Thus, M. duriventre is undoubtedly an

economically important specie for the Amazon

region (Araújo-Lima & Rufino, 2003). So, the

INTRODUCTION

health and parasites of this characid fish should be

studied.

Condition factor is an important tool for the study

of fish welfare reflecting directly on its health.

Analysis of variations in this indicator has been

used to evaluate the effects of different parasites on

hosts populations or individuals (Guidelli et al.,

2011; Silva et al., 2011a,b). Some parasites seem

not to exert negatives effects on their hosts, while

others can have deleterious effects in the health of

the hosts (Silva et al., 2011b).

For M. duriventre, literature reports the occurrence

of acanthocephalan Echinorhynchus salobrensis

Machado, 1948 in fish from Mato Grosso

(Machado-Filho, 1948), monogenoideans

Anacanthorus paraspathulatus Kritsky, Boeger &

Van Every, 1992 in fish from the Lake Janauacá in

the State of Amazonas (Kritsky et al., 1992) and

larvae of nematodes Goezia sp. and Spectatus sp. in

fish from the Paraná River (Moravec, 1998).

Nevertheless, there are no studies on the parasitic

rates for this Amazonian freshwater fish.

Since most parasites have a complex lifecycle

involving intermediate and definitive hosts, they

can be indicators of changes in the environment

and also in the fish community (Takemoto et al.,

2009; Guideli et al., 2011; Silva et al., 2011b).

Therefore, it is relevant to known the strategies in

the parasite-host relationship in wild populations

of fish (Takemoto et al., 2009; Sloboda et al., 2010;

Silva et al., 2011b), so such knowledge may later

be used in aquaculture. Parasitism can influence

wild fish populations either directly through

mortality events or indirectly by reducing the

fecundity, altering the hosts' behavior or increasing

the risk of predation (Longshaw et al., 2010;

Takemoto & Lizama, 2010). Werder & Sant-Paul

(1979) have stated that Mylossoma spp. has

farming potential. Thus, taking into consideration

the size of the Amazon fish fauna, it is evident that

there is still a lot to be studied regarding parasites of

wild populations of fish, including M. duriventre.

The present work studied the parasitic fauna of M.

duriventre from Lake Coari, in middle Solimões

River basin, State of Amazonas (central Amazon)

as well as the relative condition factor (Kn).

Fish and collection

Mylossoma duriventre specimens were collected

in the flooded forest of Lake Coari (04º04' 072”S,

063 10'004”W), a tributary of the Solimões River,

in the municipality of Coari (State of Amazonas)

for parasitological studies. All fish were collected

with appropriate different nets (ICMBIO: 11884-

1).

Parasitological examination

All fish were weighted (g), measured for total

length (cm) and necropsied in accordance with

ethical procedures for the presence of parasites.

Detailed macroscopic evaluation of the body

surface, mouth, eyes, gills and opercula were held

for each specimen. The gills were removed, placed

in slides with 0.8 % NaCl solution and analyzed

with an ordinary light microscope. Organs were

removed for parasitological examination of the

gastro intestinal tract, placed in Petri dishes

containing 0.65% NaCl solution and examined in

stereomicroscope. The methodology used for

collection, fixation (Eiras et al., 2006; Thatcher,

2006) and quantification (Tavares-Dias et al.,

2001) were those recommended in literature. The

identification of parasites followed the

recommendations from Kritsky et al. (1992),

Moravec (1998), Thatcher (2006) and Luque et al.

(2011). Ecological terms were according to Bush

et al. (1997).

Host-parasite relationship

After the determination of the body weight and the

total length of each fish, the relative condition

Neotrop. Helminthol., 6(1), 2012

factor (Kn) was calculated according to Le-Cren

(1951). Differences in the Kn of parasitized and

non-parasitized fish were compared by t test

(p<0.05). Spearman correlation coefficient (r)

was used to determine possible correlations

between the intensity of parasites and the total

length and weight of the host fish (Zar, 1999).

Physico-chemical parameters of the water

The concentration of dissolved oxygen and the

temperature were determined with a digital

oximeter. The water temperature ranged from 29.6

to 31.1 ºC and the dissolved oxygen ranged from

4.5 to 6.3 mg/L.

Fish had the gills parasitized by monogenoidean

Anacanthorus paraspathulatus (Dactylogyridae,

Anacanthorinae) and the intestine by

Eustrongylides Jägerskiöld, 1909 (Nematoda:

Dioctophymatidae) larvae. However, dominance

was of A. paraspathulatus (Table 1).

There was no difference between the Kn of

parasitized and non - parasitized by

monogenoideans and nematodes (Table 2).

In Mylossoma duriventre there was no correlation

between the intensity of A. paraspathulatus and

the weight (rs= -0.0927, p=0.399), the total length

(rs=-0.0927, p= 0.472) and the hosts' Kn (rs= -

0.0090, p=0.944).

MATERIALS AND METHODS

RESULTS

Table 1. Parasite helminthes in Mylossoma duriventre from lake Coari, middle Solimões River, State of Amazonas,

central Amazon, Brazil. EF: Examined fish; PF: Parasitized fish; P: Prevalence; MI: Mean intensity; TNP: Total

number of parasites; SD: Standard deviation.

Taxa/Parasites

Monogenoidea

Anacanthorus paraspathulatus

Nematoda

Eustrongylides sp. (Larvae)

EF/PF

70/63

70/3

P (%)

90.0

4.3

MI ± SD

316.0 ± 113.6

0.19 ± 0.4

TNP

19.763

Range

86 691

Silva & Tavares-Dias

Helminthes in Mylossoma duriventre

Table 2. Biometric parameters and relative condition factor (Kn) of Mylossoma duriventre from lake Coari, middle

Solimões River, state of Amazonas, central Amazon, Brazil. Values in parenthesis indicate the range. Different letter

in same line indicates differences by the t test.

Parameters Non-parasitized (N=7) Parasitized (N=63) p

Weight (g) 188.6 ± 45.8a 213.0 ± 42.4a 0.290

(120.0-250.0) (42.4-120.0) -

Length (cm) 19.2 ± 1.6a 20.0 ± 1.5a 0.434

(16.5-19.0) (17.0-23.0) -

Kn 1.000 ± 0.010a 1.000 ± 0.023a 0.938

(0.988 1.020) (0.934 1.069) -

This study reports a parasitic fauna in wild M.

duriventre constituted by one species from

monogenoidean specie and one species from

nematode. Contrastingly, other studies reported a

larger parasitic fauna in Aphyocharax anisitsi

Eigenmann & Kennedy, 1903, Psellogrammus

kennedyi Eigenmann, 1903, Astyanax altiparanae

Garutti & Britski, 2000 , Metynnis lippincottianus

Cope, 1870, Piaractus mesopotamicus Holmberg,

1887, Serrasalmus marginatus Valenciennes,

1837, Serrasalmus maculatus Kner, 1858 and

Salminus brasiliensis Cuvier 1816; all characid

species from the upper Paraná river (Takemoto et

al., 2009), as well as in Oxydoras niger

Valenciennes, 1821 from the Lake Coari (Silva et

al., 2011). However, the parasitic fauna of

freshwater fish may vary depending on the host's

species, the level occupied by the host in the food

chain, its age and sex, besides other biotic and

abiotic factors (Takemoto & Lizama, 2010; Silva

et al., 2011b).

Monogenoideans are parasites with direct

lifecycles which are usually host specific

(Thatcher, 2006; Takemoto et al., 2009; Takemoto

& Lizama, 2010). About 308 species of

Monogenoidea from 70 genera have been

described parasitizing 144 fish species in Amazon

and Neotropical zone, with an average of 2.14

parasites by host. Therefore, only about 3% of

Monogenoidea species are known (Thatcher,

2006), hence the number of species described

DISCUSSION tends to increase in Amazon. Anacanthorus

Mizelle & Price 1965 is one from a number of

Monogenoidea parasites found infecting the gills

of freshwater characid fish species from the

Amazon. Sixty-three species of the genus

Anacanthorus are known as parasites of freshwater

Neotropical fish, and of these parasites, sixty-two

species are found in fish from the Amazon Basin

River. However, only the A. paraspathulatus have

already been found parasitizing M. duriventre

(Kritsky et al., 1992; Thatcher, 2006).

In the gills of M. duriventre from Lake Coari, the

prevalence of monogenoidea A. paraspathulatus

(90%) was higher than that of Cosmetocleithrum

spp. (70.3%) in O. niger (Silva et al., 2011a) and

Gyrodactylus gemini Ferraz, Shinn &

Sommerville 1994 (56%) in Semaprochilodus

insignis Jardine, 1841 (Silva et al., 2011b), while

the intensity was lower that in O. niger. However,

the prevalence and the intensity were higher than

those described for Demidospermus sp. in

Auchenipterus osteomystax Miranda Ribeiro 1918

from Paraná River (Tavernari et al., 2009).

Infection rates by monogenoideans may vary

depending on the hosts' species, their

physiological and immunological status, and on

abiotic factors. The infection rates did not

influence the well-being of M. duriventre, since its

relative condition factor (Kn) was not affected by

parasitism.

Overdispersed distributions of Nematoda are

commonly observed within host fish populations

and are important for understanding many density-

Neotrop. Helminthol., 6(1), 2012

dependent processes in host–parasite interactions.

The proximate causes of such distributions are

poorly understood, especially in natural systems,

but heterogeneity among hosts in the exposure to

infective parasite stages is thought to be an

important factor. Parasites transmitted by prey fish

serving as intermediate hosts and variability in

feeding behavior among fish predators within host

populations may have a strong influence on

parasite distributions (Moravec, 1998; Martins et

al., 2009). However, omnivorous fish such as M.

duriventre (Araújo-Lima & Rufino, 2003; Soares

et al., 2007) show lower risks of parasitism

because they are primary consumers occupying

lower trophic levels in the food chain (Martins et

al., 2009; Silva et al., 2011).

The nematode Eustrongylides larvae commonly

infect fish-eating aquatic birds as their definitive

host. They have oligochaetes as their first

intermediate host and fish as their second

intermediate host or paratenic (Mitchel et al.,

2009; Sloboda et al., 2010). They may infect

different organs of freshwater fish from all over the

world, from America to Asia. Piscivorous predator

fishes can have seasonal infection due to increased

feeding activity in summer and autumn (Martins et

al., 2009). In Brazil, Eustrongylides larvae occur

in many freshwater fish species from different

families (Martins et al., 2009; Takemoto et al.,

2009; Luque et al., 2011), except M. duriventre.

However, only larvae of Eustrongylides ignotus

Jägerskiöld, 1909 (Takemoto et al., 2009; Luque et

al., 2011) and Eustrongylides tubifex Nitzsch, in

Rudophi, 1819 (Luque et al., 2011) have been

identified in fish. These endohelminths fish

parasites are of interest due to their pathogenicity

for the hosts (Mitchell et al., 2009) and their

zoonotic potential for humans (Barros et al., 2006;

Barros et al., 2009; Martins et al., 2009). In fish,

infection by Eustrongylides larvae may increase

their predation susceptibility, infected host fish

exhibit erratic movements when compared to non-

infected ones (Sloboda et al., 2010).

In M. duriventre from Lake Coari (in central

Amazon), levels of infection by Eustrongylides sp.

were low and smaller than those of

Pseudoplatystoma fasciatum Linnaeus, 1766

(Barros et al., 2006; Barros et al., 2009), Brycon

hilarii Valenciennes, 1850, Pseudoplatystoma

corruscans Spix & Agassiz, 1829, Pinirampus

pirinampu Spix & Agassiz, 1829 and Zungaro

zungaro (Humboldt, 1821) from Cuiabá river, in

the State of Mato Grosso (Barros et al., 2006) and

of Cichla piquiti Kullander & Ferreira, 2006,

Hoplias malabaricus Bloch, 1794 and Plagioscion

squamosissimus Heckel, 1840 from Paraná River,

in the state of São Paulo (Martins et al., 2009).

However, they were similar to those described for

S. marginatus, but they did not occur in M.

duriventre from Cuiabá River (Barros et al., 2006).

Nevertheless, the distribution, intensity and

prevalence of Eustrongylides sp. may be strongly

influenced by the environment and the host's

general conditions (Martins et al., 2009; Mitchel et

al., 2009), as well as by dense populations of

oligochaetes, the natural intermediate hosts of this

nematode parasite of wild fish. In addition, some

fish species may be only the transporters (paratenic

hosts) of this nematode or have an accidental

infection, as it seems to have occurred with M.

duriventre from Lake Coari, which were adult fish.

Adults M. duriventre besides leaves, also

consume fruit and seeds from the Amazonian

flooded forest and small terrestrial and aquatic

invertebrates (Claro-Júnior et al., 2004, Soares et

al., 2007). However, this omnivorous characid is a

pelagic fish which have almost no contact with

oligochaetes, the first intermediate host of the

Eustrongylides larvae.

In conclusion, the characid M. duriventre is a fish

species that migrates a few hundred km for its

reproduction (Araújo-Lima & Rufino, 2003;

Soares et al., 2007); hence this host presented a

reduced parasitic fauna in the flooded forest

(“igapó”) from Lake Coari which was constituted

basically by monogenoideans parasites. However,

the low presence of Eustrongylides larvae seems to

be due to a lack of contact with first intermediate

hosts in the environment.

Silva & Tavares-Dias

Helminthes in Mylossoma duriventre

ACKNOWLEDGEMENTS

We are grateful to Conselho Nacional de Pesquisa

e Desenvolvimento Tecnológico (CNPq) for

supporting a fellowship to Tavares-Dias, M. (#

300472/2008-0).

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Hall, New Jersey.

Correspondence to author/ Autor para

correspondencia:

Marcos Tavares-Dias

Laboratório de Aquicultura e Pesca, Embrapa

Amapá, Rodovia Juscelino Kubitschek, km 5, N°

2600, 68903-419, Macapá, AP, Brazil.

E-mail/ correo electrónico:

marcostavares@cpafap.embrapa.br

mtavaresdias @pq.cnpq.br

Received February 13, 2012.

Accepted March 26, 2012.