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Memórias do Instituto Oswaldo Cruz
Fundação Oswaldo Cruz, Fiocruz
ISSN: 1678-8060 EISSN: 1678-8060
Vol. 97, Num. 1, 2002, pp. 51-52
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Mem Inst Oswaldo Cruz, Rio de
Janeiro, Vol. 97(1) 2002, pp. 51-52
Ecological Data of Travassosnema
travassosi travassosi (Dracunculoidea: Guyanemidae) from the Humour of the
Eyes of Acestrorhynchus lacustris from Tibagi River, Paraná, Brazil
Ângela Teresa Silva-Souza/+,
Aurélia Saraiva*
Departamento de Biologia Animal e Vegetal, CCB,
Universidade Estadual de Londrina, Caixa Postal 6001, 86051-990 Londrina, PR,
Brasil *Departamento de Zoologia e Antropologia, Faculdade de Ciências,
Universidade do Porto, Porto, Portugal
+Corresponding author. Fax: +55-43-371.4207. E-mail: ateresa@uel.br
Received 28 March 2001
Accepted 13 September 2001
Code Number: oc02008
Data obtained between 1990 and 1995 provide,
for the first time, ecological information of the parasitic nematode Travassosnema
travassosi travassosi Costa, Moreira
& Oliveira, 1991 from Acestrorhynchus
lacustris (Characiformes: Acestrorhynchidae)
collected in the Tibagi River, Sertanópolis, Paraná, Brazil. These
nematode occurred with low prevalences (7.7% to 28.6%) and intensities (1 to
3) during almost the whole year. The observation of mature females throughout
the year indicate that liberation of larvae can occur during all the year around.
This is the first report on the occurrence of T.
travassosi travassosi inside the eyes.
These nematodes were mostly located in humour of the eyes (87% of cases), being
less frequently detected in tissues behind the eyes (13% of cases).
Key words: Travassosnema travassosi travassosi
- Nematoda - parasites - Acestrorhynchus lacustris - Tibagi River - Paraná
- Brazil
The genus Travassosnema Costa Moreira
& Oliveira 1991 (Dracunculoidea: Guyanemidae) is represented by medium sized
nematodes with a rounded cephalic end, without a buccal capsule and with the
oesophagus divided into an anterior muscular and a posterior glandular portions.
The posterior glandular portion of oesophagus is provided with a long dorsal
appendix extending posteriorly, a feature that makes this genus easily distinguishable
from the genus Guyanema Petter, 1974 (Costa et al. 1991, Moravec 1998).
Two subspecies of the only species T. travassosi
Costa Moreira & Oliveira, 1991 are known to occur in South American
freshwater fishes, Acestrorhynchus lacustris Reinhardt, 1874 (Characiformes:
Acestrorhynchidae) being the only known host of these parasites (Moravec 1998,
Vicente & Pinto 1999). T. travassosi travassosi Costa Moreira &
Oliveira, 1991 was detected in the tissues behind the eyes (orbits) from fishes
from the Três Marias Reservoir on the São Francisco River, State
of Minas Gerais, Brazil (Costa et al. 1991), while T. travassosi paranaensis
Moravec Kohn & Fernandes, 1993 was detected in the abdominal cavity from
fishes of the Paraná River near Guaíra, Brazil (Moravec et al.
1993). No data have been published on the prevalence and the intensity of infection
of these nematodes.
During a study of helminth parasites of the
eyes of A. lacustris conducted between 1990 and 1995 in the Tibagi River,
Paraná, Brazil, the dracunculoid nematode T. travassosi travassosi
was observed. Data related to ecological indexes of prevalence and intensity
of infection of these parasites are evaluated in this paper.
MATERIALS
AND METHODS
Nematodes were collected from both the orbits
and humour of the eyes of A. lacustris caught by waiting nets in Tibagi
River, Sertanópolis, Paraná, Brazil near the confluence to Paranapanema
River (22º30'S and 51º00'W). The study area became a semi-lotic system
after the construction of Capivara dam, on the Paranapanema River, in 1975.
Fish samples were collected between April 1990 and February 1991 (n = 51; body
length: 14.3 - 27.6 cm), August 1992 and July 1993 (n = 122; body length: 10.6
- 27.5 cm) and April 1994 and May 1995 (n = 46; body length: 10.4 - 23.9 cm).
Samples were obtained occasionally during these periods excluding from August
1992 to July 1993 when samples were obtained monthly.
Nematodes were fixed and stored in 70% ethanol
and cleared in glycerine for examination.
RESULTS
The
prevalence of T. travassosi travassosi found in A. lacustris is
shown in the Table. The intensity of infection
was usually low (1 to 3 specimens) but, in December 1992, 13 and 26 nematodes
were detected in the humour of the eyes of two hosts. In fact, T. travassosi
travassosi was mostly located inside the eyes (87%) in the humours and,
in the majority of cases, both eyes were infected (Fig.
1). Less frequently (13%), the nematodes were found in the tissues behind
the eyes, i.e. orbits.
The prevalence in the samples carried
out monthly between August 1992 and July 1993 is shown in Fig.
2. These results indicate that specimens of T. travassosi travassosi
occur in A. lacustris during almost all the year without a marked seasonal
cycle. Only 2% of nematode specimens were males, and mature females with uterus
containing larvae were observed throughout the year, indicating that the liberation
of larvae could occur in this locality during all the year. Excluding these
small larvae (probably first-stage larvae), other larval stages were never observed
in the eyes.
DISCUSSION
This is the first report on the occurrence of
T. travassosi travassosi in the humours of the eyes. This observation
seems to be important because helminth eyes parasites usually cause opacity
of the eye lenses and even blindness, symptoms that usually decrease the growth
rates due to fish difficulties to localize food and also reduction of the fish
population due to smaller fish ability to escape to predators.
In the present study, we observed that the prevalence
and the intensity of infection were much higher inside the eyes than in the
orbits where these nematodes were first detected. These parasites were present,
in the study area, usually with low values of prevalence and intensity of infection
during almost the whole year.
These parasites, both males and mature females,
were located in orbits and humours of the eyes in the examined specimens of
A. lacustris. However, it is possible that, as occurs with other dracunculoids,
other organs can also be infected by T. travassosi travassosi. For this
reason a detailed helminthological examination of the other specimens of A.
lacustris from Tibagi River will be interesting in the future.
The life cycle of T. travassosi travassosi
undoubtedly involves an intermediate host. The family Guyanemidae shows some
affinities with the closely related dracunculoid families Skrjabillanidae and
Daniconematidae (Moravec & Køie 1987, Molnár & Moravec
1994). In skrjabillanids, the first-stage larvae released from the viviparous
nematodes are taken up by the intermediate host, hematophagous branchiurids
(Argulus spp.), and third-stage larvae are inoculated by these invertebrates
into the vertebrate definitive host (Moravec 1994, 1998, Molnár &
Székely 1998, Moravec et al. 1998). According to Molnár and Moravec
(1994), Molnár (1997) and Moravec et al. (1999), dani-conematids seem
to have, because of the morphological similarity of these nematodes, a life
cycle very similar to skrjabillanids, i.e. haematophagous branchiurids could
also serve as intermediate hosts of these nematodes. For the same reason it
seems that we could speculate the same for guyanemids. This hypothesis is corroborated
by Moravec (1998) who stated that probably some blood-sucking invertebrate ectoparasites
probably serve as intermediate hosts of T. travassosi travassosi. The
elucidation of the life cycle of these nematodes requires a detailed study including
the identification of the blood-sucking ectoparasites that occur in the study
area and the search for larval stages of these nematodes in scales, skin and
subcutaneous tissues of A. lacustris.
REFERENCES
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Travassosnema gen. n. with the description of T. travassosi
sp. n. (Dracunculoidea, Guyanemidae) parasite of Acestrorhynchus lacustris
Reinhardt, 1874 (Characidae) from Três Marias Reservoir, MG, Brazil.
Mem Inst Oswaldo Cruz 86: 437-439.
- Molnár K 1997. New data on the location
of Daniconema anguillae (Nematoda: Dracunculoidea) adult stages in
eels. Bull Eur Ass Fish Pathol 17: 96-98.
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and Dordrecht, Boston, London, 473 pp.
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© 2002
Instituto Oswaldo Cruz - Fiocruz
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