versión impresa ISSN 0716-0720
Parasitol. día v.24 n.1-2 Santiago ene. 2000
Ichthyophthirius multifilis (Protozoa) in Gasteropelecus
sternicola (Linnaeus, 1758) collected in the area of
Belém, State of Pará, Brazil
The present study describes for the first time Ichthyophthirius multifilis infecting twenty ornamental fishes Gasteropelecus sternicola (white butterfly fish). Parasites were found in 100% of examined fishes. Light microscopy and scanning electron microscopy (SEM) were used in this exam. SEM showed fins destroyed by the parasites action. High prevalence of the parasitism has a high concern as those fishes are of commercial importance for Brazil.
Key words: Ichthyophthirius multifilis, Gasteropelecus sternicola, fishes, Protozoa.
Ichthyophthirius multifilis is one of the most important holotrichian ciliate parasite, which infects freshwater fishes being a cosmopolitan organism1. Its presence is easily detected in the surface of the body and gills showing white small spots2. I. multifilis probably the most harmful parasite can cause extensive lesions due to intensive infections3. In cultivated areas of Ictalurus punctatus in the USA and carps in Israel the parasite infection can cause annual loss of millions of dollars4. Although all freshwater scaleless fishes are susceptible to be infected, such as catfish and lochs, these last ones are specially vulnerable. Up to 100% mortality may occur5. This well-known disease has not been reported for Brazil frequently. A case of ichthyophthiriosis of Ancistrus sp., captured in Brazil, has been recorded. In this case the host presented a lesion on the surface of the body and the gills. Microscopically, gills revealed vascular congestive process and moderate hemorrhage. Focal hyperplasy of the secondary lamella causes their fusion6.
The present study describes I. multifilis infecting ornamental fishes named white butterfly fish, Gasteropelecus sternicola, exported to Europe (Germany and England) and Asia (Japan).
MATERIAL AND METHODS
Twenty ornamental fishes, G. sternicola, from Pará River estuary surrounding Belém, State of Pará (Brazil) were observed. Fishes were sacrificed in the Laboratory and cysts of the surface of the body and fins were collected and observed under light microscopy. For the purpose of scanning electron microscopy studies, small pieces of dorsal fins were taken off and placed immediately into a 30% solution of Glutural Dehyde Buffered at a pH 7,2 with boron cacodylate at 4ºC. They were fixed for 3 hours and rinsed into the same buffered solutions at 4ºC 24 hours. Afterwards they were fixed in 2% osmium tetroxide at 4ºC for 3 hours, dehydrate in a series of grated concentration of acetone for 15 minutes and transferred to chloroform. Finally, the sections were placed in gold grids (45 manometer) and observed with a JEOL model JSM-5400 LV at 20Kv.
RESULTS AND DISCUSSION
I. multifilis was found in 100% of examined fishes. Light microscopy revealed a wide number of actively trophont stage, possessing characteristic horseshoe -a shaped macronu-cleus- easily observed (Figure 1).
Scanning electron microscopy revealed the trophont stage breaking through the rays of the fins (Figures 2 and 3). Those parasites seem to be responsible for the changes in fishes' movements also. It is important to mention that stocks of infected aquarium fish freely exported all over the world by Brazil can easily spread the disease and result in an abrupt and substantial increase of economical loss and high level of fish mortality. Lesions caused by I. multifilis in the gills and epithelium have been reported by several authors.1,3,7-10 Meanwhile lesions located in fins caused by I. multifilis are reported for the first time using scanning electron microscopy procedure.
|Figures 2 and 3. Scanning eletron microscopy - 150X and 350X. Revealed the trophomt stage breaking through the rays of the fins.|
* Faculdade de Veterinaria _ Universidad Federal Fluminense _ Rua Vital Brazil - Niteroi - RJ - Brasil - CEP-24230 - 340. e - mail : higiene @urbi.com.br.
** Instituto de Veterinaria - Faculdade de Ciencias Agrarias do Pará - Belen _ Pará - Brasil.
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