Lesions caused by helminths of the digestive tract in estuarine fish from the Tres Palos Lagoon, Guerrero, Mexico

Abstract

THE PRESENT STUDY WAS CONDUCTED TO IDENTIFY AND COMPARE THE MICROSCOPIC AND GROSS LESIONS CAUSED BY HELMINTHS IN THE DIGESTIVE TRACT OF ARIOPSIS GUATEMALENSIS (”CUATETE”) AND ELEOTRIS PICTA (”ALAHUATE”) FROM THE TRES PALOS LAGOON IN THE STATE OF GUERRERO, MEXICO. THIRTY INDIVIDUALS FROM EACH SPECIES WERE COLLECTED IN THE MONTHS OF MAY, JULY AND DECEMBER 2001. FIFTEEN WERE USED FOR THE POSTMORTEM STUDY AND THE OTHER 15 WERE USED FOR THE PARASITOLOGICAL EXAM. THREE GROUPS OF HELMINTHS WERE IDENTIFIED: PROTEOCEPHALUS CESTODES IN THE ”ALAHUATE”; AN ACANTHOCEPHALAN IN THE ”CUATETE”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”ALAHUATE” IN WHICH IT HAD A HIGH PREVALENCE AND ABUNDANCE PROBABLY ASSOCIATED TO THE FISH´S SUSCEPTIBILITY OR THE INCREASED CONTACT DUE TO THEIR ALIMENTARY HABITS.