The life cycle of Philophthalmus aylacostoma n. sp. (Trematoda: Philophthalmidae), a new eye fluke species transmitted by Aylacostoma spp. (Gastropoda: Thiaridae) in Brazil.

Philophthalmus is a cosmopolitan genus of digeneans that includes ocular parasites of birds and mammals. Despite broad distribution and veterinary importance of these digeneans, there are still gaps in knowledge about their diversity and biology, especially in South America. Herein, we conducted morphological, life cycle, and molecular studies of megalurous cercariae found in aquatic gastropod molluscs Aylacostoma chloroticum and A. tuberculatum collected in the São Francisco River, Brazil. Adult parasites reared experimentally in the eyes of chicks are described here as Philophthalmus aylacostoma n. sp. The new species differs from its congeners known in the Americas by a combination of traits, including the sucker width ratio, the oral sucker to pharynx width ratio, egg size, and the type of vitellarium in adult forms. The new species is morphologically closest to Philophthalmus megalurus, from which it differs by the smaller body and larger eggs, as well as by the measurements of cercariae and the family of snails that act as the intermediate host. Molecular phylogenetic analysis based on 28S rDNA and comparison of cox1 sequences confirm that P. aylacostoma n. sp. is distinct from four previously sequenced named species of the genus. Moreover, cox1 sequences revealed conspecificity of our specimens with an isolate of Philophthalmus sp. previously reported, also in thiarid snails, in Paraná River, Brazil. The interspecific divergence in cox1 between the new species and other species with sequences available for comparison varied between 12 and 15%.

LARVAS DE DIGENEA EN Melanoides tuberculata (GASTROPODA: THIARIDAE) EN MEDELLÍN, COLOMBIA / Larval stages of digenea from Melanoides tuberculata (Gastropoda: Thiaridae) in Medellín, Colombia

Se describen las larvas de digeneos que se obtuvieron en Melanoides tuberculata (Gastropoda: Thiaridae), molusco dulceacuícola del que se colectaron 125 especímenes en el lago del Jardín Botánico Joaquín Antonio Uribe de Medellín. En el laboratorio se individualizaron y se estimuló la emisión cercariana con una fuente luminosa. El 9,6 % de los caracoles emitió cercarias. Los moluscos emisores se sacrificaron para obtener los demás estadios larvarios. Las larvas se montaron al microscopio, se midieron y luego se dibujaron. Los caracteres morfológicos permitieron establecer la presencia de Centrocestus formosanus (Heterophyidae) y de dos Philophthalmidae. Uno de estos es primer registro para Colombia. Se confirma la sensibilidad de M. tuberculata a infecciones por digeneos, así como la especificidad de los filoftálmidos por moluscos hospedadores de la superfamilia Cerithioidea.

The larvae of two trematodes found in the freshwater mollusk Melanoides tuberculata (Gastropoda: Thiaridae) are described. 125 snails from the Medellin’s Botanical Garden Joaquín Antonio Uribe were collected. In the laboratory, each individual was placed alone and stimulated with light in order to have cercaria emission. 9.6% of the snails released cercariae. These were separated in three morphologies. From each one, 15 individuals were measured and drawn. Photographs were taken. Based on their morphological characteritics the presence of Centrocestus formosanus (Heterophyidae) was determined. The other two morphologies were classified in the family Philophthalmidae. One of them constitutes the first register for Colombia. The sensibility of M. tuberculata to infections by digeneans, and the specificity of the family Philophthalmidae to mollusk hosts of the superfamily Cerithioidea are confirmed.