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Objective. To evidence of the presence of two species of monogeneans of the genus Cichlidogyrus that cause damage to gill tissue, in tilapia Oreochromis spp. grown in Ecuador. Materials and methods. The gills were placed in a Petri dish with boiling water so that the parasites relax, and later they were fixed in 4% formalin. The samples were checked under a stereoscope microscope. The parasites were counted and preserved in 70% ethanol for their taxonomic identification according to their morphological characteristics. The infection parameters (prevalence, mean abundance and mean intensity) were calculated for each species of parasite. For the description of histological damages, fragments of parasitized gills were fixed in 10% neutral formalin and processed by the histological paraffin embedding technique. Results. Cichlidogyrus sclerosus showed highest infection parameters, prevalence of 65%, mean abundance of 24.24 ± 68.62 and mean intensity of 37.62 ± 82.93. Cychlidogyrus dossoui was observed in a prevalence of 4.5%, mean abundance of 0.13 ± 0.66 and mean intensity of 3 ± 1.41. Both species caused hyperplasia in lamellae. Conclusions. This study constitutes the first report of infestation by Cichlidogyrus sclerosus and C. dossoui in tilapia culture systems of Ecuador. [ABSTRACT FROM AUTHOR]

In 2009, in the Tepeaca Valley, Puebla, it was found a cyst-forming nematode of the genus Heterodera associated with carrot. At this time, it is unknown the distribution in some producing municipalities, its life cycle and the histological changes on infected plant roots. Between 2008 and 2016, 28 carrot fields were sampled in six municipalities of the Tepeaca Valley. The roots were separated and white females were searched, the cysts were extracted from soil. Carrot cv. Mexicana were grown in naturally infested soil in the greenhouse, the roots were stained with fuchsine lacto glycerol acid to know the development time of each cycle phase. To describe the histological changes, the infected roots were imbibed in paraffin and sections stained with fast green-fuchsine for analysis. Heterodera sp. was found in 93 % of the plots and completed its cycle in 73 days at 20-25 °C. The histological alterations show the presence of feeding sites (syncytia) with dense and granular cytoplasm, with hypertrophied nuclei, dissolution and thickening of cell walls located mainly in the cortex and vascular cylinder. There was also the presence of lignificate areas with hyperplasia and hypertrophy. [ABSTRACT FROM AUTHOR]