Morphology and surface ultrastructure of Dadaytrema oxycephala (Digenea: Cladorchiidae) with a new host record from Peruvian Amazon floodplain

Discovery of a Digenean (Cryptogonimidae) Living in a Cleft-Lipped Goby, Sicyopterus cynocephalus (Teleostei: Gobiidae) from Ranongga Island, Solomon Islands: Analysis of Multiple Ribosomal DNA Regions

This study results from a continued investigation of the occurrence and diversity of parasites of freshwater fish in the Solomon Islands. Thus, we revealed a new host as well as a new site of infection and a new geographical area for the cryptogonimid parasite, Stemmatostoma cribbi (Digenea: Cryptogonimidae). The cryptogonimid species was identified based on general morphology and on molecular data of metacercariae found in the gills of the cleft-lipped goby, Sicyopterus cynocephalus, from Ranongga Island, Western Province of the Solomon Islands. This is the first report of a Stemmatostoma sp. digenean parasitizing fish of the genus Sicyopterus in the Indo-Pacific region and the first report of S. cribbi infection in a fish from the Solomon Islands. Phylogenetic analysis performed by Bayesian inference and maximum likelihood confirmed the presence of the cryptogonimid in a well-supported subclade of Stemmatostoma spp.

Components influencing parasitism by Dadaytrema oxycephala (Digenea: Cladorchiidae) in Neotropical fish

The components that mold the structure of parasitic fauna are used as objects of study in an attempt to find patterns in their distribution. It is known that phylogeny (represented by specificity), host ecological traits (for example, feeding habits, position of the water column, reproductive strategies, body size, and age), and the environment affect the distribution and occurrence of parasites. In tropical regions, digeneans show high diversity, and the species Dadaytrema oxycephala is known to parasitize a wide range of host species. In this context, the objective of the present study is to analyze the components that affect the occurrence of D. oxycephala in Neotropical fish. We used data from the literature that contained the abundance of this parasite, as well as the geographic location and host species, and evaluated the influence of ecological traits, specificity, and latitude on parasite abundance, using a generalized linear mixed model (GLMM). The abundance of D. oxycephala can be explained by trophic level and position in the water column and latitude. However, coevolutionary processes are also extremely important, and the distribution of this parasite was not equal, showing high abundance for the genus Piaractus, which are the preferred hosts, even if the parasite is considered generalist. In short, host ecological traits are the important components in the distribution and occurrence of D. oxycephala, as well as the latitude.

Dadaytrema oxycephala (Digenea: Cladorchiidae) in definitive host Pimelodus blochii (Pisces: Pimelodidae), with morphological and geographic distribution data in fishes from the South America

The aim of this study was to describe structural and ultrastructural morphological data of Dadaytrema oxycephala (Diesing, 1836) Travassos, 1931 in Pimelodus blochii Valenciennes, 1840 from western Amazon (Brazil), besides geographic distribution in host fishes from South America. Of 160 P. blochii examined in the rivers Acre and Iaco, 15% were infected by D. oxycephala with mean intensity of 6.5 ± 1.9 and mean abundance of 1.0 ± 5.1. All parasites were found in the intestine of the infected hosts. The structural and ultrastructural characteristics of the developmental stages of D. oxycephala are presented and discussed. Dadaytrema oxycephala has a wide geographic distribution in South America, parasitizing fish species of Characiformes and Siluriformes from Brazil, Venezuela, Argentina, Peru and Paraguay. We elucidated part of life cycle of D. oxicephala in P. blochii, which is a definitive host for this digenean.