Systematics and life cycles of four avian schistosomatids from Southern Cone of South America.

Relative to the numerous studies focused on mammalian schistosomes, fewer include avian schistosomatids particularly in the southern hemisphere. This is changing and current research emerging from the Neotropics shows a remarkable diversity of endemic taxa. To contribute to this effort, nine ducks (Spatula cyanoptera, S.versicolor, Netta peposaca), 12 swans (Cygnus melancoryphus) and 1,400 Physa spp. snails from Chile and Argentina were collected for adults and larval schistosomatids, respectively. Isolated schistosomatids were preserved for morphological and molecular analyses (28S and COI genes). Four different schistosomatid taxa were retrieved from birds: Trichobilharzia sp. in N. peposaca and S. cyanoptera that formed a clade; S.cyanoptera and S. versicolor hosted Trichobilharzia querquedulae; Cygnus melancoryphus hosted the nasal schistosomatid, Nasusbilharzia melancorhypha; and one visceral, Schistosomatidae gen. sp., which formed a clade with furcocercariae from Argentina and Chile from previous work. Of the physid snails, only one from Argentina had schistosomatid furcocercariae that based on molecular analyses grouped with T. querquedulae. This study represents the first description of adult schistosomatids from Chile as well as the elucidation of the life cycles of N.melancorhypha and T. querquedulae in Chile and Neotropics, respectively. Without well-preserved adults, the putative new genus Schistosomatidae gen. sp. could not be described, but its life cycle involves Chilina spp. and C. melancoryphus. Scanning electron microscopy of T. querquedulae revealed additional, undescribed morphological traits, highlighting its diagnostic importance. Authors stress the need for additional surveys of avian schistosomatids from the Neotropics to better understand their evolutionary history.

Tetrathyridia in an endemic lizard from Chile: molecular evidence for South America.

Mesocestoides is a controversial tapeworm with significant lack of data related to systematics and life cycles. This helminth has an indirect life cycle with vertebrates, mostly carnivorous mammals, as definitive hosts. Theoretically, a coprophagous arthropod would be the first intermediate host, and herptiles, mammals, and birds, which prey on these insects, would represent the second intermediate hosts. However, recent evidence suggests that this life cycle would require only two hosts, with no arthropods involved. In the Neotropics, although there are records of mammals and reptiles as hosts for Mescocestoides, no molecular analyses have been performed. This work aimed to record an additional intermediate host and molecularly characterize the isolated larvae. Thus, 18 braided tree iguanas (Liolaemus platei) from Northern Chile were collected and dissected during 2019. One lizard was parasitized by three morphotypes of larvae compatible with tetrathyridia of Mescocestoides. To achieve its specific identity, a molecular approach was performed: 18S rRNA and 12S rRNA loci were amplified through cPCR. The inferred phylogenies confirmed the morphological diagnosis and stated that all morphotypes were conspecifics. The sequences for both loci formed a monophyletic clade with high nodal support, representing a sister taxon to Mescocestoides clade C. This study represents the first molecular characterization of any taxon of Mescocestoides from the Neotropics. Future surveys from potential definitive hosts would help to elucidate its life cycle. Furthermore, an integrative taxonomic approach is required in additional studies from the Neotropical region, which would contribute to a better understanding of the evolutionary relationships of this genus.