Two new genera and species of avian schistosomes from Argentina with proposed recommendations and discussion of the polyphyletic genus Gigantobilharzia (Trematoda, Schistosomatidae)

Abstract

Gigantobilharzia Odhner, 1910 (Schistosomatidae) includes species that parasitize several orders of birds and families of gastropods from both freshwater and marine environments worldwide. Due to their delicate bodies, most of the species descriptions are incomplete, and lumped in the genus Gigantobilharzia, in some cases despite major morphological variability. Only three of those species have molecular sequence data but then lack a robust morphological description, making species differentiation very difficult. For this reason, several authors consider that many of the species of Gigantobilharzia should be reassigned to new genera. The aim of this paper is to describe two new genera and two new species of schistosomes using morphological and molecular characterization. We described Marinabilharzia patagonense n. g., n. sp. parasitizing Larus dominicanus from north Patagonian coast, and Riverabilharzia ensenadense n. g., n. sp. parasitizing L. dominicanus, Chroicocephalus maculipennis and Chroicocephalus cirrocephalus from freshwater Río de La Plata, in South America, Argentina. We then analysed and discussed the combinations of characters defining species of Gigantobilharzia and, based on that and on the available molecular data, we propose at least four possible new genera.

Phylogenomics and Diversification of the Schistosomatidae Based on Targeted Sequence Capture of Ultra-Conserved Elements

“…Brant and Loker [ 21 ] posit the likelihood of undiscovered schistosomatid lineages within marine environments; several studies support this within the AO clade [ 119 , 120 , 121 , 122 ]. Surveys of marine gastropod genera such as Haminoea [ 121 ] and Siphonaria [ 30 , 35 ] ( Figure 1 ) have yielded schistosomatids, but these represent more recent divergences rather than early branching members of the AO clade ( Figure 3 ). The recent, surprising discovery of an aporocotylid fish blood fluke from a dugong [ 123 ] provides further impetus to search for additional schistosomatids in marine environments.…”

“…Currently, within the Schistosomatidae, there are 17 named genera and over 130 named species [21]. Based on the sampling of larval schistosomatids, this is likely an underestimate [8,[29][30][31][32][33][34][35] of both genera and species. Historically, Schistosomatidae was divided into three subfamilies [24,36], primarily based on the morphology of adult worms.…”

Scratching the Itch: Updated Perspectives on the Schistosomes Responsible for Swimmer’s Itch around the World

“…Reference cercariae sequences in a growing database enable direct comparison with sequences from adult schistosomes or eggs obtained by investigators who may be far removed in time and space from the collectors of the cercariae from snails. Recent papers indicate that this has happened on multiple occasions [ 22 , 26 , 27 , 28 , 29 ].…”

“…The most basal schistosomes are known from marine caenogastropod snails, but more derived schistosomes largely diversified in freshwater gastropods, including freshwater or amphibious caenogastropods, with most but not all species infecting heterobranchs, particularly freshwater pulmonates. Among the most derived avian schistosome lineages, evidence consistent with host switches from freshwater back to marine gastropods have occurred on at least two occasions [ 28 , 29 ], in each case involving switches into marine heterobranchs (Siphonariida and Cephalaspidea) that are by no means close relatives of the pulmonate heterobranchs [ 47 ].…”

Schistosomes in the Persian Gulf: novel molecular data, host associations, and life-cycle elucidations

“…The discovery of avian schistosome diversity, their life-cycle elucidations and taxonomy has largely benefited from molecular phylogenetics studies ( 2 , 4 and references therein). To date, a total of 13 genera of avian schistosomes with about 70 species and 20 species-level genetically distinct lineages are known around the globe 4 , 5 . Based on the habitat where their life-cycles take place, avian schistosomes consist of freshwater and marine representatives.…”