The phylogeny of the Schistosomatidae based on three genes with emphasis on the interrelationships of Schistosoma Weinland, 1858

Abstract

S U M M A R YSchistosomes are digenean flukes, parasitic of birds, mammals and crocodiles. The family Schistosomatidae contains species of considerable medical and veterinary importance, which cause the disease schistosomiasis. Previous studies, both morphological and molecular, which have provided a good deal of information on the phylogenetics of this group, have been limited in the number of species investigated or the type or extent of molecular data used. This paper presents the most comprehensive phylogeny to date, based on the sequences of 3 genes, complete ribosomal small subunit rRNA and large ribosomal subunit rRNA, and mitochondrial cytochrome oxidase 1, sequenced from 30 taxa including at least 1 representative from 10 of the 13 known genera of the Schistosomatidae and 17 of the 20 recognized Schistosoma species. The phylogeny is examined using morphological characters, intermediate and definitive host associations and biogeography. Theories as to the origins and spread of Schistosoma are also explored. The principal findings are that Ornithobilharzia and Austrobilharzia form a sister group to the Schistosoma ; mammalian schistosomes appear paraphyletic and 2 Trichobilharzia species, T. ocellata and T. szidati, seem to be synonymous. The position of Orientobilharzia within the Schistosoma is confirmed, as is an Asian origin for the Schistosoma, followed by subsequent dispersal through India and Africa.

Conservation of CD4+ T cell-dependent developmental mechanisms in the blood fluke pathogens of humans

“…Thorough phylogenetic analyses based on combinations of morphological and molecular data support these traditional groupings (Lockyer et al, 2003). These analyses also indicate the genus Schistosoma originated in Asia, with the Asian "japonicum" group of parasites being basal or ancestral to the African "mansoni" and "haematobium" groups.…”

“…4). Because S. japonicum and the other Schistosoma of the "japonicum" group occupy a more basal or ancestral position within the genus relative to S. mansoni, these data suggest that developmental dependence on CD4 + T cells arose early in Schistosoma evolution, prior to diversification within the genus (Lockyer et al, 2003). An alternative explanation is that developmental dependence on CD4 + T cells arose multiple times during Schistosoma evolution, but the hypothesis that this adaptation evolved once and was subsequently conserved through speciation events is more parsimonious.…”

“…These analyses also indicate the genus Schistosoma originated in Asia, with the Asian "japonicum" group of parasites being basal or ancestral to the African "mansoni" and "haematobium" groups. This model is further supported by analysis of mitochondrial genome sequences (Le et al, 2000;Lockyer et al, 2003). The "japonicum" group possesses a mitochondrial gene order identical to that of other digenetic flukes and cestodes, whereas representatives of the "mansoni" and "haematobium" groups exhibit a unique gene arrangement that is different from all other flatworms.…”

“…The "japonicum" group possesses a mitochondrial gene order identical to that of other digenetic flukes and cestodes, whereas representatives of the "mansoni" and "haematobium" groups exhibit a unique gene arrangement that is different from all other flatworms. After arising in Asia, subsequent spread of Schistosoma to Africa gave rise to the two distinct "mansoni" and "haematobium" lineages (Morgan et al, 2001;Lockyer et al, 2003). Of these two, the "haematobium" group of schistosomes represents a separate and more derived lineage of African parasites than the "mansoni" group.…”

A história da disseminação dos microrganismos

“…Brazilian schistossoma mansoni derived from africa, but the dna traced the parasite back to asia (Lockyer et al, 2003). the parasite found its way from asia to human populations in africa during antiquity.…”