title: Detecting hybridization in African schistosome species: does egg morphology complement molecular species identification?
abstract: Hybrid parasites may have an increased transmission potential and higher virulence compared to their parental species. Consequently, hybrid detection is critical for disease control. Previous crossing experiments showed that hybrid schistosome eggs have distinct morphotypes. We therefore compared the performance of egg morphology with molecular markers with regard to detecting hybridization in schistosomes. We studied the morphology of 303 terminal-spined eggs, originating from 19 individuals inhabiting a hybrid zone with natural crosses between the human parasite Schistosoma haematobium and the livestock parasite Schistosoma bovis in Senegal. The egg sizes showed a high variability and ranged between 92·4 and 176·4 µm in length and between 35·7 and 93·0 µm in width. No distinct morphotypes were found and all eggs resembled, to varying extent, the typical S. haematobium egg type. However, molecular analyses on the same eggs clearly showed the presence of two distinct partial mitochondrial cox1 profiles, namely S. bovis and S. haematobium, and only a single nuclear ITS rDNA profile (S. haematobium). Therefore, in these particular crosses, egg morphology appears not a good indicator of hybrid ancestry. We conclude by discussing strengths and limitations of molecular methods to detect hybrids in the context of high-throughput screening of field samples.
authors.affiliation: Laboratory of Biodiversity and Evolutionary Genomics, Biology,University of Leuven,Ch. Deberiotstraat 32, B-3000 Leuven,Belgium.
authors.forename: Nele A M
authors.initials: NAM
authors.lastname: Boon
authors.affiliation: Department of Biology,Royal Museum for Central Africa,Leuvensesteenweg 13, B-3080 Tervuren,Belgium.
authors.forename: Wouter
authors.initials: W
authors.lastname: Fannes
authors.affiliation: Laboratory of Biodiversity and Evolutionary Genomics, Biology,University of Leuven,Ch. Deberiotstraat 32, B-3000 Leuven,Belgium.
authors.forename: Sara
authors.initials: S
authors.lastname: Rombouts
authors.affiliation: Unit of Medical Helminthology,Department of Biomedical Sciences,Institute of Tropical Medicine,Nationalestraat 155, B-2000 Antwerp,Belgium.
authors.forename: Katja
authors.initials: K
authors.lastname: Polman
authors.affiliation: Laboratory of Biodiversity and Evolutionary Genomics, Biology,University of Leuven,Ch. Deberiotstraat 32, B-3000 Leuven,Belgium.
authors.forename: Filip A M
authors.initials: FAM
authors.lastname: Volckaert
authors.affiliation: Department of Biology,Royal Museum for Central Africa,Leuvensesteenweg 13, B-3080 Tervuren,Belgium.
authors.forename: Tine
authors.initials: T
authors.lastname: Huyse
mesh_terms: D000293:Adolescent; D000818:Animals; D002648:Child; D002675:Child, Preschool; D018509:DNA, Helminth / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D003576:Electron Transport Complex IV / Q000235:genetics; D005260:Female; D015801:Helminth Proteins / Q000235:genetics; D006801:Humans; D006824:Hybridization, Genetic; D008297:Male; D024101:Mitochondrial Proteins / Q000235:genetics; D010063:Ovum / Q000166:cytology*; D012547:Schistosoma / Q000145:classification / Q000166:cytology* / Q000235:genetics; D012548:Schistosoma haematobium / Q000145:classification / Q000166:cytology / Q000235:genetics; D012675:Senegal; D055815:Young Adult
chemical_list: D018509:DNA, Helminth; D021903:DNA, Ribosomal Spacer; D015801:Helminth Proteins; D024101:Mitochondrial Proteins; D003576:Electron Transport Complex IV
keywords: 
                 Schistosoma bovis
              ; 
                 Schistosoma haematobium
              ; Senegal; barcoding; egg morphometrics; hybridization; zoonosis