Presidential Address: Sex and the Single Schistosome

Short, Robert B.

doi:10.2307/3281269

Cited by 46 publications

(24 citation statements)

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“…This species showed the highest level of heterochromatization on the sex chromosomes resulting in the largest W chromosome compared to the Z of all the Asian species, but also has the same C banding pattern as the African S. mansoni on chromosome 2 [21]. These findings lead to the hypothesis that the African schistosomes were derived from an Asian S. japonicum like ancestor as also suggested by Snyder and Loker [13] and were not polyphyletic as suggested by Short [29] (Figure 4). …”

Section: Introductionmentioning

confidence: 66%

Genomes and geography: genomic insights into the evolution and phylogeography of the genus Schistosoma

Lawton

Hirai²,

Ironside

et al. 2011

Parasites Vectors

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Blood flukes within the genus Schistosoma still remain a major cause of disease in the tropics and subtropics and the study of their evolution has been an area of major debate and research. With the advent of modern molecular and genomic approaches deeper insights have been attained not only into the divergence and speciation of these worms, but also into the historic movement of these parasites from Asia into Africa, via migration and dispersal of definitive and snail intermediate hosts. This movement was subsequently followed by a radiation of Schistosoma species giving rise to the S. mansoni and S. haematobium groups, as well as the S. indicum group that reinvaded Asia. Each of these major evolutionary events has been marked by distinct changes in genomic structure evident in differences in mitochondrial gene order and nuclear chromosomal architecture between the species associated with Asia and Africa. Data from DNA sequencing, comparative molecular genomics and karyotyping are indicative of major constitutional genomic events which would have become fixed in the ancestral populations of these worms. Here we examine how modern genomic techniques may give a more in depth understanding of the evolution of schistosomes and highlight the complexity of speciation and divergence in this group.

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Section: Introductionmentioning

confidence: 66%

Genomes and geography: genomic insights into the evolution and phylogeography of the genus Schistosoma

Lawton

Hirai²,

Ironside

et al. 2011

Parasites Vectors

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“…This peculiarity, which has been discussed mainly from an evolutionary point of view (Short 1983, Basch 1990, Combes 1991, has implications for the transmission dynamics patterns of these worms, species of which are responsible for some of the most important human helminthiases in tropical countries (schistosomiasis).…”

Section: Introductionmentioning

confidence: 99%

Pairing Probability of Schistosomes Related to Their Distribution Among the Host Population

Morand¹,

Pointier²,

Borel³

et al. 1993

Ecology

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Schistosomes are dioecious blood helminth parasites of mammals, including humans, and are responsible for schistosomiasis in tropical countries. The distribution patterns of worms among their host populations and the pairing probabilities of female schistosomes are of considerable importance in understanding transmission dynamics of this parasite. Data were obtained from field studies carried out over 8 yr on natural populations of Schistosoma mansoni, a human parasite but heavily infecting rats (Rattus rattus) in Guadeloupe. The distribution of male and female worms within the whole host population was fitted to a negative binomial, and the aggregation coefficient was estimated. The observed prevalence of male—female pairs, the observed prevalence of worms, and the observed pairing probability were calculated. Results demonstrate a strongly clumped worm distribution. Observed pairing probabilities of female worms in cases where male and female schistosomes are aggregated together within the host population are of the same order (@Aobs ranging from 0.83 to 0.97) as the expected values obtained with the May (1977) model but significantly higher than in cases where the sexes are aggregated separately. A disequilibrated sex ratio biased towards male schistosomes increases the pairing probabilities of female worms.

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“…Moreover, the type population of T. regenti clearly diered from all schistosome species by the occurrence of supernumerary B chromosomes. None of the 22 karyologically known schistosome species, including Trichobilharzia spp., carried the supernumerary chromosomes (Short 1983;BarsÏ ieneÂ 1993;S Ï pakulovaÂ et al 1997). Nevertheless, B chromosomes have been reported in hermaphroditic digenean trematodes of the genera Notocotylus, Diplodiscus, Echinostoma and Apatemon as elements of dierent size and morphology, usually one or two per cell (for review see PetkevicÏ iuteÂ and StanevicÏ iuteÂ 1999).…”

Section: Discussionmentioning

confidence: 99%

The karyotype of Trichobilharzia regenti Horák, Kolářová et Dvořák, 1998 (Digenea: Schistosomatidae), a nasal avian schistome in Central Europe

Špakulová

Horák

Dvořák

2001

Parasitology Research

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The karyotype of a European bird nasal schistosome, Trichobilharzia regenti Horák, Kolárová et Dvofák, 1998, was determined. The chromosome set comprises eight pairs, seven of which are autosomes and one sex pair consisting of ZZ in males and ZW in females. The Z is the largest chromosome of the set, having a submeta-metacentric location of centromere, while the W is a small metacentric chromosome. More than 60% of the analyzed cells originating from both male and female sporocysts contained one or two small submetacentric supernumerary B chromosomes, occurring more frequently in female than in male cells. The formula of the karyotype structure is 2n = 16 + (B), n=5m+1sm-m+ 1sm+Zsm-m/Wm+(Bsm). The C-banding method revealed small pericentric heterochromatin blocks in the sex chromosome Z and all autosomes, except pairs 5 and 6. Satellited pair 5 showed a distinct terminal band representing the nucleolar organizer. Both the W and B chromosomes contained conspicuous heterochromatin blocks at the long arm adjacent to the centromere. The currently described supernumerary chromosomes in T. regenti represent the first record of B chromosomes within the family Schistosomatidae.

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Presidential Address: Sex and the Single Schistosome

Cited by 46 publications

References 0 publications

Genomes and geography: genomic insights into the evolution and phylogeography of the genus Schistosoma

Genomes and geography: genomic insights into the evolution and phylogeography of the genus Schistosoma

Pairing Probability of Schistosomes Related to Their Distribution Among the Host Population

The karyotype of Trichobilharzia regenti Horák, Kolářová et Dvořák, 1998 (Digenea: Schistosomatidae), a nasal avian schistome in Central Europe

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