title: Cytogenetics of Aspidogaster limacoides (Trematoda, Aspidogastrea): karyotype, spermatocyte division, and genome size.
abstract: A detailed cytogenetic analysis of the aspidogastrean fluke Aspidogaster limacoides revealed a karyotype consisting of six medium-sized chromosome pairs. The first and the last pairs were two-armed while four remaining were one-armed; 2n = 12, n = 1 m + 1 m - sm + 4a. Fluorescence in situ hybridization with 18S ribosomal DNA (rDNA) probe detected a single cluster of ribosomal genes (NOR) located in pericentromeric regions of the long arms of the third chromosome pair in a site of secondary constriction apparent in meiotic prophase, especially in diplotene. The silver nitrate staining showed only a single active NOR site on one of homologous chromosomes in the majority of spermatogonia and spermatocyte divisions. A course of meiosis corresponded to standard schemes. The nucleolus was apparent in early meiotic spermatocytes and disintegrated by the end of pachytene. For the first time in Aspidogastrea, the genome size was determined. The flow cytometry showed 1.21 pg DNA per haploid nucleus in A. limacoides which is in accordance with relatively low genome sizes of other flukes and tapeworms (Neodermata). A comparison of cytogenetic data available to date in the fluke sister groups Aspidogastrea and Digenea suggests that the lower chromosome number of Aspidogastrea might represent an ancestral condition and their split might have been accompanied by an increase in chromosome number via either chromosome fissions or paleopolyploidy.
authors: Institute of Parasitology, Slovak Academy of Sciences, Hlinkova 3, 04001, Košice, Slovakia, bombarova@saske.sk.
authors: Marta
authors: M
authors: Bombarová
authors: Marta
authors: M
authors: Špakulová
authors: Martin
authors: M
authors: Kello
authors: Petr
authors: P
authors: Nguyen
authors: Eva
authors: E
authors: Bazsalovicsová
authors: Ivica
authors: I
authors: Králová-Hromadová
mesh_terms: D000818:Animals; D002455:Cell Division; D002467:Cell Nucleus / Q000235:genetics; D002875:Chromosomes / Q000235:genetics; D003582:Cytogenetics; D005260:Female; D059646:Genome Size; D049751:Genome, Helminth; D017404:In Situ Hybridization, Fluorescence; D059785:Karyotype; D008297:Male; D008540:Meiosis; D008938:Mitosis; D013090:Spermatocytes / Q000166:cytology*; D013091:Spermatogenesis; D014200:Trematoda / Q000145:classification / Q000166:cytology* / Q000235:genetics*
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