Dynamic meiotic behavior and evolutionary insights of supernumerary B chromosomes in the hangingfly Bittacus cirratus (Mecoptera, Bittacidae)
Supernumerary B chromosomes are significant dispensable genetic elements that follow their own species-specific evolutionary pathways. Despite their widespread occurrence, comprehensive analyses of their meiotic behavior remain limited. In this study, we present the first systematic investigation of...
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Pensoft Publishers
2025-06-01
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| Series: | Comparative Cytogenetics |
| Online Access: | https://compcytogen.pensoft.net/article/153340/download/pdf/ |
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| author | Le-Le He Ying Miao He-Hong Wang Jie Zhang Bao-Zhen Hua |
| author_facet | Le-Le He Ying Miao He-Hong Wang Jie Zhang Bao-Zhen Hua |
| author_sort | Le-Le He |
| collection | DOAJ |
| description | Supernumerary B chromosomes are significant dispensable genetic elements that follow their own species-specific evolutionary pathways. Despite their widespread occurrence, comprehensive analyses of their meiotic behavior remain limited. In this study, we present the first systematic investigation of B chromosome morphology and meiotic behavior in the hangingfly Bittacus cirratus Tjeder, 1956 using cytogenetic approaches. The male basal chromosome numbers of B. cirratus is 2n = 30 + XO, with 0–5 polymorphic B chromosomes. Intraspecific B chromosome polymorphism manifests as various distinct morphotypes ranging from punctiform, bicentric, and ring-shaped to larger coiled forms, indicating that the B chromosomes may undergo rapid structural changes. During meiosis, B chromosomes display transmission drive through asymmetric segregation, preferentially accumulating in one daughter cell. Most B chromosomes formed univalents, with few forming bivalents or trivalents at meiosis I. Three unconventional retention mechanisms were identified in univalent B chromosomes: (1) associating with a nonhomologous chromosome, (2) accumulating near spindle poles, and (3) contributing to unequal spindle formation. Based on the abundant chromosomal changes of A chromosomes and stable XX/XO sex determination, we infer that the B chromosomes likely originated from multiple A chromosomes in B. cirratus. The roles of B chromosomes in the cell cycle and individual fitness are briefly discussed, and the evolutionary scenario is putatively put forward for the diversification of B chromosomes. |
| format | Article |
| id | doaj-art-b38fc862586d4a84bd4abfb3de0da17c |
| institution | OA Journals |
| issn | 1993-078X |
| language | English |
| publishDate | 2025-06-01 |
| publisher | Pensoft Publishers |
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| series | Comparative Cytogenetics |
| spelling | doaj-art-b38fc862586d4a84bd4abfb3de0da17c2025-08-20T02:30:30ZengPensoft PublishersComparative Cytogenetics1993-078X2025-06-01199110710.3897/compcytogen.19.153340153340Dynamic meiotic behavior and evolutionary insights of supernumerary B chromosomes in the hangingfly Bittacus cirratus (Mecoptera, Bittacidae)Le-Le He0Ying Miao1He-Hong Wang2Jie Zhang3Bao-Zhen Hua4Northwest A&F UniversityNingxia UniversityNorthwest A&F UniversityNorthwest A&F UniversityNorthwest A&F UniversitySupernumerary B chromosomes are significant dispensable genetic elements that follow their own species-specific evolutionary pathways. Despite their widespread occurrence, comprehensive analyses of their meiotic behavior remain limited. In this study, we present the first systematic investigation of B chromosome morphology and meiotic behavior in the hangingfly Bittacus cirratus Tjeder, 1956 using cytogenetic approaches. The male basal chromosome numbers of B. cirratus is 2n = 30 + XO, with 0–5 polymorphic B chromosomes. Intraspecific B chromosome polymorphism manifests as various distinct morphotypes ranging from punctiform, bicentric, and ring-shaped to larger coiled forms, indicating that the B chromosomes may undergo rapid structural changes. During meiosis, B chromosomes display transmission drive through asymmetric segregation, preferentially accumulating in one daughter cell. Most B chromosomes formed univalents, with few forming bivalents or trivalents at meiosis I. Three unconventional retention mechanisms were identified in univalent B chromosomes: (1) associating with a nonhomologous chromosome, (2) accumulating near spindle poles, and (3) contributing to unequal spindle formation. Based on the abundant chromosomal changes of A chromosomes and stable XX/XO sex determination, we infer that the B chromosomes likely originated from multiple A chromosomes in B. cirratus. The roles of B chromosomes in the cell cycle and individual fitness are briefly discussed, and the evolutionary scenario is putatively put forward for the diversification of B chromosomes.https://compcytogen.pensoft.net/article/153340/download/pdf/ |
| spellingShingle | Le-Le He Ying Miao He-Hong Wang Jie Zhang Bao-Zhen Hua Dynamic meiotic behavior and evolutionary insights of supernumerary B chromosomes in the hangingfly Bittacus cirratus (Mecoptera, Bittacidae) Comparative Cytogenetics |
| title | Dynamic meiotic behavior and evolutionary insights of supernumerary B chromosomes in the hangingfly Bittacus cirratus (Mecoptera, Bittacidae) |
| title_full | Dynamic meiotic behavior and evolutionary insights of supernumerary B chromosomes in the hangingfly Bittacus cirratus (Mecoptera, Bittacidae) |
| title_fullStr | Dynamic meiotic behavior and evolutionary insights of supernumerary B chromosomes in the hangingfly Bittacus cirratus (Mecoptera, Bittacidae) |
| title_full_unstemmed | Dynamic meiotic behavior and evolutionary insights of supernumerary B chromosomes in the hangingfly Bittacus cirratus (Mecoptera, Bittacidae) |
| title_short | Dynamic meiotic behavior and evolutionary insights of supernumerary B chromosomes in the hangingfly Bittacus cirratus (Mecoptera, Bittacidae) |
| title_sort | dynamic meiotic behavior and evolutionary insights of supernumerary b chromosomes in the hangingfly bittacus cirratus mecoptera bittacidae |
| url | https://compcytogen.pensoft.net/article/153340/download/pdf/ |
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