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In the Amazon, some species of Loricariidae are at risk of extinction due to habitat loss and overexploitation by the ornamental fish market. Cytogenetic data related to the karyotype and meiotic cycle can contribute to understanding the reproductive biology and help management and conservation programs of these fish. Additionally, chromosomal mapping of repetitive DNA in Loricariidae may aid comparative genomic studies in this family. However, cytogenetics analysis is limited in Amazonian locariids. In this study, chromosomal mapping of multigenic families was performed in Scobinancistrus aureatus, Scobinancistrus pariolispos and Spatuloricaria sp. Meiotic analyzes were performed in Hypancistrus zebra and Hypancistrus sp. "pão". Results showed new karyotype for Spatuloricaria sp. (2n=66, NF=82, 50m-10sm-6m). Distinct patterns of chromosomal organization of histone H1, histone H3 and snDNA U2 genes were registered in the karyotypes of the studied species, proving to be an excellent cytotaxonomic tool. Hypotheses to explain the evolutionary dynamics of these sequences in studied Loricariidae were proposed. Regarding H. zebra and H. sp. "pão", we describe the events related to synapse and transcriptional activity during the meiotic cycle, which in both species showed 26 fully synapsed bivalents, with high gene expression only during zygotene and pachytene. Both Hypancistrus species could be used may be models for evaluating changes in spermatogenesis of Loricariidae., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2023. Published by The Company of Biologists Ltd.)

Background: This is the first record of the alien shrimp Mierspenaeopsis sculptilis in Brazil. The invasion was detected within Marine Extractive Reserves based on eight specimens accidentally caught by local fishermen using trawlnets focused on fisheries of native species. These specimens were transported to the Laboratory of Applied Genetics and morphologically identified as Mierspenaeopsis sculptilis (rainbow shrimp). The taxonomic status of analyzed samples was confirmed by DNA barcoding using a 627-bp fragment of the Cytochrome C Oxidase Subunit I (COI) gene., Results: A single haplotype was recovered from the eight specimens, being identical to a haplotype reported in India, where this species naturally occurs, and in Mozambique, where the rainbow shrimp is considered an invasive species. The present analyses indicated a putative invasive route (i.e., India-Mozambique-Brazil) mediated by shipping trade., Conclusions: This study presents the first record of Mierspenaeopsis sculptilis in Brazil, in areas of extractive reserves on the Amazon coast. Notably exotic species can cause imbalance in the ecosystem, harming native species. In view of this, the registration of new invasions is essential as they contribute to the implementation of control plans., (© 2023. The Author(s).)