Chromosomal organization of multigene families and meiotic analysis in species of Loricariidae from Brazil

[bekateen]

de Almeida, B.R.R., Souza, L.F., Alves, T.A., Cardoso, A.L., de Oliveira, J.A., Ribas, T.F.A., Dos Santos, C.E.V., do Nascimento, L.A.S., Sousa, L.M., Sampaio, M.I.D.C. and Martins, C. 2023. Chromosomal organization of multigene families and meiotic analysis in species of Loricariidae (Siluriformes) from Brazilian Amazon, with description of a new cytotype for genus Spatuloricaria. Biology Open, pp.bio-060029.

In 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.

Keywords:Repetitive DNA, Meiosis, Histone, Fish, U2 snDNA

[Jools]

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It's a really interesting paper, thanks for posting. I know it's not the main thrust of it, but if I read it right (I had to look up a LOT of words), another paper that supports all/most of the stripey Xingu Hypancistrus being one species with a lot of pattern variation?

Jools

PS The paper opens with "In [the] Amazon, some species of Loricariidae are at risk of extinction due to habitat loss and overexploitation by the ornamental fish market". Another example where habitat loss and over-exploitation by the fish export trade is conflated and has little reference material listed in the paper. It leaves us with broad threats to "some" species' ongoing survival. I feel statements around over-exploitation by the fish trade would be more impactful if it, like the recent H. zebra paper, had a bit more data.

Beltrão, H., et al's 2021 paper on fish illegally taken from the Brazilian Amazon lists 31 species of Loricarid including undescribed species. Broadly let's say there are 700 described spp. of Loricariid and add in a couple of hundred of undescribed species you can readily see 1000 spp. It's also harder to quantify over-exploited (Vs. trafficked) particularly when a particular species is impacted by both habitat loss and over-explotation. Is it more impactful to say 5% of species of Loricariid are illegally exported more impactful? This drops to 3% if we estimate undescribed taxa.

Over-exploitation is a real threat to several high-profile taxa. Maybe it's my over-attention to detail, but to say "some" species of a family of over 680 species are endangered by two markedly different threats misses an opportunity to educate better and inform those of us dead set against the destruction of natural habitat and keenly supportive of the preservation of species.