Suchergebnisse

[EN] Elasmobranchs are one of the most endangered vertebrate groups on the planet, but despite this situation the use of reproductive techniques in elasmobranch conservation strategies has been scarce. Among these techniques, sperm preservation is a potential tool for ex situ conservation and aquaria sustainability. However, there are no widespread preservation protocols for elasmobranch sperm, and shark sperm cryopreservation has never been achieved before. Here we present the establishment of successful cryopreservation protocols for elasmobranch sperm, tested in several species. We have formulated a sperm extender that can be used for different elasmobranch species, capable of maintaining sperm motility for several weeks. Additionally, we achieved the cryopreservation of sperm by previously diluting it in our extender and supplementing it with different combinations of cryoprotectants. The effects of methanol and dimethyl sulfoxide as permeating cryoprotectants were evaluated, as well egg yolk as a nonpermeating cryoprotectant. Sperm quality was assessed by studying the motility and membrane integrity post-thawing, demonstrating its effectiveness in the 10 species tested, including two which are considered Critically Endangered. This is the first time that shark sperm cryopreservation has been reported, broadening our knowledge of the reproductive techniques that can be applied to elasmobranchs and laying the foundations for the first cryobanks for shark and ray sperm. Outcomes from this study will be useful for ex situ conservation efforts developed by public aquaria. A regular supply of frozen sperm will reduce the problems that result from the transport of specimens, inbreeding or lack of synchronized reproductive cycles in captivity. ; Study partially funded by the Fundacion Biodiversidad (PRCV00683). PG-S has a contract from the European Union through the Operational Program of the European Social Fund (ESF) of the Comunitat Valenciana 2014-2020 ACIF 2018 (ACIF/2018/147). VG has a postdoc contract from ...

[EN] Sperm activation involves ion fluxes as well as a previous maturation in the seminal plasma, something which has not been studied in depth in marine fish species. pH and potassium are probably involved in sperm maturation and motility in the European eel, as indicated in previous studies. In this work, the absolute intracellular concentration of potassium in European eel sperm has been determined for the first time. In addition, the intracellular pH (pH(i)) of quiescent eel spermatozoa was determined by two methods (nigericin and null point) that gave similar results, 7.4-7.6. The natural pH(i) range of sperm samples in the quiescent stage was 7.4-8.0, with no evident relationship with sperm motility. However, a linear correlation was seen between sperm motility and the pH of the diluent or extracellular pH (pH(e)), as well as between the pH(i) and the pH of the diluent. The change post-activation in seawater (ASW) depended on the initial pH(e) of the diluent medium. Activation with ASW induced an internal alkalinization of the cells when the sample had previously been diluted in a pH(e) 8.0; an acidification when pH(e) > 8, and no pH(i) variation when pH(e) was 8.0. These experiments indicated that a careful selection of the diluents should be performed before measuring natural pH(i) changes in sperm cells. Thus, studies on the specific seminal plasma composition of marine fish species are necessary before studying their physiology. Furthermore, our study indicates that intracellular alkalinization is not a universal fact during sperm activation. (C) 2020 Elsevier Inc. All rights reserved. ; Funded by the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No 642893 (IMPRESS). Victor Gallego has a postdoc grant from the MICIU (Juan de la Cierva-Incorporacion; IJCI-2017-34200 ; Pérez Igualada, LM.; Gallego Albiach, V.; Asturiano, JF. (2020). Intracellular pH regulation and sperm motility in the European eel. Theriogenology. 145:48-58. ...

[EN] Paralogues pairs are more frequently observed in eels (Anguilla sp.) than in other teleosts. The paralogues often show low phylogenetic distances; however, they have been assigned to the third round of whole genome duplication (WGD), shared by all teleosts (3R), due to their conserved synteny. The apparent contradiction of low phylogenetic difference and 3R conserved synteny led us to study the duplicated gene complement of the freshwater eels. With this aim, we assembled de novo transcriptomes of two highly relevant freshwater eel species: The European (Anguilla anguilla) and the Japanese eel (Anguilla japonica). The duplicated gene complement was analysed in these transcriptomes, and in the genomes and transcriptomes of other Actinopterygii species. The study included an assessment of neutral genetic divergence (4dTv), synteny, and the phylogenetic origins and relationships of the duplicated gene complements. The analyses indicated a high accumulation of duplications (1217 paralogue pairs) among freshwater eel genes, which may have originated in a WGD event after the Elopomorpha lineage diverged from the remaining teleosts, and thus not at the 3R. However, very similar results were observed in the basal Osteoglossomorpha and Clupeocephala branches, indicating that the specific genomic regions of these paralogues may still have been under tetrasomic inheritance at the split of the teleost lineages. Therefore, two potential hypotheses may explain the results: i) The freshwater eel lineage experienced an additional WGD to 3R, and ii) Some duplicated genomic regions experienced lineage specific rediploidization after 3R in the ancestor to freshwater eels. The supporting/opposing evidence for both hypotheses is discussed. ; This study received funding from the project REPRO-TEMP (AGL2013-41646-R) funded by the Spanish Ministry of Economy and Competitiveness, and from the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No 642893 (IMPRESS), which ...