Microplastic pollution: a review of techniques to identify microplastics and their threats to the aquatic ecosystem.

Microplastics (MPs), small synthetic particles, have emerged as perilous chemical pollutants in aquatic habitats, causing grave concerns about their disruptive effects on ecosystems. The fauna and flora inhabiting these specific environments consume these MPs, unwittingly introducing them into the intricate web of the food chain. In this comprehensive evaluation, the current methods of identifying MPs are amalgamated and their profound impacts on marine and freshwater ecosystems are discussed. There are many potential risks associated with MPs, including the dangers of ingestion and entanglement, as well as internal injuries and digestive obstructions, both marine and freshwater organisms. In this review, the merits and limitations of diverse identification techniques are discussed, including spanning chemical analysis, thermal identification, and spectroscopic imaging such as Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, and fluorescent microscopy. Additionally, it discusses the prevalence of MPs, the factors that affect their release into aquatic ecosystems, as well as their plausible impact on various aquatic ecosystems. Considering these disconcerting findings, it is imperative that appropriate measures should be taken to assess the potential risks of MP pollution, protect aquatic life and human health, and foster sustainable development.

Optimization of protocols for microinjection-based delivery of cryoprotective agents into Japanese whiting Sillago japonica embryos.

Microinjection has proven useful for introduction of low-permeability cryoprotective agents (CPAs) into fish eggs or embryos for cryopreservation. In this work, we examined the suitable conditions for single or combined microinjection into the perivitelline space (PS) and the yolk mass (YM) of embryos of the Japanese whiting, an alternative marine fish model for embryo cryopreservation studies. The parameters examined were injection volume, CPA type and concentration, vehicle (diluent), and suitable developmental stage. Somites and tail elongation embryos tolerated single or combined injection with 2.1 and 15.6 nl in the PS and YM, respectively, whereas earlier embryonic stages tolerated only up to 8.2 nl in the YM. The injected solutions diffused rapidly throughout the PS and YM and remained contained within each compartment unless in the case of structural damage caused by injection of larger volumes. Yamamoto solution was marginally better as a vehicle for microinjection of CPAs than fish Ringer and phosphate buffer saline whereas » artificial sea water was clearly unsuitable. Ethylene glycol was well tolerated by embryos in all developmental stages whereas 1, 2-propylene glycol was suitable only for early embryonic stages. Overall, microinjection was efficient in delivering high loads of CPAs inside whiting embryos more swiftly than previously obtained for this species by immersion-based impregnation protocols. Embryos microinjected with CPAs showed a decrease in embryo nucleation temperature and an increase in chilling tolerance. CPA-microinjected embryos will provide valuable materials to optimize the remaining parameters that are critical for successful cryopreservation such as cooling and warming strategies.

Effects of ultrasound on permeation of cryoprotectants into Japanese whiting Sillago japonica embryos.

Cryopreservation of fish embryos requires the swift uptake of considerable amounts of cryoprotectant (CPA) but this process is hampered by the low permeability of the egg chorion. This study examined the relative efficiency of ultrasound to promote the incorporation of CPAs in two different embryonic developmental stages (somites and tail elongation) of Japanese whiting Sillago japonica and performed a preliminary cryopreservation trial using the best conditions determined during the study. Embryos tolerated ultrasound densities up to 37.5 W/cm2 well for up to 3 min but had significant mortality at 50 W/cm2. Hatching rates of somites embryos sonicated at 37.5 W/cm2 for 1-3 min in 10 and 20% Me2SO solutions were comparable (61-72%) to that of sonication in artificial seawater (65-86%) but decreased sharply at the concentration of 30% (0-55%); at similar conditions, tail elongation embryos had comparatively lower survival. Me2SO content of sonicated embryos at the somites and tail elongation stages increased significantly by 58-191% and 27-123%, respectively, compared to controls exposed to Me2SO without ultrasound. Pre-exposure to Me2SO before sonication increased the CPA uptake further by 36% without impairing survival. A preliminary cryopreservation trial after ultrasound-mediated impregnation of somites embryos with a CPA solution containing 20% PG and 10% MeOH did not yield live embryos after freeze-thawing but resulted in a significant decrease of nucleation temperature and increase of the proportion of morphologically intact embryos after freeze-thawing. These results suggest that sonication might be useful for fish embryo cryopreservation although it may require combination with other techniques to enhance CPA permeation.

Surrogate production of eggs and sperm by intrapapillary transplantation of germ cells in cytoablated adult fish.

Germ cell transplantation (GCT) is a promising assisted reproductive technology for the conservation and propagation of endangered and valuable genetic resources. In teleost fish, GCT in adult gonads has been achieved only in male recipients, limiting greatly the usefulness of this technique in situations where both sexes need equal and timely attention for conservation and/or propagation. Here we describe a simplified GCT approach that ultimately leads to production of donor-derived eggs and sperm in considerably short time. Donor germ cells isolated from young pejerrey Odontesthes bonariensis (Atherinopsidae) were transplanted non-surgically through the genital papilla into the sexually mature gonads of Patagonian pejerrey O. hatcheri recipients whose gonads have been depleted of endogenous GCs by heat (26°C) and chemical treatment (four doses of Busulfan at 30 mg/kg and 40 mg/kg for females and males, respectively). Transplanted spermatogonial and oogonial cells were able to recolonize the recipients' gonads and produce functional donor origin eggs and sperm within 7 months from the GCT. We confirmed the presence of donor-derived gametes by PCR in 17% and 5% of the surrogate O. hatcheri fathers and mothers, respectively. The crosses between surrogate fathers and O. bonariensis mothers yielded 12.6-39.7% pure O. bonariensis and that between a surrogate mother and an O. bonariensis father yielded 52.2% pure O. bonariensis offspring. Our findings confirm that transplantation of germ cells into sexually competent adult fish by non-surgical methods allows the production of functional donor-derived eggs and sperm in a considerably short time. The methods described here could play a vital role in conservation and rapid propagation of endangered fish genetic resources.