Stem cells can be described as raw materials for building the bodies of organisms. Stem cells have the unique ability to build any type of specialized cells found in individual tissues. Stem cells in adults are usually no longer a tabula rasa, but they still retain part of their stemness, which was proven by scientists from the Faculty of Fisheries and Water Conservation of the University of South Bohemia in České Budějovice as per the example of common carp (Cyprinus carpio L.) produced by interspecific surrogate parents – goldfish (Carassius auratus).

Germ stem cells – male spermatogonia and female oogonia are found in gonads. These cells give rise to gametes – sperm and eggs. Male spermatogonia were successfully isolated from carp gonads and transplanted into goldfish larvae, which served as surrogate parents. In the surrogate parents, the transplanted cells resumed gamete production, and more importantly, the transplanted spermatogonia in surrogate females changed their male fate into female fate and later produced eggs carrying the male's genetic information, including sex chromosomes.

The presented study is the most distant surrogacy in vertebrates with the successful production of viable donor-derived offspring. The genera Cyprinus and Carassius diverged about 34 million years ago. If we compare the evolutionary distance to humans, then with more than a good dose of imagination, for example, a baboon could become his surrogate parent. More importantly, the production of carp offspring has been demonstrated through 10-100x smaller goldfish surrogates, opening up a novel way for conservation and propagation of genetic resources of this globally important species. At the same time, the possibilities of surrogacy in cyprinids with the potential use for the rescue of endangered members of this family were confirmed, when offspring of the endangered species can be produced through commonly bred species.

Detailed information is publicly available in the original article Franěk, R., Kašpar, V., Shah, M.A., Gela, D., Pšenička, M., 2021. Production of common carp donor-derived offspring from goldfish surrogate broodstock. Aquaculture 534: 736252. https://doi.org/10.1016/j.aquaculture.2020.736252.

Severe weather events, such as long‐term droughts, are challenging for many freshwater species. To survive drought, freshwater crayfish tend to inhabit shelters or burrows where they can remain in contact with water or high humidity environments. However, it is not known whether embryogenesis or post‐embryonic development can occur without free standing water.

To address this question, members of the Laboratory of Ethology of Fish and Crayfish conducted experiments using artificial burrows with high air humidity and using marbled crayfish as a model species. The ovigerous females were transferred to simulated burrows without free water, but with high air humidity. A control group of females was kept in burrows with free water. Successful hatching was achieved in both groups. In the further experiment, ovigerous females were transferred to simulated burrows with no free water but high air humidity and post‐embryonic development were observed. Following successful hatching, offspring moulted to the second developmental stage (stage 2 juveniles). Stage 2 juveniles remained viable with‐out free water for 20 days, but further development was not observed. However, when placed back into fully aquatic conditions, they moulted to independent stage 3 later on.

These results demonstrated the ability of marbled crayfish to undergo terminal phases of embryogenesis, including hatching, as well as early post‐embryonic development under high air humidity conditions only, which is not achievable in the European native crayfish. Post‐embryonic development was suspended in the absence of free water, and successfully resumed when re‐immersed. This highlights importance of drought-oriented adaptations of freshwater organisms as well as capacities of marbled crayfish as an invasive parthenogenetic species.

Detailed information can be found in the original article: 

Guo, W., Kubec, J., Veselý, L., Hossain, S.Md., Buřič, M., McClain, R., Kouba, A., 2019. High air humidity is sufficient for successful egg incubation and early post‐embryonic development in the marbled crayfish (Procambarus virginalis). Freshwater Biology 64: 1603–1612.

Members of the Laboratory of Germ Cells succeeded as the first ones in the delivery of nanoparticles (iron oxide) into primordial germ cells (gamete precursors) in vivo. The nanoparticles were micro-injected into germ plasm of embryo just after fertilization. This specific cytoplasm has a crucial role for formation and differentiation of germ cells. The nanoparticles were fluorescently tagged which enabled tracing of the primordial germ cell migration during embryogenesis. After arrival of the primordial germ cells into germinal ridge (future gonads), the development of these cells was possible using microtomography. This method opens new possibilities to study germ cells development in vivo, isolate these cells using a magnet (followed by in vitro cultivation, cryopreservation and transplantation into surrogate parents) or conversely their elimination for sterilization purpose and production of surrogate parents using hypothermia (heating in alternating electromagnetic field). Furthermore, our study was performed on valuable sturgeons, which are one of the most critically endangered group of species according to the Red List of Threatened Species.

Detailed information can be found in the original article: Khanzai Baloch, A.R., Fučíková, M., Rodina, M., Metscher, B., Tichopád, T., Shah, A.M., Franěk, R., Pšenička, M., 2019. Delivery of Iron Oxide Nanoparticles into Primordial Germ Cells in Sturgeon. Biomolecules 9: 333.

The rate of spread of invasive species into new localities is alarming. It is increasingly common that several such species meet at the same locality. These species put severe pressure on local populations of native species. Due to their ability to effectively utilize food resources, changes in the food webs could possibly result in collapses of entire ecosystems.

In this study, we focused on a locality with two, respectively three co-occurring non-native crayfish species – marbled crayfish, spiny-cheek crayfish, and red swamp crayfish. These species belong to important invasive species in Europe. Using stable isotopes analysis, we investigated their trophic niches at the studied locality. We found that the trophic niches of spiny-cheek crayfish and marbled crayfish are reduced in the presence of red swamp crayfish and that this species preys on the formerly mentioned. Thus, we had the opportunity to get a deeper insight into their trophic relationships.

Detailed information can be found in: Veselý, L., Ruokonen, T.J., Weiperth, A., Kubec, J., Szajbert, B., Guo, W., Ercoli, F., Bláha, M., Buřič, M., Hämäläinen, H., Kouba, A., 2021. Trophic niches of three sympatric invasive crayfish of EU concern. Hydrobiologia 848: 727–737.

Most fishes are reproducing externally in the water, and this requires a broad set of evolutionary adaptations that will allow to support the whole process, including the specific structure of the gametes or features which support a new organism while developing in the water. These adaptations include in particular the evolution of a dense protective shield around the egg, which in most fish species has only one minute opening, called the micropyle, allowing the penetration of the spermatozoa through it.

Fertilization in the water entailed the appearance of a sophisticated system of spermatozoa motility initiation and further support of propagation using the “power” of external factors, e.g., ionic content or osmolarity of the medium servings as triggers. Many sea invertebrate organisms, which are broadcast spawners, use the water to spread the chemical signals from their eggs to the male gametes, allowing them to find each other. The scientists have uncovered the amazing membrane-associated system of receptors, channels and other molecules, making possible the precise guidance of the spermatozoa on its way to the egg in these marine invertebrates.

Freshwater fish are quite unique among all externally fertilizing organisms due to the specific conditions of the environment in which they live and reproduce, In particular, one of the features is the extremely low osmolarity, which acts extremely negative on the cells. This conditions make the need for a specific support of cell encounters even more apparent. The eggs of many externally fertilizing freshwater fish species are released into the external milieu surrounded by a coat of ovarian fluid which contain various ions, proteins, amino acids, sugars, etc. in proportions being ideal for supporting and protecting eggs and sperm against the harmful effect of freshwater.

There are data that show the positive effect of ovarian fluid or substances released by the eggs on the behavior of male gametes and finally the outcome of fertilization. Some of the research results show the biased choice of genetic material from a specific parent caused by the presence of ovarian fluid, e.g. resulted from the enhanced sperm motility traits of particular male etc. The specific mechanisms of this selection in externally fertilizing fish are still unclear, which makes further research in the field highly promising.

The members of the Laboratory of Reproductive Physiology are studying the phenomena of post-copulative female control over gamete encounter believing that new knowledge in this area will contribute not only to the fundamental physiology of reproduction but also to the optimization of artificial reproduction technologies.

More information can be found in the following article: Kholodnyy, V., Gadêlha, H., Cosson, J., Boryshpolets, S., 2020. How do freshwater fish sperm find the egg? The physicochemical factors guiding the gamete encounters of externally fertilizing freshwater fish. Reviews in Aquaculture 12: 1165–1192.

Polyploidization refers to the multiplication of one or more complete chromosome sets in an organism and represents an important step in evolution and speciation. Polyploidy, i.e. the status when the organism already has a higher number of chromosome sets in every cell, provides beneficial genetic flexibility and broad adaptive responses, i.e., additional gene copies theoretically allow evolution under reduced selective constraint and the acquisition of novel gene functions that contribute to adaptation.

The occurrence of polyploidy in vertebrates is rather sporadic compared to invertebrates and plants, and is mostly restricted to amphibians and ray-finned fishes. The highest chromosome count of any vertebrate to date (2n ~ 446) was documented in Ptychobarbus dipogon, a cyprinid fish from the Tibetan Plateau.

Critically endangered sturgeons, having undergone three whole genome duplication events, represent an exceptional example of ploidy plasticity in vertebrates. Three extant ploidy groups, combined with autopolyploidization, interspecific hybridization, and the fertility of hybrids are important issues in sturgeon conservation and aquaculture.

Solving the CSF grant „Genome duplication in sturgeon evolution and impact on their biology“ (18-09323S), we studied the cases and outcomes of induced polyploidization. Artificial suppression of the first mitotic division alone, or in combination with suppression of the second meiotic division of functionally tetraploid zygotes (4n, C-value = 4.15) of Siberian sturgeon Acipenser baerii and Russian sturgeon A. gueldenstaedtii resulted in fry of various ploidy levels—diploid/hexaploid (2n/6n) mosaics, hexaploid, octoploid juveniles (8n), and dodecaploid (12n) larvae. Counts between 477 to 520 chromosomes in octoploid juveniles of both sturgeons confirmed the modal chromosome numbers of parental species had been doubled. This exceeds the highest previously documented chromosome count among vertebrates in the cyprinid fish Ptychobarbus dipogon and it demonstrates that the sturgeon genome can undergo numerous alterations of ploidy without severe physiological consequences, producing individuals with a range of ploidy levels and extremely high chromosome numbers.

For detailed information see the original article: Lebeda, I., Ráb, P., Majtánová, Z., Flajšhans, M., 2020. Artificial whole genome duplication in paleopolyploid sturgeons yields the highest documented chromosome number in vertebrates. Scientific Reports 10, Article No 19705 (IF = 3.998; Q1; DOI: 10.1038/s41598-020-76680-4).

Growing human population and demands for quality protein source resulted in fully- or over-exploitation of 80% of the world’s fish stocks. This has led to continuous growth of global aquaculture production being one of the fastest growing food-producing sectors. The current freshwater aquaculture production relies mainly on several species (e.g. grass carp, silver carp, common carp, Nile tilapia, Atlantic salmon). Hence, in order to increase the sustainable development of aquaculture, the diversification of fish production is of crucial importance while the European perch (Perca fluviatilis L.) is one of promising candidates. Its high market value along with increasing consumer demands make European perch suitable for recirculating aquaculture systems (RAS). However, despite the fact that the species has been introduced in RAS technology more than two decades ago, the volume of European perch production is still not high enough to meet market demands. Poor growth capacity, small size and fragility of the larvae are usually cited as one of limiting factors. Yet, these traits can be enhanced by implementing the biotechnological practices, e.g. domestication, selective breeding etc.

According to several studies the zootechnical traits are variable among geographically different European perch populations implying that genetically divergent populations show different growth characteristics in controlled conditions. Indeed, genetic improvements, together with the selection of suitable strains can considerably improve the development of profitable percid industry in the near future, yet no comprehensive comparison of growth characteristics of European perch influenced by genetic differentiation has been done to date.

Czech research team (University of South Bohemia in České Budějovice, Czech Republic) together with French colleagues (University de Lorraine in Nancy, France) performed an experiment where they investigate the effects of genetic differentiation on zootechnical traits. Three geographically different European perch populations from the Czech Republic, Slovakia and Poland were compared for survival, growth parameters, and cannibalism in standardized conditions in RAS during 115 days post-hatching (dph). These results were coupled with a genetic assessment based on four mitochondrial markers: cytochrome b, D-loop of control region, 16S rRNA, and cytochrome oxidase I.

The differences obtained during the rearing were mainly observed between genetically differentiated Polish population vs. genetically undifferentiated Slovak and Czech populations. At the end of experiment, specific growth rate of Polish population was significantly higher than in the rest populations. Cannibalism and mortality were similar at 115 dph among all populations, excluding influence of genetic basis on these parameters. However, we also observed small variation in aquaculture performance among fish of genetically similar populations. This could be explained by a) an underestimation of the genetic variation based on analysis of only four mitochondrial markers, b) a consequence of different health status, pre-collection environment, or transgenerational effects. Therefore, further studies are needed to assess the importance of these factors in geographic differentiation of aquaculture performance.

Detailed information can be found in the original article: Vanina, T., Gebauer, R., Toomey, L., Stejskal, V., Rutegwa, M., Kouřil, J., Bláha, M., Lecocq, T., 2019. Genetic and aquaculture performance differentiation among wild allopatric populations of European perch (Percidae, Perca fluviatilis). Aquaculture 503: 139–145.

Fish are the most numerous and diverse group of vertebrates. They occupy all types of aquatic habitats differing in salinity (from fresh to sea water), depth (from surface to nearly eight kilometers depth), and temperature (from -2 to 44 °C). The structure of fish reproductive system as well as their mode of reproduction are equally diverse. In contrast to external fertilization in most modern actinopterygian fishes, internal fertilization in cartilaginous fishes was retained from common ancient ancestor of fishes, reptiles, birds, and mammals. The same evolutionary origin of internal fertilization in extant chondrichthyan fishes and other groups of vertebrates predicts common traits in the structure and function of germ cells.

In frame of the Czech Science Foundation project (No. 16-03754S “The evolution of sperm capacitation: pioneering study in taxonomically isolated cartilaginous fish”), the researchers of our faculty in close collaboration with the members of Neotropical Ichthyology Laboratory, Universidade Estadual Paulista “Júlio de Mesquita Filho” (UNESP), Ilha Solteira, Brazil have studied some aspects of sperm biology in ocellate river stingray Potamotrygon motoro (representative of freshwater cartilaginous fish, see Fig. 1).

For the first time for cartilaginous fishes, sperm motility parameters were evaluated, and we found that stingray spermatozoa differ a lot from actinopterigian sperm in terms of structure, physiology and motility characteristics. They are unusually elongated cells, morphologically more similar to spermatozoa of birds and amphibians rather than to actinopterigians’ ones (see Fig. 2). They acquire motility in the male reproductive tract and can increase their velocity by contact with the uterine fluid in the female reproductive tract, a process similar to epididymal sperm maturation and capacitation well known in mammals, while possessing a lipid composition mostly similar to birds. The 3D motion of spermatozoon flagellum, giving rise to a screw-like progression of this gigantic cell, is also complicated and under our specific attention now (see video). All described characteristics are very specific among the animal kingdom, and we are fascinated by these unusual motile cells and looking forward to the next steps in understanding their functioning.

Detailed information can be found in the following articles:

- Dzyuba, V., Shelton, W.L., Kholodnyy, V., Boryshpolets, S., Cosson, J., Dzyuba, B., 2019. Fish sperm biology in relation to urogenital system structure. Theriogenology 132: 153–163.
- Dzyuba, V., Ninhaus-Silveira, A., Kahanec, M., Veríssimo-Silveira, R., Rodina, M., Holt, W.V., Dzyuba, B., 2019. Sperm motility in ocellate river stingrays: evidence for post-testicular sperm maturation and capacitation in Chondrichthyes. Journal of Zoology 307: 9–16.
- Dzyuba, V., Sampels, S., Ninhaus-Silveira, A., Kahanec, M., Veríssimo-Silveira, R., Rodina, M., Cosson, J., Boryshpolets, S., Selinger, M., Sterba, J., Dzyuba, B., 2019. Sperm motility and lipid composition in internally fertilizing ocellate river stingray Potamotrygon motoro. Theriogenology 130: 26–35.

...No, it is just his heart beating.

There are several types of heart rate measurement methods that are based on different principles. In both humans and crayfish, the principle of measuring reflected infrared light is used. In humans, the sensor looks like a finger peg that you get in the hospital. In the case of the crayfish, then as a small box with wires attached to the back of the crayfish. Both devices monitor cardiac activity. In crayfish, cardiac activity is monitored because its change reflects changes in the quality of the water in which the crayfish lives. This principle is technically called bio-indication and crayfish is therefore used as a rapid bioindicator of the occurrence of undesirable substances in water.

There are limitations to measuring cardiac activity using infrared light, so researchers from the Laboratory of Signal and Image Processing, along with researchers from the Acoustics Laboratory at University of Le Mans, have been looking for new ways to monitor cardiac activity. The heart distributes blood across the body of the crayfish by mechanical contractions. These contractions cause vibrations that correspond in frequency to the heartbeat. Therefore, a sensitive accelerometer was placed on the crayfish, which allows you to measure the vibrations of objects. The accelerometer records all movements of the object and converts them into an electrical signal. So if something vibrates regularly, the signal will take a periodic form.

This procedure not only makes it possible to measure the cardiac activity of the crayfish, but also makes it possible to detect the movement of the crayfish (the periodical signal is lost). This is an advantage over the current infrared solution, which must use a camera to detect motion.

Detail information can be found in the original paper Novak, A., Cisar, P., 2020. Crayfish heart rate monitoring with an accelerometer. Ecological Indicators 111: 105993. (IF 2018 = 4,490; AIS 2018 = 0,899).

Living organisms are stable chemical objects created by spontaneous organization. Once an embryo is created, it "knows" by itself how to organize chemicals to form a human. Similar processes of chemical self-organization can be observed, for example, in a mixture of malonic acid, sulfuric acid, bromine, bromide and a transition metal complex catalyst (reaction of Belousov-Žabotinski). Here, too, the development can be observed through various stages up to "maturity" characterized by the same dynamic structure. The "chemical embryo" can be recreated by re-shuffling the mixture similarly as the organism re-emerges from the germ cells. The researchers at the Institute of Complex Systems of the FFPW USB analysed a very simple model, which counts only two factually linear processes, internal growth and diffusion. When experimenting with noise levels, they found conditions where it is possible to simulate development from a "chemical embryo" to adulthood, i.e. chemical turbulence. The basic qualitative characteristics of the development of a living organism can already be seen in this simple model.

But the result raises an even more fundamental question: Is the description of the world correct using differential equations? Should not be described by means of discrete mathematics and illusion of continuity replaced with noise. We all know that matter consists of discrete molecules as well as larger discrete objects. Are not the problems faced by the mathematical description of natural phenomena systematically given due to erroneous assumptions?

Videos:
- The Belousov-Zhabotinski experiment
- The hodgepodge machine with noise

Article by Dalibor Štys, Renata Štysová Rychtáriková, Anna Zhyrová, Kryštof Štys and Petr Jizba (Noisy hodgepodge machine and the observed mesoscopic behavior in non-stirred Belousov-Zhabotinsky reaction: Optimal noise and hidden noise in the Hodgepodge machine) was published in The European Physical Journal Special Topics in March 2019.

Neonicotinoid pesticides were introduced in the mid-1990s, and since then, they are commonly used as insecticide in crop production and veterinary medicine. These substances show lower toxicity to vertebrates compared to organophosphates and carbamate insecticides but are highly toxic to invertebrates. In 2013, the European Union banned some of neonicotinoids forbidding their use, because of growing evidence that these pesticides affect domesticated honey bees and further wild pollinators. Neinicotinoids, like most agricultural substances, reached ground and surface water, where they threaten other non-target organisms and cause other environmental problems.

Because these are relatively new substances and most studies deal mainly with harmful effects on insects, scientists from the Faculty of Fisheries and Protection of Waters of the University of South Bohemia in Vodňany in cooperation with the colleagues from the Universities of Messina and Padova focused on one of still widely used neonicotinoid insecticide Calypso 480 SC (thiacloprid) and its effects on bivalve Mediterranean mussel (Mytilus galloprovincialis). Mussels are very important filter organisms that are able to accumulate large amounts of pollutants. They are often used as suitable bioindicators of pollution and at the same time in the Mediterranean represent one of the important sources of livelihood for humans.

Calypso had negative effects on behaviour, vitality and the ability of hepatopancreatic cells regulate their volume, haemolymph biochemical parameters, enzyme activity and histopathological damage to gills and hepatopancreas of mussels during the 20 days laboratory test. Research showed that Calypso has a negative effect on mussels, thus we could be assumed other negative effects on other non-target invertebrates and the environment. This study is followed by other experiments, which will monitor other effects of Calypso and the active substance thiaclopride on non-target aquatic organisms.

Detailed information can be found in the original article: Stara, A., Pagano, M., Capillo, G., Fabrello, J., Sandova, M., Vazzana, I., Zuskova, E., Velisek, J., Matozzo, V., Faggio, C., 2020. Assessing the effects of neonicotinoid insecticide on the bivalve mollusc Mytilus galloprovincialis. Science of the Total Environment 700, 134914.

The study was financially supported by the project Development of USB: International Mobility MSCA IF (No. CZ.02.2.69/0.0/0.0/17_050/0008486).

Caviar from hybrids is almost impossible to identify from pure species caviar without reliable DNA-based technique. Similarly, identification of sturgeon species is very complicated and requires molecular genetic techniques” says Milos Havelka, who works on sturgeon research at Faculty of Fisheries and Protection of Waters, University of South Bohemia.
Researchers from University of South Bohemia in cooperation with Hokkaido University in Japan developed new method for identification of beluga sturgeon and its caviar. Beluga caviar is the most costly in the trade. Less valuable roe from other species or hybrids is sometimes fraudulently sold as beluga caviar. “Using modern methods of molecular genetics, we identified species-specific variants in genome of beluga and sterlet sturgeons. Taking advantage of these variants, we have developed simple method allowing identification of beluga, sterlet and their interspecific bester hybrid. Importantly, the tool works for caviar and requires only one roe for analyses” adds M. Havelka.    
Developed tool should contribute to better, more reliable, regulation and control of global trade of high value sturgeon products as well as to their management and conservation. The protocol is straightforward and thus can be easily implemented across laboratories.

Detailed info is available in original article: Havelka, M., Fujimoto, T., Hagihara, S., Adachi, S., Arai, K. 2017. Nuclear DNA markers for identification of Beluga and Sterlet sturgeons and their interspecific Bester hybrid. Scientific Reports. Doi: 10.1038/s41598-017-01768-3

Figure 1. Caviar sample ready to be analysed.
Figure 2. Schematic workflow of caviar sample analysis using developed method.

Sturgeons are famous for the black caviar – the most expensive luxury roe. Nowadays, most of species from Acipenseridae family became critically endangered (17 out of 27 species). Such situation happened because of several factors: overfishing, poaching, pollution of water surface and dam constructions. Nowadays the restoration of the sturgeon populations is dependent on artificial reproduction. However the sturgeon reproduction is not easy. The sturgeons reach maturation quite late. Some species, such as beluga (Huso huso), become matured around 20 years. Therefore it is very important to understand biology of reproduction of these fishes.

Viktoriia Iegorova and colleagues from the Laboratory of Germ Cells, Faculty of Fisheries and Protection of Waters described fertilization aspects, which are unique throughout the whole animal kingdom. Namely two fertilization mechanisms were observed: 1) physiological polyspermy (penetration of numerous spermatozoa into an egg) and 2) karyogamy (fusion of sperm and egg pronuclei) with an additional plasmogamy (fusion of egg cytoplasm with accessory spermatozoa). The study demonstrates that during fertilization, numerous spermatozoa (up to 10) penetrate into the egg cytoplasm due to higher number of micropyles. These spermatozoa have trend to degenerate with time, and usually only one sperm pronucleus fuses with the egg pronucleus. However, some spermatozoa, which did not fuse with the egg pronucleus and escaped from the degradation mechanisms, can also participate in the development and give rise to fishes, called “polyspermic mosaics”. Such mosaics were distinguished by characteristic cleavage pattern, demonstrated a higher number of blastomeres at the 2 to 4 cell stage with a characteristic mosaic haploid/diploid ploidy. In this research it was confirmed that the diploid cells contain maternal and paternal genetic information, while the haploid cells possess only a paternal genome. Surprisingly these mosaics develop normally and survive similar to the control fish.

The obtained discovery gave us a possibility to produce a first viable hybrids originating from three interspecific parents in different combinations between Acipenser gueldenstaedtii, A. baerii and A. ruthenus. In other words, one descendant has one mother and two fathers of different species, where sperm pronucleus of one species fuses with egg pronucleus of second species resulting in diploid line and the sperm pronucleus of third species fuses with egg cytoplasm and give rise to the haploid line.

These findings can open a new approach in biotechnology such as production of clonal gametes.

Detailed information on obtained results can be found in publications:

Iegorova, V., Psenicka, M., Lebeda, I., Rodina, M., Saito, T. Polyspermy produces viable haploid/diploid mosaics in sturgeon. Biology of Reproduction, 2018, 99(4), 695–706.
Iegorova, V., Psenicka, M., Saito, T. First evidence of viable progeny from three interspecific parents in sturgeon. Fish Physiology and Biochemistry, 2018. DOI 10.1007/s10695-018-0553-6.

The impact of killer shrimp on crayfish.

Freshwater ecosystems worldwide are facing the establishment of non-native species, which, in certain cases, exhibit invasive characteristics. The impacts of invaders on native communities are often detrimental, while the number and spread of non-native invasive species are increasing. This is resulting in novel and often unexpected combinations of non-native and native species in natural communities. While the impact of invaders on native species is well-documented, the interactions of more non-native invaders are less studied.

We assessed the potential of an invasive amphipod, the killer shrimp Dikerogammarus villosus, to cope with other established invaders in European waters, the North American crayfish represented by signal crayfish Pacifastacus leniusculus, and marbled crayfish Procambarus virginalis. The main goal of this study was to investigate if killer shrimp, besides their role as prey of crayfish (also confirmed here), can significantly influence their stocks by predating upon their eggs, hatchlings, and free-moving early juveniles. Our results confirmed that killer shrimp can predate not only on free-living juveniles and lost eggs but even directly on eggs and hatchlings attached to a female’s abdomen where they are incubated and actively guarded by a mother. Our findings illustrate the high voracity and competitiveness of killer shrimp as well as unexpected boldness (or even impudence) of this small creature which can affect even much bigger taxa by its pressure on their different developmental stages. Due to this aggressiveness, boldness, and voracity killer shrimp is not only possible prey for fish and crayfish but also their strong competitor. Species with smaller eggs and first developmental stages are more prone to killer shrimp predation as presented by higher predation on marbled crayfish marbled eggs and juveniles than those of signal crayfish.

Further detailed information can be found in the original article: Roje, S., Veselý, L., Švagrová, K., Kozák, P., Kouba, A., Buřič, M., 2021. Pilferer, a murderer of innocents or prey? The impact of killer shrimp (Dikerogammarus villosus) on crayfish. Aquatic Sciences 83: 5. (IF 2019 = 2.402; Q2).

Nanotechnology can be defined as the study, design, creation, synthesis, manipulation and application of functional materials at the nanometer scale. In recent years nanotechnology has emerged tremendous potential in improving aquaculture to fulfill the increased demands for animal protein requirements around the globe. In the current review article, we have comprehensively summarized the available literature focusing on the applications of different kinds of nanoparticles in aquaculture and fisheries. To this end, we first highlighted how this technology is being used in the delivery of vaccines, in the purification of water from heavy toxic metals as well as coliforms and in the delivery of nutrients that play a significant role in scaling up growth and immunological parameters in fish. On the other hand, contrary to their usefulness, we also described the toxicity and adverse effects that nanotechnology-based materials and products exert not only on the environment but ultimately also on human health. Therefore, finally we discussed the importance and need for ecofriendly, non-toxic natural strategies to promote sustainable aquaculture. This included the discussion about natural bioactive compounds which are being used predominantly in aquaculture as growth enhancers and immunomodulators, herein with an example of curcumin. But unfortunately, their low bioavailability in aqueous solutions hinder their efficacy. This led us to introduce Pickering emulsions which are known to be safe and have high stability and are predominantly used as delivery systems for these compounds in an attempt to boost up their bioavailability.

Detailed information can be found in the original article: Shah, B.R., Mraz, J., 2020. Advances in nanotechnology for sustainable aquaculture and fisheries. Reviews in Aquaculture 12: 925–942.

The redclaw crayfish, native to northern Australia and southern New Guinea, is among the largest freshwater decapods. It matures early and is highly fertile. Despite generally preferring slow-moving streams in its native range, it has a broad environmental tolerance, making it capable of establishing populations when introduced to a wide range of conditions and habitats. These biological and ecological features render it a highly suitable and popular species for aquaculture worldwide, the second most important crayfish species (after the red swamp crayfish). Also, its unique colouration fuels demand and value among aquarium enthusiasts, making it attractive for the aquarium pet trade. Today, redclaw is widely translocated (67 countries/territories), and various established wild populations (22 countries) have been reported worldwide. Information on its potential or observed impacts, however, is sparse and often anecdotal. To address this gap, we compiled a comprehensive review on this species, covering its taxonomy and description, biology and ecology, and distribution accompanied with documented introduction pathways. Based on these, biological and socio-economic classifications and species distribution modelling were conducted. We call attention to the importance of managing this prominent introduced species in the aquaculture and aquarium pet trade.

Detailed information can be found in following articles:

- Haubrock, P.J., Oficialdegui, F.J., Zeng, Y., Patoka, J., Yeo, D.C.J., Kouba, A., 2021. The redclaw crayfish: A prominent aquaculture species with invasive potential in tropical and subtropical biodiversity hotspots. Reviews in Aquaculture 13: 1488–1530.
- Haubrock, P.J., Oficialdegui, F.J., Kouba, A., 2021. Redclaw – an aquaculture jewel or invader? Worldfishing & Aquaculture (April): 26–27.
- Oficialdegui, F.J., Haubrock, P.J., Kouba, A., 2021. Are we making the same mistake again? The redclaw crayfish, a prominent aquaculture species introduced worldwide. Aquaculture Magazine 47 (1): 30–32.

Potential distribution of redclaw projected globally based on both introduced and native populations.