Hybridization of fsh - cuses and its sgnificance astract

Hybrydyzacja jest krzyżowaniem się osobników dwu populacji, które różnią się jedną lub więcej podstawowymi cechami dziedzicznymi. Proces ten związany jest z introgresją, która jest trwałym włączeniem genów z jednego zespołu różniących się populacji do drugiego zespołu [22]. Koniecznym, ale nie wystarczającym punktem wyjścia do powstania hybrydowego gatunku, jest rosnący zasięg zróżnicowanej genetycznie populacji, wchodzącej w kontakt pozbawiony barier rozrodczych lub, kiedy izolacja reprodukcyjna załamała się np. w wyniku zaburzeń w środowisku [12]. Hybrydowy takson jest niezależnie ewoluującą, historycznie stabilną populacją lub grupą populacji posiadającą unikatowe kombinację cech dziedzicznych, wywodzących się z krzyżowania przedstawicieli z dwu lub więcej oderwanych zespołów np. ras, podgatunków czy gatunków. Stabilność i ewolucyjna niezależność, jest podstawą dla wyróżnienia taksonu pochodzenia hybrydowego, z przypadkowej hybrydyzacji międzygatunkowej [22].Hybridization is the crossing of individuals of two populations that differ in one or more of the basic hereditariness features. In the nature there are reproduction isolation mechanisms that are blocking interspecies hybridization of animals. In fish, more often than in other vertebrates, interbreeding occurs. This is due to external fertilization and the specificity of the living environment. Under breeding conditions hybridization of fish, including salmonids, is easy to implement and under natural conditions in interspecific hybrids such as salmon and trout appear to relatively rare, due to the presence of insulating mechanisms, mostly related to the separation of spawning sites. One of the main factors causing hybridization is, as a result of anthropogenic activities, disruption of the normal water conditions causing fluctuation of water level in rivers and reduction area of spawning sites. Hybridization is a process that has a significant role in the process of evolution and the creation of new species. Hybridization is often used in biotechnology, in order to obtain specimens of advantageous, in terms of aquaculture, features. Thanks to hybrydization populations are obtained with higher tolerance to cold, salinity, ammonia and better growth rates and greater resistance to disease. Note however that, given the growth of known hybrid taxa, it is essential to conduct comprehensive research on the hybridization of fish, in order to preserve and develop natural resources, and full understanding of physical and ecological changes will allow to protect better clean species. It is therefore necessary to protect natural populations against breeding individuals from experiments, which is not always realized. To preserve the natural populations it is crucial to protect limited areas species occurence, which is important especially when conducting restock and catches of fish. It is very important to preserve or restore the correct state of the natural environment and to consider each decision relating to implementation of new species due to exposure of wild populations to introgression. Hybridization advantageous in terms of biotechnology is therefore a major threat to wild populations, which, through appropriate measures, should be especially protected

Annual development of gonads of pumpkinseed, Lepomis gibbosus (Actinopterygii: Perciformes: Centrarchidae) from a heated-water discharge canal of a power plant in the lower stretch of the Oder River, Poland

Background. The pumpkinseed, Lepomis gibbosus (Linnaeus, 1758), known also as pumpkinseed sunfish, is native to eastern and central North America. Its introduction to Europe has resulted in fast spreading of the species over the continent. In Poland, the pumpkinseed has found favourable conditions for living and reproduction in water bodies artificially heated by thermal power plants. The aim of this study was to determine the annual cycle of gonad development of the pumpkinseed population inhabiting the warm-water canal of the Dolna Odra power plant (NW Poland), which has not been studied before at this location. Materials and methods. The pumpkinseed individuals were caught in the heated-water discharge canal of the Dolna Odra power plant. The average water temperature in the canal was by 6–8ºC higher than that of the river. The analysis of the annual cycle of gonad development was performed in both sexes using histological methods. The fish were aged 3+ to 6+. A standard paraffin technique and Heidenhain’s iron hematoxylin staining were used. Results. In the site surveyed, the spawning season for females lasted from the beginning of May through August, i.e., was longer than in the native range of this fish species. In one female caught in September, the ovaries contained oocytes in the stage of vitellogenesis. The oocytes in the stage of atresia were found rarely in the fish caught from April through June. Mature testes in males were found between late April and September, i.e., throughout the spawning period of the females. Few male anomalies of the sexual cycle were observed, e.g., in October, they were found to engage in another cycle of spermatogenesis and spermatozoa production. Moreover, the presence of large groups of degenerating cells in the seminal tubules was observed throughout the year, but was particularly evident between September and February. Conclusion. The results have confirmed the high colonisation abilities of the pumpkinseed. As a consequence of global warming, the studied canal with post-cooling water may become a starting point of expansion of this species to other bodies of water. Upon a considerable climate warming, this species could threaten the native species

Sexual cycle of white bream, Blicca bjoerkna (Actinopterygii, Cypriniformes, Cyprinidae), from three sites of the lower Oder River (NW Poland) differing in temperature regimes

Background. One of the largest European populations of white bream, Blicca bjoerkna  (Linnaeus, 1758), can be found in the estuary of the Oder River. This fish is not only very abundant in this area but also attains sizes that have no match in other areas of central Europe.  In search for the clues behind such reproductive success we decided to study the annual development cycle of gonads of white bream from three sites in the lower Oder River, north-western Poland, differing in temperature regimes (depending on their position and the distance from the discharge outlet of the Dolna Odra Power Plant). Materials and methods. White bream individuals were obtained from the three sites as bycatch of commercial fishing in 2009 and 2010. Three sites were sampled: (1) the Oder River above the power plant, (2) the warm-water canal with post-cooling water discharged from the power plant, and (3) Lake Dąbie, 20 km below the warm-water canal. The fish age was determined as 2+ through 9+. In total, 506 females and 190 males were designated for histological analyses. The analysis of the annual cycle of gonad development was performed in both sexes using histological methods. A standard paraffin technique and Heidenhain’s iron hematoxylin staining were used. Results. In the Oder River, spawning of white bream lasted from early May to late June. In Lake Dąbie, it extended until the beginning of July. The spawn was laid in 2 or 3 portions. In the warm-water canal spawning began one month earlier, in April. The bream males from the thermally unaffected Oder River were ready for reproduction approximately one month earlier than the females and maintained their reproductive potential similarly to the females. Males from the warm-water canal became sexually mature two months earlier (February) than those from the river above the power plant. Conclusion. In waters with elevated temperature, gametogenesis of white bream occurs without problems and the fish exhibit a typical pace of growth depending on the temperature. In the perspective of climate warming, white bream will be able to maintain its status of a common species in the natural waters of the region

Sexual cycle of white bream, Blicca bjoerkna (Actinopterygii, Cypriniformes, Cyprinidae), from three sites of the lower Oder River (NW Poland) differing in temperature regimes

Background. One of the largest European populations of white bream, Blicca bjoerkna  (Linnaeus, 1758), can be found in the estuary of the Oder River. This fish is not only very abundant in this area but also attains sizes that have no match in other areas of central Europe.  In search for the clues behind such reproductive success we decided to study the annual development cycle of gonads of white bream from three sites in the lower Oder River, north-western Poland, differing in temperature regimes (depending on their position and the distance from the discharge outlet of the Dolna Odra Power Plant). Materials and methods. White bream individuals were obtained from the three sites as bycatch of commercial fishing in 2009 and 2010. Three sites were sampled: (1) the Oder River above the power plant, (2) the warm-water canal with post-cooling water discharged from the power plant, and (3) Lake Dąbie, 20 km below the warm-water canal. The fish age was determined as 2+ through 9+. In total, 506 females and 190 males were designated for histological analyses. The analysis of the annual cycle of gonad development was performed in both sexes using histological methods. A standard paraffin technique and Heidenhain’s iron hematoxylin staining were used. Results. In the Oder River, spawning of white bream lasted from early May to late June. In Lake Dąbie, it extended until the beginning of July. The spawn was laid in 2 or 3 portions. In the warm-water canal spawning began one month earlier, in April. The bream males from the thermally unaffected Oder River were ready for reproduction approximately one month earlier than the females and maintained their reproductive potential similarly to the females. Males from the warm-water canal became sexually mature two months earlier (February) than those from the river above the power plant. Conclusion. In waters with elevated temperature, gametogenesis of white bream occurs without problems and the fish exhibit a typical pace of growth depending on the temperature. In the perspective of climate warming, white bream will be able to maintain its status of a common species in the natural waters of the region

Annual reproductive cycle of Chinese sleeper Perccottus glenii, Dybowski, 1877 (Teleostei: Gobiiformes: Odontobutidae) an invasive fish inhabiting Central Europe

AbstractChinese sleeper is an invasive species from South Asia inhabiting Eastern and Central Europe. So far, no detailed analysis of the reproductive cycle of Chinese sleepers has been conducted. The aim of the study was to describe the reproductive cycle of Chinese sleepers in the Wilanówka River, Vistula tributary (Poland, Central Europe). Fish morphometric data, age, gonadal maturity, and absolute and relative fecundity of females were analysed. A standard paraffin technique and six-stage scales were used to assess the gonad development and maturation in both sexes. The age of the studied fish ranged from 0+ to 6+.The female-to-male ratio was 1:1. Females and males mature at age 1+.The smallest female and male reaching maturity were 3.8 and 3.7 cm long, respectively. An extended spawning season from the beginning of April to mid-September was determined based on gonadal maturity analysis. The mean absolute fecundity was 2,971 (180–19,656) oocytes. The male reproductive system comprises paired testis (spermatogenic region, blackish color) and paired testicular gland (secretory region, whitish color). In both regions, seasonal changes were observed. Male gonads during winter had completed spermatogenesis, and the lobules were filled with spermatozoa. Very fast spermatogenesis and overlapping of reproductive cycles have been observed in Chinese sleeper males. Almost all year round testis contains spermatozoa. In the new habitat examined, this species was characterized by earlier maturation and longer reproduction season, compared to the native habitat and other native species of the examined area. Moreover, high female fecundity, multiple spawning, and lower investment in the development of gonads in males allow maintaining vitality and protecting the nest, contribute to the species competitiveness and successful colonization of new areas