Vlastimil Šlechta

Morphology, composition and fertilization of carp eggs: a review

Abstract This paper is a review of the literature on eggs of carp (Cyprinus carpio L.) and some related species and includes data taken from the former USSR and eastern European countries. Reported data relate to fecundity, egg morphology and composition, and fertilization. Information is also available on the ovarian fluid composition with characterization of proteins and lipids. The fecundity of common carp is very high, ranging from 100 000 to 300 000 eggs · kg−1 body weight per oogenetic cycle, with one cycle/year in the case of females reared in an outside natural pond environment. The diameter and weight of the eggs are in the range of 1.24–1.42 mm and 0.86–1.41 mg, respectively. The ooplasm includes large amounts of yolk and various organelles (endoplasmic reticulum, Golgi apparatus, mitochondria), cortical granules and alveolae. The main characteristics of cyprinid ovarian fluid are an osmotic pressure of about 300 mOsm, a Mg2+ concentration of 2.58 mM and a high ovarian fluid pH of 9. Energy in the form of ATP which is necessary for egg metabolism originates from glycolytic and oxidative reactions. The egg has a relatively thick vitelline envelope (VE) or zona radiata which is reorganized into the fertilization envelope (FE) after fertilization. The micropyle located at the animal pole is a funnel-shaped structure leading spermatozoa to the ooplasmic surface on which a fertilization cone develops after fertilization. A site of sperm attachment is identified on the plasma membrane at the level of the internal aperture of the micropylar canal. Major differences are observed between the two outermost VE and FE layers, as revealed by electron microscopy, enzyme or carbohydrate cytochemistry, and imunohistochemistry. FE extracts have strong bactericidal and fungicidal effects.

Top-crossing with paternal inheritance testing of common carp (Cyprinus carpio L.) progeny under two altitude conditions

Abstract Weight, survival and heterosis were tested in hybrids by means of top-crossing at low and high altitudes (350 and 750 m, respectively) above the sea level. A Hungarian mirror carp strain (HSM) was chosen for testing as a maternal strain. The HSM, a wild Amur carp strain (AC), Ropsha carp strain (ROP) and Tata carp strain (TAT) were used as the paternal strains. The first season of the top-crossing test was performed by means of separate rearing of each group of fry with controls in four ponds at each altitude. In the second and third seasons, up to 3-year-old carp were grown in communal stocks for all groups in three ponds at each altitude. The highest significant corrected weight gain and survival in low and high altitudes during three seasons were obtained with the HSM×ROP and HSM×AC crossbreds. The lowest significant corrected weights were obtained with the HSM×TAT crossbred and HSM purebred, respectively. The highest significant heterosis effect both at low and high altitudes was obtained for both HSM×ROP and HSM×AC crossbreds compared to the HSM×TAT crossbred as predicted from the genetic distances between the strains. Moreover, the HSM×ROP crossbred was best adapted for altitude, regions or management in pond stations.

Genetic resources of commercially important fish species in the Czech Republic: present state and future strategy

Abstract Since 1996, the Czech governmental programme on gene resources conservation of commercially important fish species has supported in situ conservation of rare/endangered breeds of common carp ( Cyprinus carpio ; nine breeds) and of rainbow trout ( Oncorhynchus mykiss ; three breeds) by keeping broodstock of each as live gene banks on selected farms. Effective population size ( N e ) is maintained at 120. As fish are not included yet in the Czech animal breeding act, the programme encourages fisheries policy makers and farm managers to protect pure local breeds parallely to a general tendency to import breeds, use crossbreds for production or move breeds among farms. Since most breeds are defined by reproductive and performance traits only, their genetic structure is currently being investigated by enzyme polymorphism analysis to determine their value to the programme. A data records system is being introduced to the breeders that combines fish tagging and a locally-developed computer programme to store information. The experimental cryopreserved sperm bank is being extended to meet the needs of ex situ conservation. Since 1997, the programme has expanded to include eight strains of tench ( Tinca tinca ), two strains of wels ( Silurus glanis ), two coregonid species ( Coregonus lavaretus maraena and Coregonus peled ) and two acipenserid species ( Acipenser ruthenus and Huso huso ).

Rare and asymmetrical hybridization of the endemic Barbus carpathicus with its widespread congener Barbus barbus.

In endemic species that co-occur with widespread congeners, hybridization can lead to an influx of novel and beneficial genetic variation, but high rates of introgression may cause genetic swamping of the endemic species and have detrimental effects on its survival potential. This study examines hybridization between sympatric populations of the Carpathian barbel Barbus carpathicus, a recently discovered cryptic species with a restricted range, and the widespread common barbel Barbus barbus. Based on six diagnostic allozyme loci, a microsatellite locus and mtDNA, hybrids were found to be present at multiple localities within the Vistula River drainage (Baltic Sea) as well as in the Tisza River system of the Danube River drainage (Black Sea). However, the numbers of hybrids were very low; four individuals of 230 fish sampled from the Vistula drainage. Bayesian assessment of their nuclear genotypes suggested that two hybrids in the Vistula drainage and nine in the Tisza system were F1 generation, and one in the Vistula drainage and one in the Tisza system were backcrosses (BC) to B. barbus, while no F2 or BC to B. carpathicus were detected. No hybrid carried B. carpathicus mtDNA and cytonuclear linkage disequilibria showed significant positive associations between hybrid genotypes and B. barbus mtDNA, suggesting unidirectionality in the interspecific mating with a disproportionate contribution of B. barbus mothers. Despite geographically broad occurrence of hybrids, these data provide evidence of strong constraints on hybridization in the native breeding habitats and the lack of introgression towards B. carpathicus.

Genetic diversity and phylogenetic origin of brown trout Salmo trutta populations in eastern Balkans

The study focuses on the phylogenetic origin and genetic diversity of brown trout in the eastern part of the Balkan Peninsula. It further aims to reveal the impact of human-mediated transfers and stocking with non-indigenous trout on the populations in this area. For these purposes, mtDNA control region and microsatellite variation of 204 individuals from 16 populations were analysed. The results indicate that mtDNA haplotypes from the lower Danube basin and southern Black Sea basins differ substantially from a subclade of the Danubian lineage consisting of haplotypes found so far in the most of the Danube basin and in the Caspian and Aral Sea basins. Considering also the results of demographic analyses, this study evidences a complex evolutionary history of brown trout in the southern and western parts of the Black Sea basin. In the Aegean Sea basin, a high frequency of the central haplotype of Adriatic mtDNA lineage has been found. The other Adriatic lineage haplotypes found in this basin differ from the central haplotype by one mutational step only, indicating a recent evolution of the Adriatic lineage in the Aegean Sea basin. Substantial genetic differentiation among populations and basins was revealed. The hybridization with Atlantic brown trout was indicated in both sea basins, but especially in the Danube basin. Compared to other European regions, it can be inferred that the introgression of exogenous brown trout in the eastern Balkan populations is rather low.

A Ploidy Difference Represents an Impassable Barrier for Hybridisation in Animals. Is There an Exception among Botiid Loaches (Teleostei: Botiidae)?

One of the most efficient mechanisms to keep animal lineages separate is a difference in ploidy level (number of whole genome copies), since hybrid offspring from parents with different ploidy level are functionally sterile. In the freshwater fish family Botiidae, ploidy difference has been held responsible for the separation of its two subfamilies, the evolutionary tetraploid Botiinae and the diploid Leptobotiinae. Diploid and tetraploid species coexist in the upper Yangtze, the Pearl River and the Red River basins in China. Interestingly, the species ‘Botia’ zebra from the Pearl River basin combines a number of morphological characters that otherwise are found in the diploid genus Leptobotia with morphological characters of the tetraploid genus Sinibotia, therefore the aim of the present study is to test weather ‘B.’ zebra is the result of a hybridisation event between species from different subfamilies with different ploidy level. A closer morphological examination indeed demonstrates a high similarity of ‘B.’ zebra to two co-occurring species, the diploid Leptobotia guilinensis and the tetraploid Sinibotia pulchra. These two species thus could have been the potential parental species in case of a hybrid origin of ‘B.’ zebra. The morphologic analysis further reveals that ‘B.’ zebra bears even the diagnostic characters of the genera Leptobotia (Leptobotiinae) and Sinibotia (Botiinae). In contrast, a comparison of six allozyme loci between ‘B.’ zebra, L. guilinensis and S. pulchra showed only similarities between ‘B.’ zebra and S. pulchra, not between ‘B.’ zebra and L. guilinensis. Six specimens of ‘B.’ zebra that were cytogenetically analysed were tetraploid with 4n = 100. The composition of the karyotype (18% metacentric, 18% submetacentric, 36% subtelocentric and 28% acrocentric chromosomes) differs from those of L. guilinensis (12%, 24%, 20% and 44%) and S. pulchra (20%, 26%, 28% and 26%), and cannot be obtained by any combination of genomes from L. guilinensis and S. pulchra. Phylogenetic reconstructions based on sequence data of the mitochondrial cytochrome b gene and the nuclear RAG-1 gene invariably places ‘Botia’ zebra as sister species to S. pulchra, while L. guilinensis is only distantly related. The presented combination of genetic data demonstrates that ‘B.’ zebra is not the result of a hybridisation, but a species of tetraploid genus Sinibotia with a striking morphological evolution towards an enormous similarity with a co-occurring, but not directly related species. The complete lack of knowledge of the ecology of these species, their main predators or their ecological interactions hampers any conclusion regarding the evolutionary advantage of such adaptation.