Sex steroids in diploid and triploid gibel carp (Carassius gibelio) of both sexes in different phases of the reproductive cycle.

The changes in concentrations of 17ß-estradiol (E2), testosterone (T), 11-ketotestosterone (11-KT) in the gonads and plasma of diploid and triploid gibel carp (Carassius gibelio) from the Siemianowka Reservoir, the Vistula River drainage were quantified and compared using an enzyme immunoassay. The phase of gonad maturity was based on histological analysis and the gonadosomatic index. All fish had properly developed gonads in the pre-spawning, spawning and late spawning phases of the reproductive cycle in the fish collected in April, June and October, respectively. Diploid and triploid females and males did not differ in mean GSI in all reproductive phases. In October, ovaries of most females contained vitellogenic oocytes, testes had large numbers of spermatozoa. The hormone concentrations in both tissues depended mainly on the reproductive phase, but not on ploidy. The patterns of changes in E2 concentrations was similar in females and males. In the pre-spawning phase, diploid and triploid females showed differences in the concentrations of 11-KT in gonads and plasma, and T in plasma. Diploid males differed in pattern of T concentrations in gonads and plasma, while all males showed a similar pattern of 11-KT plasma concentrations. Spermatozoa observed in triploid males suggest that they participate in reproduction. Gibel carps, regardless of ploidy, had an extended period of reproduction, which makes this invasive species a potentially greater threat to native ichthyofauna. The sex androgen concentrations that differed between 2 n and 3 n females could be physiological factors potentially contributing to the coexistence of gynogenetic C. gibelio females and sexual diploids.

Variable occurrence of apoptosis in the testes of diploid and sterile allotetraploid Cobitis (Teleostei, Cobitidae) males during the reproductive cycle.

Cobitis species exist in both diploid and diploid-polyploid (d-p) populations, but mostly occur in the latter. They are considered an important model organism to study the biology and physiology of natural hybrid and polyploid vertebrates. Indeed, polyploidization causes a huge stress for in terms of cell physiology and alters spermatogenesis in polyploid fish. The most extensively studied mode of germ cell death during spermatogenesis in vertebrates is apoptosis. The aim of this study was to examine caspase-3 immunoexpression in the testes of Cobitis taenia from a diploid population as well as C. taenia and sterile tetraploid Cobitis from d-p populations before, during and after spawning. The obtained results suggest a different performance of apoptosis in the testes of C. taenia from the two studied populations and seems to be conditioned by their role as the only sperm donors in d-p populations. Moreover, apoptosis was an active cell death process in the testes of tetraploid Cobitis.

The Legacy of Sexual Ancestors in Phenotypic Variability, Gene Expression, and Homoeolog Regulation of Asexual Hybrids and Polyploids.

Hybridization and polyploidization are important evolutionary processes whose impacts range from the alteration of gene expression and phenotypic variation to the triggering of asexual reproduction. We investigated fishes of the Cobitis taenia-elongatoides hybrid complex, which allowed us to disentangle the direct effects of both processes, due to the co-occurrence of parental species with their diploid and triploid hybrids. Employing morphological, ecological, and RNAseq approaches, we investigated the molecular determinants of hybrid and polyploid forms. In contrast with other studies, hybridization and polyploidy induced relatively very little transgressivity. Instead, Cobitis hybrids appeared intermediate with a clear effect of genomic dosing when triploids expressed higher similarity to the parent contributing two genome sets. This dosage effect was symmetric in the germline (oocyte gene expression), interestingly though, we observed an overall bias toward C. taenia in somatic tissues and traits. At the level of individual genes, expression-level dominance vastly prevailed over additivity or transgressivity. Also, trans-regulation of gene expression was less efficient in diploid hybrids than in triploids, where the expression modulation of homoeologs derived from the "haploid" parent was stronger than those derived from the "diploid" parent. Our findings suggest that the apparent intermediacy of hybrid phenotypes results from the combination of individual genes with dominant expression rather than from simple additivity. The efficiency of cross-talk between trans-regulatory elements further appears dosage dependent. Important effects of polyploidization may thus stem from changes in relative concentrations of trans-regulatory elements and their binding sites between hybridizing genomes. Links between gene regulation and asexuality are discussed.

Evidence of the sterility of allotetraploid Cobitis loaches (Teleostei, Cobitidae) using testes ultrastructure.

The diploid-polyploid populations of Cobitis distributed in Poland are usually composed of the spined loach Cobitis taenia or, less often, the Danubian loach C. elongatoides and their triploid (females) and tetraploid hybrids (females and males). The aim of this study was to determine whether tetraploid males participate in the reproduction process by analyzing their testis ultrastructure and the process of spermatogenesis in comparison with diploid males of both parental species. Tetraploid loaches were obtained from three different diploid-polyploid populations distributed in Poland. The structure of Cobitis testes are typical for most Teleostei fish with cystic-type spermatogenesis. The successive stages of developing germ cells are enclosed within cysts formed by the Sertoli cells. This paper morphologically describes the different germ cell stages of spermatogenesis (spermatogonia, spermatocytes, spermatids, and spermatozoa) of C. taenia and C. elongatoides and provides a pioneering ultrastructural analysis of tetraploid Cobitis testes which reveals their unusual structure for the first time. Thus, cysts with normal spermatogonia and spermatocytes (pachyten or leptoten stages) containing synaptonemal complexes were present and no spermatids or spermatozoa were observed. Moreover, in contrast to previously analyzed diploid species, single cells or all of the cells within the cysts displayed chromatin condensation and/or chromatin fragmentation. The obtained results clearly demonstrated that tetraploid males are sterile and diploids are fertile and are the only sperm donors in the reproduction processes of diploid-polyploid Cobitis populations.

Ploidy-dependent survival of progeny arising from crosses between natural allotriploid Cobitis females and diploid C. taenia males (Pisces, Cobitidae).

Crosses between 21 triploid hybrid Cobitis females and 19 C. taenia (2n = 48) males led to viable progeny; whereas no embryonic development was observed in crosses with tetraploid males (4n = 98). The ploidy status of 491 progenies randomly selected with flow cytometry (316) or chromosome analysis (175) revealed an average of 55.2 % triploids and 44.8 % tetraploids, but the ratio of 3n versus 4n fish did change during development. In the first 2 days after hatching, approximately 65.1 % of tetraploid larvae were observed. Their number decreased significantly to 30.8 and 6.2 % on average during 2-5 and 10-15 months of life, respectively. The karyotype of tetraploid progeny (4n = 98) included 3n = 74 chromosomes of the parental female and n = 24 of C. taenia male. The number of tetraploid progeny indicated indirectly that about 66 % of eggs from 3n females were fertilized with C. taenia. The rest of the eggs developed clonally via gynogenesis or hemiclonally via hybridogenesis into triploids of the same karyotype structure as parental females. We have documented for the first time that (at least under experimental conditions) tetraploids are commonly formed, but are less viable than triploids, and a ratio similar to what is found under natural conditions is finally attained. The current explanation concerning the ploidy and karyotype structure of the progeny confirms that the eggs of 3n Cobitis females are not only capable of maintaining all chromosomes but are also capable of incorporating the sperm genome, thus creating the potential to produce tetraploids.

Mechanism of phytoestrogen action in Leydig cells of ganders (Anser anser domesticus): Interaction with estrogen receptors and steroidogenic enzymes.

Phytoestrogens (PE) are plant-derived compounds that have an estrogen-like activity and they can influence male and female reproduction. The possible mechanisms of PE action may be including: the binding to estrogen receptors (ER) and the interaction with the key steroidogenic enzymes. The aim of this study was to investigate if PE has effect on steroidogenesis of gander testicular cells by above-described pathways. The Leydig cells were isolated from testes of White Koluda ganders at the peak of their reproductive activity (March). These Leydig cells (1 × 10(5)per mL) were pre-incubated with the ER inhibitor - ICI 182, 780 (100 nM) for 3 h and then these cells were incubated with PE (5 and 50 µM): genistein, daidzein, equol and coumestrol during next 20 h or untreated control and the Leydig cells that were previously treated (20 h) with genistein (5 and 50 µM) were incubated for next 6 h with steroid intermediates (20 µM) as testosterone (T) precursors: hydroxycholesterol, pregnenolone, progesterone and androstenedione. Concentrations of T in the samples of incubation medium were measured using radioimmunoassay. Genistein, daidzein, and equol (5 and 50 µM) decreased (P < 0.05) T secretion by incubated gander Leydig cells and ICI 182, 780 did not eliminate the inhibitory effect of these PE. After genistein (50 µM) treatment, basal and stimulated with 22R-hydroxycholesterol, pregnenolone, progesterone and androstenedione, T production by testicular cells was decreased (P < 0.05). In contrast, genistein at lower dose (5 µM) did not affect the stimulatory effects of testosterone precursors. In conclusion, the inhibition of testosterone secretion by the phytoestrogens in gander Leydig cells did not depend on estrogen receptors. The suppression of steroidogenesis in these cells may be in part conducted by interaction of phytoestrogens with key steroidogenic enzymes. However, further studies are required to elucidate the phytoestrogen mechanism of action in gander testicular cells.

Immunolocalization of aquaporin-1, -5, and -7 in the avian testis and vas deferens.

Thirteen mammalian aquaporin (AQP) isoforms have been identified, and they have a unique tissue-specific pattern of expression. AQPs have been found in the reproductive system of both male and female humans, rats, and mice. However, tissue expression and cellular and subcellular localization of AQPs have been poorly investigated in the male reproductive system of birds. The localization of AQP subtypes (AQP1, 2, 3, 4, 5, 7, 8, 9, and 11) in the goose testis and vas deferens has been studied through immunohistochemistry and immunobloting. Interestingly, the testicular and deferential tissues were positive for AQP1, -5, and -7 but not the others. AQP1 immunoreactivity was detected in the capillary endothelial cells of testis and vas deferens. AQP5 was localized in the interstitial tissue of the testis, including Leydig cells, as well as in the basal cells of vas deferens. Double-labeling confocal microscopy revealed coexpression of AQP5 with capillary AQP1 in the testis. AQP7 was expressed in elongated spermatid and spermatozoa tails in the testis, as well as spermatozoa tails in the vas deferens. These results suggest that several subtypes of AQPs are involved in the regulation of water homeostasis in the goose male reproductive system.

Seasonal changes in the hypothalamo-pituitary-gonadal axis in birds.

Seasonal reproduction in birds is the adaptation to breed at the time of the greatest survival of young. This exact moment is mainly imposed by the photoperiod which stimulates the hypothalamo-pituitary-gonadal axis and starts breeding season. This article summarizes present knowledge concerning: 1/ perception and transduction of light into the biological signal; 2/ model of the avian photoperiodic response; 3/ seasonal changes in hypothalamic secretion of gonadotropin-releasing hormone (GnRH), vasoactive intestinal polipeptide (VIP), as well as the gonadotropin inhibitory hormone (GnIH); 4/ seasonal interactions between pituitary hormones; 5/ seasonal morphological and functional changes within the avian gonads.