Cytogenetic and histological studies of the brook trout, Salvelinus fontinalis (Mitchill), and the Arctic char, S-alpinus (L.) hybrids

Although brook trout and the Arctic char hybrids are able to reproduce, individuals with decreased fertility or even fish that are unable to produce any gametes have been also described. Abnormal gonadal development and disturbances in the gamete production in the char hybrid offspring may be triggered by the odd chromosome number and disturbances in their pairing during meiosis. To verify this hypothesis, cytogenetic examination and the gonadal histology analysis of the brook trout x Arctic char hybrids were carried out. Diploid chromosome number in the studied char (F-1) hybrids varied from 82 to 84 (FN = 99-102). Among 28 hybrids, 12 males, three females, nine intersex individuals and two sterile specimens were described. In the case of two individuals, gonads were not found. Diploid chromosome numbers in the males and intersex individuals varied from 82 to 84. Chromosome numbers in the females were 82 and 83 chromosomes. Two sterile fish exhibited karyotypes composed of 82 and 84 chromosomes. Predominance of the ovarian component in the intersex gonads and gonadal sex ratio distortion towards the males suggested hybrid females had problems with gonadal differentiation. However, the lack of the clear relationship between chromosome number and gonadal development in the studied hybrids did not support our hypothesis that odd chromosome number may be responsible for such reproductive disturbances in the hybrid individuals. We have presumed that sterility and intersexual development of the gonads may be caused by interactions between brook trout and Arctic char genes on the sex chromosomes and autosomes rather than unpairing of the parental chromosomes.Polish National Science Center (NCN) [N N311 525240]info:eu-repo/semantics/publishedVersio

Degradation of Potassium Rock by Earthworms and Responses of Bacterial Communities in Its Gut and Surrounding Substrates after Being Fed with Mineral

BACKGROUND: Earthworms are an ecosystem's engineers, contributing to a wide range of nutrient cycling and geochemical processes in the ecosystem. Their activities can increase rates of silicate mineral weathering. Their intestinal microbes usually are thought to be one of the key drivers of mineral degradation mediated by earthworms,but the diversities of the intestinal microorganisms which were relevant with mineral weathering are unclear. METHODOLOGY/PRINCIPAL FINDINGS: In this report, we show earthworms' effect on silicate mineral weathering and the responses of bacterial communities in their gut and surrounding substrates after being fed with potassium-bearing rock powder (PBRP). Determination of water-soluble and HNO(3)-extractable elements indicated some elements such as Al, Fe and Ca were significantly released from mineral upon the digestion of earthworms. The microbial communities in earthworms' gut and the surrounding substrates were investigated by amplified ribosomal DNA restriction analysis (ARDRA) and the results showed a higher bacterial diversity in the guts of the earthworms fed with PBRP and the PBRP after being fed to earthworms. UPGMA dendrogram with unweighted UniFrac analysis, considering only taxa that are present, revealed that earthworms' gut and their surrounding substrate shared similar microbiota. UPGMA dendrogram with weighted UniFrac, considering the relative abundance of microbial lineages, showed the two samples from surrounding substrate and the two samples from earthworms' gut had similarity in microbial community, respectively. CONCLUSIONS/SIGNIFICANCE: Our results indicated earthworms can accelerate degradation of silicate mineral. Earthworms play an important role in ecosystem processe since they not only have some positive effects on soil structure, but also promote nutrient cycling of ecosystem by enhancing the weathering of minerals

Cryptic Diversity of African Tigerfish (Genus Hydrocynus) Reveals Palaeogeographic Signatures of Linked Neogene Geotectonic Events

The geobiotic history of landscapes can exhibit controls by tectonics over biotic evolution. This causal relationship positions ecologically specialized species as biotic indicators to decipher details of landscape evolution. Phylogeographic statistics that reconstruct spatio-temporal details of evolutionary histories of aquatic species, including fishes, can reveal key events of drainage evolution, notably where geochronological resolution is insufficient. Where geochronological resolution is insufficient, phylogeographic statistics that reconstruct spatio-temporal details of evolutionary histories of aquatic species, notably fishes, can reveal key events of drainage evolution. This study evaluates paleo-environmental causes of mitochondrial DNA (mtDNA) based phylogeographic records of tigerfishes, genus Hydrocynus, in order to reconstruct their evolutionary history in relation to landscape evolution across Africa. Strong geographical structuring in a cytochrome b (cyt-b) gene phylogeny confirms the established morphological diversity of Hydrocynus and reveals the existence of five previously unknown lineages, with Hydrocynus tanzaniae sister to a clade comprising three previously unknown lineages (Groups B, C and D) and H. vittatus. The dated phylogeny constrains the principal cladogenic events that have structured Hydrocynus diversity from the late Miocene to the Plio-Pleistocene (ca. 0–16 Ma). Phylogeographic tests reveal that the diversity and distribution of Hydrocynus reflects a complex history of vicariance and dispersals, whereby range expansions in particular species testify to changes to drainage basins. Principal divergence events in Hydrocynus have interfaced closely with evolving drainage systems across tropical Africa. Tigerfish evolution is attributed to dominant control by pulses of geotectonism across the African plate. Phylogenetic relationships and divergence estimates among the ten mtDNA lineages illustrates where and when local tectonic events modified Africa's Neogene drainage. Haplotypes shared amongst extant Hydrocynus populations across northern Africa testify to recent dispersals that were facilitated by late Neogene connections across the Nilo-Sahelian drainage. These events in tigerfish evolution concur broadly with available geological evidence and reveal prominent control by the African Rift System, evident in the formative events archived in phylogeographic records of tigerfish

Primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an immune-mediated chronic cholestatic liver disease with a slowly progressive course. Without treatment, most patients eventually develop fibrosis and cirrhosis of the liver and may need liver transplantation in the late stage of disease. PBC primarily affects women (female preponderance 9–10:1) with a prevalence of up to 1 in 1,000 women over 40 years of age. Common symptoms of the disease are fatigue and pruritus, but most patients are asymptomatic at first presentation. The diagnosis is based on sustained elevation of serum markers of cholestasis, i.e., alkaline phosphatase and gamma-glutamyl transferase, and the presence of serum antimitochondrial antibodies directed against the E2 subunit of the pyruvate dehydrogenase complex. Histologically, PBC is characterized by florid bile duct lesions with damage to biliary epithelial cells, an often dense portal inflammatory infiltrate and progressive loss of small intrahepatic bile ducts. Although the insight into pathogenetic aspects of PBC has grown enormously during the recent decade and numerous genetic, environmental, and infectious factors have been disclosed which may contribute to the development of PBC, the precise pathogenesis remains enigmatic. Ursodeoxycholic acid (UDCA) is currently the only FDA-approved medical treatment for PBC. When administered at adequate doses of 13–15 mg/kg/day, up to two out of three patients with PBC may have a normal life expectancy without additional therapeutic measures. The mode of action of UDCA is still under discussion, but stimulation of impaired hepatocellular and cholangiocellular secretion, detoxification of bile, and antiapoptotic effects may represent key mechanisms. One out of three patients does not adequately respond to UDCA therapy and may need additional medical therapy and/or liver transplantation. This review summarizes current knowledge on the clinical, diagnostic, pathogenetic, and therapeutic aspects of PBC

Extraction of a synthetic androgen from fish muscle and quantitation by high performance liquid chromatography.

A rapid, reproducible extraction procedure was developed to recover the synthetic androgen 17 alpha-methyltestosterone (MT) from fish muscle. A single extraction with chloroform-methanol (2:1 V/V), followed by elution from mini-columns with various methanol concentrations, yielded an extraction efficiency of greater than 70%. Resolution of MT from testosterone was complete and reliable quantitation was achieved utilizing reversed-phase high performance liquid chromatography. Endogenous testosterone was not detectable in 1-g muscle samples, but MT was detected in fish muscle 6 h after adult Tilapia aurea were fed a diet containing the steroid

Tissue distribution and elimination of radiolabelled methyltestosterone fed to sexually undifferentiated blue tilapia

Populations of monosex male Oreochromis aureus can result when the synthetic androgen 17α-methyltestosterone (MT) is fed to sexually undifferentiated fish; however, concerns exist over residues of the androgen remaining in fish destined for human consumption. Radioactivity in the carcass and viscera was evaluated in juvenile fish fed steroid-incorporated diet (tritium and carbon-14 labelled MT and 30 μg unlabelled MT/g feed) for 21 days, and depletion was monitored for 21 days after return to an untreated diet. Radioactivity was detected in the carcass within 1 h after initial feeding and reached highest levels by 6 h. Most of the radioactivity (> 90%) was in the viscera during the 21 days the radio-labelled diet was being fed. Radioactivity was eliminated exponentially, decreasing by 90% within 24 h after the last feeding. After 21 days of feeding untreated diet, < 1% of the original radioactivity remained (representing about 5 ng MT/g of tissue), and was evenly distributed between carcass and viscera. The observed low levels of residual radioactivity at conclusion of the sex reversal period, as well as anticipated dilution through growth during the culture of fish to marketable size, support the conclusion that no potential health hazard exists for people who eat fish that have been fed MT as juveniles. © 1986

Sex genotype and sex phenotype contribute to growth differences between male and female channel catfish

Channel catfish Ictalurus punctatus have an XX female-XY male genotypic system of sex determination, and male channel catfish grow faster than females. Through selective breeding and appropriately timed hormone administration, we have produced phenotypic male channel catfish with a YY sex genotype and female channel catfish with an XY or YY sex genotype. In this study, we evaluated the relative role of sex genotype and sex phenotype in regulating sexually dimorphic growth in this important aquaculture species. Ten families of genotypic XY male fish were produced by matings of normal XX female fish with YY male fish, and females were produced by hormonal feminization of a subsample from each family. The growth rate and body composition of sibling males and females in ponds where the sexes were maintained together were compared with those in ponds where the sexes were maintained separately. Generally, phenotypic males had higher body weight (15.25% and 11.36% when the sexes were together or separated, respectively), standard length (3.28% and 2.24%, respectively), and condition factor (2.94 and 2.65, respectively), while phenotypic females had higher liposomatic index (7.11% and 13.69%, respectively) and dress-out percentage (0.91% and 1.06%, respectively). Statistical differences between the phenotypic sexes were not as consistent as observed in previous studies with normal males and females because growth and body composition differences were enhanced when the sexes were maintained together; however, monosex culture restrained these differences. These results demonstrate that sex genotype and sex phenotype both contribute to the male growth advantage in channel catfish and provide further evidence that monosex male culture would produce an economic gain of about 5% for the industry compared with conventional mixed-sex culture. © Copyright by the American Fisheries Society 2007