Occurrence of two forms of Y chromosome in rainbow trout (Oncorhynchus mykiss) males from Rutki strain

Morphologically differentiated sex chromosomes are found in only few salmonid species. Some populations of rainbow trout, Oncorhynchus mykiss, exhibit chromosomal polymorphism related to sex. We found sex-related chromosomal polymorphism in fish from the synthetic Rutki strain, Poland, in approximately 85% (n = 22) of examined males (XY-like) whereas the remaining males (n = 4) possessed chromosomes similar to these observed in females (XX-like). To investigate whether males possessing XX-like chromosomes were genotypic males or genotypic females with altered phenotypic sex, androgenetic progeny of four males (representing both XY-like and XX-like forms, n = 2 + 2) was examined. Androgenetic progeny (F₁) of all four fathers consisted of both phenotypic females and males. F₁ male progeny of two fathers showed XX-like chromosomes whereas F₁ male progeny of the other two fathers possessed YY-like (supermale) chromosomes. F₁ were reared further until they were sexually mature. Two males from each of four F₁ families were used to produce F₂ androgenetic and control F₂ generation. All F₂ individuals, androgenetics and control, were phenotypic males at sexual maturation. The results indicate that males possessing XX-like chromosomes are genetic males and they are not sex-reversed females. Thus, the Y chromosome can exist in different morphological forms in farmed rainbow trout. The Y^S chromosome (shorter form, unlike the X chromosome) has a shorter or absent p-arm and lacks the pericentromeric cluster of AT-rich chromatin and the 5S rDNA sequences that are found in the Y^L chromosome (longer form, like the X chromosome).     

Opportunities and challenges for analysis of wildlife trade using CITES data – seahorses as a case study

相似文献   

Magnitude and Occurrence Probability of Soil Loss: A Risk Analytical Approach for the Plot Scale For Two Sites in Lower Austria

Long‐term contribution of soil loss events depends on both – the magnitude and the occurrence probability – but oftentimes, a limited observation period impedes the assessment of the temporal soil loss distribution. In this research, the event‐based soil loss from two plot locations in Lower Austria (Mistelbach and Pixendorf) was linked with the event‐based rainfall erosivity (EI₃₀) to assess the temporal soil loss distribution using long‐term rainfall data from two meteorological stations in Lower Austria. For both plot locations, a risk analysis was performed to (i) assess the long‐term average annual soil loss and to (ii) evaluate the contribution of incremental erosion events according to different event return periods. The risk analysis showed that in Pixendorf the events <20 years return period dominatingly contribute to long‐term soil loss, because the contribution of the events >20 years return period is progressively reduced through the low occurrence probability. On the contrary, in Mistelbach the soil loss magnitudes of the extreme events overcome the effect of the low occurrence probability, and consequently, the contribution of the extreme events (>20 years return period) is dominant. The spatially variable contribution of the erosion events reveals the need for spatially customized soil conservation strategies. A risk analytical approach may help to allocate the driving events and thus to define proper event design magnitudes for local soil conservation planning. Copyright © 2014 John Wiley & Sons, Ltd.