[A series of mutable alleles of the white locus in Drosophila melanogaster]

Habitat compression and ecosystem shifts as potential links between marine heatwave and record whale entanglements

Climate change and increased variability and intensity of climate events, in combination with recovering protected species populations and highly capitalized fisheries, are posing new challenges for fisheries management. We examine socio-ecological features of the unprecedented 2014–2016 northeast Pacific marine heatwave to understand the potential causes for record numbers of whale entanglements in the central California Current crab fishery. We observed habitat compression of coastal upwelling, changes in availability of forage species (krill and anchovy), and shoreward distribution shift of foraging whales. We propose that these ecosystem changes, combined with recovering whale populations, contributed to the exacerbation of entanglements throughout the marine heatwave. In 2016, domoic acid contamination prompted an unprecedented delay in the opening of California’s Dungeness crab fishery that inadvertently intensified the spatial overlap between whales and crab fishery gear. We present a retroactive assessment of entanglements to demonstrate that cooperation of fishers, resource managers, and scientists could mitigate future entanglement risk by developing climate-ready fisheries approaches, while supporting thriving fishing communities.

Climate-driven extreme events may have strong local impacts on marine organisms and fisheries. Here the authors report increased whale entanglements in the northeast Pacific following a marine heatwave, and propose compression of coastal upwelling habitat as the potential driver.

Tandem duplications in Drosophila melanogaster. III. Intrachromosomal exchange of a heterozygous tandem duplication

During meiosis the two parts of a tandem duplication are able to pair in a double loop instead of pairing with the corresponding region of the homologous chromosome. The frequency of intrachromosomal exchange within this double loop was measured in heterozygous females of tandem duplicationDp(1; 1)Grby the phenotypes of the exceptional F1males. The intrachromosomal exchange frequency is increased significantly by both the ‘interchromosomal effect’ of heterozygous inversions in the autosomes and by a double inversion in the homologousXchromosome. Distribution of the exchange events depends on the pairing situation and its frequency within the double loop. The analysis of clusters of intrachromosomal recombinants observed favours the assumption that this exchange type is exclusively a meiotic event.

Tandem duplications in Drosophila melanogaster II. Meiotic pairing and exchange in heterozygous tandem duplications

In heterozygous females of tandem duplication Dp(1; 1) Gr, y(2) (w(-)spl sn(3)) (w(c) sn(3)) the frequency and distribution of exchange events were measured by the phenotypically different F1 recombinants. In comparison with wild type chromosomes the crossover values were strongly reduced within the heterozygous chromosome sections (between white and singed from 19.5 per cent to 2.1 per cent). Additionally, there was 0.24 per cent intrachromosomal exchange in the same chromosome section after the formation of a double loop (Fig.2). Crossing over was also reduced in both chromosome regions adjacent to the heterozygous duplication. A comparison of the conceivable pairing configurations with those configurations which are indicated by the recombinants gives an initial insight into the pairing behaviour of heterozygous tandem duplications during meiosis. The hypothesis of "polarized pairing" in Drosophila melanogaster is disproved by this kind of experiment.Crossover values within and adjacent to the duplication were also measured in heterozygous tandem duplications differing in the genetic length of their duplicated section. Here, meiotic pairing behaviour was found to depend on the genetic length and other parameters of the duplicated section. Conceivable sources for the different kinds of behaviour are discussed.