Evidence of diadromy in the French Polynesian Kuhlia malo (Teleostei: Percoidei) inferred from otolith microchemistry analysis

Abstract – Strontium/Calcium (Sr/Ca) and Barium/Calcium (Ba/Ca) ratios were measured in 60 otoliths of the French Polynesian flagtail Kuhlia malo. Both elemental ratios were needed to correctly distinguish residence in marine, brackish and fresh water. High Sr/Ca and low Ba/Ca around the nucleus of all otoliths provided evidence of marine residency during the early life of all individuals. At about 0.5 mm from the core, Ba/Ca increased rapidly and remained high in all otoliths. High and unstable Sr/Ca ratios were attributed to estuarine residency, whereas low and stable Sr/Ca ratios were attributed to freshwater residency. These chemical signatures inferred that following recruitment to rivers, some fish remained in the estuary, while others moved upstream. Some individuals shared their time between fresh and brackish waters later in life. The findings of this study have important implications for the protection of nearshore, brackish and freshwater environments for the conservation of this French Polynesian diadromous species.     

Mechanisms of evolution in Rickettsia conorii and R. prowazekii

Rickettsia conorii is an obligate intracellular bacterium that causes Mediterranean spotted fever in humans. We determined the 1,268,755-nucleotide complete genome sequence of R. conorii, containing 1374 open reading frames. This genome exhibits 804 of the 834 genes of the previously determined R. prowazekii genome plus 552 supplementary open reading frames and a 10-fold increase in the number of repetitive elements. Despite these differences, the two genomes exhibit a nearly perfect colinearity that allowed the clear identification of different stages of gene alterations with gene remnants and 37 genes split in 105 fragments, of which 59 are transcribed. A 38-kilobase sequence inversion was dated shortly after the divergence of the genus.     

Simplified performance assessment methodology for addressing soil quality of nature-based solutions

Journal of Soils and Sediments - In urban areas, soil functions are deeply impacted by all human activities, e.g., water infiltration, carbon storage, and chemical substances degradation potential....     

Selfish DNA in protein-coding genes of Rickettsia

Rickettsia conorii, the aetiological agent of Mediterranean spotted fever, is an intracellular bacterium transmitted by ticks. Preliminary analyses of the nearly complete genome sequence of R. conorii have revealed 44 occurrences of a previously undescribed palindromic repeat (150 base pairs long) throughout the genome. Unexpectedly, this repeat was found inserted in-frame within 19 different R. conorii open reading frames likely to encode functional proteins. We found the same repeat in proteins of other Rickettsia species. The finding of a mobile element inserted in many unrelated genes suggests the potential role of selfish DNA in the creation of new protein sequences.     

Green roof ageing or Isolatic Technosol’s pedogenesis?

Purpose

Green roofs (GR) offer a way to improve several ecosystem services in cities. However, the performances of GR are basically considered as steady over time whereas they are living media subject to ageing that are rarely managed by their owners. This study transposes a pedological approach to evaluate changes in GR physical structure and chemical composition over time.

Materials and methods

A full-scale experimental plot with various vegetation cover was studied. A dedicated sampling strategy was implemented to monitor substrate’s evolution over 4 years. Then, physical and chemical characterisation (carbon and nitrogen contents, particle size distribution, porosity, soil water retention) was conducted and compared to results on the original substrate.

Results and discussion

The upper layer of the substrate (0 to 5 cm depth) contained a large amount of fine and short roots whereas the root density was much smaller in the lower layer of the substrate (5 to 10 cm depth). There was a global drop of the organic carbon content from 5 % in the initial substrate to 2 % in the 4-year-old substrate. On the contrary, the nitrogen concentration has increased by 0.4 % during the same period. The mesoporosity decreased drastically from 0.11 to 0.02 cm³ cm^?3. On the whole substrate, the <2-mm particles fraction was smaller after 4 years (12.5 %) than in the initial substrate (18.2 %) which was especially obvious in the upper horizon (9.5 %). Additionally, the monitored properties also varied significantly as a function of soil cover (sedum, moss and bare soil). Evidences of an early pedogenesis were highlighted such as poral evolution and fine particles eluviation.

Conclusions

In conclusion, the study demonstrated the effects of time, climate and vegetation on physical and chemical properties of green roof substrate. They are not only classified as Isolatic Technosols due to their composition and implementation; they also exhibit one of the major characteristic of young Technosols: a fast and intense pedogenesis.