Glycogen in Crustacean Fast and Slow Muscles

Ultrastructural examination of crayfish superficial (tonic)and deep (phasic) abdominal extensor muscles reveals a distributionand quantitative difference in glycogen between these muscles.Both superficial and deep fibers have a dense accumulation ofglycogen in the interfibrillar sarcoplasm. In addition, thesuperficial extensors, but not the deep extensors, contain glycogenin the I band region. The glycogen granules are of the ßtype and can be removed enzymatically. The superficial medialand lateral fibers contain more glycogen than the medial andlateral deep fibers. A possible functional role for this differenceis suggested.     

Paternity exclusion in a community of wild chimpanzees using hypervariable simple sequence repeats

We report the use of hypervariable simple sequence repeat (SSR) nuclear loci to study paternity in a community of wild chimpanzees ( Pan troglodytes schweinfurthii ) in Gombe National Park, Tanzania. All 43 living members of a habituated community were sampled and 35 were genotyped at 8 SSR loci using DNA amplified from hair. Paternity exclusions were performed for 25 chimpanzees including 10 for whom the mother was also genotyped. In each case 12–20 males were potential fathers based on their age and/ or direct observation of sexual behaviour. 179 tests involving potential father/offspring combinations were performed. In four cases the data permit the probable identification of the previously undetermined father; these are the first such determinations for free-ranging chimpanzees, and the first based on non-invasive sampling. In another four cases we were able to exclude all but two to five potential fathers, and in the remaining cases we were able to exclude all living males. For molecular ecologists SSR genotype databases offer important advantages over currently popular minisatellite DNA fingerprinting: they can be analysed unequivocally using traditional population genetics techniques and they can be expanded through time and space by other researchers.     

Diatom immigration drives biofilm recovery after chronic copper exposure

1. The impact of immigration on the recovery of diatom assemblages after chronic exposure to copper was investigated in laboratory microcosms. 2. We examined the recovery trajectories of copper‐contaminated biofilms after reducing copper stress and with or without the possibility of immigration from unimpaired communities. 3. The biofilms mixed with unimpaired communities returned to a ‘control’ assemblage structure within 6 weeks, with recovery patterns depending on the endpoint considered (i.e. 2 weeks for relative abundances of diatom species but 6 weeks for total diatom biomass). In contrast, no recovery was observed in assemblages placed under control conditions without external immigrants. 4. Immigration has important effects on the recovery of quantitative and qualitative characteristics of biofilms.     

Transformation of vivianite by anaerobic nitrate-reducing iron-oxidizing bacteria

In phosphate-rich environments, vivianite (Fe^II₃(PO₄)₂, 8H₂O) is an important sink for dissolved Fe(II) and is considered as a very stable mineral due to its low solubility at neutral pH. In the present study, we report the mineralogical transformation of vivianite in cultures of the nitrate-reducing iron-oxidizing bacterial strain BoFeN1 in the presence of dissolved Fe(II). Vivianite was first transformed into a greenish phase consisting mostly of an amorphous mixed valence Fe-phosphate. This precipitate became progressively orange and the final product of iron oxidation consisted of an amorphous Fe(III)-phosphate. The sub-micrometer analysis by scanning transmission X-ray microscopy of the iron redox state in samples collected at different stages of the culture indicated that iron was progressively oxidized at the contact of the bacteria and at a distance from the cells in extracellular minerals. Iron oxidation in the extracellular minerals was delayed by a few days compared with cell-associated Fe-minerals. This led to strong differences of Fe redox in between these two types of minerals and finally to local heterogeneities of redox within the sample. In the absence of dissolved Fe(II), vivianite was not significantly transformed by BoFeN1. Whereas Fe(II) oxidation at the cell contact is most probably directly catalyzed by the bacteria, vivianite transformation at a distance from the cells might result from oxidation by nitrite. In addition, processes leading to the export of Fe(III) from bacterial oxidation sites to extracellular minerals are discussed including some involving colloids observed by cryo-transmission electron microscopy in the culture medium.     

Xylem phenology and wood production: resolving the chicken‐or‐egg dilemma

Delays in the start of the growing season reduce the period available for growth and the amount of xylem production. However, a higher number of developing tracheids could prolong cell differentiation and, consequently, lengthen the growing season. The relationship between the amount and duration of cell production in the xylem remains an unresolved issue. The aim of this study was to resolve the chicken‐or‐egg causality dilemma about duration of growth and cell production through simple‐ and double‐cause models. This was achieved by (1) analysing the intra‐annual growth dynamics of the xylem in Picea mariana (Mill.) BSP during 2006–2009 in two contrasting sites of the boreal forest of Quebec, Canada, and (2) extracting the dates of onset and ending of xylem formation and the number of radial cells along the tree ring. A higher number of cells was linked to an earlier onset (r = 0.74) and later ending (r = 0.61) of cell differentiation. The absence of a relationship between the residuals of the onset and ending of xylogenesis (r_p = ?0.06) indicated that cell production influenced the correlation between the two phenophases of the xylem. These results demonstrated that a higher number of cells produced delay the ending of xylem maturation, so extending the duration of wood formation.