Are phthalate ester contaminants in northern fulmar preen oil higher in birds that have ingested more plastic?

Degradation of dimethyl isophthalate (DMI) and dimethyl phthalate ester (DMPE) was investigated using microorganisms isolated from mangrove sediment of Hong Kong Mai Po Nature Reserve. One enrichment culture was capable of utilizing DMI as the sole source of carbon and energy, but none of the bacteria in the enrichment culture was capable of degrading DMI alone. In co-culture of two bacteria, degradation was observed proceeding through monomethyl isophthalate (MMI) ester and isophthalic acid (IPA) before the aromatic ring opening. Using DMI as the sole carbon and energy source, Klebsiella oxytoca Sc and Methylobacterium mesophilicum Sr degraded DMI through the biochemical cooperation. The initial hydrolytic reaction of the ester bond was by K. oxytoca Sc and the next step of transformation was by M. mesophilicum Sr, and IPA was degraded by both of them. In another investigation, a novel bacterium, strain MPsc, was isolated for degradation of dimethyl phthalate ester (DMPE) also from the mangrove sediment. On the basis of phenotypic, biochemical and 16S rDNA gene sequence analyses, the strain MPsc should be considered as a new bacterium at the genus level (8% differences). This strain, together with a Rhodococcus zopfii isolated from the same mangrove sediment, was able to degrade DMPE aerobically. The consortium consisting of the two species degraded 450mg/l DMPE within 3 days as the sole source of carbon and energy, but none of the individual species alone was able to transform DMPE. Furthermore, the biochemical degradation pathway proceeded through monomethyl phthalate (MMP), phthalic acid (PA) and then protocatechuate before aromatic ring cleavage. Our results suggest that degradation of complex organic compounds including DMI and DMPE may be carried out by several members of microorganisms working together in the natural environments.

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Uropygial gland and bib colouration in the house sparrow

10.7287/peerj.preprints.1774v1 ◽

2016 ◽

Author(s):

Gregorio Moreno-Rueda

Keyword(s):

Body Condition ◽

Passer Domesticus ◽

Uropygial Gland ◽

Short Term ◽

House Sparrows ◽

Gland Size ◽

Plumage Colouration ◽

Preen Oil ◽

Male House

Birds frequently signal different qualities by plumage colouration, mainly during mating. However, plumage colouration is determined during the moult, and therefore it would indicate the quality of individual birds during the moult, not its current quality. Recent studies, however, suggest that birds could modify plumage colouration by using cosmetic preen oil. In this study, I show that bib colouration is related to uropygial gland size and body condition in male house sparrows (Passer domesticus). Moreover, I conducted an experiment in which a group of sparrows were inoculated with an antigen, mimicking an illness. In control birds, short-term changes in bib colouration were related to both body condition and change in uropygial gland size. Therefore, birds that spent more preen oil (thus, reducing uropygial gland size), showed a greater colouration change. However, bib colouration did not change with use of preen oil in experimental birds inoculated with the antigen. That is, the simulated illness cancelled the effect of preen oil on bib colouration. Given that the experiment did not affect preen oil production, this finding suggests that the immune challenge provoked a change in the composition of preen oil, affecting its cosmetic properties. In short, the results of this study suggest that (1) male house sparrows produce cosmetic preen oil that alters the colouration of their bibs; (2) the more effort in preening, the more change in bib colouration; and (3) in this way, bib colouration has the potential to signal current health status, since less healthy birds showed less capacity to change bib colouration.

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