In vitro and in vivo studies of lead immobilization by synthetic hydroxyapatite

Apatite appears a useful compound for removing lead from water, due to its ability to immobilize the metal by precipitation. In dilute solution, dissolved hydroxyapatite [HA, Ca1O(P04)6(OH)2] provided phosphates that were reactive with aqueous lead (molar ratio HA/Pb= 1/10) forming precipitates at around pH 6. These dissolved at a more acidic pH (3). Solid HA in contact with Pb2+ions, led to the formation of pyromorphite [Pblo(P04)6(OH)2], identified by X-ray diffraction and insoluble at pH tested (3-8). The amount of pyromorphite increased with the weight ratio of HA/Pb. When this one increased from 1 to 1000, lead precipitated as pyromorphite rose from 19 to 99%. In vivo experiments on rats confirmed the in vitro results. In fact, lead bioavailability assessed by intestinal perfusion was unchanged in the presence of dissolved HA, whereas it was significantly lower in the presence of solid HA, evaluated by gastric intubation, at a weight ratio equal to 10 (amount of lead absorbed decreased by 60%). Apatite could bean effective means of immobilizing lead in drinking or sewage, since accidental pyromorphite ingestion does not yield bioavailable lead.     

4-n-Nonylphenol and 17-beta estradiol may induce common DNA effects in developing barnacle larvae

There is a growing concern over the potential effects of environmental endocrine disrupters on both human and wildlife populations. However, to date, minimal research has been conducted to determine the effect of estrogens and xenoestrogens at the DNA level. In this study, we used the random amplified polymorphic DNA (RAPD) assay to evaluate the effects on the genomic DNA of barnacle larvae that had been exposed to 17beta-estradiol (E2) and low concentrations of 4-n-nonylphenol (NP). DNA effects include DNA damage as well as mutations and possibly other effects at the DNA level that can be induced by chemical or physical agents that directly and/or indirectly interact with genomic DNA. Not only did exposure to NP and E2 induce changes in RAPD profiles in the exposed barnacle larvae when compared to control patterns, but also, and more importantly, there were similarities in the RAPD modifications in the exposed populations that had been treated to either chemical. We propose that NP and E2 induced some common DNA effects in barnacle larvae and that these specific modifications in RAPD patterns may arise as a consequence of hot spot DNA damage (e.g. DNA adducts) and/or mutations (point mutations or genomic rearrangements). This could help to explain how xenoestrogens mimic the effects produced by natural estrogens. In conclusion, in the field of endocrine disruption, the study of DNA effects induced by estrogens and/or xenoestrogens warrants further investigation. Indeed, changes at the DNA levcl may be the precursors of some of the numerous effects reported at higher levels of biological organisation such as the feminization of males, developmental abnormalities, and infertility.     

Escalating fights for rank-order position between male swordtails (Xiphophorus helleri): Effects of prior rank-order experience and information transfer

Summary A previous hypothesis which we originally based on standardized mirror tests was examined. It stated that subordinate males from socially stabilized groups, when confronted with a strange male of similar fighting ability, tend to take the offensive; in contrast, dominant males tend to wait and see and to increase their aggressiveness only as far as necessary to counter the aggressive actions of the opponent. 30 highly escalating fights between well matched opponents, either with different or with the same prior rank-order experience, were recorded on video tape and then analysed in detail. Rank-order experience affected neither the escalation level nor the outcome of the fights. However, in the first nonescalated stage of the fights all measures of unilateral aggressive actions were higher in the omega than in the alpha males. This is contrary to expectations based on the theory of social conditioning; nor can it yet be explained by game-theory models. We then discuss why it should pay subordinates to be more offensive and to show higher levels of unilateral aggression than dominants. Some current aspects of game theory are supported by our data: (1) Threat display is a poor predictor of attack and fleeing, and simply informs the opponent that the threatening individual will probably just stay and avoid further escalations. (2) Relative fighting ability is demonstrated during highly-escalated fighting by delivering Fin Grips, the most effective and costly attack pattern. The high energetic costs of Fin Grips can be compensated by reducing the rate of Biting. (3) Probably, the combatants did not transfer information about their intentions, i.e. they concealed their intentions as to what they were going to do next. Contrary to the predictions of game theory, winners and losers showed some differences in Pecking early in the nonescalated stage of the fights, the prospective losers exhibiting more Pecking than the winners.This study was supported by grants from the Deutsche Forschungsgemeinschaft     

Global effects of extreme temperatures on wild bumblebees

Climate plays a key role in shaping population trends and determining the geographic distribution of species because of limits in species’ thermal tolerance. An evaluation of species tolerance to temperature change can therefore help predict their potential spatial shifts and population trends triggered by ongoing global warming. We assessed inter- and intraspecific variations in heat resistance in relation to body mass, local mean temperatures, and evolutionary relationships in 39 bumblebee species, a major group of pollinators in temperate and cold ecosystems, across 3 continents, 6 biomes, and 20 regions (2386 male specimens). Based on experimental bioassays, we measured the time before heat stupor of bumblebee males at a heatwave temperature of 40 °C. Interspecific variability was significant, in contrast to interpopulational variability, which was consistent with heat resistance being a species-specific trait. Moreover, cold-adapted species are much more sensitive to heat stress than temperate and Mediterranean species. Relative to their sensitivity to extreme temperatures, our results help explain recent population declines and range shifts in bumblebees following climate change.     

Invasion costs,impacts, and human agency: response to Sagoff 2020

Article impact statement: In an era of profound biodiversity crisis, invasion costs, invader impacts, and human agency should not be dismissed.