Correlation between bioassay-derived P4501A1 induction activity and chemical analysis of clam (Laternula elliptica) extracts from McMurdo Sound, Antarctica

Variable levels of halogenated aromatic hydrocarbons were measured in clams (Laternula elliptica) collected from McMurdo Sound, Antarctica. Clams collected in and near Winter Quarters Bay contained high levels of organochlorine compounds, particularly polychlorinated biphenyls (PCBs). A strong gradient has been documented in Winter Quarters Bay that been linked to human activities at McMurdo Station. The activity of clam extracts as inducers of P4501A1-dependent ethoxyresorufin O-deethylase (EROD) activity was determined using in vitro bioassays utilizing rat hepatoma H4IIE cells. The extracts which exhibited the highest induction activities were those derived from clams collected in contaminated areas. Additionally, there was an excellent linear correlation between induced EROD activity versus total PCB levels (r²=0.96). The complimentary nature of both the analytical and bioanalytical data confirms the utility of the latter assay and provides a method for estimating the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) toxic equivalents in extracts from marine biota.     

Greening of arid cities by residual water reuse: a multidisciplinary project in northern Chile

This paper describes a project in northern Chile aimed to promote the development of appropriate green areas and gardens for arid regions under prevalent conditions of shortage of water and high salt content in soil and water. Field studies were conducted to test the suitability of selected salt-tolerant native and introduced plants for ornamental use. Plant growth, water and soil quality, marine spray, climate, wastewater treatment and irrigation operating problems were the subject of specific studies and discussion.     

Temporal variability of bioavailable Cd,Hg, Zn,Mn and Al in an upwelling regime

Monthly variability of Cd, Hg, Zn, Mn and Al concentrations in mussels (Mytilus californianus) soft tissue and brown seaweed (Macrocystis pyrifera) was studied at a pristine rocky shore off San Quintin Bay, Baja California, México. The results were related to climatic and hydrographic conditions and to the physiological state of the mussels (condition index) by correlation analysis and principal component analysis (PCA). A "normalization" to account for the variability induced by the physiological state of the mussel was performed. The PCA was performed in two ways to relate the environmental variables and the condition index to: (1) the metal concentrations in mussels, and (2) the "normalized" mussel concentrations. The association of the variability of Cd with the upwelling season was revealed in both PCAs. The temporal variability of this metal in mussels was highly correlated to that in seaweed, suggesting that the dissolved phase determined the variability of Cd in mussels. However, for Hg, Zn, Mn and Al the results from both PCAs were different. The first PCA showed the relationship of these metals to pluvial precipitation and to the condition index. The PCA for the normalized mussel concentrations showed that, after eliminating the effect of the condition index, only Al was related to pluvial precipitation. Manganese, and to a less degree Zn, were related to these metals in seaweed. Because zinc is an essential element in mussels, some regulation of their internal concentrations is likely. Mercury was not detected in seaweed, but because of its reactive nature, it is not expected that the dissolved fraction could be a significant pathway; therefore, it can be concluded that its temporal variability was determined by the variability in the condition index only.     

Ozone dynamics and deposition processes at a deforested site in the Amazon basin

The goal of this study is to investigate the impact of deforestation on ozone dynamics and deposition in the Brazilian Amazon basin. This goal is accomplished through i) analyses of ozone levels and deposition rates at a deforested site during the rainy season; and ii) comparisons of these data with similar information derived at a forest. At the pasture site maximum ozone mixing ratios reach 20 parts per billion on a volume basis (ppbv) but about 6 ppbv prevail over the forest. Maximum ozone deposition velocities for pastures can reach 0.7 cm s-1, which is about threefold lower than values derived for forests. Combining ozone abundance and deposition velocities, pasture maximum ozone fluxes reach approximately 0.2 microgram (ozone) m-2 s-1. This flux represents approximately 70% of the deposition rates measured over the forest. Hence, this study suggests that conversion of rainforests to pastures could lead to a net reduction (30%) in the ozone sink in the Amazon.     

Loss of mating opportunities influences refuge use in the Iberian rock lizard,<Emphasis Type="Italic"> Lacerta monticola</Emphasis>

Because time spent in refuge may be costly if prey lose opportunities to forage, fight, or mate, prey allow predators to approach closer before beginning to flee when opportunity costs are high. Because the same opportunity costs may apply to refuge use as to escape, prey should make similar trade-offs between risk of emerging and cost of remaining in refuge. In the Iberian rock lizard, Lacerta monticola, we studied the effects of sex, reproductive season, speed of predator approach, and potential loss of mating opportunities on time spent in refuge following simulated predatory attacks. Lizards of both sexes adjusted refuge use to the level of risk by spending more time in refuge when approached rapidly than slowly. Females remained in refuge for equal times in the mating and postreproductive seasons, but males emerged sooner during the mating season, suggesting adjustment to a cost of lost opportunity to search for mates during the mating season. When a tethered female was nearby, males emerged from refuge earlier than if no female was present, indicating a trade-off between risk and mating opportunity. Approach speed affected emergence time when females were absent, but not when a female was present. Approach speed did not affect the probability that, after emerging, a male would return to court the female. For males that courted females intensely (bit them) before entering refuge, approach speed did not affect latency to emerge, but males that courted less intensely emerged sooner if approached slowly than rapidly. These findings show that males adjust the length of time spent in refuge to both risk of predation and reproductive cost of refuge use.Communicated by A. Mathis     

Novel system of communication in crickets originated at the same time as bat echolocation and includes male-male multimodal communication

The Science of Nature - The capability of producing sounds and vibrations is well known in insects and is thought to be a form of intra- and interspecific communication. Sounds and vibrations are...