Chemical defense: incorporation of diet-derived pyrrolizidine alkaloid into the integumental scales of a moth (<Emphasis Type="Italic">Utetheisa ornatrix</Emphasis>)

Summary. Evidence is presented that pyrrolizidine alkaloid acquired by Utetheisa ornatrix (Lepidoptera, Arctiidae) as a larva from Crotalaria foodplants is incorporated in part into the scales of the adult. A single forewing of a male or female moth may contain in the order of 6 to 13 g monocrotaline in its scale cover or about 1 to 2% of the moths systemic monocrotaline content. Based on estimates of the number of scales per forewing, the monocrotaline content of individual scales is calculated to be in the order of 0.1 and 0.2 ng monocrotaline per male and female scale, respectively. This amounts to concentrations of about 1 and 3%, values roughly at a par with the average systemic concentration (0.5-0.6%) previously determined for monocrotaline in Utetheisa. It is argued that the presence of pyrrolizidine alkaloid in the moths scale coating could account for the promptness with which adult Utetheisa are rejected by spiders. It is suggested further that chemical impregnation of scales with substances deterrent to predators may be more widespread among insects than generally assumed.     

Diel and seasonal changes in the distribution of fish on a southeast Brazil sandy beach

The effect of diel and seasonal changes in the distribution of fishes on a subtropical sandy beach on the southeastern coast of Brazil were studied. Seine netting was carried out on both seasonal and diel scales between July 1998 and June 1999. A total of 46 fish species was recorded, six being numerically dominant: Anchoa tricolor, Gerres aprion, Harengula clupeola, Atherinella brasiliensis, Mugil liza and Diapterus rhombeus. Seasonal changes in abundance of dominant species were detected. Species dominant in winter were Anchoa tricolor, H. clupeola and Atherinella brasiliensis; in spring, Anchoa tricolor and G. aprion; in summer G. aprion and D. rhombeus; and in autumn M. liza and H. clupeola. Overall, diel patterns did not reveal any significant trends; however, if we consider each season separately, an increase in A. tricolor abundance was recorded during the day in winter/spring, being replaced at night by H. clupeola in winter, and by G. aprion in spring. Increases in number of individuals and biomass at sunset, and decreases during the night were recorded. The winter/spring inshore/offshore movements at diel scale performed by the three most abundant species demonstrate that diel fluctuation acts more at a species-specific level than at a structural one; in summer there was no evidence of diel movements due to a heavy influx of G. aprion and D. rhombeus, which use the area throughout day and night, increasing overall abundance. Seasonal movements seems to be related to ontogenetic change in species, while diel movements in the fish assemblage seem to be more related to physiological requirements, such feeding activity of each particular species, than to physico-chemical conditions.Communicated by O. Kinne, Oldendorf/Luhe     

Variation and persistence of the middle rocky intertidal community of central Chile,with and without human harvesting

Humans are an important intertidal predator in central Chile. Following a five-year study we report on the effects of the exclusion of humans from the rocky intertidal at Las Cruces, central Chile. The middle intertidal of harvested and non-harvested areas diverged in species diversity and composition during the experiment. In harvested areas the middle intertidal rocky shore was dominated throughout the study by a monoculture of mussels, Perumytilus purpuratus. When humans were excluded, the middle intertidal community switched to one dominated by barnacles (predominantly Jehlius cirratus and Chthamalus scabrosus); this community has persisted for at least three years, despite the presence of forces e.g. mussel larvae, that have the potential to alter the community structure. Such changes were mediated by the muricid gastropod Concholepas concholepas, a key-stone predator. As a consequence of the above changes, the species diversity, H', (primary space occupiers) in the non-harvested area increased from H'=0 at the beginning of the study in 1983 (when the middle intertidal community was dominated by mussels), to values ca H'=2 toward the middle of the study in 1984 (which coincided with the maximum predatory impact of C. concholepas) and subsequently decreasing to ca H'=0.5 at the end of the study in 1987 (when the middle intertida community was dominated by barnacles).Please address all correspondence to J. C. Castilla, Department of Zoology, University of Washington, Seattle, Washington 98195, USA, until March 1990     

Accumulation of mesozooplankton in a wake area as a causative mechanism of the “island-mass effect”

Mesozooplankton biomass (as displacement volume and protein content) and electron-transport system (ETS) activity have been studied in the coastal waters around the Canary Islands. Increases in biomass and ETS activity, on a unit volume basis, were observed in the wakes of the islands. The biomass values obtained in the leeward area for Gran Canaria Island were up to ten times higher than those observed for typical oceanic waters around this archipelago. Sampling was performed in May 1986 at the end of the characteristic vertical mixing period in these waters. Relatively strong winds were recorded prior to sampling. Specific ETS activity was higher at the windward stations on the island shelf. This correlates with the observation in a recent study of increased primary production on the shelf area, where turbulence produced by the northerly trade winds has a marked effect. The persistence of this turbulence during a prolonged wind-pulse results in an accumulation of organisms in the wake of the islands due to current dynamics. This process is proposed as being an important causative mechanism of the island-mass effect. Different biomass values were recorded between circular and oblong islands. The latter are oriented towards the current and the northerly trade winds, and display significantly lower biomass values than the former.     

Deposition and Fate of Lead in a Forested Catchment, Lesni Potok, Central Czech Republic

The deposition of trace elements and their fate in a forest ecosystemhas been monitored at the experimental site, Lesni Potok catchment (LP), with granite bedrock. The catchment is located 30 km ESE from Prague. Annual bulk Pb-deposition flux F_Pb was 3.41 kg km^-2 a^-1 in 1994 and gradually decreased to 0.49 kg km^-2 a^-1 in 2001. The decrease is comparable with those observed in Germany and in the U.S.A. in the 1970s and 1980s. The total sales ban of leaded gasoline in the Czech Republic since January 2001 was accompanied by a pronounced decrease of F_Pb in a single year. The residual Pb-deposition flux is assigned to both the long-range transport of fine-grained vehicular lead aerosol (with a long residence time in the atmosphere) and to theemissions from power plant boilers burning lignite mined in the Czech northwest coal basin. The F_Pb of lead correlates stronglywith those of As, Cd, Cu, Zn and Be, the typical metals in coal fly ash, at two monitored sites. Topsoil horizons contain elevated concentrations of Pb (53–67 mg kg^-1), which are of anthropogenicorigin. Soils in the riparian areas contain increased concentrations of Pb when compared to soils on the hillslope areas. Significant amounts of Pb were found on a stream substrate and Fe-precipitate sampled from the stream. Low concentrations of Pb in bark and bole wood suggest that the uptake of Pb by vegetation is negligible. The very small surface water outputs (average of 0.002 kg km^-2 a^-1) compared to inputs (average of 1.890 kg km^-2 a^-1) from the LP catchment indicate an ongoing accumulation of Pb in a forested landscape.     

Spatial and temporal patterns and the socioeconomic impacts of landslides in the tropical and mountainous Colombian Andes

Landslides are a natural hazard that presents a major threat to human life and infrastructure. Although they are a very common phenomenon in Colombia, there is a lack of analysis that entails national and comprehensive spatial, temporal, and socioeconomic evaluations of such events based on historical records. This study provides a detailed assessment of the spatial and temporal patterns and the socioeconomic impacts associated with landslides that occurred in the country between 1900 and 2018. Two national landslide databases were consulted and this information was complemented by local and regional landslide catalogues. A total of 30,730 landslides were recorded in the 118-year period. Rainfall is the most common trigger of landslides, responsible for 92 per cent of those registered, but most fatalities (68 per cent) are due to landslides caused by volcanic activity and earthquakes. An ‘fN curve’ revealed a very high frequency of small and moderate fatal landslides in the time frame.     

Screening of phthalic acid esters in raw materials,premixes and feed additives

Phthalates are animal carcinogens and may cause death or tissue deformities. Samples of feedstuffs collected in 2005 and 2006 from industrial feed manufacturers in the Czech Republic were analysed for contamination with phthalic acid esters (PAEs), specifically di-2-ethylhexyl phthalate (DEHP) and di-n-butyl phthalate (DBP). Samples of feed additives, premixes and raw materials were collected (year 2005, n = 26). For soybean oil, the total volume of phthalates measured (DBP + DEHP) reached a level of 131.42 mg kg⁻¹; for rapeseed oil, fish meal and animal fats, the levels measured were 15.00, 7.96 and 58.87 mg kg⁻¹, respectively. The lowest level of DBP + DEHP was found in corn (2.03 mg kg⁻¹). Since phthalates were detected, samples of feed additives (n = 28) and raw materials (n = 28) were collected again in 2006. The highest levels of DBP + DEHP were found in raw materials containing fat. Phthalate levels in rapeseed oil samples ranged from 1.38 to 32.40 mg kg⁻¹ DBP + DEHP. For feed additives, contamination levels in vitamins and amino acids ranged from 0.06 to 3.15 and 1.76 to 4.52 mg kg⁻¹ DBP + DEHP, respectively. Here, we show that the levels of PAEs found in cereals such as wheat, barley and corn may be regarded as being alarmingly high, because cereals make up the largest proportion of compound feed of farm animals.     

Age effect on the antioxidant activity of Daphnia magna (Anomopoda: Daphniidae): does younger mean more sensitivity?

It has been accepted that for most species newborns and senescent organisms are more sensitive than other ages to environmental stressors. Nevertheless, it must be considered that there are several biochemical and physiological compensatory processes which are not expressed with the same magnitude during the whole life cycle. With this aim, Daphnia magna individuals of different age were exposed to hexavalent chromium, Cr (VI), at two different sublethal concentrations (0.032 and 0.0064 mg l(-1)), and the activity of some antioxidant enzymes such as catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR) and glutathione peroxidase (GPx) were evaluated during most of the life cycle of this cladoceran. The antioxidant enzymatic activity showed an inverse relationship with respect to age. The activity of CAT, GR and GPx were increased in the two treated groups, at all life stages tested. On the other hand, the activity of SOD decreased in the same groups. Both, increase and decrease in the antioxidant enzymatic activities, showed significant differences with respect to the control group, being higher for the 0.032 mg l(-1) group. The Cr (VI) LC50 was also estimated for these age groups, finding statistical differences among them. Even though adults exhibited higher responses, these enzymatic activity changes should not be interpreted as higher sensitivity, since the daphnids acute chromium toxicity followed a different pattern, with increasing LC50 values according to age.     

Natal dispersal in two mice species with contrasting social systems

We compared the natal dispersal behaviour of two mice species under laboratory conditions. Natal dispersal is a movement of an animal from its birthplace to its breeding area. This behaviour is known to be influenced by the mating system. In polygamous species, males are more likely to disperse, while in most of the monogamous species, both sexes disperse. Our subjects, the house mouse (Mus musculus) and the mound-building mouse (Mus spicilegus) are two sympatric species of the genus Mus. Both are native in Hungary, but they differ in their habitat type mating system and overwintering strategy. The house mouse is a polygynous species and adapted to human environment, known for mature and reproduce early. On the contrary, the mound-building mice are monogamous, and they inhabit extensively used agricultural fields, where they spend the unfavourable winter period in nest chambers under mounds, which they construct from soil and plant material. Successful overwintering for this species demands delayed maturity and reduced dispersion during the winter. Our results showed that the natal dispersal of these two species differ; both sexes of the mound-building mice dispersed later than the house mice, where a difference between sexes also occurs; house mice males dispersed earlier than females. The mound-building mice showed no sexual dimorphism in this behaviour.