Responses of female lizards,<Emphasis Type="Italic"> Lacerta monticola</Emphasis>, to males' chemical cues reflect their mating preference for older males

Female mate choice based on visual traits appears to be rare in lizards. Field observations suggest that females of the lizard Lacerta monticola preferred to mate with larger/older males. Although older males are usually green and larger, and younger males brown and smaller, there is some overlap in size and coloration between age classes. Thus, visual cues may not always be reliable indicators of a male's age. We hypothesized that female mate-choice preferences may be based on males' pheromones, which might transmit information about characteristics such as age. In a laboratory experiment, we analyzed the effect of age of males on attractiveness of their scents to females. When we offered scents of two males of different age, females associated preferentially with scents of older males. This suggested that females were able to assess the age of males by chemical signals alone, and that females preferred to be in areas scent-marked by older males. Thus, females may increase their opportunities to mate with males of high quality, or may avoid harassment by sneaking young males. This result agreed with field observations on females mating with old males, and rejection of advances by young males. Our results also suggested that female preference for older males may depend on their own body size. Large females showed a strong preference for older males, whereas smaller females were not so selective. This, together with males' preference for large females, might lead to size-assortative matings. We suggest that the quality and/or quantity of male pheromones could communicate to the female heritable male genetic quality (i.e. age) and thereby serve as the basis of adaptive female choice in lizards.Communicated by W.E. Cooper     

Proliferation kinetics of mussel (Mytilus galloprovincialis) gill cells

A technique of sister chromatid differentiation (SCD) using bromodeoxyuridine (BrdU) incorporation and a modification of the fluorescence plus Giemsa (FPG) method was employed to determine cell-proliferation kinetics in gill tissue of the mussel Mytilus galloprovincialis. Dose-dependent proliferation inhibition was examined. In vivo administration of BrdU for 12, 24, 36, 48, 60, 72, 84, and 96 h was studied. Our data show that the highest yield of second-generation metaphase plates is obtained after 60 h BrdU treatment; the duration of a cell cycle is 24 to 30 h. On the basis of these data, a BrdU incorporation period of 48 to 60 h would seem to be most appropriate for the sister chromatid exchange (SCE) tests carried out in gill cells of M. galloprovincialis, whereas the 12 to 24 h exposure would give the best results for replication band analysis.     

Chemosensory cues allow male lizards<Emphasis Type="Italic"> Psammodromus algirus</Emphasis> to override visual concealment of sexual identity by satellite males

Males of many species of lizards show conspicuous breeding colors but, in some species, young competitively inferior males conceal their sexual identity by a female-like dull coloration that allows them to evade aggression from dominant males and to adopt an alternative satellite-sneaking mating tactic. However, large males of the lizard Psammodromus algirus reacted aggressively to young intruder males despite their female-like coloration, suggesting that they might have the ability to recognize competitor males by chemosensory cues. We experimentally manipulated the head coloration (brown vs orange) and scents (male vs female) of small young males. For staged agonistic encounters, we compared the response of resident unmanipulated large males to the different manipulated small males. When we manipulated only the color of small males, the response of resident large males was independent of the paint manipulation; brown and orange males elicited a similar aggressive response. However, when we also manipulated the scent, small males painted orange or brown, but bearing the scent of males, received a significantly higher number of aggressive responses than small males painted orange or brown, but bearing the scent of females. The results showed that, at close range, the reaction of large males to manipulated individuals was dependent on the scent, whereas color seemed to be less important. Coloration may be, however, more important in long-distance communication as shown by the outcome of the first encounters. Also, orange coloration may increase the intensity of the aggressive response. Effective sex recognition by territorial large males is important in natural situations to avoid sneak matings by young male competitors. Thus, even if small males visually conceal their sexual identity, chemosensory cues allow large males to identify them at close range.     

Studies on the defensive behaviour ofHypselodoris species (Gastropoda: Nudibranchia): Ultrastructure and chemical analysis of mantle dermal formations (MDFs)

The mantle dermal formations (MDFs) ofHypselodoris webbi (D'orbigny, 1839), andH. cantabrica (Bouchet and Ortea, 1980) are globular sub-epidermal structures located in the cephalic and caudal regions. Histologically they consist of an accumulation of vacuolate cells surrounded by a basal lamina and an outer muscular capsule. Chemical analysis ofH. webbi MDFs reveals the presence of high concentrations of longifolin, a well known deterrent furanosesquiterpenoid that had been previously isolated from this species. In the present paper it is demonstrated that the great majority of longifolin accumulated in the mantle ofH. webbi is stored in the MDF vacuolar cells. This finding strongly suggests that such structures act as chemical weapons against predation, mainly protecting vital organs such as the head, rhinophores and gills.     

Case selection by a limnephilid caddisfly [Potamophylax latipennis (Curtis)] in response to different predators

Some organisms use morphological structures obtained by behavioural processes to lower mortality by predation. We test whether larvae of the limnephilid caddisfly Potamophylax latipennis (Curtis) vary their responses to the presence of different predators (dragonfly naiads, fire salamander larvae or brown trout) by choosing organic or mineral cases. We offered both case types to larvae, and simulated differences in predation risk using water conditioned with chemicals from the different predators. Our results show that Potamophylax larvae detect and discriminate predators using water-borne chemical cues and alter their choice of case type according to the perceived predation risk. Moreover, the distribution of larvae bearing cases of different anti-predator value matches the spatial variation in predation risk in the field.     

Allelopathic potential of Cistus ladanifer chemicals in response to variations of light and temperature

Summary. Earlier studies have demonstrated the allelopathic potential of the exudate of Cistus ladanifer leaves, and have identified the compounds responsible for the effect. It is here shown that the effect of each of these compounds and their interactions on germination and seedling development varies depending on the light and temperature parameters to which they are subjected. The allelochemicals show a fairly heterogeneous response when studied separately, there being no general pattern to the behaviour. When they act conjointly, however, their activity is enhanced by high temperatures, and the greatest phytotoxicity in inhibiting both germination and seedling development is attained with high temperatures and long photoperiods. These results suggest that the environmental factors temperature and photoperiod may alter the allelopathic effect of Cistus ladanifer. Received 5 December 2001; accepted 11 March 2002.     

Size-assortative mating and non-reciprocal copulation in a hermaphroditic intertidal limpet: test of the mate availability hypothesis

Mating behaviour and mating patterns are affected to a large extent by body size in both hermaphrodites and gonochorists. Detailed research on mating patterns, mate choice, pre- and post-copulatory sexual selection in marine pulmonates is wanting, thus warranting more attention as a study system in the future. The simultaneous hermaphroditic limpet Siphonaria capensis (Pulmonata: Basommatophora) shows size-dependent fecundity, and acts as a suitable organism to test the effects of body size on mating patterns, mating success, gender expression and reciprocity in hermaphroditic marine gastropods. We mainly used bootstrap resampling techniques to estimate the effects of different factors on mating patterns. In the populations studied, a strong size-assortative mating pattern was observed, where small-scale spatial distribution of potential mating partners (the mate availability hypothesis) could explain 65% of this pattern, while mate choice and mating constraints explaining the rest. No significant difference in mating success between limpets with different body size was found, even though in one population, the sperm recipients were larger than the non-copulating limpets. Interestingly, we found that intromission was non-reciprocal during copulations. This may mean that this species does not conform to the common rule of reciprocity predicted for hermaphrodites, unless there is sex-role alternation between individuals in a mating pair. The mating partners consisted of similar sized, acting males and females, thus without any indication of the body size determining the gender expression. The matings took place in early mornings only at spring tides and the animals were observed laying egg masses only during neap tides. Since siphonariid limpets possess both a spermatheca and a seminal vesicle, which may have either a sperm storing and/or digestive function, post-copulatory sexual selection (e.g., sperm competition) cannot be dismissed.     

A laboratory technique for investigation of diffusion and transformation of volatile organic compounds in low permeability media

A laboratory diffusion cell technique that permits spatial and temporal estimates of porewater concentrations over short intervals suitable for estimation of effective diffusion coefficients (De) and degradation rate constants (k) of volatile organic compounds (VOCs) in saturated low permeability media is presented. The diffusion cell is a sealed cylinder containing vapour reservoirs for sampling, including a vapour reservoir source and an array of vapour-filled "mini-boreholes", which are maintained water- and sediment-free by slightly negative porewater pressures. The vapour reservoirs were sampled by Solid Phase Micro-Extraction (SPME), resulting in minimal disturbance to the experimental system. Porewater concentrations are estimated from the measured vapour concentrations. Experiments were conducted using a non-reactive medium and five VOCs with a range in partitioning properties. Calibration experiments showed that equilibrium partition coefficients could be used for calculating concentrations in the vapour reservoir source from concentrations in the SPME coating after a 1-min microextraction and that the reservoir concentration was insignificantly affected by sampling. However, equilibrium was not reached during the one-min extraction of the boreholes; the microextraction reduced the borehole vapour concentrations, leading to diffusion of VOCs from porewater into the vapour-filled borehole. Thus, empirical partitioning coefficients were required for the determination of porewater VOC concentrations. The experimental data and numerical modelling indicate masses extracted by SPME extraction are relatively small, with minimal perturbation on processes studied in diffusion experiments. This technique shows promise for laboratory investigation of diffusion and transformation processes in low permeability media.     

Hexazinone and simazine dissipation in forestry field nurseries

Hexazinone and simazine field dissipation was studied in two different soils from Spain (Toledo and Burgos), devoted to forest nurseries for Pinus nigra. Laboratory experiments (adsorption-desorption isotherms, leaching experiment and degradation study) were carried out to determine possible mechanisms of dissipation. Higher adsorption was observed for hexazinone in Toledo (KfT = 0.69) compare to in Burgos soil (KfB = 0.20) probably due to the higher organic matter (OM) content of Toledo soil. No differences in adsorption were obtained for simazine in both soils (KfT = 1.27; KfB = 1.34). In every case, adsorption was higher for simazine than for hexazinone, in both soils. The total recovery of hexazinone in the leachates from handpacked soil columns was higher in Burgos (100%) than in Toledo (80%), because of the larger adsorption of hexazinone in this last soil. No differences in simazine leaching between both soils were found, although the total amount of pesticide recovered in leachates (40% in the two soils) was lower for simazine than for hexazinone. Finally, lower degradation was found in Burgos (t1/2 = 91 d) vs Toledo (t1/2 = 47 d), directly related with the high OM content of Toledo. No half-life was calculated for simazine in Toledo because no changes in herbicide soil content were observed during the period of time studied. In the case of Burgos, the half-life for simazine was 50 days. The field residues study showed larger persistence of simazine than hexazinone mainly due to the higher adsorption and lower mobility of simazine in the two soils. The lower persistence of hexazinone in Toledo soil than in Burgos soil is related to the larger rainfall occurred in this soil besides the higher degradation of this herbicide observed in Toledo soil. The much lower temperature in Burgos than in Toledo soil during winter contribute to the higher persistence of the two herbicides in Burgos soil.     

Comparison of toxicological impacts of integrated and chemical pest management in Mediterranean greenhouses

The goal of this paper is to assess the relative impacts of pest-control methods in greenhouses, based on current LCA tools. As a case study, the relative impacts of two tomato production methods, chemical pest management (CPM) and integrated pest management (IPM), are assessed. The amount of the active ingredients applied, the fate of the ingredients in the various greenhouse and environmental compartments, the human exposure routes via the various compartments and the inherent toxicity of the ingredients were taken into account in the relative impact calculations. To assess the importance of model selection in the assessment, pesticide-specific fate and exposure factors for humans and aquatic and terrestrial ecosystems, used to aggregate pesticide emissions, were calculated with two different models: (1) the USES-LCA model, adapted in order to calculate the pesticide transfer from greenhouse air and soil to fruits, and (2) the empirical model critical surface time (CST). Impact scores have in general shown a higher level of potential contamination in greenhouses treated with CPM compared to IPM (a factor of 1.4 to 2.3). Relative impacts have been shown highly dependent on the selection of specific pesticides and crop stage development at the moment of pesticide application. This means that both CPM and IPM could be improved by a careful selection of pesticides. In order to improve the relative impact calculations, future research in pesticide transfer to food will be necessary.