Evolution, radiation and chemotaxonomy of Lamellodysidea, a demosponge genus with anti-plasmodial metabolites

Sponges of the family Dysideidae (Dictyoceratida) are renowned for their diversity of secondary metabolites, and its genus Lamellodysidea, particularly Lamellodysidea herbacea, is the most studied taxon biochemically. Despite its importance, the taxonomic status of L. herbacea—whether it is a distinct species or a species complex—has never been assessed. Recent biochemical profiling revealed anti-plasmodial activity of brominated compounds in Lamellodysidea of the Pacific. Here, we present a comparative chemotaxonomic and molecular analysis of selected Dysideidae from the Pacific and the Indian Ocean (New Caledonia, Great Barrier Reef, Fiji, Mayotte, Guam, Palau). We investigated the phylogenetic relationships between the populations and assessed their bioactive (PBDE) compounds in order to unravel the taxonomic status of this commercially important group of sponges and assessed patterns of dispersal and biochemical variation. The molecular phylogeny was based on the internal transcribed ribosomal spacer and compared against a PBDE phylogeny for several specimens. Molecular data revealed a diversity of Indo-Pacific L. herbacea populations, also reflected by different PBDE compound profiles. Molecular and biochemical data also revealed a Lamellodysidea species new to science. Several specimens misidentified as Lamellodysidea were detected based on their position on different clades in the molecular phylogeny and their production of different halogenated compounds (brominated vs. chlorinated). The direct comparison of molecular and biochemical data also provided evidence for the occurrence of a host switch event and support for the theory that abiotic factors, such as sedimentation, affect the chemical constituents produced in L. herbacea.     

Modelling coupled peach tree-aphid population dynamics and their control by winter pruning and nitrogen fertilization

Nitrogen fertilization and winter pruning are commonly used to control crop production in peach [Prunus persica (L.) Batsch] orchards. They are also known to affect the dynamics of Myzus persicae (Sulzer) (Homoptera: Aphididae) aphid populations via bottom-up regulation processes. Interactions between crops and pests can cause complex system behaviour in response to management practices. An integrated approach will therefore improve the understanding of the effects of these two cultural practices on aphid and peach performances.We developed a simulation model that describes the cultural control of interacting peach tree and aphid population dynamics. It uses the principles of common trophic models while gathering available knowledge and explicit assumptions on peach and aphid functioning and the effects of cultural practices.The model was able to qualitatively reproduce the system behaviour observed in the field. It accounted for actions and feedback such as stimulation of foliar growth by winter pruning, consecutive aphid population increase, subsequent damage to foliage, and partial compensatory growth of foliage. The model also reproduced low losses in fruit production due to aphid infestations. However, it called for further integration of ‘long-term’ effects. Analysis of the model showed the complexity of peach tree and aphid responses to leaf N × winter pruning interactions. Simulations indicated that fruit production losses remained low within a range of realistic values of leaf N and pruning intensity, whereas manipulating peach and aphid dynamics, their interactions and their relationships to practices could result in higher losses.The model is useful to evaluate the relevance of cultural practices for a bottom-up regulation of aphid dynamics in crop-pest management. After considering other control methods and fruit quality, it can be used to find a combination of practices that optimises trade-offs between fruit production and environmental conservation goals. A modelling approach that links crop growth and pest population dynamics and integrates management practice effects has strong potential for improving crop-pest management in an integrated crop production context.     

Development of a sampling method for the simultaneous monitoring of straight-chain alkanes, straight-chain saturated carbonyl compounds and monoterpenes in remote areas

Studies have shown that biogenic compounds, long chain secondary compounds and long lifetime anthropogenic compounds are involved in the formation of organic aerosols in both polluted areas and remote places. This work aims at developing an active sampling method to monitor these compounds (i.e. 6 straight-chain saturated aldehydes from C6 to C11; 8 straight-chain alkanes from C9 to C16; 6 monoterpenes: α-pinene, β-pinene, camphene, limonene, α-terpinene, & γ-terpinene; and 5 aromatic compounds: toluene, ethylbenzene, meta-, para- and ortho-xylenes) in remote areas. Samples are collected onto multi-bed sorbent cartridges at 200 mL min(-1) flow rate, using the automatic sampler SyPAC (TERA-Environnement, Crolles, France). No breakthrough was observed for sampling volumes up to 120 L (standard mixture at ambient temperature, with a relative humidity of 75%). As ozone has been shown to alter the samples (losses of 90% of aldehydes and up to 95% of terpenes were observed), the addition of a conditioned manganese dioxide (MnO(2)) scrubber to the system has been validated (full recovery of the affected compounds for a standard mixture at 50% relative humidity--RH). Samples are first thermodesorbed and then analysed by GC/FID/MS. This method allows suitable detection limits (from 2 ppt for camphene to 13 ppt for octanal--36 L sampled), and reproducibility (from 1% for toluene to 22% for heptanal). It has been successfully used to determine the diurnal variation of the target compounds (six 3 h samples a day) during winter and summer measurement campaigns at a remote site in the south of France.     

The impact of human frequentation on coastal vegetation in a biosphere reserve

We aimed to assess the impacts of recreational trampling on rare species, plant communities and landscape structure in the Iroise Biosphere Reserve (western France). Focusing on coastal grasslands, we first identified indicators discriminating human-induced short grasslands (i.e. maintained short by intensive trampling) from natural short grasslands (i.e. maintained by environmental constraints): the presence of lichens and succulent or woody species, which are known to be highly sensitive to trampling, as well as a shallow soil were good indicators of natural short grasslands. Recreational activities affected the majority of plots containing rare species, but one third of rare species (according to their habitat preference) appeared currently not threatened by recreational activities. The other rare species were found in grasslands with low trampling intensity and were not found in grasslands with greater trampling intensity. One lichen species (Teloshistes flavicans) was not affected by trampling intensity, while two plants species (Scilla verna and Ophioglossum lusitanicum) showed higher abundances when trampling was low to medium. When it occurs in natural short grasslands, tourist trampling reduced drastically plant species richness. However, when considering maritime high grasslands, we observed that species richness was higher under low trampling vs. no trampling, but decreased at higher trampling intensity. At a landscape scale, the mean annual rate of path creation was about 1.6% and tourist trampling has already completely destroyed 3.5ha of natural coastal vegetation. Trampling of maritime-high grassland has also created 31ha of short grasslands, which represent 50.8% of the whole short grassland habitat of the island. Moreover trampling affected respectively, 41% and 15% of natural short grasslands and maritime-high grasslands. One of the main suggestions for managers to minimise trampling impacts should be to protect areas of rocky soil covered by short grassland that are still non-trampled and not impacted. Fortunately, this appears compatible with a relatively free access of visitors to coastal areas, as tourists can be redirected towards maritime-high grasslands, an habitat which is less impacted by tourism in terms of affected surface, soil cover, loss of species, or presence of rare species host.     

Increasing foraging group size increases scrounger use and reduces searching efficiency in nutmeg mannikins (<Emphasis Type="Italic">Lonchura punctulata</Emphasis>)

Social foragers can benefit from others' success by joining and sharing their food discoveries. In a producer-scrounger (PS) system, foragers can either search for food themselves (play producer) or search for joining opportunities (play scrounger), but not both at the same time. Empirical evidence is accumulating to show that the joining decision of ground-feeding birds like nutmeg mannikins (Lonchura punctulata) can be modeled by a PS game. However some predictions remain to be tested. For instance, foragers are predicted to increase their use of the scrounger tactic as group size increases. Also, one consequence of the incompatibility between producer and scrounger tactics is that the per capita searching efficiency should decrease as the use of scrounger increases. I tested these predictions in an indoor aviary using four flocks of nutmeg mannikins. I manipulated the stable equilibrium frequency (SEF) of the scrounger tactic by varying group size and the finder's share. As predicted by PS games, birds increased their use of scrounger as group size increased. Also, the per capita interval between patch discoveries increased and the per capita finding rate decreased as conditions called for a higher SEF of scrounger. I discuss why the decreased searching efficiency observed likely follows from the incompatibility between producer and scrounger tactics rather than from artifacts of the conditions used or from any form of interference.     

Distribution and fate of metals in the dispersion plume of a major municipal effluent

The environmental impacts of municipal wastewater discharges on receiving waters are numerous and inputs of contaminants such as metals can cause toxicity to organisms in receiving waters. The effluents generated by the treatment plant of the city of Montreal, Canada, the largest such facility in the St. Lawrence Valley, was investigated to determine the environmental fate of trace metals in the receiving waters. Total and extractable metal concentrations were determined and physico-chemical parameters were measured to characterize the receiving waters and evaluate their influence on the fate and behaviour of metals released from the urban effluent. Our results showed that particulate metals near the effluent discharge point are highly reactive and their distribution seems to be significantly influenced by the abundance of HCl-reactive iron and manganese, which act as trace-metal carriers. The partitioning of metals between dissolved and particulate phases varies along the effluent dispersion plume and therefore could strongly influence the exposure routes for aquatic organisms that are exposed to the various contaminants released from the effluent.     

The phototoxicity of non-carcinogenic polycyclic aromatic hydrocarbons in aquatic organisms

Anthracene, fluoranthene, and pyrene are phototoxic in , first instar larvae of , late embryonic forms of , and fish ( ). Since polycyclic aromatic hydrocarbons are generated in the combustion processes held responsible for the damages of acid rain, and they are introduced into the environment through other means as well, the high phototoxicity of the major pollutants, which are not carcinogenic, suggests that greater attention must be given to their environmental significance.     

Inverse modeling of BTEX dissolution and biodegradation at the Bemidji, MN crude-oil spill site

The U.S. Geological Survey (USGS) solute transport and biodegradation code BIOMOC was used in conjunction with the USGS universal inverse modeling code UCODE to quantify field-scale hydrocarbon dissolution and biodegradation at the USGS Toxic Substances Hydrology Program crude-oil spill research site located near Bemidji, MN. This inverse modeling effort used the extensive historical data compiled at the Bemidji site from 1986 to 1997 and incorporated a multicomponent transport and biodegradation model. Inverse modeling was successful when coupled transport and degradation processes were incorporated into the model and a single dissolution rate coefficient was used for all BTEX components. Assuming a stationary oil body, we simulated benzene, toluene, ethylbenzene, m,p-xylene, and o-xylene (BTEX) concentrations in the oil and ground water, respectively, as well as dissolved oxygen. Dissolution from the oil phase and aerobic and anaerobic degradation processes were represented. The parameters estimated were the recharge rate, hydraulic conductivity, dissolution rate coefficient, individual first-order BTEX anaerobic degradation rates, and transverse dispersivity. Results were similar for simulations obtained using several alternative conceptual models of the hydrologic system and biodegradation processes. The dissolved BTEX concentration data were not sufficient to discriminate between these conceptual models. The calibrated simulations reproduced the general large-scale evolution of the plume, but did not reproduce the observed small-scale spatial and temporal variability in concentrations. The estimated anaerobic biodegradation rates for toluene and o-xylene were greater than the dissolution rate coefficient. However, the estimated anaerobic biodegradation rates for benzene, ethylbenzene, and m,p-xylene were less than the dissolution rate coefficient. The calibrated model was used to determine the BTEX mass balance in the oil body and groundwater plume. Dissolution from the oil body was greatest for compounds with large effective solubilities (benzene) and with large degradation rates (toluene and o-xylene). Anaerobic degradation removed 77% of the BTEX that dissolved into the water phase and aerobic degradation removed 17%. Although goodness-of-fit measures for the alternative conceptual models were not significantly different, predictions made with the models were quite variable.     

Client preferences by Caribbean cleaning gobies: food,safety or something else?

Predation risk is amongst the most pervasive selective pressures influencing behaviour and animals have been repeatedly shown to trade-off foraging success for safety. We examined the nature of this trade-off in cleaning symbioses amongst Caribbean coral reef fishes. We predicted that cleaning gobies (Elacatinus evelynae and Elacatinus prochilos) should prefer fish clients that pose a low risk of predation (e.g. herbivores) over clients that may have more ectoparasites but pose a higher risk (e.g. piscivores). Our field observations revealed that cleaners did clean preferentially client species with more parasites but predatory and non-predatory clients had similar ectoparasite loads. Despite the lack of a foraging advantage for inspecting predators, cleaners did not avoid risky clients. On the contrary, a larger proportion of visiting predators than non-predators was inspected, gobies initiated more interactions with predatory clients, and predators were attended to immediately upon arrival at cleaning stations. This preferential treatment of dangerous clients may allow the rapid identification of cleaners as non-prey item or may be due to the effect of predators on the rest of the cleaners’ clientele, which avoided cleaning stations whilst predators were present. Dealing with potentially risky clients may allow gobies to regain access to their main food source: non-predatory clients.