Evidence for receptor-linked activation of phospholipase D in rat parotid glands. Stimulation by carbamylcholine, PMA and calcium.

In order to test if phospholipase D (PLD) activity exists in the rat parotid gland, we took advantage of the fact that, in the presence of ethanol, PLD generates phosphatidylethanol (PEth) via a transphosphatidylation reaction. Lipid extracts of parotid acini prelabelled with [3H]myristic acid were analyzed by thin layer chromatography to determine [3H]phosphatidylethanol ([3H]PEth) formation. Carbamylcholine (1 mM) stimulated [3H]PEth formation in the presence of 2% ethanol, this effect was completely inhibited by atropine (10 microM). PMA (0.1-1 microM) and ionomycine (10 microM) also caused [3H]PEth generation. We conclude that a phospholipase D activity is present in the rat parotid gland and is regulated by muscarinic cholinergic receptors. Protein kinase C and calcium could also modulate this activity. This report provides the first evidence for the existence and receptor-linked regulation of phospholipase D in an exocrine gland, the rat parotid gland.     

Blue light effects on rose photosynthesis and photomorphogenesis

Through its impact on photosynthesis and morphogenesis, light is the environmental factor that most affects plant architecture. Using light rather than chemicals to manage plant architecture could reduce the impact on the environment. However, the understanding of how light modulates plant architecture is still poor and further research is needed. To address this question, we examined the development of two rose cultivars, Rosa hybrida‘Radrazz’ and Rosa chinensis‘Old Blush’, cultivated under two light qualities. Plants were grown from one‐node cuttings for 6 weeks under white or blue light at equal photosynthetic efficiencies. While plant development was totally inhibited in darkness, blue light could sustain full development from bud burst until flowering. Blue light reduced the net CO₂ assimilation rate of fully expanded leaves in both cultivars, despite increasing stomatal conductance and intercellular CO₂ concentrations. In ‘Radrazz’, the reduction in CO₂ assimilation under blue light was related to a decrease in photosynthetic pigment content, while in both cultivars, the chl a/b ratio increased. Surprisingly, blue light could induce the same organogenetic activity of the shoot apical meristem, growth of the metamers and flower development as white light. The normal development of rose plants under blue light reveals the strong adaptive properties of rose plants to their light environment. It also indicates that photomorphogenetic processes can all be triggered by blue wavelengths and that despite a lower assimilation rate, blue light can provide sufficient energy via photosynthesis to sustain normal growth and development in roses.     

Ecotourism disturbance to wildfowl in protected areas: historical, empirical and experimental approaches in the Camargue, Southern France

Ecotourism is becoming very popular, especially in protected areas where wildlife concentrate and is easier to observe, but the consequences of associated disturbance have seldom be quantified other than in the short-term, making the sustainability of this activity untested. We combined a historical, an empirical and an experimental approach to assess the long-, medium- and short-term consequences of disturbance to wintering wildfowl (Anatidae) in a wetland of international importance in the Camargue, Southern France. In the short-term, disturbance made teal (Anas crecca) move away temporarily from observation blinds without leaving the waterbody. Wildfowl fed more after disturbance, disrupting their normal resting activities. In the medium-term, waterbodies with more tourists did not host fewer birds: conversely the most heavily disturbed one hosted the highest wildfowl density. In the long term, wildfowl numbers were not related with the number of visitors. When practiced with appropriate guiding of people, and where appropriate facilities are provided to limit human disturbance as done here, ecotourism may not affect wintering wildfowl other than reversibly in the very short term. The legitimate demand of the public for access, even in fragile protected areas, may therefore be sustainable under some conditions.     

Blood and cloacal swab sampling for avian influenza monitoring has no effect on survival rates of free‐ranging ducks

Concerns about the spread of avian influenza viruses (AIVs) have led to cloacal swab sampling of hundreds of thousands of birds worldwide as part of AIV surveillance schemes, but the effects of cloacal swabbing have not been adequately evaluated. We tested for differences between swabbed, swabbed and bled, and non‐sampled wild ducks in terms of live re‐encounter and dead recoveries for Common Pochard Aythya ferina and Tufted Duck Aythya fuligula, and also determined re‐encounter and recovery rates for Mallard Anas platyrhynchos and Common Teal Anas crecca. No effects of sampling methods were detected, except in Teal. Re‐encounter rates were lower in sampled Teal than in controls, with annual re‐encounter probabilities being 25% and 35% lower in males and females, respectively. Teal possibly left or avoided sampling sites, or sought sites where they were less detectable after sampling. In general, no deleterious effects were found, suggesting that cloacal swabbing and blood sampling are suitable methods for conducting AIV surveillance in ducks.     

Breeding mute swan habitat selection when accounting for detectability: a plastic behaviour consistent with rapidly expanding populations

A number of native and exotic animal species show dramatic population increases in terms of both numbers and geographic range. Understanding the habitat selection processes behind such increases is crucial to implement adequate management measures. Mute swan (Cygnus olor) populations have experienced a tremendous demographic and geographic expansion in Western Europe during the twentieth century, colonizing a wide variety of aquatic habitats. We aimed at assessing how swans select nesting sites during the pre-laying and laying periods on medium to large fishponds (from 10 to 50 ha) in Eastern France, while accounting for detectability biases and testing for the effects of fishpond spatial configuration, vegetation resources, human disturbance and habitat management. Our results demonstrate that the mute swan is a non-selective species regarding its nesting habitat among such fishponds, using these independently from the parameters considered although fishpond characteristics varied. Although mute swan is one of the least cryptic Anatidae, owing to its white colour and large size, detection of breeding pairs remained imperfect for each over several sampling occasions. However, because we repeated the sampling sessions, detection of swan pairs by the end of the monitoring period was as high as 0.94. These results are consistent with previous assertions that the mute swan is a species of high ecological plasticity, which may partly explain its recent colonization rates. Given that even swan breeding events were imperfectly detected on each occasion, we highlight the fact that most studies of breeding ducks (which are more cryptic) would be considerably improved by better considering detection biases.     

Robust estimation of survival and contribution of captive‐bred Mallards Anas platyrhynchos to a wild population in a large‐scale release programme

The survival of captive‐bred individuals from release into the wild to their first breeding season is crucial to assess the success of reintroduction or translocation programmes, and to assess their potential impact of wild populations. However, assessing the survival of captive‐bred individuals following their release is often complicated by immediate dispersal once in the wild. Here, we apply Lindberg's robust design model, a method that incorporates emigration from the study site, to obtain true estimates of survival of captive‐bred Mallards Anas platyrhynchos, a common duck species released on a large scale in Europe since the 1970s. Overall survival rate from release in July until the onset of the next breeding season in April was low (0.18 ± 0.07 se) and equivalent to half the first‐year survival of local wild Mallards. Higher overall detectability and temporary emigration during the hunting period revealed movements in response to hunting pressure. Such low survival of released Mallards during their first year may help prevent large‐scale genetic mixing with the wild population. Nevertheless, by combining our results with regional waterfowl counts, we estimated that a minimum of 34% of the Mallards in the region were of captive origin at the onset of the breeding season. Although most released birds quickly die, restocking for hunting may be of sufficient magnitude to affect the wild population through genetic homogenization or loss of local adaptation. Robust design protocols allow for the estimation of true survival estimates by controlling for permanent and temporary emigration and may require only a moderate increase in fieldwork effort.     

A flyway perspective on food resource abundance in a long-distance migrant, the Eurasian teal (Anas crecca)

Two frequent assumptions about the evolution of long-distance migration in birds are that they travel long distances annually to reach food-rich areas for breeding, and that they time their migratory journey to be at staging sites when the latter provide the best feeding conditions. These assumptions have rarely been properly tested, and there is no study in which a species’ major food types have been measured by standardized methods throughout a flyway and over a large part of the year. We here present such data for Eurasian teal (Anas crecca), converted to a common energetic currency, and collected at wintering, spring staging and breeding sites. Teal did not time migration to maximize local food abundance; most birds left wintering and spring staging sites before a sharp increase in invertebrate food abundance occurred. On the other hand, hatching of ducklings coincided with a peak in invertebrate food abundance on boreal breeding lakes. Mean overall food abundance (invertebrates and seeds combined) did not differ between wintering sites in southern France and breeding sites in northern Sweden at the time of breeding. Our results are inconsistent with the hypothesis that long-distance migration in dabbling ducks has evolved because adult birds gain an immediate pay-off in increased food abundance by flying north in spring. However, our data confirm a selective advantage for breeding at higher latitudes, because hatching of ducklings may coincide with a peak in invertebrate emergence and because longer days may increase the duration of efficient foraging.