Importance du sédiment dans la distribution des Lingules

Log-probability curves of grain-size distribution have been analysed of sediments collected in three previously described localities occupied by either Lingula anatina or L. reevei (Brachiopoda, Inarticulata). The grain-size population transported by saltation (average about 92–223 μm), generally associated with traction load population, determines Lingula distribution. The two preferential substrates of both studied species (density > 100 individuals/m^-2) are compact and stable sediments under moderate water currents: either coarse sands and gravels clogged by fine and very fine sands, or fine, very fine and clay sands (saltation populations more than 60%). As soon as the suspension population and/or traction increase in the sediment to the detriment of the saltation population, the density of Lingula decreases rapidly. Nevertheless, if grain-size distribution and populations have a primordial function for Lingula , other ecological features (i.e. the environmental fauna, high occurrence of digging species, the available nutrients) will affect the distribution and sometimes become prevailing. The absence of important changes in the shell shape of Lingula since its origin suggests that the grain-size requirements remained about the same.     

Rainfall distribution is the main driver of runoff under future CO2-concentration in a temperate deciduous forest

Reduced stomatal conductance under elevated CO₂ results in increased soil moisture, provided all other factors remain constant. Whether this results in increased runoff critically depends on the interaction of rainfall patterns, soil water storage capacity and plant responses. To test the sensitivity of runoff to these parameters under elevated CO₂, we combine transpiration and soil moisture data from the Swiss Canopy Crane FACE experiment (SCC, 14 30–35 m tall deciduous broad‐leaved trees under elevated CO₂) with 104 years of daily precipitation data from an adjacent weather station to drive a three‐layer bucket model (mean yearly precipitation 794 mm). The model adequately predicts the water budget of a temperate deciduous forest and runoff from a nearby gauging station. A simulation run over all 104 years based on measured sap flow responses resulted in only 5.5 mm (2.9%) increased ecosystem runoff under elevated CO₂. Out of the 37 986 days (1 January 1901–31 December 2004), only 576 days produce higher runoff in the elevated CO₂ scenario. Only 1 out of 17 years produces a CO₂‐signal >20 mm a^?1, which mostly depends on a few single days when runoff under elevated CO₂ exceeds runoff under ambient conditions. The maximum signal for a double preindustrial CO₂‐concentration under the past century daily rainfall regime is an additional runoff of 46 mm. More than half of all years produce a signal of <5 mm a^?1, because trees consume the ‘extra’ moisture during prolonged dry weather. Increased runoff under elevated CO₂ is nine times more sensitive to variations in rain pattern than to the applied reduction in transpiration under elevated CO₂. Thus the key driver of increased runoff under future CO₂‐concentration is the day by day rainfall pattern. We argue that increased runoff due to a first‐order plant physiological CO₂‐effect will be very small (<3%) in a landscape dominated by temperate deciduous forests, and will hardly increase flooding risk in forest catchments. Monthly rainfall sums are unsuitable to realistically model such CO₂ effects. These findings may apply to other ecosystems with comparable soil water storage capacity.     

Heterochrony and allometry: the analysis of evolutionary change in ontogeny

The connection between development and evolution has become the focus of an increasing amount of research in recent years, and heterochrony has long been a key concept in this relation. Heterochrony is defined as evolutionary change in rates and timing of developmental processes; the dimension of time is therefore an essential part in studies of heterochrony. Over the past two decades, evolutionary biologists have used several methodological frameworks to analyse heterochrony, which differ substantially in the way they characterize evolutionary changes in ontogenies and in the resulting classification, although they mostly use the same terms. This review examines how these methods compare ancestral and descendant ontogenies, emphasizing their differences and the potential for contradictory results from analyses using different frameworks. One of the two principal methods uses a clock as a graphical display for comparisons of size, shape and age at a particular ontogenic stage, whereas the other characterizes a developmental process by its time of onset, rate, and time of cessation. The literature on human heterochrony provides particularly clear examples of how these differences produce apparent contradictions when applied to the same problem. Developmental biologists recently have extended the concept of heterochrony to the earliest stages of development and have applied it at the cellular and molecular scale. This extension brought considerations of developmental mechanisms and genetics into the study of heterochrony, which previously was based primarily on phenomenological characterizations of morphological change in ontogeny. Allometry is the pattern of covariation among several morphological traits or between measures of size and shape; unlike heterochrony, allometry does not deal with time explicitly. Two main approaches to the study of allometry are distinguished, which differ in the way they characterize organismal form. One approach defines shape as proportions among measurements, based on considerations of geometric similarity, whereas the other focuses on the covariation among measurements in ontogeny and evolution. Both are related conceptually and through the use of similar algebra. In addition, there are close connections between heterochrony and changes in allometric growth trajectories, although there is no one-to-one correspondence. These relationships and outline links between different analytical frameworks are discussed.     

AGE DETERMINATION OF ARIANTA ARBUSTORUM (L.) (PULMONATA) BASED ON GROWTH BREAKS AND INNER LAYERS

The pulmonate snail Arianta arbustorum from the Swiss Alps wasaged using thin sections of the shell margins cut from markedindividuals. Shell layers at the apertural lip and growth breaksin the juvenile can give a reliable estimate of age. (Received 16 May 1986;     

Soft–part preservation in heteromorph ammonites from the Cenomanian–Turonian Boundary Event (OAE 2) in north–west Germany

Abstract: From thinly laminated marlstones of the Hesseltal Formation, representing the Late Cenomanian Oceanic Anoxic Event (OAE) 2, at Lengerich in the Teutoburger Wald (Westfalen, north‐west Germany), 17 sediment‐compacted baculitid ammonites with carbonised and partially phosphatised soft parts are recorded. Some preserve remains of the buccal mass, including jaws (occasionally articulated) and radulae, as well as of the cephalic cartilage, such as eye capsules. Such have not yet been recorded previously for the order Ammonoidea. In addition, originally unmineralised parts found preserved in these specimens include extensive portions of the digestive tract, the siphonal tube, false colour patterns (megastriae), as well as traces of what would appear to be the oviduct. At the same levels, patches with numerous isolated horny upper and rarer lower jaws as well as radulae occur; these may represent regurgitates or faeces of larger predators. The cephalopod remains described were deposited in an epicontinental setting, possibly at palaeodepths between 200 and 600 m. In this particular Late Cretaceous fossil Lagerstätte, upper jaws and anaptychi of ammonites rank among the commonest fossils.     

The Effect of Salinity Changes Upon the Physiology of Eulittoral Green Macroalgae from Antarctica and Southern Chile: II INTRACELLULAR INORGANIC IONS AND ORGANIC COMPOUNDS

The effects of hypo- and hypersaline treatments ranging from7–68% on the intracellular inorganic ion and organic soluteconcentrations were determined in the eulittoral green macroalgaeUlothrix implexa, Ulothrix subflaccida, Enteromorpha bulbosa,Acrosiphonia arcta, and Ulva rigida from Antarctica and SouthernChile. The main inorganic cations were K⁺, Na⁺, and Mg²⁺ inall species. The major osmolyte in E. bulbosa, A. arcta, andU. rigida was K⁺ at increasing salinities. In both Ulothrixspecies, however, K⁺ levels declined during hypersaline stressand Na⁺ concentrations rose significantly. The main inorganicanions were Cl^-, SO²_4-, and PO³_4- in all algae, while E. bulbosaand U. rigida also contained NO⁺₃. A. arcta showed an extremelyhigh SO^2-₄ content. The organic solutes proline, sucrose, andß-dimethylsulphoniopropionate (DMSP) played an importantrole in osmotic acclimation. The occurrence of three organicosmolytes suggests an additional function of these solutes ascryoprotectants in the cold-water macroalgae investigated.     

Nutritional status and the foraging behaviour of Bactrocera tryoni with particular reference to protein bait spray

Poisoned protein baits comprise a recognized method for controlling tephritid fruit flies in the form of a ‘lure‐and‐kill’ technique. However, little is known about how a fly's internal protein and carbohydrate levels (i.e. nutritional status) might influence the efficacy of this control. In the present study, the relationships between the internal levels of protein (as measured by total body nitrogen) and carbohydrate (as measured by total body carbon) of the fruit fly Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) are investigated, as well as its foraging behaviours in response to protein, fruit and cue‐lure (a male‐specific attractant) baits. Small cage behavioural experiments are conducted using flies from cultures of different nutritional status and wild flies sampled from the field during the fruiting cycle of a guava crop. For female flies, increasing total body nitrogen is correlated with decreased protein foraging and increased oviposition activity; increasing total body carbon levels generate the same behavioural changes except that the oviposition response is not significant. For males, there are no significant correlations between changes in total body nitrogen and total body carbon and protein or cue‐lure foraging. For wild flies from the guava orchard, almost all of them are sexually mature when entering the crop and, over the entire season, total body nitrogen and total body carbon levels are such that protein hunger is unlikely for most flies. The results infer strongly that the requirements of wild, sexually mature flies for protein are minimal and that flies can readily gain sufficient nutrients from wild sources for their physiological needs. The results offer a mechanistic explanation for the poor response of male and mature female fruit flies to protein bait spray.