A comparative study of sex pheromone reception in the Hadeninae (Lepidoptera: Noctuidae)

Abstract A comparative study of the olfactory responses to pheromone compounds was performed in twenty-four species of Hadeninae. Electroantennograms (EAG) were recorded on male moths in response to thirty compounds and the response profiles of each species were analysed by factorial correspondence analysis. A limited number of molecules were found active and the most effective stimuli were Z9 tetradecenes and Z11 hexadecenes. The species of the Mythimna genus were most sensitive to aldehydes. Tholera decimalis did not respond to any of the molecules tested. The species belonging to the Mamestra and the Orthosia genera responded to a variety of molecules and no simple correlation was found between the genus and the EAG sensibility. Pheromone reception is discussed in relation to the taxonomy and the evolution of olfactory communication in Hadeninae.     

Mate guarding in relation to seasonal changes in the energy reserves of two freshwater amphipods (Gammarus fossarum and G. pulex)

1. We assessed sex‐specific seasonal changes in major energy storage compounds (triglycerides, glycogen) in Gammarus fossarum and Gammarus pulex collected from the field, with respect to their reproductive activity. 2. The dynamics of stored energy followed a seasonal pattern in both species and sexes. Moreover, over a 4‐year period, these changes were independent of the year in which they were investigated. Stored energy reached a peak in late winter, but was depleted in late summer and early autumn, coinciding with the reproductive periods. 3. Triglyceride (annual mean ± SD) accounted for 79.7 ± 11.9% of the total stored energy and was responsible for the seasonal pattern. In contrast, glycogen contributed a lesser percentage (20.3 ± 11.9%). Over the study period, the amount of stored energy ranged between 0.39 and 4.08 kJ g^?1 dry mass (triglyceride: 0.19–3.69 kJ g^?1 dry mass; glycogen: 0.14–0.80 kJ g^?1 dry mass). 4. In both species, the energy reserves of males were drastically depleted shortly before the cessation of precopulatory mate guarding in the field, thus offering a bioenergetic explanation for the reproductive period in these two widespread species.     

Multiple mating in wild Drosophila melanogaster revisited by microsatellite analysis

The occurrence of multiple mating in Drosophila melanogaster is of particular interest to evolutionary biologists, as seminal fluid has some toxic effects for females. Thus, it has been predicted that the number of matings per females should be low. We have tested this prediction with seven highly polymorphic microsatellite loci in inseminated females from a Viennese D. melanogaster population. In contrast to the predicted low number of matings and previous studies in natural populations, we identified the genotypes of four to six different males fertilizing the offspring of each female tested. Potential causes and consequences are discussed.     

AMMONOID SHELL STRUCTURES OF PRIMARY ORGANIC COMPOSITION

Abstract:  Palaeozoic and Mesozoic cephalopod conchs occasionally reveal dark organic coatings at the aperture. A number of these coatings, including still unrecorded examples, are described, figured and interpreted herein. On the basis of elemental analysis, actualistic comparison and a comparison with Triassic bivalves, some of these coatings are shown to consist of apatite and primarily probably of conchiolin (and also probably melanin). In several Mesozoic ammonoid genera such as Paranannites , Psiloceras , Lytoceras , Phylloceras , Harpoceras and Chondroceras , some of these coatings (recorded herein for most of these taxa for the first time) are interpreted as a structure similar to the black band, which was previously known only from Recent Allonautilus and Nautilus . In contrast to these nautilid genera, however, the organic material of some Mesozoic ammonoids was not deposited on the inside of the shell but externally, albeit positioned at the terminal aperture as in Recent nautilids. Some ammonoids of Carboniferous and Triassic age show several such bands at more or less regular angular distances on the ultimate whorls and at the aperture, e.g. Nomismoceras , Gatherites , Owenites , Paranannites , Juvenites and Melagathiceratidae gen. et sp. nov. Triassic material from Oman shows that the black coating was probably secreted from the inside, because the position of this organic deposit changes from interior to exterior in an anterior direction (i.e. adaperturally). This structure has previously been referred to as a 'false colour pattern' and is here interpreted as having been formed at an interim aperture or megastria ('alter Mundrand'). All structures discussed in the paper are considered to have been secreted by a single organ and to have been initiated by some form of stress or adverse conditions. Thus, certain environmental parameters and growth anomalies appear to have influenced their formation.     

Influence of thermoperiod and photoperiod on reproductive diapause in Bruchidius atrolineatus (Pic) (Coleoptera, Bruchidae)

Abstract Bruchidius atrolineatus (Pic) is a common pest infesting cowpea seeds ( Vigna unguiculata Walp) in Africa. In the Sahelian zone, the adults are in reproductive diapause during the dry season. Diapause induction depends on the climatic conditions during embryonic and post-embryonic development. A strain of B. atrolineatus originating from the Niamey (13^oN) was reared in different thermoperiodic and photoperiodic conditions. In the thermoperiodic regime 40:25^oC, in continuous darkness, induction of diapause was dependent on the duration of the thermophase. Photoperiod could also influence diapause induction but the response depended on the temperature. When the beetles were reared in conditions of LD 12:12 h, 40:25^oC, for seven generations, the proportion of diapausing adults decreased and their sensitivity to photoperiod increased. In LD 14:10 h, 40:25^CC, the proportion of diapausing adults remained high regardless of the photoperiod. In these conditions, the first emerging adults were sexually active and were used for selection of a strain with a low incidence of diapause. After twelve generations, the proportion of diapausing beetles was lower than 5%. The responses of this selected strain to photo- and thermoperiods were reduced. The sensitivity of B. atrolineatus to photoperiod and thermoperiod could be controlled by genetic systems as observed in other insect species.     

Response of three lotic assemblages to riparian and catchment‐scale land use: implications for designing catchment monitoring programmes

1. Although many studies have focussed on the effects of catchment land use on lotic systems, the importance of broad (catchment) and fine (segment/reach) scale effects on stream assemblages remain poorly understood. 2. Nine biological metrics for macrophytes (498 sites), benthic macroinvertebrates (491) and fish (478) of lowland and mountain streams in four ecoregions of France and Germany were related to catchment and riparian buffer land use using partial Redundancy Analysis and Boosted Regression Trees (BRTs). 3. Lotic fauna was better correlated (mean max., r = 0.450) than flora (r = 0.277) to both scales of land use: the strongest correlations were noted for mountain streams. BRTs revealed strong non‐linear relationships between mountain assemblage metrics and land use. Correlations increased with increasing buffer lengths, suggesting the importance of near‐stream land use on biotic assemblages. 4. Several metrics changed markedly between 10–20% (mountain ecoregions) and 40–45% (lowland) of arable land use, irrespective of the buffer size. At mountain sites with >10% catchment arable land use, metric values differed between sites with <30% and sites with >30% forest in the near‐stream riparian area. 5. These findings support the role of riparian land use in catchment management; however, differences between mountain and lowland ecoregions support the need for ecoregion‐specific management.     

Dissolved humic substances – ecological driving forces from the individual to the ecosystem level?

1. This review focuses on direct and indirect interactions between dissolved humic substances (HS) and freshwater organisms and presents novel opinions and hypotheses on their ecological significance. Despite their abundance in freshwaters, the role of HS is still inadequately understood. These substances have been considered too large to be taken up by freshwater organisms. On the contrary, here we present evidence that dissolved HS are indeed taken up and interact directly and/or indirectly with freshwater organisms. 2. We show that dissolved HS exert a mild chemical stress upon aquatic organisms in many ways; they induce molecular chaperones (stress shock proteins), induce and modulate biotransformation enzymes and modulate (mainly inhibiting) the photosynthetic release of oxygen by freshwater plants. Furthermore, they produce an oxidative stress, which may lead to membrane oxidation. HS modulate the multixenobiotic resistance activity and probably other membrane‐bound pumps. This property may lead to the increased bioaccumulation of xenobiotic chemicals. Furthermore, they can modulate the numbers of offspring in a nematode and feminise fish and amphibians. The ecological consequences of this potential remain obscure at present. HS also have the potential to act as chemical attractants (as shown with a nematode). 3. In some macrophytes and algae we show that HS interfere with photosynthesis and growth. For instance, the presence of HS suppresses cyanobacteria more than eukaryotic algae. By applying a quantitative structure activity relationship approach, we show that quinones in the HS interfere with photosynthetic electron transport. We show that even Phragmites leachate can act as a kind of phytotoxin. HS also have the potential to suppress fungal growth, as shown with the water mould Saprolegnia parasitica and force the fungus to respond by spore production. 4. In very soft, humic freshwaters, such as the Rio Negro, Brazil, HS stimulate the uptake of essential ions, such as Na and Ca, at extremely low pH (3.5–4.0) and prevent the ionoregulatory disturbance induced by acid waters, thereby enabling fish to survive in these environments. 5. We discuss whether or not HS are directly utilised by aquatic microorganisms or via exoenzymes, which may be washed in from the terrestrial catchment. There is accumulating evidence that the quality of the HS controls microbial growth. In total, net‐heterotrophy may result from HS‐mediated suppression of primary production by the quinone structures and/or from HS‐mediated support of microbial growth. As there is also evidence that HS have the potential to support photoautotrophic growth and suppress microbial growth, the opposite community effect could result. Consequently, dissolved organic carbon (DOC) has to be chemically characterised, rather than simply measuring bulk DOC concentration. 6. In sum, dissolved HS interact with freshwater organisms in a variety of ways in unenriched humic lakes. In addition to the well known effects of HS on light regime, for example, and the direct and indirect supply with carbon (energy), other interactions may be much more subtle. For instance, HS may induce internal biochemical stress defence systems and have the potential to cause acclimatisation and even adaptation. We are just at the beginning of understanding these interactions between dissolved HS and freshwater organisms.