VARIABILITY OF THE GENITAL SYSTEM OF HELIX POMATIA L., 1758 AND H. LUCORUM L., 1758 (GASTROPODA: STYLOMMATOPHORA)

This paper examines the variability of the genital characters ofHelix pomatia and H. lucorum. Some of these characters are commonlyused to distinguish the two closely related species. Variationswithin and between populations are also investigated. The highvariability of these characters can frequently lead to identificationerrors, especially in eastern Europe. Correct identificationof these edible snails is also of commercial importance, differentspecies having a different price. The reciprocal nature of themale parts of the genitalia and the bursa stalk and diverticulumcomplex is pointed out. A possible function of the diverticulumis suggested on the basis of size relations between genitalsystem features. (Received 12 August 1999; accepted 11 April 2000)     

Strong genetic cohesiveness between Italy and North Africa in four butterfly species

The sea acts as an effective dispersal barrier for most terrestrial animal species. Narrow sea straits, therefore, often represent areas where species are able to disperse from one land mass to another. In the Mediterranean Sea, the narrowest connecting points between North Africa and Europe are the Strait of Gibraltar and the Strait of Sicily. In the past, climatic oscillations caused changing sea levels and thus influenced the permeability of these sea straits. We analysed the genetic structure of four butterfly species that all occur on both sides of the Strait of Sicily. In all four species, we observed a lack of genetic differentiation between the populations of North Africa and those of Italy. Species distribution models support the strong cohesiveness in that they show a largely continuous glacial distribution over Italy and North Africa. The data obtained reveal that there was a large exchange of individuals between Italy and the eastern Maghreb during the last ice age. This might not only be the case for the species under investigation in the present study, but also might represent a more general pattern for mobile thermophilic western Palearctic species. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 818–830.     

Relationships between Bulb Size, Apex Size and Flowering in Bulbous Iris cv. Ideal

Large, retarded bulbs of the Iris cv. Ideal flower readily after exposure to appropriate preplanting conditions, whereas smaller bulbs flower with decreased frequency. Flower initiation occurs when apices from large, retarded bulbs are cultured on either Murashige-Skoog medium supplemented with gibberellic acid, or on the same medium without gibberellic acid on which scales from large bulbs have been incubated. Since floral initiation seldom occurs in explants from small bulbs, it is likely that reduced flowering of small bulbs relates in part to characteristics of the apical meristem. Apical dome diameter is one characteristic of retarded (and freshly dug) bulbs that is positively correlated with bulb size. However, whereas prolonged storage at retarding temperature increases the frequency of flowering of smaller bulbs, there is not a concomitant increase in apical dome diameter. Moreover, the ratio of apical dome diameter to bulb size in freshly dug bulbs does not increase measurably with later digging date indicating that apical dome size is not correlated with bulb maturity.     

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.