The paper describes work in progress the application of process-oriented modeling to situation assessment within a research project in limnology. In the field study, some 50 lakes in Southern Germany are monitored in order to explore and document the changes in the distribution of a particular aquatic plant, Najas marina, and understand their preconditions. The ultimate objective is using this ...

The ventral surface of the pond skater, Gerris najas, is covered with a hair pile extremely resistant to water penetration. It is possible that the hydrofuge properties of the hair pile are maintained by an oil released from glands opening out on to the general body surface. Holdgate (1955) has reported findings indicating that many surface-dwelling and surface-breathing aquatic insects activel...

Three pregnane-type steroids, including a new metabolite, 3β-methoxy-5,20-pregnadiene (1) along with two known analogues, 3β-acetoxy-5,20-pregnadiene (2) and 5α-pregna-1,20-dien-3-one (3) were isolated from the soft coral Scleronephthya flexilis. Standard spectroscopic techniques were used to determine the structure of new steroid 1. The absolute stereochemistry of steroid 2 was confirmed by X-...

Cryptic sympatric species arise when reproductive isolation is established in sympatry, leading to genetically divergent lineages that are highly similar morphologically or virtually indistinguishable. Although cryptic sympatric species have been reported in various animals, fungi, and protists, there are few compelling examples for plants. This investigation presents a case for cryptic sympatr...

The re-colonization of aquatic habitats by angiosperms has presented a difficult challenge to plants whose long evolutionary history primarily reflects adaptations to terrestrial conditions. Many aquatics must complete vital stages of their life cycle on the water surface by means of floating or emergent leaves and flowers. Only a few species, mainly within the order Alismatales, are able to co...

Winter survival of organisms has a crucial effect on their fitness in a seasonal environment. We tested whether overwinter survival of male water striders, Aquarius najas (De Geer) (Heteroptera: Gerridae), is associated with the time of season they leave the water for winter diapause. This was performed by comparing parameters of males leaving the water at the beginning of autumn and 1 month la...