The Term 'Fossa Bridgei' and Five Endocranial Fossae in Teleostome Fishes

Laterally on each side of the dorsal surface of the otic region of the endocranium of some teleostome fishes are two distinct depressions. Nearly sixty years ago Stensiö regarded these depressions in the sturgeon Acipenser ruthenus as one unit and called it 'fossa bridgei'. Since then this term has been employed by comparative ichthyologists in various meanings, which has hindered communication and interpretation. A disposal presented here eliminates this contusion and sheds light on the homologies of some of the fossae on the dorsal of the teleostome endocranium.     

Trichomes of the seed fern Blanzyopteris praedentata: implications for plant–insect interactions in the Late Carboniferous

The fronds and compound tendrils of the Stephanian (Late Carboniferous) seed fern Blanzyopteris praedentata possess several types of trichomes, two of which may, based on their morphology, have functioned as deterrents against herbivores. Bands of upwardly curved trichomes, occurring on the adaxial surfaces of tendrils, frond- and pinna rachides, are also known from extant plants, where they create mechanical obstacles. Other trichomes that are glandular occur on most parts of the foliage and tendrils and represent a different form of defence mechanism. These trichomes apparently possessed a touch-sensitive mechanism that opened the secretory cell when touched. They are interpreted as functionally similar to the so-called 'explosive' trichomes of certain extant Cucurbitaceae and Solanaceae. Studies of living Oleander aphids ( Aphis nerii ) on Sicana odorifera (Cucurbitaceae) demonstrate the effectiveness of the physical component of this defence. When touched and ruptured by an aphid, the trichomes of S. odorifera rapidly release a sticky exudate, which adheres to the animal's legs; the accumulation of exudate on the legs eventually impedes the aphid. Based on these studies, hypotheses are presented on the types of animals that might have been deterred by the glandular trichomes of B. praedentata in the Late Carboniferous.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 141 , 133–149.     

Show your true colour: cues for male mate preference in an intra‐specific mimicry system

1. Polymorphism limited to the female sex occurs in a variety of animal species and has been shown to be an attractive model system for examining general questions in signal detection theory. 2. When observed in damselflies, typically one female morph is an example of sexual dimorphism, whereas the other is considered as a functional malemimic that resembles the male's phenotype in several traits. 3. While several studies focused on male harassment and subsequent cost/benefit trade‐offs in female morphs, it remains understudied at the proximate level, which precise cues are relevant to mate‐searching males for discriminating among potential mates. 4. In the present study, we scored male mate preference to natural and manipulated phenotypes in the polymorphic damselfly Nehalennia irene Hagen. 5. In contrast to expectation, male preference did not change when colour was manipulated and male preference remained consistently for andromorph > male > gynomorph across treatments. 6. This suggests that cues other than body coloration primarily affect male mate preference in the present study system.     

Guard Cell Pressures and Wall Properties during Stomatal Opening

Pressures required to produce stomatal apertures of differentwidths have been measured in guard cells of T. virginiana andC. communis. These pressures are lower than those that coulddevelop in guard cells at full turgor on account of their osmoticproperties. During the Spannungsphase the metabolism of guardcells seems to contribute towards a reduction of the elasticmodulus of their walls, whereas during the motorphase the volumetricmodulus of the cell as a whole, apparently increases gentlyat first and then more markedly as maximum apertures are approached.     

Seed banks cause elevated generation times and effective population sizes of Arabidopsis thaliana in northern Europe

It is commonly found that effective population sizes of natural populations are much smaller than census sizes of plants and animals. However, theoretical studies have shown that factors rarely investigated empirically, like seed banks in plants and diapause in animals, may have profound influence on effective sizes. Here we investigate whether the presence of seed banks can explain the relatively high genetic variability observed in northern European Arabidopsis thaliana populations with small census sizes. We have genotyped three above- and below- ground cohorts in 27 Norwegian populations using single nucleotide polymorphism markers. Although the populations varied extensively in levels of variability within and between cohorts, standard genetic population measures were comparable to those obtained in previous studies on above-ground cohorts using microsatellite markers. Estimated effective population sizes are larger for total populations (containing both seed bank and above-ground cohorts for 1 year) compared to each of the cohorts considered separately. Using a conservative approach, we find that the effective sizes are larger than census sizes of local populations, and that the effective generation time is higher than 1 year (3–4 years, on average), making A. thaliana a perennial semelparous plant at many northern European localities.     

Efficiency of Root Respiration of a Flood-Tolerant and a Flood-Intolerant Senecio Species as Affected by Low Oxygen Tension

A method was described to determine root growth respiration and root maintenance respiration rate of plants, grown in culture solutions of high and low oxygen concentrations, during linear growth. Root growth respiration of aerobically grown plants was three to four times lower in the flood-intolerant Senecio jacobaea L. than in the flood-tolerant species. Senecio aquaticus Hill. Root growth respiration of Senecio aquaticus Hill decreased by a factor two to three upon transplantation to a culture solution of low oxygen tension. The difference in root growth respiration between aerobically and anaerobically grown Senecio aquaticus Hill was ascribed to the presence of a highly active non-phosphorylating oxidase.     

Effects of Water Stress on the Resistance to Uptake of Carbon Dioxide in Tobacco

An attempt was made to determine the relative importance ofthe stomata in restricting CO₂ uptake under conditions of waterstress. The air-phase and liquid-phase resistances to uptakeof CO₂ were determined from measurements of the rates of assimilationand transpiration and the corresponding concentration gradientsof CO₂ and H₂O vapour. The results showed that the air-phaseresistances (stomata) could account for only half the reductionin the rate of photosynthesis accompanying water stress. Experimentsin which air was passed through the leaf confirmed that waterstress restricted CO₂ fixation within the leaf itself. The resultsand their possible explanation are discussed in relation toother work.