Cyathidium plantei sp. n., an extant cyrtocrinid (Echinodermata, Crinoidea)—morphologically identical to the fossil Cyathidium depressum (Cretaceous, Cenomanian)

A new species of the holopodid genus Cyathidium was found on rocks off Grande Comore in a depth of around 200 m. Based on external morphology of resting animals, the new species Cyathidium plantei sp. n is described, with emphasis on comparison to the only other extant species ( C. foresti ) as well as to the four extinct representatives of the genus. Concerning morphological characters, the new species is almost identical to the Cretaceous C. depressum . A cladistic analysis of the entire family, including the genus Holopus, shares a peculiar pattern of bending of the arms, which in principle is an apomorphic character of the family and in detail shows variations within the family. In addition, stratigraphic data are used for the determination of the evolutionary direction. This analysis reveals that the two recent species are closely related to each other, and to the fossil C. depressum . from which the entire family is probably derived.     

The Effect of Kinetin on Stomatal Opening and the Rate of Intake of Carbon Dioxide in Mature Primary Leaves of Barley

Treatment of mature primary leaves of barley with 3x10^–6M solutions of kinetin resulted in increased rates of net assimilationof carbon dioxide. The resulting reduction in the concentrationof carbon dioxide inside the leaves was considered as one factorcausing the observed decreases in stomatal resistances, but,in addition, kinetin appeared to affect the stomatal mechanismdirectly.     

Effects of phenotypic variation onto body temperature and flight activity in a polymorphic insect

Abstract.  According to biophysical principles, colour and size are important phenotypic factors that may influence body temperature and activity in ectothermic insects. In taxa showing female-limited polymorphism, males and female morphs differ in body colour, size and activity pattern. However, no previous study has evaluated whether such phenotypic and behavioural variation relates to differences between males and female morphs in thermal properties. In the present study, the relationships between body colour, size, activity and body temperature are examined under laboratory and field conditions, for the polymorphic damselfly Enallagma cyathigerum (Charpentier, 1840) (Odonata: Zygoptera). Contrary to expectation, males and female colour morphs of this species do not differ in thermal properties (i.e. heating characteristics or field body temperatures). When questioning phenotype and activity, temperature does not appear to be relevant for understanding the maintenance of female-limited polymorphism.     

Competition between Shoots in Stands of Clonal Plants

Abstract Data on shoot turnover, shoot size distributions and individual shoot growth in stands of clonal plants are reviewed and compared with shoot density regulation in non-clonal plants. Shoots are the smallest units capable of independent existence in clonal as well as unitary plants and this comparison allows an investigation of the impact of integration and other factors on clonal shoot dynamics. Physiological integration, the capacity of clonal plants to exchange resources and growth substances between interconnected shoots, has long been held responsible for the ability of clonal plants to prevent shoot overproduction and for the general lack of density-dependent mortality and self-thinning. A review of published data leads to the conclusion that the effects of integration on shoot dynamics in clonal plants have been overestimated. Other characteristics such as the density-dependent control of meristem activity, the synchronization of shoot growth in spring and the maximum shoot size, seem more important for the deviating behaviour of shoot populations of clonal plants.     

Cellular Behaviour Modulated by Ions: Electrophysiological Implications

. This essay considers the responses of Paramecium and other ciliates to the inorganic ion environment from an elec-trophysiological point of view. In reviewing data from published and unpublished sources it is shown that ions affect the cellular behaviour in multiple ways because the transmembrane potential can change due to the alteration of equilibrium potentials, ion conductances and surface charges of the membrane. Sensory input including effects from the ionic environment converge upon the membrane potential which has a temporal and spatial summing function. Hyperpolarizing and depolarizing potential shifts from the set point are near-simultaneously and omnidirectionally transmitted along the membrane including the ciliary boundaries. The membrane potential regulates ciliary motility via an intraciliary messenger, Ca²⁺, which can enter, and presumably leave, the cytosol directly adjacent to the ciliary motor. Integration of the responses of thousands of cilia occurs in accordance with the electrical and structural provisions of the cell. Potential-regulated motor and behavioural responses attenuate with time. This phenomenon, which has been loosely termed adaptation, has an electrophysiological basis in analogy to membrane accommodation following sustained stimulus input. The mechanisms of adaptation serve to restore, in principle, the membrane resting state and, thereby, the sensitivity to depolarizing and hyperpolarizing shifts of the membrane potential and the cell's responsiveness to environmental stimuli, respectively. For the inorganic ions involved in chemosensation the terms attractant and repellent are not applicable. They should be reserved to signalling substances which per se can define the behaviour of the cell.     

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.