Ontogenetically stable dimorphism in a lacertid lizard (Acanthodactylus boskianus) with tests of methodology and comments on life-history

Recent arguments in the literature prompted us to compare methods for assessing sexual dimorphism in body proportions of lacertid lizards, using Acanthodactylus boskianus . Although expressing body-part measurements as proportional to head length was the most effective method, we recommend using trunk length for the baseline as a general method for lizards. We also argue that, when aiming to assess sexual dimorphism in body proportions of lizards, if the context is ecological, all available adults should be included. However, for morphology and taxonomy, small sub-samples of the largest individuals that maximally express their genetic morphological potential should be used. In A. boskianus , the sexual dimorphism of mensural characters in adults was typical: males were larger, with relatively larger head and appendages. However, the ontogeny of this dimorphism was unusual in that the differences existed already in youth and thereafter persisted isometrically. The sexual dimorphism of meristic characters was male-biased in numbers of femoral pores and of caudal vertebrae, and female-biased in numbers of ventral plates along the trunk and of precaudal vertebrae. Size dimorphism may conceivably play a role in sex recognition because two potential visual cues (i.e. size dimorphism and dichromatism) appear to complement each other.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society 2009, 97 , 275–288.     

High precision measurements of atmospheric concentrations and plant exchange rates of carbonyl sulfide using mid‐IR quantum cascade laser

Linking measurements of carbonyl sulfide (COS) with those of carbon dioxide (CO₂) has a potential in providing a powerful tracer of gross CO₂ fluxes between the atmosphere and land plants, a critical element in understanding the response of the land biosphere to global change. A new application of online COS, CO₂ and water vapor measurements based on newly designed mid‐infrared (IR) dual quantum cascade laser (QCL) spectrometer measures COS and CO₂ (at 2056 cm^?1) and water vapor (at 2190 cm^?1), with detectors cooled thermoelectrically (at ?43 °C) or with liquid nitrogen (?197 °C) for improved precision. Using the cryogenic detectors with averaging time of 1 s, precision was 50 pmol mol^?1, 0.4 μmol mol^?1 and 0.01 mmol mol^?1 for COS, CO₂ and water vapor, respectively (14, 0.2 and 0.003, respectively, for 60 s averaging time). We measured COS concentrations in ambient air, and changes in the rates of COS, CO₂ and water vapor exchange of attached leaves in response to changes in light intensity and ambient COS concentrations. The results were consistent with those of nononline gas chromatography–mass spectrometry for COS and IR gas analyzer for CO₂ and water vapor, with a high linear correlation for a broad range of concentrations (R²= 0.85 for COS and R²= 1.00 for CO₂ and water vapor). The new methodology opens the way for lab and field explorations of COS fluxes as a powerful new tracer for CO₂ exchange in the land biosphere.     

The Effect of Drying Rate on the Survival of Three Desiccation-tolerant Angiosperm Species

The effect of drying rate on the survival of three angiospermresurrection plants, Craterostigma wilmsii (homoiochlorophyllous),Xerophyta humilis (poikilochlorophyllous) and Myrothamnus flabellifolius(homoiochlorophyllous) was examined. All species survived slowdrying, but only C. wilmsii was able to survive rapid drying.C. wilmsii was rapidly able to induce protection mechanismssuch as folding of cell walls to prevent mechanical stress andcurling of leaves to minimize light stress, and thus survivedfast drying. Rapid drying of X. humilis andM. flabellifoliusappeared to allow insufficient time for complete induction ofprotection mechanisms. In X. humilis, there was incomplete replacementof water in vacuoles, the photosynthetic apparatus was not dismantled,plasma membrane disruption occurred and quantum efficiency ofphotosystem II (F_V/F_M) did not recover on rehydration. Rapidlydried leaves of M. flabellifolius did not fold tightly againstthe stem and F_V/F_Mdid not recover. Ultrastructural studies showedthat subcellular damage incurred during drying was exacerbatedon rehydration. The three species co-occur in environments inwhich they experience high desiccation pressures. C. wilmsiihas few features to retard water loss and thus the ability forrapid induction of subcellular protection is vital to survival.X. humilis and M. flabellifolius are able to retard water lossand protection is acquired relatively slowly. Copyright 1999Annals of Botany Company Chlorophyll fluorescence, Craterostigma wilmsii, drying rate, Myrothamnus flabellifolius, resurrection plant, ultrastructure, Xerophyta humilis.     

The Effect of Ultraviolet Radiation and Sucrose on IAA Levels in Spirodela oligorhiza

U.v. radiation significantly lowers the IAA level in frondsof Spirodela oligorhiza. Fronds grown in the light on mediumsupplemented with sucrose had much higher IAA levels than frondsgrown on medium lacking sucrose. The results suggest that u.v.-inducedabscission in Spirodela and the reduction of abscission by sucroseare both related to their effect on endogenous IAA levels.     

Fossil embryos and adult Viviparidae from the Early–Middle Pleistocene of Gesher Benot Ya'aqov, Israel: ecology, longevity and fecundity

Ashkenazi, S., Klass, K., Mienis, H.K., Spiro, B. & Abel, R. 2010: Fossil embryos and adult Viviparidae from the Early–Middle Pleistocene of Gesher Benot Ya'aqov, Israel: ecology, longevity and fecundity. Lethaia, Vol. 43, pp. 116–127.
A unique fossil assemblage of the extinct freshwater viviparids Viviparus apameae galileae and Bellamya sp. with intact embryos enabled the assessment of population ecology parameters applied so far only to recent living populations. The assemblage, from the Early Middle Pleistocene site of Gesher Benot Ya'aqov, occurs in the sedimentary sequence above the Matuyama Brunhes Boundary (MB boundary) at 0.78 Ma. This fossil assemblage is related to a shoreline habitat that was affected by desiccation during a sudden drop in water level. In both species, the youngest females with embryos had five or more whorls, with heights of >24.8 and >16.1 mm in Viviparus and Bellamya respectively. Comparison of shell height and width, aperture height and width and the ratio of shell height/width indicated that females are significantly longer and larger than the shells without embryos. Longevity was estimated as at least 9 years for Viviparus and 8 years for Bellamya and lifetime fecundity of female viviparids was estimated based on longevity and reproductive period. The high number of reproducing females and high number of embryos indicate favourable habitat and climate conditions for both Viviparidae. The fossil Viviparidae from GBY have the characteristics of organisms that are K-selected by natural selection forces. □ Fecundity , fossil embryos , longevity , molluscs , Pleistocene , reproductive output , sexual dimorphism , viviparids.