Multiplication In Vitro of Limonium estevei Fdez. Casas

Plantlets of Limonium estevei Fdez. Casas, an endangered Spanishspecies, were successfully regenerated from nodal segments excisedfrom young seedlings. Initiation of multiple adventitious budswere obtained in MS modified medium plus 1 mg l^–1 IBAand 0·1 mg l^–1 BAP. Rooting was achieved by transferof the isolated shoots to fresh MS medium without plant growthregulators. Fully grown plants were established in a pottingmix and are growing well in a greenhouse. Limonium estevei, in vitro multiplication, adventitious regeneration     

Functional Analysis of the Intrathalline and Intracellular Chlorophyll Concentrations in the Lichen Family Umbilicariaceae

Intrathalline and intracellular chlorophyll concentrations togetherwith thallus structure were studied in 12 species of the lichenfamily Umbilicariaceae in order to explore pigment limitationsfor light absorption and for maximum rates of net photosynthesis(A_max). Species from high light environments tended to haverelatively low chlorophyll concentrations and vice versa. Chlorophyllconcentration on a surface area basis of all species studiedwas sufficient to absorb 80–99% of the incident light,which led us to believe that chlorophyll concentration was nota limiting factor for A_max. A_maxof Umbilicariaceae was smallerthan A_maxof leaves of vascular plants, both on a dry weightand on a surface area basis. These differences slightly decreasedbut did not disappear when referred to the chlorophyll concentrationof the photosynthetic tissues, but reference units had a confoundingeffect in the comparisons. Differences in A_maxon a dry weightbasis between Umbilicariaceae and vascular plants disappearedwhen comparisons were made with the whole plant and not simplywith the leaf. We found a significant, inverse relationshipbetween amount of alga and chlorophyll concentration withinthe algal cells in the lichens studied. This was interpretedas a mechanism to avoid pigment self-shading within the algallayer, distributing more efficiently the photosynthetic pigmentsover a given surface area, and is the first indication of sucha mechanism in lichens. It is suggested that thallus structureand physiology have a larger influence on the observed low A_maxofthe lichens studied than chlorophyll content. Algal cells; chlorophyll concentration; lichens; light harvesting; net photosynthesis; stereology; thallus structure; Umbilicariaceae     

Ecological and historical filters constraining spatial caddisfly distribution in Mediterranean rivers

1. Contemporary species distributions are determined by a mixture of ecological and historical filters acting on several spatial and temporal scales. Mediterranean climate areas are one of the world's biodiversity hotspots with a high level of endemicity, which is linked to complex ecological and historical factors. 2. This paper explores the ecological and historical factors constraining the distribution of caddisfly species on a large regional scale. A total of 69 taxa were collected from 140 sampling sites in 10 Iberian Mediterranean river basins. Approximately 74% of taxa can be considered rare, with the southern basins (the Baetic–Riffian region) having greater endemicity. The greatest richness, involving a mixture of northern and southern species, was found in the transitional area between the Baetic–Riffian region and the Hesperic Massif. 3. The historical processes occurring during the Tertiary (i.e. the junction of the Eurasian and African plates) explained 3.1% of species distribution, whereas ecological factors accounted for 20.7%. Only 0.3% was explained by the interaction of history and ecology. A set of multi‐scale ecological variables (i.e. basin, reach and bedform characteristics) defined five river types with specific caddisfly assemblages. The commonest caddisfly species accounted for the regional distribution pattern, while rare taxa contributed to the explanation of subtle patterns not shown by common species. 4. Despite the importance of historical factors for biogeography and the large scale used in our study, ecological variables better explained caddisfly distribution. This may be explained by the length of time since the historical process we are considering, the high dispersion and colonisation capacity of many caddisfly species, and the strong environmental gradient in the area. Because of the historical and environmental complexity of Mediterranean areas, rare taxa should be included in ecological studies so that the singularity of these ecosystems is not missed.     

Effect of thermal acclimation on preferred temperatures in two mygalomorph spiders inhabiting contrasting habitats

Variations in the preferred temperatures during the rest periods of Grammostola rosea Walckenaer and Paraphysa parvula Pocock, two mygalomorph spiders occupying different habitats in central Chile, are analyzed. The former inhabits arid and semi‐arid lowland near plant communities, composed of shrubs (evergreens with small leathery leaves) and small trees; the latter is found in the central mountains of the Chilean Andes, above 2000 m.a.s.l. The preferred temperatures of these spiders at different times of day and exposure to cold (15 °C) and warm (25 °C) acclimation temperatures are compared. Body mass does not affect the preferred temperature of the larger spider G. rosea, although P. parvula, a spider with half of the body mass of G. rosea, shows a decrease in preferred temperature with body mass. This can be explained by a higher plasticity and thermal sensitivity of the smaller species as result of increased surface : volume ratio. The preferred temperature increases with the hour of the day under both acclimation conditions in P. parvula and in cold‐acclimated G. rosea, which is likely associated with crepuscular and nocturnal behaviour in both species. Grammostola rosea shows temperature preferences lower than those of P. parvula under both acclimation conditions. The increase of the acclimation temperature from 15 to 25 °C results in an increment of 2–3 °C in the preferred temperature of P. parvula but only 0.2 °C in that of G. rosea. Two contrasting lifestyle strategies are found: a small mygalomorph spider with phenotypic plasticity and adaptation to the fluctuating environment of high altitude, and a large mygalomorph spider with higher thermal inertia adapted to the more stable environment of lowlands.     

Energy storage during the transition from endogenous to exogenous feeding in Australian redclaw crayfish Cherax quadricarinatus (Von Martens, 1898)

Summary

The Australian redclaw crayfish Cherax quadricarinatus hatches at an advanced stage. Two post-hatching stages rely on yolk reserves before the organism becomes a juvenile. After a juvenile appears, the yolk is depleted and young crayfish might spend a few days among female pleopods before starting to feed independently. During this phase, the juvenile organism needs alternative energy sources. Offspring from three females were analyzed with histological and histochemical techniques, from hatching until reaching the 2-week juvenile stage, to trace digestive system development and internal organ lipid and glycogen accumulation. Neutral lipids are stored in specialized cells of the hepatopancreatic tissue until the juvenile stage is reached. An increasing rate of accumulation was found. Glycogen was stored in hepatopancreas and tail muscle cells until post-embryo II, and no increasing or decreasing rate was found in storage functions.     

FLUORESCENT MEASUREMENTS OF DNA, RNA AND PROTEINS TO PERFORM COMPARATIVE ANALYSES OF MICROBIAL COMMUNITIES FROM THE ENVIRONMENTS

Simple and rapid methods for the quantification of DNA, RNA and proteins using specific fluorescent dyes are proposed for the comparison and monitoring of microbial communities from the environment. The purpose of this study was the use of straightforward in situ methods which voided the need for preservation of samples and the risk of potential degradation and quantitative changes during transportation. Aside from this, methods used to obtain information on environmental microbial communities are generally time-consuming and present certain difficulty above all when working on solid substrates such as soils and rocks. New generation fluorescent dyes that bind specifically to DNA, RNA and proteins allow simple and rapid estimates of these biomolecules in crude environmental samples.

PRACTICAL APPLICATIONS

Monitoring the metabolic state of microbial communities on different substrates and environments is a requirement for comparing samples and assessing the participation of microorganisms in a variety of processes. Solid substrates are not easily analyzed by microscopic techniques and they require long processing times and tedious work. Aside from this, only a minor fraction (<1%) of microorganisms in most natural environments can be cultured in standard microbiological media ( Ward et al. 1990 ). Other studies using incorporation of labeled substrates to approach activity rates or biomolecule extractions represent complex and long procedures during environmental studies.In order to evaluate microbial communities in a variety of substrates and environments, rapid and simple methods are proposed by measuring DNA, RNA and/or proteins using specific fluorescent dyes, without a need for prior purification, from crude solid samples.