The GIRK1 Brain Variant GIRK1d and Its Functional Impact on Heteromultimeric GIRK Channels

Four isoforms of GIRK channels (GIRK1–4) have been described in humans. In addition, several splice variants of more or less unknown function have been identified from several tissues and species. In our study, we investigated the structure and function of a new variant of GIRK1 that has been isolated from rat brain. Because of wide similarities with a previously described variant, we also named it GIRK1d. This variant lacks a region corresponding to exon 2 of full-length GIRK1, leading to a truncated GIRK1 that lacks the main part of the C-terminus. To study GIRK1d we used the Xenopus laevis expression system, the two-electrode voltage clamp method, and confocal laser scan microscopy. We found that our GIRK1d variant preferentially binds GIRK2 or GIRK4 over GIRK1. Furthermore, it largely reduces conductances mediated by GIRK1/2 or GIRK1/4 hetero-multimeric channels when coexpressed and nearly totally abolishes currents when replacing GIRK1 in hetero-multimeric channels.     

Patterns of Phanerozoic carbonate platform sedimentation

Carbonate platforms changed substantially in spatial extent, geometry, composition and palaeogeographical distribution through the Phanerozoic. Although reef construction and carbonate platform development are intimately linked today, this was not the case for most of the Phanerozoic. Carbonate production by non-enzymatic precipitation and non-reefal organisms is mostly responsible for this decoupling. Non-reefal carbonate production was especially prolific during times of depressed reef growth, balancing losses in reef carbonate production. Palaeogeographical distribution and spatial extent of Phanerozoic carbonate platforms exhibit trends related to continental drift, evolutionary patterns within carbonate platform biotas, climatic change and, possibly, variations in ocean chemistry. Continental drift moved large Palaeozoic tropical shelf areas into higher latitudes, thereby reducing the potential size of tropical platforms. However, the combined global size of carbonate platforms shows no significant decline through the Phanerozoic, suggesting that availability of tropical shelf areas was not a major control of platform area. This is explained by the limited platform coverage of low-latitude shelves (42% maximum) and occasional high-latitude excursions of platform carbonates. We speculate that reduced tropical shelf area in the icehouse tropics forced the migration of the many carbonate-secreting organisms into higher latitudes and, where terrigenous input was sufficiently low, extensive carbonate platform could develop.     

Sensory Motor Interfacing in Acoustic Behavior of Anurans

SYNOPSIS. Anurans respond to different acoustic signals in adistinct manner. Moreover, acoustic behavior strongly dependson the inner state of the animal and the social context. Neuroanatomicalstudies as well as extra- and intracellular recordings werecarried out to examine the problem of audio-motor interfacing.Acoustic signals are processed in a partly hierarchical andpartly distributed manner in the anuran central nervous system.Features are represented in a topographical manner. Auditorymaps in the midbrain torus semicircularis are read by a subsetof neurons of the laminar and magnocellular subnuclei, whichinterconnect the auditory pathway and premotor centres. These,in turn, feed into neural networks controlling vocalization,locomotion, or autonomic functions. Our data on the cytoarchitectonicorganization and connectivity of the interfacing neurons giverise to a population coding hypothesis which may explain thedifferential evaluation of acoustic signals. Additionally, immunohistochemicalfindings reveal strong neuromodulatory and hormonal input, especiallyonto interfacing neurons, suggesting intense influence on thephysiological properties of these cells.     

Mechanisms and regulation of reduction-based iron uptake in plants

Despite the usually high abundance of iron (Fe) in soils, the low solubility of Fe-bearing minerals restricts the available Fe pools in most aerobic soils to levels that are far below those required for microbial or plant growth. To acquire the necessary amounts of Fe from the environment, organisms have evolved mechanisms that enhance the solubility and dissolution rate of Fe(iii) oxyhydroxides prevailing in aerobic soils. Chemically, these mechanisms are based on weakening of the Fe–O bond by reduction, chelation and protonation. Physiologically, two distinct and in all known cases mutually exclusive strategies can be distinguished: the excretion of siderophores capable of solubilizing external ferric Fe and subsequent uptake of the ferric siderophore complex; and reduction of Fe(iii) prior to uptake of the more soluble Fe²⁺ ion. With the exception of graminaceous species, in which Fe uptake is based on the former mechanism, the latter strategy is found in all cormophytes and certain algae, yeast and bacteria. In higher plants, the increase in their capacity to convert extracellular ferric to ferrous Fe is part of a series of physiological and morphological events that act in concert to achieve appropriate internal levels of Fe. It is this amalgam of features that determines the Fe efficiency of a species or cultivar that in turn affects the yield of economically important plants and the natural distribution of species. Adaptive changes to limited Fe availability have been studied at the molecular, physiological and whole-plant level. This review summarises current knowledge of the components of reduction-based Fe uptake in plants and presents an integrated view of the present understanding of mechanisms that control the rate and extent of Fe absorption by roots.     

Natural history of the non-solitary sheetweaving spider Anelosimus jucundus (Araneae: Theridiidae)

Field observations were made on one Panamanian population of Anelosimus jucundus. Almost all webs were found in a relatively exposed area, on small shrubs and composites. This is in contrast to A. eximius , a colonial congeneric which in our study site built its large webs along moist, fern-covered banks. Web structure varied with different plant substrates; for example, only some of the webs incorporated a clearly defined lower sheet. Webs were built by penultimate instar females, and perhaps by adult females and males. In some cases, several adult females inhabited a web, but they remained under separate leaf canopies; during census observations co-operative efforts were not noted. Prey consisted mainly of winged insects. Juvenile sex ratio was about equal. The degree of sociality demonstrated by A. jucundus is discussed.     

Eocene tortoise beetles from the Green River Formation in Colorado,U.S.A. (Coleoptera: Chrysomelidae: Cassidinae)

Abstract The fossil history of leaf beetles (Chrysomelidae) is relatively poorly documented despite an abundance of available material. Of particular interest is the origin and radiation of the diverse tortoise beetles, a derived group within Cassidinae s.l. (=Cassidinae + Hispinae) defined by the exophagous life history and specialized morphology of the immature stages. Cassidinae is also a group with relatively few fossil records that can be assigned with any degree of certainty. Here we report two of the oldest definitive tortoise beetle fossils, Eosacantha delocranioides gen.n. et sp.n. and Denaeaspis chelonopsis gen.n. et sp.n. , from the Eocene Green River Formation (ca. 47 million years old) in northwestern Colorado, U.S.A. Owing to the fine level of preservation, many important features can be observed and are coded into the recent cladistic analysis for the subfamily. Phylogenetic analysis highlights that both genera have affinities with modern lineages, one restricted to the Old World and the other restricted to the Neotropics. Although Cassidinae as a whole extend into the Cretaceous, the available information suggests that the tortoise beetles perhaps originated and diversified during the Early Tertiary. As such, the morphological and biological transitions from the leaf‐mining hispiforms to the distinctive tortoise‐like cassidiforms, with their elaborate defensive larval shields and other unique behaviours, probably took place during the latest Paleocene or earliest Eocene. These Green River fossils are the oldest yet to document the specialized morphology associated with the transition in cassidine feeding and immature biology.     

The serphitid wasps (Hymenoptera: Proctotrupo‐morpha: Serphitoidea) of Canadian Cretaceous amber

Five new species and one new genus of Serphitidae microhymenoptera are described from Upper Cretaceous (Campanian) amber originating at the Grassy Lake locality in Alberta, Canada. New taxa include Serphites hynemani sp.n. , Serphites bruesi sp.n. , Serphites kuzminae sp.n. , Serphites pygmaeus sp.n. and Jubaserphites ethani gen. et sp.n. Topotype material for the type species of Serphites, Serphites paradoxus Brues is re‐illustrated and redescribed in greater detail, clarifying the characteristics of the species for comparison with the numerous serphitids that have been described subsequent to the work of Brues. We provide the first comprehensive report of known serphitid specimens in Canadian amber, draw comparisons with taxa in other Cretaceous deposits, and comment upon the palaeoecological connotations of the relatively diverse and morphologically disparate Canadian serphitid assemblage.