Flow velocity underpins microhabitat selection by gobies of the Australian Wet Tropics

1. Water flow is a critical driver of aquatic ecosystem health and function. Amid rising concerns over changing flow regimes, there is an urgent need to understand the functional mechanisms by which flow influences patterns of freshwater biodiversity. 2. We explored the functional link between flow velocity and microhabitat specialisation in a speciose group of freshwater gobies (comprising over half the total fish species richness) within insular streams of the Australian Wet Tropics under base flow conditions. We addressed two particular questions: (i) What is the relative selectivity of species towards streambed composition and water flow velocity? and (ii) Can patterns of microhabitat occupation be explained by differences in intrinsic flow performance among species? To answer these questions, we combined visual field observations of microhabitat use with flow tank assessments of flow speed performance. 3. Tropical freshwater gobies displayed strong specificity towards flow velocities, while being relatively non‐selective towards streambed composition. At opposite extremes of the spectrum, we found Sicyopterus lagocephalus occupying high‐flow (>1.0 ms^?1) microhabitats while Redigobius bikolanus selected slower‐flow (<0.05 ms^?1) areas. These patterns of microhabitat flow specificity were largely explained by the different abilities of species to swim and/or cling to the substratum under these different flow settings. 4. Our findings confirm suggestions that predictable base flows in tropical streams support habitat specialists, which include one species capable of occupying areas of extremely high flow that very few other fishes can withstand. 5. The functional link between flow and gobioid fish distribution patterns could occur throughout tropical streams of the Indo‐Pacific and Caribbean as a widespread phenomenon that may help inform stream flow management guidelines to maintain this substantial component of tropical freshwater biodiversity around the globe.     

Growth and sporulation of Oidium begoniae: development of a deterministic model

Growth and sporulation of Oidium begoniae (begonia powdery mildew) on detached leaves was observed daily under a stereomicroscope. A mathematical model of growth and sporulation was constructed based on the patterns observed. The essential components of the model are three genetically fixed components of colony growth and sporulation and six components which changed with environmental and physiological conditions. The genetically fixed components were: the ultimate number of germ tubes, the hyphal growth unit (HGU or mean length supporting one branch), and the diurnal periodicity of sporulation. These components were shown to have approximately the same values at 15 and 21 °C. Components which varied with temperature were: the latent periods of germination, branching and sporulation, the time taken to reach the ultimate germ tube number, and the number of conidiophores per HGU, The derived equations were tested against observed sporulation and resulted in highly significant correlations. Similar results were obtained with published observations for Erysiphe graminis f. sp. hordei. This colony-level model can be used as units to construct models of disease progress and suggests that it is theoretically possible to model disease in the field from laboratory studies. The model can be used in computer simulations of colony growth as demonstrated by a computer program in the Appendix.     

Affinities in C3Cyperus lineages (Cyperaceae) revealed using molecular phylogenetic data and carbon isotope analysis

Maximum likelihood and Bayesian analyses of nrDNA (ETS1f) and plastid DNA (rpl32‐trnL, trnH‐psbA) sequence data are presented for ‘C₃Cyperus’ (Cyperaceae). The term ‘C₃Cyperus’ indicates all species of Cyperus s.l. that use C₃ photosynthesis linked with eucyperoid vegetative anatomy. Sampling comprises 77 specimens of 61 different taxa, representing nearly all previously recognized subdivisions of C₃Cyperus and the segregate genera Courtoisina, Kyllingiella and Oxycaryum. According to our results, the Cyperus clade is divided in six well‐supported clades. The first of these clades (clade 1) forms three subclades largely corresponding to Cyperus sections Haspani, Incurvi and Diffusi. Clade 2 comprises the entirely New World C. section Luzuloidei sensu Denton (1978). Clade 3 is a highly diverse clade including two subclades: clade 3a, C. sections Pseudanosporum and Anosporum plus the segregate genera Courtoisina and Oxycaryum; and clade 3b, C. section Fusci. Clade 4 corresponds to C. section Alternifolii and clade 5 to C. section Leucocephali plus the segregate genus Kyllingiella. The sixth clade is a well‐supported monophyletic clade encompassing all C₄Cyperus s.l. species (‘C₄Cyperus’). This study establishes a phylogenetic framework for future studies. © 2011 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, 167 , 19–46.     

CHEMICAL STIMULUS DETERMINANTS OF CAT GENICULATE GANGLION CHEMORESPONSIVE GROUP I UNIT DISCHARGE

Cat geniculate ganglion group I neurons preferentially innervatereceptors on fungiform papillae on the reai and sides of thetongue with fibers of large diameter. They display low spontaneousactivity rates and are responsive to distilled water and manyinorganic acids. In a study testing a wide variety of organiccompounds, it was found that group I units were discharged bycompounds with carboxylic and phosphoric acid groups. A fewnitrogen compounds were also effective. In all cases the responsewas pH dependent in that maximum discharge occurred when thesolution pH was at or below the pKa of the active chemical group.The compounds most active in the pH region 5.0–7.0 provedto be nitrogen heterocyclic compounds (pyridine or thiazolidine)or compounds with a heterocyclic nitrogen component (imidazolering). Only the proton donor form of the molecule seemed tostimulate. ^*This research was supported in part by NSF Grant GB-41446X.     

The sequence of porcine αs1-casein cDNA: evidence for protein variants generated by altered RNA splicing

A cDNA library was constructed from mRNA isolated from lactating porcine mammary gland and screened with a bovine alpha s1-casein cDNA clone. Three classes of cDNA isolated varied in the number of bases within the coding region. The full length porcine alpha s1-casein cDNA is 1124bp and codes a preprotein of 206 amino acids. The other two classes of alpha s1-casein cDNA lacked 18bp and 60bp respectively when compared to the 1124-bp cDNA sequence. PCR amplification confirmed the presence of these sequences in total RNA. These differences appear to be due to altered RNA splicing.     

Signal transduction in Mimosa pudica: biologically closed electrical circuits

Biologically closed electrical circuits operate over large distances in biological tissues. The activation of such circuits can lead to various physiological and biophysical responses. Here, we analyse the biologically closed electrical circuits of the sensitive plant Mimosa pudica Linn. using electrostimulation of a petiole or pulvinus by the charged capacitor method, and evaluate the equivalent electrical scheme of electrical signal transduction inside the plant. The discharge of a 100 µF capacitor in the pulvinus resulted in the downward fall of the petiole in a few seconds, if the capacitor was charged beforehand by a 1.5 V power supply. Upon disconnection of the capacitor from Ag/AgCl electrodes, the petiole slowly relaxed to the initial position. The electrical properties of the M. pudica were investigated, and an equivalent electrical circuit was proposed that explains the experimental data.