Search results for " Systematics."
showing 10 items of 4820 documents
Eurhomalea exalbida (Bivalvia): A reliable recorder of climate in southern South America?
2012
Abstract Due to the lack of suitable high-resolution archives, regional and continental-scale climate dynamics of southern South America are not well understood. Shells of the long-lived, shallow-marine bivalve mollusk, Eurhomalea exalbida (Dillwyn), are likely to contain information on the past water temperatures. As yet, however, no rigorous calibration study has been presented so that growth history traits and the reliability of shell oxygen isotope-based temperature estimates remain unknown. Shell growth patterns and oxygen isotope ratios of four young specimens of E. exalbida from the Falkland Islands (Southwest Atlantic) were analyzed and cross-calibrated with environmental parameters…
Unique growth pattern of Metoposaurus diagnosticus krasiejowensis (Amphibia, Temnospondyli) from the Upper Triassic of Krasiejów, Poland
2013
Morphology and bone histology of femora, tibiae, and fibulae of the temnospondyl Metoposaurus diagnosticus krasiejowensis from the Upper Triassic locality of Krasiejow (Poland) are studied for the first time. The growth pattern of Metoposaurus as preserved in a small growth series of femora, shows a regular alternating sequence of fast and slow growth phases, which are interpreted as representing zones and annuli. The slow growth phases (annuli) of the inner and outer cortex as well as those of different specimens are of a regular broad thickness. Such broad annuli are so far unknown for any vertebrate and make the growth pattern for Metoposaurus unique. These slow growth phases always cont…
Pretarsal structures in the family Cydnidae sensu lato (Hemiptera: Heteroptera: Pentatomoidea)
2010
New data on the pretarsus in Cydnidae sensu lato are presented; 56 species of 38 genera are studied based on the SEM techniques. Pretarsal structures in Cydnidae s.l. are demonstrated to be not uniform; some are typically pentatomoid, and some are atypical for Pentatomoidea. Structures associated with the unguitractor plate, described for the first time by Weirauch (2005) in Reduviidae, and not reported for Cydnidae s.l. in the past, are described for the first time.
Effects of intensity and duration of infection by a hemiparasitic plant, Rhinanthus serotinus, on growth and reproduction of a perennial grass, Agros…
1999
Arising from annual variation in parasitic plant population densities, substantial yearly changes may occur in the parasitic load of an individual perennial host. We conducted two two-year greenhouse pot experiments to examine the effects of varying intensities and duration of infection by an annual root hemiparasitic plant, Rhinanthus serotinus, on the growth and reproduction of its perennial host grass, Agrostis capillaris. In the first experiment, one host plant was growing either alone or under a load of 1 or 3 root hemiparasitic plants for one growing season, and during the next season all hosts continued their life free of hemiparasites. In the second experiment, the host plants eithe…
The microstructural variability of the intercentra among temnospondyl amphibians
2014
The histology of the vertebral centrum of the morphologically diverse Temnospondyli is poorly known. In this study, the variability of the histological framework of various taxa from several Permian and Triassic localities was investigated for the first time. Twelve intercentra, forming the anterior part of the diplospondylous centra of temnospondyls, were examined histologically. The intercentra of all studied taxa share a highly vascularized cortex on the ventro-lateral side and primary and secondary trabecular, endochondral bone on the dorsal side. A high variability is present, among others, within the arrangement of the vascular cavities, the density of the trabeculae and the distribut…
Toward a Phylogenetic Classification of the Lauraceae: Evidence from matK Sequences
2000
Abstract The larger part of the matK gene and the (3′−) adjacent spacer have been sequenced and used for phylogenetic analyses in 48 species of Lauraceae from all parts of their geographical range, and in three outgroup taxa. Except for the aberrant genera Hypodaphnis and Cassytha, the genetic divergence within the family is surprisingly low. In spite of this, several clades receive sufficient support to change our current concepts of relationships within the family. Particularly well supported is a Beilschmiedia–Cryptocarya clade that had been recognized by wood anatomy, but not in most of the recent morphological systems. The separation between taxa with involucrate and non-involucrate in…
The unique skeleton of siliceous sponges (Porifera; Hexactinellida and Demospongiae) that evolved first from the Urmetazoa during the Proterozoic: a …
2007
Abstract. Sponges (phylum Porifera) had been considered as an enigmatic phylum, prior to the analysis of their genetic repertoire/tool kit. Already with the isolation of the first adhesion molecule, galectin, it became clear that the sequences of the sponge cell surface receptors and those of the molecules forming the intracellular signal transduction pathways, triggered by them, share high similarity to those identified in other metazoan phyla. These studies demonstrated that all metazoan phyla, including the Porifera, originate from one common ancestor, the Urmetazoa. The sponges evolved during a time prior to the Ediacaran-Cambrian boundary (542 million years ago (myr)). They appeared du…
Properties of locust muscle 6-phosphofructokinase and their importance in the regulation of glycolytic flux during prolonged flight
1987
6-Phosphofructokinase (PFK, EC 2.7.1.11) from the flight muscle of the locust (Locusta migratoria) was purified to a specific activity of 80 μmol min−1 (mg protein)−1 (at 25°C). 1. The enzyme is made up from subunits ofMr-81600, and the smallest catalytically active form is likely to be a tetramer. 2. PFK activity is markedly affected by the pH of the assay; the optimum pH was at about 8. 3. Physiological concentrations of ATP strongly inhibit locust PFK by shifting the S0.5 for fructose 6-phosphate (concentration required for 50% of maximum activity) out of the physiological concentration range. At pH 7.4 and about physiological concentrations of ATP, the curve of PFK activity against the …
Kairomonal effect of walking traces from Euschistus heros (Heteroptera: Pentatomidae) on two strains of Telenomus podisi (Hymenoptera: Scelionidae)
2003
. The semiochemical cues used by geographically isolated strains of the parasitoid, Telenomus podisi (Ashmed), to find eggs of the stink bug Euschistus heros were investigated. Two strains of Te. podisi, maintained on eggs of a South American host (E. heros) were studied. One parasitoid strain originated from specimens collected near Brasilia, Brazil (SA strain), and a second strain originated from specimens collected at Beltsville, Maryland (NA strain). Cold tolerance tests of adults from the NA and SA Te. podisi strains, analyses of the cuticular hydrocarbons between the two strains, and crossing experiments between strains each indicated consistent differences between the NA and SA stra…
Trichromatic color vision in the salamander (Salamandra salamandra)
1995
Spectral sensitivity functions were measured between 334 nm and 683 nm in Salamandra salamandra by utilizing two behavioral reactions: the negative phototactic response, and the prey catching behavior elicited by a moving worm dummy. The action spectrum of the negative phototactic response revealed 3 pronounced maxima: at 360–400 nm, at 520–540 nm, and at 600–640 nm. In the range around 450 nm, there was a “reaction gap” where sensitivity could not be measured. The action spectrum of the prey catching behavior was entirely different: maximal sensitivity was found at 500 nm and at 570 nm. Between 500 nm and 334 nm sensitivity decreased continuously for about 1 log unit (Fig. 6).