Search results for " Systematics"
showing 10 items of 6576 documents
Tooth replacement rates in early chondrichthyans: a qualitative approach
2009
The continuous replacement of teeth throughout their lifetime is a common characteristic of most chondrichthyans. This process was already present in the earliest representatives of the group. It has been well established that different species of extant sharks show rapid tooth replacement rates; however, some authors have suggested that in early chondrichthyans this rate might have been much slower. Here we present a qualitative approach to analyse tooth replacement rates in the Early Devonian shark Leonodus carlsi, the earliest tooth-bearing shark known to date. For this, we have examined 1,103 isolated teeth from Celtiberia, Spain. Our study provides strong evidences of an extremely slow…
Enameloid microstructure in the oldest known chondrichthyan teeth
2009
Botella, H., Donoghue, P.C.J and Martinez-Perez, C. 2009. The enameloid microstructure of the oldest known chondrichthyan teeth. — Acta Zoologica (Stockholm) 90 (Suppl. 1): 103‐108 Previous studies on tooth enameloid microstructure in several chondrichthyan taxa spanning the phylogeny of the group provided support for the homology of chondrichthyan tooth enameloid. This hypothesis requires that a single crystallite enameloid (SCE) monolayer must be present in the teeth of the most primitive chondrichthyan. However, the dental microstructure of the earliest sharks has yet to be investigated. We have studied the tooth enameloid microstructure of the two oldest tooth-bearing shark species curr…
Chemical composition of the essential oil of Centaurea grinensis Reuter and Centaurea apiculata Ledeb: Growing wild in Croatia and Bulgaria, respecti…
2016
AbstractIn the present study, the chemical composition of the essential oils from aerial parts of Centaurea grinensis Reuter (K) collected at Žuta Lova, near Senj (Croatia), and aerial parts (L1) and flowers (L2) of C. apiculata Ledeb. collected near Rebro village, near Breznik town, Znepole Region (Bulgaria), both belonging to subgenus Lopholoma (Cass.) Dobrocz, was evaluated by GC and GC-MS. The main components of K were 4-vinyl guaiacol (21.5%), hexadecanoic acid (16.2%), acetophenone (12.5%). Caryophyllene oxide (15.8%) together with sphathulenol (14.5%) and humulene epoxide II (9.4%) were recognized as the main constituent of both the aerial part (L1) and flowers (L2) of C. apiculata. …
Last millennium northern hemisphere summer temperatures from tree rings: Part I: The long term context
2016
Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала. Large-scale millennial length Northern Hemisphere (NH) temperature reconstructions have been progressively improved over the last 20 years as new datasets have been developed. This paper, and its companion (Part II, Anchukaitis et al. in prep), details the latest tree-ring (TR) based NH land air temperature reconstruction from a temporal and spatial perspective. This work is the first product of a consortium called N-TREND (Northern Hemisphere Tree-Ring Network Development) which brings together dendroclimatologists to identify a collective strategy for improving large-scale summer temperature reconstructions…
Not just the sum of its parts : Geographic variation and nonadditive effects of pyrazines in the chemical defence of an aposematic moth
2022
Chemical defences often vary within and between populations both in quantity and quality, which is puzzling if prey survival is dependent on the strength of the defence. We investigated the within- and between-population variability in chemical defence of the wood tiger moth (Arctia plantaginis). The major components of its defences, SBMP (2-sec-butyl-3-methoxypyrazine) and IBMP (2-isobutyl-3-methoxypyrazine), are volatiles that deter bird attacks. We hypothesized that (1) variation in the chemical defences of male wood tiger moths reflects the local predation pressure; (2) observed differences in quantity and quality of defence among populations have a genetic basis; and (3) increasing con…
Comparative transcriptomics of albino and warningly‐coloured caterpillars
2021
Abstract Coloration is perhaps one of the most prominent adaptations for survival and reproduction of many taxa. Coloration is of particular importance for aposematic species, which rely on their coloring and patterning acting as a warning signal to deter predators. Most research has focused on the evolution of warning coloration by natural selection. However, little information is available for color mutants of aposematic species, particularly at the genomic level. Here, I compare the transcriptomes of albino mutant caterpillars of the aposematic wood tiger moth (Arctia plantaginis) to those of their full sibs having their distinctive orange‐black warning coloration. The results showed >29…
Inheritance in the water frog Rana ridibunda Pallas, 1771 - Is it Mendelian or hemiclonal?
2008
The genome of Rana ridibunda has been detected in all known hybridogenetic water frog systems. This raises the question whether R. ridibunda is pre-adapted to reproduce hemiclonally by hybridogenesis. We allozymatically compared genotypes of primary oocytes and somatic cells of R. ridibunda females from several sites in southern France. In case of hemiclonal reproduction only one allele per locus is expected to be detectable in oocytes. However, patterns detected from oocytes of analysed females were not different from those of sexually reproducing water frogs. We therefore conclude that R. ridibunda in southern France reproduces sexually and is not pre-adapted to hemiclonal reproduction.
Chromosome Painting in Cercopithecus petaurista (Schreber, 1774) Compared to Other Monkeys of the Cercopithecini Tribe (Catarrhini, Primates)
2023
The Cercopithecini tribe includes terrestrial and arboreal clades whose relationships are controversial, with a high level of chromosome rearrangements. In order to provide new insights on the tribe’s phylogeny, chromosome painting, using the complete set of human syntenic probes, was performed in Cercopithecus petaurista, a representative species of the Cercopithecini tribe. The results show C. petaurista with a highly rearranged karyotype characterized by the fission of human chromosomes 1, 2, 3, 5, 6, 8, 11, and 12. These results compared with the literature data permit us to confirm the monophyly of the Cercopithecini tribe (fissions of chromosomes 5 and 6), as previously proposed by ch…
Evaluating the performance of artificial neural networks for the classification of freshwater benthic macroinvertebrates
2014
Abstract Macroinvertebrates form an important functional component of aquatic ecosystems. Their ability to indicate various types of anthropogenic stressors is widely recognized which has made them an integral component of freshwater biomonitoring. The use of macroinvertebrates in biomonitoring is dependent on manual taxa identification which is currently a time-consuming and cost-intensive process conducted by highly trained taxonomical experts. Automated taxa identification of macroinvertebrates is a relatively recent research development. Previous studies have displayed great potential for solutions to this demanding data mining application. In this research we have a collection of 1350 …
Methane-oxidizing and photoautotrophic bacteria are major producers in a humic lake with large anoxic hypolimnion
2011
Heterotrophic processes are considered to prevail in lakes with high terrestrial loading and a high content of dissolved organic carbon. However, previous studies have shown abundant methanotrophic bacteria (MOB) and photoautotrophic green sulphur bacteria (GSB) in some boreal lakes. We used genetic and lipid biomarkers to follow the seasonal succession of the abundance and carbon biomass of the major bacterial groups in Lake Mekkojarvi, a small Finnish polyhumic lake with a large anoxic hypolimnion. Biomarkers were based on length heterogeneity analysis of 16S rRNA gene amplification by polymerase chain reaction (PCR) (LH-PCR) and on phospholipid fatty acid (PLFA) analysis. Representative …