Search results for " Systematics."
showing 10 items of 4820 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…
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…
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 …
Sisubiotus hakaiensis sp. nov. (Tardigrada, Macrobiotidae), a new tardigrade species from Calvert Island (British Columbia, Canada)
2022
Tardigrades reports from British Columbia (Canada) trace back to 1908 and numerous species have been recorded from this region, despite the relatively few published sampling studies. We describe by integrative taxonomy (light microscopy morphology, morphometrics, and DNA sequencing) a new tardigrade species, Sisubiotus hakaiensis sp. nov. from the British Columbia central coast. The new species has been found in moss collected from a vertical rock outcrop near the Hakai Institute Calvert Island Field Station. Sisubiotus hakaiensis sp. nov. differs from all the other known species in the genus by the presence of a labyrinthine layer inside the egg process walls, whereas no consistent differe…
Additions to terrestrial flora of Tunisia: occurrence and taxonomic notes
2020
We document new records of 11 vascular taxa. Some were found in the wild for the first time and, therefore, are new reports to terrestrial flora of Tunisia. One species, Ranunculus acris L., is reported for the first time for North Africa. Parietaria cretica L. is confirmed for North Africa. Details about the distribution and habitats of the 11 species are provided, and comments on their status and taxonomy are included.
Gill area explains deviations from body size–metabolic rate relationship in teleost fishes
2022
Whether gill area constrains fish metabolism through oxygen limitation is a debated topic. Here, the authors provide insights into this question by analysing mass-specific metabolic rates across 44 teleost fishes extracted from FishBase. They explore whether species deviations from metabolic rates predicted by body mass can be explained by species gill area. They show that the gill area explains c. 26%–28% of species-level deviations from mass-specific metabolic rates. Their findings suggest that gill area might indeed be one of the factors limiting metabolic rate in fishes.
Red list of threatened vascular plants in Italy
2021
Italy has a rich natural heritage, which is dangerously under pressure. In recent years, there is an increased awareness of the crucial role of plants in ecosystem functioning and in providing ecosystem services. Consequently, an updated Red List of the Italian vascular flora was compiled in this work, at the request of the Ministry for Environment, Land and Sea Protection, with the scientific support of the Italian Botanical Society. The IUCN Red List criteria were applied to 2,430 Italian native vascular plant taxa to assess their current extinction risk and to highlight the major threats affecting the Italian flora. Our results revealed that 54 taxa (2.2% of the assessed taxa) are extinc…