Hormonal control of hemolymph lipoprotein ice nucleators in overwintering freeze-susceptible larvae of the stag beetle Ceruchus piceus: adipokinetic hormone and juvenile hormone

Summary Freeze-resistant overwintering larvae of the stag beetle Ceruchus piceus do not produce antifreezes in winter, but instead lower their supercooling points by seasonal removal of lipoprotein ice nucleators (LPINs) from the hemolymph. The normal lipid transport function of these lipoproteins becomes less essential during winter because of the low temperatures and the diapause state of the larvae. Adipokinetic hormone (AKH) and juvenile hormone (JH) were shown to be involved in the control of supercooling abilities and LPIN levels. Treatment of midwinter larvae with AKH resulted in an increase in ice nucleator activity within 2 h, associated with elevated levels of LPINs, as demonstrated by Western blots derived from native PAGE gels probed with polyclonal antibodies to the LPINs. AKH also stimulated the release of LPIN in vitro from cultured fat bodies. In contrast, JH treatments of larvae with high hemolymph ice nucleator contents (either autumn or spring larvae) caused a decrease in ice nucleator activity and supercooling points. However, Western blots showed increased LPIN levels in these JH treated larvae. Apparently, this JH-induced, inactive form of LPIN lacks some component(s) essential for ice nucleator activity.Abbreviations AKH Adipokinetic hormone - Apo-I Apolipoprotein-I - Apo-II Apolipoprotein-II - JH Juvenile hormone - LPIN Lipoprotein ice nucleator - PAGE Polyacrylamide gel electrophoresis - SDS Sodium dodecyl sulfate - SCP Supercooling point - THP Thermal hysteresis protein - HDLp High density lipophorin - VHDLp Very high density lipophorin     

Phylogeography and taxonomic status of trout and salmon from the Ponto‐Caspian drainages,with inferences on European Brown Trout evolution and taxonomy

Current taxonomy of western Eurasian trout leaves a number of questions open; it is not clear to what extent some species are distinct genetically and morphologically. The purpose of this paper was to explore phylogeography and species boundaries in freshwater and anadromous trout from the drainages of the Black and the Caspian Seas (Ponto‐Caspian). We studied morphology and mitochondrial phylogeny, combining samples from the western Caucasus within the potential range of five nominal species of trout that are thought to inhabit this region, and using the sequences available from GenBank. Our results suggest that the genetic diversity of trout in the Ponto‐Caspian region is best explained with the fragmentation of catchments. (1) All trout species from Ponto‐Caspian belong to the same mitochondrial clade, separated from the other trout since the Pleistocene; (2) the southeastern Black Sea area is the most likely place of diversification of this clade, which is closely related to the clades from Anatolia; (3) The species from the Black Sea and the Caspian Sea drainages are monophyletic; (4) except for the basal lineage of the Ponto‐Caspian clade, Salmo rizeensis, all the lineages produce anadromous forms; (5) genetic diversification within the Ponto‐Caspian clade is related to Pleistocene glacial waves; (6) the described morphological differences between the species are not fully diagnostic, and some earlier described differences depend on body size; the differences between freshwater and marine forms exceed those between the different lineages. We suggest a conservative taxonomic approach, using the names S. rizeensis and Salmo labrax for trout from the Black Sea basin and Salmo caspius and Salmo ciscaucasicus for the fish from the Caspian basin.     

Maintenance of the supercooled state in the gut fluid of overwintering pyrochroid beetle larvae, Dendroides canadensis : role of ice nucleators and antifreeze proteins

  The effect of gut fluid ice nucleators and antifreeze proteins on maintenance of supercooling was explored in fire-colored beetle larvae, Dendroides canadensis, via seasonal monitoring of supercooling points, antifreeze protein activity and ice nucleator activity of gut fluid and/or larvae. During cold hardening in the field, freeze-avoiding larvae evacuated their guts and depressed larval supercooling points. Analysis of gut fluid indicated supercooling points and ice nucleator activity decreased, whereas antifreeze protein activity increased as winter approached. Suspensions of bacteria isolated from guts of feeding larvae collected in spring/summer had higher supercooling points than those from midwinter-collected non-feeding larvae, suggesting bacterial ice nucleators are removed from midwinter gut fluid. The ice nucleation active bacterium Pseudomonas fluorescens was isolated from gut fluid of feeding larvae but was absent in winter. When mixed with purified D.␣canadensis hemolymph antifreeze proteins (structurally similar and/or identical to those in gut fluid), the cumulative ice nucleus spectra of P. fluorescens suspensions were shifted to lower temperatures indicating an inhibitory effect on the bacteria's ice-nucleating phenotype. By extending larval supercooling capacity, both gut clearing and masking of bacterial ice nucleators by antifreeze proteins may contribute to overwintering survival in supercooled insects. Accepted: 8 August 1996     

Vegetation establishment, succession and microsite frost disturbance on glacier forelands within patterned ground chronosequences

Aim The impact of microscale frost disturbance on vegetation colonization and successionary trends was examined within patterned ground features of Little Ice Age chronosequences. The goal was to investigate and compare vegetation response to micro‐site frost disturbance with that of previous studies done at a coarser landscape scale. Location The study sites occur on Little Ice Age glacier forelands within Jotunheimen, Norway (61°–62° N). The forelands of the glaciers Slettmarkbreen, Styggedalsbreen and Vestre Memurubreen have been well studied providing chronological controls for landscape studies. Sorted patterned ground features are found within the chronosequences, typically declining with frost intensity and disturbance with increasing terrain age. Methods Micro‐plots (8.3 × 8.3 cm) were placed at the inner borders and centres of patterned ground features. Species were identified and per cent species cover and per cent cover of life‐form category were noted. Nonparametric Kruskal–Wallis and Mann–Whitney U‐tests were used to test for differences between percent cover of life‐form categories within patterned ground features as well as to identify thresholds of successional change across the chronosequences. Results Significant relationships between life‐from groups and patterned ground positions of varying ages were deduced using nonparametric statistics. Findings were then used to discuss trends of succession within patterned ground features and across the chronosequences. Vegetation establishment occurs at the border positions of young (< 30 years) patterned ground features. With time and distance from the ice margin, vegetation encroaches inwards toward the disturbed centres. Succession within patterned ground exhibits several stages: (1) bryophytes/crusts and lichens, (2) grasses/sedges and (3) woody shrubs. The occurrence of forbs was sporadic and generally non‐significant. Main conclusions Frost disturbance in patterned ground appears to delay successional trends of vegetation communities when compared with previous studies on ‘stable’ terrain, producing micro‐site lag effects. These small patches of disturbed ground are therefore important regarding vegetation assemblages across the landscape and are unlikely to be detected at the landscape scale.     

Molecular cloning of an ice nucleation gene from Erwinia ananas and its expression in Escherichia coli

Abstract An approximately 7 kbp genomic DNA fragment was cloned from an ice nucleation-active (ina) strain of Erwinia ananas and defined as to its restriction enzyme site. When the DNA fragment was introduced into E. coli MM294, a potent ice nucleation activity was expressed. Both 0.7 kbp truncation from the 5'-end and 1.7 kbp truncation from the 3'-end were also effective in expressing the ice nucleation activity in E. coli . Therefore, the resulting DNA fragment of approximately 5 kbp was considered to be an ina gene and named ina A. It existed as a unique gene in this strain of E. ananas . No corresponding ina gene existed in an ice nucleation-inactive strain of E. milletiae .     

Climatic changes during the past 1300 years as deduced from the sediments of Lake Nakatsuna, central Japan

Limnological features and sediment characteristics were studied in Lake Nakatsuna, a mesotrophic lake in central Japan. The lake is dimictic, and is anoxic in the hypolimnion during thermal stratification from May to September. In an attempt to reconstruct paleoclimatic changes around the lake, a sediment core taken from the lake center spanning the past 1300 years was analyzed for its organic and inorganic contents. Climatic influences were examined on the variation of total organic carbon (TOC), total nitrogen (TN), and sand contents. Short- and long-term fluctuations in TOC, TN, and sand contents are evident, and variation in atmospheric temperature appears to be important for their long-term variability. The sediment record from AD 900 to 1200 indicates hot summers and warm winters with less snow accumulation, whereas the record from AD 1200 to 1950 is characterized by high variation of temperature, with three cool phases from AD 1300 to 1470, 1700 to 1760, and 1850 to 1950. The warm period from AD 900 to 1200 corresponds well to the Medieval Warm Period, and the second and third cool phases are related to the Little Ice Age. Received: February 16, 2001 / Accepted: June 7, 2001     

The influence of impact source on variables associated with strain for impacts in ice hockey

Concussion can occur from a variety of events (falls to ice, collisions etc) in ice hockey, and as a result it is important to identify how these different impact sources affect the relationship between impact kinematics and strain that has been found to be associated to this injury. The purpose of this research was to examine the relationship between kinematic variables and strain in the brain for impact sources that led to concussion in ice hockey. Video of professional ice hockey games was analyzed for impacts that resulted in reported clinically diagnosed concussions. The impacts were reconstructed using physical models/ATDs to determine the impact kinematics and then simulated using finite element modelling to determine maximum principal strain and cumulative strain damage measure. A stepwise linear regression was conducted between linear acceleration, change in linear velocity, rotational acceleration, rotational velocity, and strain response in the brain. The results for the entire dataset was that rotational acceleration had the highest r² value for MPS (r² = 0.581) and change in rotational velocity for cumulative strain damage measure (r² = 450). When the impact source (shoulder, elbow, boards, or ice impacts) was isolated the rotational velocity and acceleration r² value increased, indicating that when evaluating the relationships between kinematics and strain based metrics the characteristics of the impact is an important factor. These results suggest that rotational measures should be included in future standard methods and helmet innovation and design in ice hockey as they have the highest association with strain in the brain tissues.     

Climate–growth relationship of tree species from a mixed stand of Apuseni Mts., Romania

We present the first results of a dendroecological investigation on three prevailing species growing in the Apuseni Mountains. In this study we succeeded in building up about 200-year long local master chronologies for spruce, fir and beech. These chronologies will serve as a reference for crossdating of (sub-fossil) logs that were preserved in ice caves at the Apuseni Mts.

The analysis of climate–growth relationship provided interesting and different results for the three studied species: we found significant correlations between the beech chronology and the mean temperature of the prior July, autumn and January of the actual year as well as the weather conditions at the beginning of the vegetation period. Conifers yielded coherent results for the mean temperature of prior July and sum of precipitation in April. In addition, fir seems to be favouring above-average temperatures in January and February. The coherent and significant correlations with the April precipitation suggest a common coniferous phenomenon. Finally, beech index showed negative correlation with April temperature.