Competitive exclusion along climate gradients: energy efficiency influences the distribution of two salmonid fishes

We tested the importance of thermal adaptations and energy efficiency in relation to the geographical distribution of two competing freshwater salmonid fish species. Presence–absence data for Arctic char and brown trout were obtained from 1502 Norwegian lakes embracing both temperature and productivity gradients. The distributions were contrasted with laboratory‐derived temperature scaling models for food consumption, growth and energy efficiency. Thermal performances of the two species were almost identical. However, Arctic char exhibited double the growth efficiency (per unit of food) and appear to have out‐competed brown trout from cold, low‐productivity lakes, perhaps by scramble competition. Brown trout, for which previous reports have shown to be aggressive and dominant, have likely excluded the more energy‐efficient Arctic char from relatively warm, productive lakes, perhaps by contest competition. Competitive interaction changing in outcome with lake productivity, rather than thermal performance, is likely a major determinant of the range distribution of the two species. Our study highlights the need for more focus on choice of relevant ecophysiological traits in ecological climate impact studies and species distribution modelling.     

Association of polymorphism at COL3A and CTLA4 loci on chromosome 2q31-33 with the clinical phenotype and in-vitro CMI status in healthy and leprosy subjects: a preliminary study

Two genetic loci, viz. COL3A and CTLA4, located within the chromosome 2q31-33 region in the vicinity of the proposed syntenic site of the mouse “Bcg” locus were genotyped by the polymerase chain reaction in leprosy patients and healthy individuals. All the subjects studied were assessed as in-vitro responders/non-responders to mycobacterial antigens. Simple sequence length polymorphism analysis revealed five (236 to 312 bp) and eight (84 to 120 bp) allelomorphs for COL3A and CTLA4, respectively. Our preliminary analysis showed a significant association between the 250-bp COL3A allelomorph in the homozygous condition and the multibacillary form of leprosy (P < 0.05; relative risk = 5.5). Another allelic (312 bp) variant of COL3A was significantly correlated with non-responsiveness to M. leprae antigens in vitro (P < 0.01). The 104-bp allelomorph of CTLA4 was not observed in any of the 25 cases of leprosy. This absence was statistically significant (P < 0.05) when compared with normal healthy controls and depicted a high relative risk (RR = 25.83). An additional observation of the predominance of a unique 84-bp CTLA4/CTLA4-like allelomorph was observed in the Indian subjects studied. Received: 28 October 1996 / Accepted: 13 February 1997     

Ly-6A.2 expression regulates antigen-specific CD4+ T cell proliferation and cytokine production.

Ly-6 proteins appear to serve cell adhesion and cell signaling function, but the precise role of Ly-6A.2 in CD4+ T lymphocytes is still unclear. Overexpression of Ly-6A.2 in T lymphocytes has allowed us to analyze the influence of elevated Ly-6A.2 expression on T cell function. In this study we report reduced proliferation of CD4+ T cells overexpressing Ly-6A.2 in response to a peptide Ag. Moreover, the Ly-6A.2-overexpressing CD4+ cells generated elevated levels of IL-4, a key factor that propels the differentiation of naive CD4+ T cells into Th2 subset. The hyporesponsiveness of Ly-6A.2 transgenic CD4+ T cells is dependent on the interaction of Ly-6A.2 T cells with the APCs and can be reversed by blocking the interaction between Ly-6A.2 and a recently reported candidate ligand. Overexpression of Ly-6A.2 in CD4+ T cells reduced their Ca(2+) responses to TCR stimulation, therefore suggesting effects of Ly-6A.2 signaling on membrane proximal activation events. In contrast to the observed Ag-specific hyporesponsiveness, the Ly-6A.2 transgenic CD4+ T cells produced IL-4 independent of the interactions between Ly-6A.2 and the candidate Ly-6A.2 ligand. Our results suggest that 1) interaction of Ly-6A.2 with a candidate ligand regulates clonal expansion of CD4+ Th cells in response to an Ag (these results also provide further functional evidence for presence of Ly-6A.2 ligand on APC); and 2) Ly-6A.2 expression on CD4+ T cells promotes production of IL-4, a Th2 differentiation factor.     

North-east Atlantic and Mediterranean species of the genus Buffonellaria (Bryozoa, Cheilostomata): implications for biodiversity and biogeography

In this study we revise the cheilostome bryozoan genus Buffonellaria Canu & Bassler, 1927 and its Mediterranean and north-east Atlantic species, thereby addressing several existing problems. First, a lectotype for the type species, Buffonellaria divergens (Smitt, 1873) from Florida, is chosen, which proves to be distinct from the European species. Second, the two hitherto established north-east Atlantic species [ Buffonellaria nebulosa ( Jullien & Calvet, 1903 ) and Buffonellaria porcellanum Arístegui Ruiz, 1987], are redescribed, which were poorly documented until now. Third, close inspection of material, collected from Spitsbergen to tropical West Africa, using scanning electron microscopy reveals that the actual number of species, all previously referred to either B. divergens or Stephanosella biaperta (Michelin, 1848), is distinctly greater in the north-east Atlantic than has been previously acknowledged. As a result, seven new species are introduced ( Buffonellaria acorensis sp. nov. , Buffonellaria antoniettae sp. nov. , Buffonellaria arctica sp. nov. , Buffonellaria harmelini sp. nov. , Buffonellaria jensi sp. nov. , Buffonellaria muriella sp. nov. , and Buffonellaria ritae sp. nov. ), whereas two are left in open nomenclature. With the increase in number of species, the extremely broad geographical range of distribution assumed for B. divergens breaks down to numerous restricted areas. However, although most species have only been reported from a single location, B. arctica sp. nov. seems to have a fairly wide distribution in the Arctic region.  © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society , 2008, 152 , 537–566.     

Analysis of Indian population based on Y-STRs reveals existence of male gene flow across different language groups

A study of three different Y-specific microsatellites (Y-STRs) in the populations from Uttar Pradesh (UP), Bihar (BI), Punjab (PUNJ), and Bengal (WB), speaking modern indic dialects with its roots in Indo-Aryan language, and from South of India (SI), speaking the South Indian languages with their root in Dravidian language, has shown that the predominant alleles observed represent the whole range of allelic variation reported in different population groups globally. These results indicate that the Indian population is most diverse. The similarity between the allelic variants between the populations studied by others in Africa and Asia and in this study between WB, PUNJ, UP, BI, and SI are of interest. It demonstrates that these population groups, housed in eight states of the country in different geographic locations, broadly correspond with Indo-Aryan and Dravidian language families. Further, our analyses based on haplotype frequency of different marker loci and gene diversity reveals that none of the population groups have remained isolated from others. High levels of haplotype diversity exist in all the clusters of population. Nonsignificant results based on Markov chain steps and Slatkin's linearized genetic distances indicate that there has been migration to and from in these population groups. However, some of the marginally significant interpopulation differences could be attributed to one or more of the castes with high diversity embedded within the population groups studied. Haplotype sharing between populations, F(ST) statistics, and phylogenetic analysis identifies genetic relatedness to be more between individuals belonging to two different states of India, WB and PUNJ, followed by UP and BI, whereas SI branched out separately.     

Necessity of nuclear and mitochondrial genome analysis prior to assisted reproductive techniques/intracytoplasmic sperm injection

Assisted reproductive technique (ART) has revolutionized the management of severe male factor infertility and in some countries 5% babies are conceived through ART/intra cytoplasmic sperm injection (ICSI). However, the carry-home live birth rate after several ART cycles is low (18-25%) and this is financially, physically and emotionally crippling for the couples. Genetic factors could lead to pre or post-implantation failure and thus explain for low ART success rate. Thus, this study was planned to understand, if infertile men harbour genetic abnormalities which may be iatrogenically transmitted by ART and adversely affect growth potential of embryo. Ninety infertile men underwent semen, cytogenetic, Yq microdeletion and mitochondrial mutation analysis. Of these, 14.4% cases harboured cytogenetic abnormality, and 8.89% Yq microdeletions. A high frequency of mitochondrial mutations was found in 23 men with asthenospermia. It is important to understand that through ART genetic abnormalities are transmitted to offspring, resulting in impaired growth and development potential of embryo and poor take-home live birth rate. Thus, genetic analysis is strongly recommend in all men with idiopathic infertility who opt for ART to counsel couples and provide them with most adapted therapeutics.     

Hierarchical regulation of pelagic invertebrates in lakes of the northern Great Plains: a novel model for interdecadal effects of future climate change on lakes

Endorheic lakes of the northern Great Plains encompass a wide range of environmental parameters (e.g., salinity, pH, DOC, Ca, nutrients, depth) that vary 1000‐fold among sites and through the past 2000 years due to variation in basin hydrology and evaporative forcing. However, while many environmental parameters are known to individually influence zooplankton diversity and taxonomic composition, relatively little is known of the hierarchical relationships among potential controls or of how regulatory mechanisms may change in response to climate variation on diverse scales. To address these issues, we surveyed 70 lakes within a 100 000 km² prairie region to simulate the magnitude of environmental change expected to occur over 100–1000 years and to quantify the unique and interactive effects of diverse environmental parameters in regulating pelagic invertebrate community structure at that scale. Multivariate analyses showed that salinity was the principal correlate of changes in invertebrate composition among lakes, with a sequential loss of taxa between salinities of 4 and 50 g total dissolved solids L^?1 until one to two species predominated in highly saline systems. In contrast, changes in the concentrations of Ca²⁺ and other mineral nutrients exerted secondary controls of invertebrate assemblages independent of salinity, whereas lake depth provided a tertiary regulatory mechanism structuring species composition. In contrast to these large‐scale hierarchical patterns, seasonal surveys (May, July, September) of a subset of 21 lakes in each of 2003–2005 revealed that annual meteorological variation had no measurable effect on pelagic invertebrates, despite large differences in temperature, precipitation, and evaporation arising from regional droughts. Together these findings show that pelagic invertebrate communities in saline lakes are resilient to interannual variability in climate, but suggest that lakes of the northern Great Plains may provide a sensitive model to forecast centennial effects of future climate change.     

Seasonal and Experimentally Induced Changes in the Ultrastructure of Chloroplasts of Pinus silvestris

The ultrastructure of chloroplasts in mesophyll cells of Pinus silvesris was examined under the electron microscope. Secondary needles were regularly sampled from a tree in a natural stand for one year. Primary needles from one-year-old seedlings exposed to frost hardening and dehardening conditions in a controlled environment chamber were also studied. These seedlings were exposed to 8 or 55 W m^-2. All needles were put in fixative at the different sampling dates and stored in a refrigerator until they were prepared for electron microscopy at the end of the experimental period. During the summer the choroplasts were symmetrically shaped and heavily loaded with starch. The membrane systems were well developed and consisted of both grana and stroma thylakoids. In autumn and during early artificial frost hardening the starch content was reduced, the chloroplasts appeared amoeboid and membrane-free stroma regions were seen. Later the chloroplasts became swollen and aggregated in one part of the cell. Starch was lost and the chloroplasts aggregated earlier at 8 W m^-2 than at 55 W m^-2. During winter the stroma thylakoids were first reduced in number and later even the grana thylakoids were damaged, resulting in mostly disorganized single membranes. Also the chloroplast envelope disappeared. In spring and early summer the chloroplasts migrated to the proximity of the cell walls. The membrane systems were reorganized and starch accumulated. During the first days of artificial dehardening the photosynthetic membranes were severely damaged, especially at 55 W m^-2, but soon new membranes were formed. Starch accumulated earlier at 55 than at 8 W m^-2. The reported ultrastructural variations are discussed in relation to functional and biochemical fluctuations caused by the season or by artificial variations in the climate as demonstrated earlier.     

Laboratory studies of egg development and diapause in Isoperla obscura (Plecoptera) from a mountain stream in Norway

SUMMARY 1. A laboratory study of egg development of the stonefly Isoperla obscura (Zetterstedt) collected from the stream Flybekken (southern Norway, 61°25'N, 8°48'E, 1373 m a.s.l.) showed a short diapause followed by a prolonged period of postdiapause quiescence.
2. Diapause occurred over a wide range of temperatures (−20°C to +8°C), but 0–1°C was the most favourable for fast diapause development and successful hatching. Diapause development required temperatures below 12°C, but sub-zero diapause temperatures increased mortality during the postdiapause phase, as well as reducing hatching success.
3. The threshold for initiation of postdiapausal development was about 1–2°C. Development rate increased and variation in development time decreased at higher water temperatures. These may be important characteristics to ensure seasonal and geographical synchrony of development in individual populations. Low postdiapausal temperatures were unfavourable, despite a subsequent increase in water temperature. No response to postdiapausal photoperiod was detected.
4. The results agreed well with conditions noted in the natural environment, and with the abundance of this species at high altitudes and latitudes in Fennoscandia. Nevertheless, Isoperla obscura also occurs in streams in the maritime parts of western Norway. The results of the present study suggest that egg development in these populations will prove to be different.