The endocrine regulation of aging by insulin-like signals

Reduced signaling of insulin-like peptides increases the life-span of nematodes, flies, and rodents. In the nematode and the fly, secondary hormones downstream of insulin-like signaling appear to regulate aging. In mammals, the order in which the hormones act is unresolved because insulin, insulin-like growth factor-1, growth hormone, and thyroid hormones are interdependent. In all species examined to date, endocrine manipulations can slow aging without concurrent costs in reproduction, but with inevitable increases in stress resistance. Despite the similarities among mammals and invertebrates in insulin-like peptides and their signal cascade, more research is needed to determine whether these signals control aging in the same way in all the species by the same mechanism.     

Genetic resistance of carp (Cyprinus carpio L.) to Trypanoplasma borreli: influence of transferrin polymorphisms

In serum most of the iron molecules are bound to transferrin (Tf), which is a highly polymorphic protein in fish. Tf is an essential growth factor for mammalian trypanosomes. We performed a series of experiments with Trypanoplasma borreli to detect putative correlations between different Tf genotypes of common carp (Cyprinus carpio L.) and susceptibility to this blood parasite. Five genetically different, commercially exploited carp lines (Israelian 'D', Polish 'R2' and 'K', Ukrainian 'Ur', Hungarian 'R0') and a reference laboratory cross ('R3xR8') were challenged with T. borreli and parasitaemia measured to determine susceptibility to the parasite. Among the commercial carp lines, Israelian 'D' carp were identified as most and Polish 'R2' carp as least susceptible, and used to produce a next generation and reciprocal crosses. These progenies were challenged with T. borreli and parasitaemia measured. We demonstrated significant effects of genetic background of the carp lines on susceptibility to T. borreli. This genetic effect was preserved in a next generation. We also observed a significant male effect on susceptibility to T. borreli in the reciprocal crosses. Serum samples from a representative number of fish from two infection experiments were used for Tf genotyping by polyacrylamide gel electrophoresis (PAGE), identifying DD, DG and DF as most frequent Tf genotypes. We could detect a significant association of the homozygous DD genotype with low parasitaemia in the least susceptible 'R2' (and 'K') carp lines and the lack of a such an association in the most susceptible 'D' carp line. Upon examination of parasite growth in vitro in culture media supplemented with 3% serum taken from fish with different Tf genotypes, we could show a faster decrease in number of parasites in culture media with serum from DD-typed animals.     

Multiple introductions determine the genetic structure of an invasive species population: American mink Neovison vison in Poland

Genetic diversity of feral and ranch American mink was studied in order to understand the processes of invasion and the possible influence of multiple introductions on the feral mink population in Poland. Tissue samples obtained from feral mink taken from 10 sites across Poland (196) and from ranch mink at nine mink farms (147) were genotyped at 14 microsatellite loci. Genetic differentiation among the separate regions and sites indicated some restriction in gene flow among them (pairwise F_ST values), and greater variation at microsatellite loci for feral mink was attributed to differences among sites rather than among regions (AMOVA). A Mantel test demonstrated a positive association of pairwise genetic and geographic distances. A total of five clusters of feral mink were identified and their spatial distribution partially reflected regional distribution, but also suggested that there were other factors (human-mediated propagule pressure) shaping mink genetic structure. Feral and ranch mink belong to two genetically separate clusters and an assignment test showed that 34 feral mink (17%) were assigned to the ranch mink clusters. The proportion of feral mink assigned to ranch mink clusters correlated with the size of the farm breeding stocks in the districts where sampling sites were located. High human-mediated propagule pressure (particularly in western Poland) increases feral population genetic diversity and overwhelms genetic structure and potential management units, making the control of mink populations less successful. Our results indicate that reducing number of escapees from farms should be required management action.     

Pan‐continental invasion of Pseudorasbora parva: towards a better understanding of freshwater fish invasions

In recent years, policy‐makers have sought the development of appropriate tools to prevent and manage introductions of invasive species. However, these tools are not well suited for introductions of non‐target species that are unknowingly released alongside intentionally‐introduced species. The most compelling example of such invasion is arguably the topmouth gudgeon Pseudorasbora parva, a small cyprinid species originating from East Asia. A combination of sociological, economical and biological factors has fuelled their rapid invasion since the 1960s; 32 countries (from Central Asia to North Africa) have been invaded in less than 50 years. Based on a combination of monitoring surveys (2535 populations sampled) and literature reviews, this paper aims to quantify and characterise important invasion parameters, such as pathways of introduction, time between introduction and detection, lag phase and plasticity of life history traits. Every decade, five new countries have reported P. parva introduction, mainly resulting from the movement of Chinese carps for fish farming. The mean detection period after first introduction was 4 years, a duration insufficient to prevent their pan‐continental invasion. High phenotypic plasticity in fitness related traits such as growth, early maturity, fecundity, reproductive behaviour and the ability to cope with novel pathogens has predisposed P. parva to being a strong invader. The Pseudorasbora parva invasion has provided quantitative data for the development of 1) early warning systems across different spatial scales; 2) rapid eradication programmes prior to natural spread in open systems and 3) sound risk assessments with emphasis on plasticity of life history traits.     

Effect of soil drought on growth and yield of maize (Zea mays L.) hybrids grown under compacted soil

In this study, we examined responses of maize hybrids differing in susceptibility to soil compaction and drought in the case of their separate or combined action. We ran field and greenhouse experiments and determined effects on grain yield, biomass, weight of 1000 grains, shoot and roots dry matter (DM), shoot-to-roots ratio, harvest index, plant height, emergence index, leaf area and greening and root number and length. Individual and combined effects of both stresses were observed in the field and greenhouse. Compared with plants growing in loose soil and optimal irrigation (LI), the resistant hybrids in treatments HI, LD and HD showed a smaller reduction in GY, BY, S, R, R_N and R_L than the sensitive. In both groups, stress influence on HA, W-1000, LA and SPAD was smaller and the differences were insignificant. Compared with LI treatment, the roots of LD, HI and HD increased their DM, number and length in the upper level of the soil profile and the number of roots developed at 0–30° and 30–60° in relation to the root main axis. Analysis of those traits in the hybrids resistant and sensitive to both stress factors enabled to explain a defence response. Our study demonstrated that soil compaction and soil drought, which usually occurs simultaneously, caused significant changes in components of plant yield and showed plant plasticity in response to environmental factors under natural conditions.