Maternal survival costs in an asocial mammal

Maternal characteristics, social dynamics, and environmental factors can all influence reproduction and survival and shape trade‐offs that might arise between these components of fitness. Short‐lived mammals like the golden‐mantled ground squirrel (GMGS; Callospermophilus lateralis) tend to maximize effort toward current reproduction at the expense of survival but may be complicated by other aspects of the species’ life history and environment. Here, we use 25 years of data (1995–2020) collected from a population of GMGS at the Rocky Mountain Biological Research Laboratory in Gothic, Colorado, to test the effect of several maternal characteristics (e.g., age, experience, and timing of litter emergence), social context (e.g., litter sex ratio and kin density), and environmental context (e.g., date of bare ground and length of vegetative growing season) on survival of reproductive female GMGS using Cox proportional hazard models. Our results indicated that social dynamics (i.e., density) and environmental conditions (i.e., standardized first day of permanent snow cover and length of growing season) explained significant variation in annual maternal survival, while maternal characteristics did not. A higher density of related breeding females and the total number of females (both related and unrelated to the focal mother) were associated with an increase in the mortality hazard. A later standardized date of the first day of permanent snow cover and a shorter growing season both reduced the maternal mortality hazard. Together, our results suggest that factors extrinsic to the squirrels affect maternal survival and thus may also influence local population growth and dynamics in GMGS and other short‐lived, territorial mammal species.     

Innate and Learned Predator Recognition Mediated by Chemical Signals in Eurycea nana

Effective and efficient predator recognition and avoidance are essential for the persistence of prey populations, especially in habitats where non-native predators have been introduced. Predator recognition studies are commonly couched within a learned or innate dichotomous framework; however, characteristics of some systems or species could favor innate recognition combined with the ability to alter avoidance responses based on experience with predators. Eurycea nana is a fully aquatic salamander inhabiting a system with a diverse, yet temporally stable, community of native and non-native opportunistically foraging fish predators. To examine predator recognition, we examined avoidance responses (decreased activity) of predator-naïve (first-generation, captive-reared) and predator-experienced (recently collected) E. nana to the chemical cues of a native predator, a non-native predator, a non-predator, and a blank control. Both predator-naïve and predator-experienced E. nana significantly lowered activity in response to the native fish predator when compared with a blank control. Interestingly, predator-naïve E. nana decreased activity in response to the non-native fish predator while predator-experienced E. nana did not. These results indicate that while there is an innate component to predator recognition in E. nana , experience and risk assessment may also be important.     

Enzymes of serine biosynthesis in Rhodopseudomonas capsulata

Rhodopseudomonas capsulata has been shown to possess all the enzymatic activities of both the phosphorylated and nonphosphorylated pathways of serine biosynthesis. In addition there was an active serine hydroxymethyltransferase which catalyzed the reversible interconversion of serine and glycine. In cells grown photosynthetically with malate as the carbon source, the activities of the phosphorylated pathway enzymes were substantially higher than the analogous reactions of the nonphosphorylated sequence. l-Serine (1 mm) caused approximately 60%, inhibition of the first enzyme of the phosphorylated route, 3-phosphoglyceric acid dehydrogenase, but was less effective in inhibiting the last enzyme, phosphoserine phosphatase. Glycine also exerted a regulatory effect on this pathway but it was not as potent an inhibitor as serine. The inhibitions caused by serine and glycine were simply additive; there was no evidence of concerted feedback inhibition of the phosphorylated pathway by these amino acids.     

Adhesive properties associated with the Vir plasmid: a transmissible pathogenic characteristic associated with strains of invasive Escherichia coli

Escherichia coli strain S5 (O15:K+:H21) isolated from a septicaemic lamb and previously shown to possess a virulence plasmid, Vir, attached in vitro to calf epithelial tissue from the ileum, oesophagus and trachea in the presence of 0.5% (w/v) D-mannose. The Vir+ recombinant strains 711v and H209av, which had received the Vir plasmid(s) from strain S5, also attached to these epithelia but the parent strains 711 and H209a without the Vir plasmid were non-adhesive. The attachment of the Vir+ strain 711v to intestinal brush borders was inhibited by antiserum to live Vir+ strain H209av but not by antiserum to strain H209a lacking Vir. No adherence occurred with Vir+ organisms grown at 18 degrees C or after heating at 65 degrees C. Adhesion was unaffected by 0.5% (w/v) formaldehyde. Glucosamine, mannosamine, their N-acetyl derivatives and wheat germ lectin each inhibited attachment of Vir+ strain 711v to brush border epithelia.     

PTPRN2 and PLCβ1 promote metastatic breast cancer cell migration through PI(4,5)P2‐dependent actin remodeling

Altered abundance of phosphatidyl inositides (PIs) is a feature of cancer. Various PIs mark the identity of diverse membranes in normal and malignant cells. Phosphatidylinositol 4,5‐bisphosphate (PI(4,5)P₂) resides predominantly in the plasma membrane, where it regulates cellular processes by recruiting, activating, or inhibiting proteins at the plasma membrane. We find that PTPRN2 and PLCβ1 enzymatically reduce plasma membrane PI(4,5)P₂ levels in metastatic breast cancer cells through two independent mechanisms. These genes are upregulated in highly metastatic breast cancer cells, and their increased expression associates with human metastatic relapse. Reduction in plasma membrane PI(4,5)P₂ abundance by these enzymes releases the PI(4,5)P₂‐binding protein cofilin from its inactive membrane‐associated state into the cytoplasm where it mediates actin turnover dynamics, thereby enhancing cellular migration and metastatic capacity. Our findings reveal an enzymatic network that regulates metastatic cell migration through lipid‐dependent sequestration of an actin‐remodeling factor.     

HKT1;5-like cation transporters linked to Na+ exclusion loci in wheat, Nax2 and Kna1

Bread wheat (Triticum aestivum) has a greater ability to exclude Na⁺ from its leaves and is more salt tolerant than durum wheat (Triticum turgidum L. subsp. durum [Desf.]). A novel durum wheat, Line 149, was found to contain a major gene for Na⁺ exclusion, Nax2, which removes Na⁺ from the xylem in the roots and leads to a high K⁺-to-Na⁺ ratio in the leaves. Nax2 was mapped to the distal region on chromosome 5AL based on linkage to microsatellite markers. The Nax2 locus on 5AL coincides with the locus for a putative Na⁺ transporter, HKT1;5 (HKT8). The Nax2 region on 5AL is homoeologous to the region on chromosome 4DL containing the major Na⁺ exclusion locus in bread wheat, Kna1. A gene member of the HKT1;5 family colocates to the deletion bin containing Kna1 on chromosome 4DL. This work provides evidence that Nax2 and Kna1 are strongly associated with HKT1;5 genes.     

Rest-activity rhythms characteristics and seasonal changes in seasonal affective disorder

ABSTRACT

Identifying objectively measurable seasonal changes in 24-h activity patterns (rest-activity rhythms or RARs) that occur in seasonal affective disorder (SAD) could help guide research and practice towards new monitoring tools or prevention targets. We quantified RARs from actigraphy data using non-parametric and extended cosine based approaches, then compared RARs between people with SAD and healthy controls in the summer (n = 70) and winter seasons (n = 84). We also characterized the within-person seasonal RAR changes that occurred in the SAD (n = 19) and control (n = 26) participants who contributed repeated measures. Only controls had significant winter increases in RAR fragmentation (intra-daily variability; in controls mean winter-summer changes (log scale) = 0.05, 0.21 standard deviation, p = 0.03). In SAD participants only, estimated evening settling times (down-mesor) were an average of 30 min earlier in the winter compared with the summer (1-h standard deviation, p = 0.045). These RAR characteristics correlated with greater fatigue (Spearman r = 0.36) but not depression symptom severity. Additional research is needed to ascertain why healthy controls, but not people with SAD, appear to have increased RAR fragmentation in the winter. People with SAD lacked this increase in RAR fragmentation, and instead had earlier evening setting in the winter. Prospective and intervention studies with greater temporal resolution are warranted to ascertain how these seasonal behavioral differences relate to fatigue pathophysiology in SAD. Future research is needed to determine whether extending the winter active period, even in relatively fragmented bouts, could help reduce the fatigue symptoms common in SAD.     

Resource limitation,predation risk and compensatory growth in a damselfly

Periods of poor nutrition during early development may have negative fitness consequences in subsequent periods of ontogeny. In insects, suppression of growth and developmental rate during the larval stage are likely to affect size and timing of maturity, which in turn may lead to reduced reproductive success or survivorship. In light of these costs, individuals may achieve compensatory growth via behavioural or physiological mechanisms following food limitation. In this study, we examined the effects of a temporary period of food restriction on subsequent growth and age and size at maturity in the larval damselfly Ischnura verticalis (Odonata: Coenagrionidae). We also asked whether this temporary period of reduced nutrition affected subsequent foraging behaviour under predation risk. I. verticalis larvae exposed to a temporary food shortage suffered from a reduced growth rate during this period relative to a control group that was fed ad libitum. However, increased growth rates later in development ensured that adult body size measurements (head and pronotum widths) did not differ between the treatments upon emergence. In contrast, adult dry mass did not catch up to that of the controls, indicating that the increased growth rates for size dimensions occur at the cost of similar gains in mass. Predators reduced foraging effort of larvae, but this reduction did not differ between control larvae and those previously exposed to poor nutrition.     

Variations in Red Snapper oocyte development and spawning in relation to environmental and habitat parameters

Environmental Biology of Fishes - The reproductive biology of Red Snapper, Lutjanus campechanus, is well understood, but there is little information on the impact of environmental, climatic, and...     

A comparison of survey and focal follow methods for estimating individual activity budgets of cetaceans

Activity budget data are essential for determining behavioral responses to physiological and ecological variables. Yet, few studies are available to investigate the robustness, accuracy, and biases of the methods used to estimate activity budgets for cetaceans. In this study, we compare activity budgets of 55 adult female bottlenose dolphins in Shark Bay, Australia derived from two methods: surveys (n = 6,903) and focal follows (n = 1,185, totaling 2,721 h of observation). Activity budgets estimated from survey data differed in all behavioral states compared to focal follow data. However, when controlling for temporal autocorrelation, only time spent socializing and time spent traveling remained disparate between the methods. To control for biases associated with assigning group‐level behavior to individuals, we also compared survey and focal follow activity budgets for lone females. Here we found differences between methods in time spent foraging and traveling regardless of whether we controlled for temporal autocorrelation, which suggests detection biases likely play a role in explaining differences in activity budget estimates between the two methodologies. Our results suggest that surveys are less representative of individual‐level activity budgets, and thus, when individual‐level knowledge about behavior is needed, focal follows are preferred.