Epigenetic Maternal Effects on Endogenous Rhythms in Precocial Birds

Development involves interactions between genetic and environmental influences. Vertebrate mothers are generally the first individuals to encounter and interact with young animals. Thus, their role is primordial during ontogeny. The present study evaluated non‐genomic effects of mothers on the development of rhythms of precocial Japanese quail (Coturnix c. japonica). First, we investigated the influence of mothering on the ontogeny of endogenous rhythms of young. We compared circadian and ultradian rhythms of feeding activity of quail reared with or without adoptive mothers. More brooded than non‐brooded quail presented a circadian and/or an ultradian rhythm. Thus, the presence of the mother during the normal brooding period favors, in the long term, expression of rhythms in the young. Second, we investigated the influence of rhythmic phenotype of the mother on the development of endogenous rhythms of young by comparing quail brooded by circadian‐rhythmic adoptive mothers (R) to quail brooded by circadian‐arrhythmic adoptive mothers (A). More R‐brooded than A‐brooded quail expressed circadian rhythmicity, and circadian rhythm clarities were greater in R‐brooded than A‐brooded quail. Ultradian rhythmicity did not differ between R‐ and A‐brooded quail, nor between R and A adoptive mothers. Thus, the rhythmic phenotypes of quail mothers influence the rhythmic phenotypes of their young. Our results demonstrate that mothers of precocial birds influence epigenetically the ontogeny of endogenous rhythms of the young they raise.     

Morphology and physiology of the serotonin-immunoreactive putative antennal lobe feedback neuron in the male silkmoth Bombyx mori

In the male silkmoth Bombyx mori, olfactory information is relayed from olfactory receptor neurons in the antennae to the antennal lobe, and then to a variety of protocerebral neuropils. Currently, very little is known about neuromodulators that may affect the dynamics of this olfactory neural network. Immunocytochemical studies have revealed the presence of a serotonin-immunoreactive (SI) neuron that, in several insect species, is thought to provide feedback to the antennal lobe. To date, no studies have revealed details of this neuron's physiology. Using intracellular recording and staining, the silkmoth SI neuron (in two individuals) was first characterized physiologically and then stained with Lucifer Yellow to reveal morphological details. Immunocytochemical methods were also used to confirm the presence of serotonin. The silkmoth SI neuron branched in many important brain neuropils such as the mushroom body, central body, lateral accessory lobe and antennal lobe. The SI neuron in both individuals fired spontaneous, long duration action potentials, and responded to mechanosensory stimuli to the antennae.     

Cooperative Anti-Invasive Effect of Cdc42/Rac1 Activation and ROCK Inhibition in SW620 Colorectal Cancer Cells with Elevated Blebbing Activity

Rho GTPases are key regulators of tumour cell invasion and therefore constitute attractive targets for the design of anticancer agents. Several strategies have been developed to modulate their increased activities during cancer progression. Interestingly, none of these approaches took into account the existence of the well-known antagonistic relationship between RhoA and Rac1. In this study, we first compared the invasiveness of a collection of colorectal cancer cell lines with their RhoA, Rac1 and Cdc42 activities. A marked decrease of active Cdc42 and Rac1 correlated with the high invasive potential of the cell lines established from metastatic sites of colorectal adenocarcinoma (LoVo, SKCo1, SW620 and CoLo205). Conversely, no correlation between RhoA activity and invasiveness was detected, whereas the activity of its kinase effector ROCK was higher in cancer cell lines with a more invasive phenotype. In addition, invasiveness in these colon cancer cell lines was correlated with a typical round and blebbing morphology. We then tested whether treatment with PDGF to restore Cdc42 and Rac1 activities and/or with Y27632, a chemical inhibitor of ROCK, could decrease the invasiveness of SW620 cells. The association of both treatments substantially decreased the invasive potential of SW620 cells and this effect was accompanied by loss of membrane blebbing, restoration of a more elongated cell morphology and re-establishment of E-cadherin-dependent adherens junctions. This study paves the road to the development of therapeutic strategies in which different Rho GTPase modulators are combined to modulate the cross-talk between Rho GTPases and their specific input in metastatic progression.     

Local weather and body condition influence habitat use and movements on land of molting female southern elephant seals (Mirounga leonina)

Southern elephant seals (Mirounga leonina) are known to move and aggregate while molting, but little is known about their behavior on land during this time. In this study, 60 adult females were monitored (23 with GPS tags) during four molting seasons, between 2012 and 2016 at Kerguelen Archipelago, Indian Ocean. Population surveys were recorded each year (N = 230 daily counts), and habitat use was analyzed in relation to the stage of the molt and local weather. Based on stage of molt, habitat use, and movements on land, we classified the molt of elephant seals into three phases: (1) a “search phase” at the initial stage of molt when grass and wallow habitats were used and characterized by greater mean distances travelled on land per day compared with the two other phases; (2) a “resident phase”: during initial and mid‐stage of molt when animals were found in grass and wallow habitats but with less distance moved on land; and (3) a “termination phase” at the final stage of molt where grass and beach habitats were occupied with no change in distances. Windchill and solar radiation influenced individual distances moved per day (mean 590 ± 237.0 m) at the mid‐ and final stage of molt such that animals travelled greater distances on days of low windchill or high solar radiation. Individual variation in distance moved and relative habitat use were also linked to body mass index (BMI) at arrival on the colony, as females with higher BMI moved less and preferred beach habitat. Moreover, the individual rate of molt increased with the use of wallows. Aggregation rate tended to be negatively correlated with distances moved. We therefore suggest that individuals face an energetic trade‐off while molting, balancing energy expenditure between movement and thermoregulation.     

Foster rather than biological parental telomere length predicts offspring survival and telomere length in king penguins

Because telomere length and dynamics relate to individual growth, reproductive investment and survival, telomeres have emerged as possible markers of individual quality. Here, we tested the hypothesis that, in species with parental care, parental telomere length can be a marker of parental quality that predicts offspring phenotype and survival. In king penguins (Aptenodytes patagonicus), we experimentally swapped the single egg of 66 breeding pairs just after egg laying to disentangle the contribution of prelaying parental quality (e.g., genetics, investment in the egg) and/or postlaying parental quality (e.g., incubation, postnatal feeding rate) on offspring growth, telomere length and survival. Parental quality was estimated through the joint effects of biological and foster parent telomere length on offspring traits, both soon after hatching (day 10) and at the end of the prewinter growth period (day 105). We expected that offspring traits would be mostly related to the telomere lengths (i.e., quality) of biological parents at day 10 and to the telomere lengths of foster parents at day 105. Results show that chick survival up to 10 days was negatively related to biological fathers’ telomere length, whereas survival up to 105 days was positively related to foster fathers’ telomere lengths. Chick growth was not related to either biological or foster parents’ telomere length. Chick telomere length was positively related to foster mothers’ telomere length at both 10 and 105 days. Overall, our study shows that, in a species with biparental care, parents’ telomere length is foremost a proxy of postlaying parental care quality, supporting the “telomere – parental quality hypothesis.”     

Spatiotemporal Spike Coding of Behavioral Adaptation in the Dorsal Anterior Cingulate Cortex

The frontal cortex controls behavioral adaptation in environments governed by complex rules. Many studies have established the relevance of firing rate modulation after informative events signaling whether and how to update the behavioral policy. However, whether the spatiotemporal features of these neuronal activities contribute to encoding imminent behavioral updates remains unclear. We investigated this issue in the dorsal anterior cingulate cortex (dACC) of monkeys while they adapted their behavior based on their memory of feedback from past choices. We analyzed spike trains of both single units and pairs of simultaneously recorded neurons using an algorithm that emulates different biologically plausible decoding circuits. This method permits the assessment of the performance of both spike-count and spike-timing sensitive decoders. In response to the feedback, single neurons emitted stereotypical spike trains whose temporal structure identified informative events with higher accuracy than mere spike count. The optimal decoding time scale was in the range of 70–200 ms, which is significantly shorter than the memory time scale required by the behavioral task. Importantly, the temporal spiking patterns of single units were predictive of the monkeys’ behavioral response time. Furthermore, some features of these spiking patterns often varied between jointly recorded neurons. All together, our results suggest that dACC drives behavioral adaptation through complex spatiotemporal spike coding. They also indicate that downstream networks, which decode dACC feedback signals, are unlikely to act as mere neural integrators.     

A place to hide in the home-cage decreases yolk androgen levels and offspring emotional reactivity in Japanese quail

An animal''s emotional responses are the result of its cognitive appraisal of a situation. This appraisal is notably influenced by the possibility of an individual to exert control over an aversive event. Although the fact that environment controllability decreases emotional responses in animals is well established, far less is known about its potential trans-generational effects. As the levels of avian yolk hormones can vary according to the mother''s environment, we hypothesized that housing environment of mothers would modulate the quality of her eggs and in turn her offspring''s behaviour. Two groups of female Japanese quail were constituted: a group that had access to a place to hide in their home-cage (Hd, n = 20) and a group that had nowhere to hide (NoHd, n = 20) when stressed. Both groups were submitted to daily human disturbances for a twenty-day-period. Hd females produced eggs with both less testosterone and androstenedione than did NoHd females. The emotional and social reactivity of Hd females'' offspring were lower and their growth was slower than those of NoHd females'' offspring. Our results show that a minor difference in housing environment had substantial effects on eggs and offspring. The presence of a shelter probably helped quail to cope with daily human disturbances, producing less reactive offspring. This transgenerational effect caused by an opportunity to hide could lead to applications in care of laboratory animals, conservation biology and animal welfare.     

Body regional distribution and stratification of fatty acids in the blubber of New Zealand sea lions: implications for diet predictions

Fatty acids (FAs) from blubber are often analysed to assess the diet of marine mammals. However, distribution of blubber FAs is not necessarily uniform along the body. It is therefore important to understand the deposition of dietary fat to be able to estimate the diet. We analysed the FA compositions of the thoracic ventral (T region) blubber of 28 New Zealand (NZ) sea lions Phocarctos hookeri by-caught by the southern arrow squid Nototodarus sloani fishery. Each blubber sample was divided into an inner and an outer layer. For 16 of these 28 animals, the pelvic dorsal (P) region was also sampled. The influence of body region and layer was statistically tested on the distribution of blubber FAs. We found minimal differences between the P and T regions (3 out of 29 FAs). The outer blubber layer was more concentrated in short-chain monounsaturated FAs, and less concentrated in saturated FAs, but the degree of stratification was small. Diet predictions from quantitative FA signature analysis (QFASA) applied on different body regions were similar. When applied to different blubber layers, QFASA gave some variation in the contribution of rattails (~25 % in outer blubber vs. ~12 % in inner blubber). Nonetheless, diet predicted from both layers was dominated by similar prey species: octopus, hoki and rattails. Hoki and rattails shared a similar ecological niche. Therefore, feeding ecology of NZ sea lions inferred from the inner or the outer blubber would lead to the same conclusions. In the case of NZ sea lions, the outer layer of blubber, if the only sample accessible, could be a useful tissue for diet inference from FAs.     

Rhythmic birds show a better social integration than arrhythmic birds

The activity rhythms of Japanese quail vary from one individual to another. Performing a divergent selection, we obtained one line of quail expressing a robust circadian rhythmicity of feeding activity (R) and one line of quail expressing circadian arrhythmicity of feeding activity (A). We questioned whether the endogenous rhythmicity of an individual could predict its integration in a group. For that, we introduced either an R- or an A-line chick into stable groups of standard chicks. First, we evaluated proximity and synchronization of the introduced chicks on the activities of the other group members. R-chicks remained spatially and temporally closer to other group members than did A-chicks. Second, we evaluated interactions of the introduced chicks and the level of their acceptance by the other group members. R-chicks were more competent to gain access to food than were A-chicks, and separation from their group stressed R-chicks more than A-chicks. Last, successive introductions assessed age effects: before, around, and after dispersal time (～11th day of chicks' life). Most differences between R- and A-chicks were observed between their 7th and 15th day of life. In conclusion, individual endogenous rhythms predict social integration.     

Radioecological Risk Assessment of Low Selenium Concentrations through Genetic Fingerprints and Metabolic Profiling of Soil Bacterial Communities

In a context of environmental risk assessment of nuclear ⁷⁹Se radionuclide, the impact of low Se-selenite concentrations (0.008 and 8 mg kg⁻¹) on bacterial communities of two soils, a silty clay loam and a sandy soil, was investigated over a 6-month incubation time. This Se-selenite was partially labelled with ⁷⁵Se. The state of the Se-impacted bacterial communities was analyzed through total bacterial counts, DNA fingerprints (ARISA profiles) and metabolic profiling (carbon substrate utilization patterns). Furthermore, the genetic diversity of bacterial populations involved in Se volatilization was evaluated by tpm (thiopurine methyltransferase gene) profiling. Emissions of ⁷⁵Se and CaCl₂-extractable ⁷⁵Se were measured by γ-spectrometry and scintillation analysis. Se-selenite inputs changed transiently the substrate utilization patterns of bacterial communities but did not affect the other indicators. Se volatilization was at its highest level just after adding Se-selenite and for about 1 week. This volatilization was proportional to the added Se-selenite concentrations. It was 100-fold higher in silty clay loam, even though Se bioavailability was reduced in this soil. The soils were amended with crushed grass 3 months after the addition of Se-selenite. This organic amendment affected the organization of bacterial communities and increased the Se-volatilizing activities of both soils. Original soil organic carbon and bacterial diversity and activities seemed responsible for the different levels of Se emissions observed in soils. tpm lineages, encoding Se methyltransferases, were detected in both soils, confirming the broad distribution of tpm-harbouring bacteria and their probable role in the emissions of volatile Se. Five distinct groups of tpm were recorded per soil, with tpmI lineage being detected throughout the incubation period. This study demonstrates the ability of bacterial communities at volatilizing Se concentrations inferior to geochemical backgrounds and suggests that a probable transfer of nuclear Se will occur through volatilization after an environmental spill.