HOW AND WHEN DO LAMBS RECOGNIZE THE BLEATS OF THEIR MOTHERS?

ABSTRACT

In domestic sheep Ovis aries, the mother and the young display a preferential bond for each other that relies on multimodal inter-individual recognition. Lambs show a preference for their own dam shortly after birth, and this is important for their survival. The role of acoustic cues in this early preference for the mother is not clear. The aim of the present work was to analyze the timing of acoustic recognition of the mother and to identify the physical parameters used in the recognition of maternal bleats by the lamb.

In a first study, we investigated the ability of lambs to discriminate between the bleats of their own mother and an alien equivalent mother in a two-choice test. Both ewes were hidden behind a canvas sheet and lambs were not allowed to approach the dams closer than 1 m, thus preventing visual as well as olfactory perception. Tests were conducted 12 hr, 24 hr or 48 hr after birth (n=19 or 20/group). An indication of vocal discrimination was already present at 24 hr and at 48 hr lambs spent significantly more time near their mother than near the alien dam.

In a second step, we investigated which physical parameters of the bleats were important for recognition. For this, we conducted playback experiments with modified bleats at two weeks postpartum. Ours results show that lambs pay attention to a combination of various time, energy and frequency parameters: timbre (distribution of energy within the spectrum), amplitude and frequency modulations appear to be the most important parameters encoding the individual signature.

We conclude that vocal recognition between the ewe and her lamb plays an important role in the display of preferential mother-young bond from very early on. Our studies also demonstrate that the encoding of the individual signature is not limited to the frequency domain but rather involves a multiparametric encoding process.     

TCR beta chain that forms peptide-independent alloreactive TCR transfers reduced reactivity with irrelevant peptide/MHC complex

A major feature of the TCR repertoire is strong alloreactivity. Peptides presented by allogeneic MHC are irrelevant for recognition by a subset of alloreactive T cells. To characterize peptide-independent TCRs at the molecular level, we forced the expression of a TCRbeta chain isolated from a peptide-independent alloreactive CD8+ T cell line. The alloreactive TCR repertoire in the transgenic mouse was peptide dependent. However, analysis of essential TCR contacts formed during the recognition of self-MHC-restricted Ag showed that fewer contacts with peptide were established by the transgenic TCRbeta chain, and that this was compensated by additional contacts formed by endogenous TCRalpha chains. Thus, reduced interaction with the peptide appears to be a transferable feature of the peptide-independent TCRbeta chain. In addition, these findings demonstrate that reactivity to peptides is preferred over the reactivity to MHC during the formation of the TCR repertoire.     

Occurrence of Fusarium langsethiae Strains Isolated from Durum Wheat in Italy

Surveys on the occurrence of type A trichothecenes in wheat, and particularly for the T‐2 and HT‐2 toxins, and information on the biology and epidemiology of the causative Fusarium species (i.e. F. langsethiae, F. sporotrichioides) are scarce in Italy, as compared to the more common type B trichothecene, deoxynivalenol and its producers. This 4‐year monitoring of phytopathogenic Fusarium species on 183 seed lots of durum wheat shows wide distribution of F. langsethiae in Italy and the potential of several isolates of this fungus to produce high amounts of T‐2 and HT‐2 in wheat. Fusarium langsethiae was observed for approximately 48% of the analysed samples, with a maximum incidence for a single lot of 10.5%. Fusarium sporotrichioides was observed only in 2011, with an average incidence of 2% (range, 0–3%). A collection of F. langsethiae isolates representative of the main cultivation areas in Italy was established. These isolates showed great variability for their toxin production in vitro. Of 28 strains, all except one isolate can produce the T‐2 and HT‐2 toxins. HT‐2 was generally in greater amounts than T‐2, with an average concentration ratio for HT‐2 to T‐2 of 2.1 (range, 0.7–5.4). The artificial inoculation of wheat with three isolates of F. langsethiae produced no Fusarium head blight symptoms under field conditions. However, significantly higher incidence of F. langsethiae was seen on the kernels of inoculated plants, compared to the uninoculated controls.     

Life history consequences of larval foraging depth differ between two competing Anopheles mosquitoes

1. Anopheline larvae are surface feeders and allocate most of their time to search for food at the water surface. However, species of the Anopheles gambiae Giles complex may also show bottom feeding. The consequences of this foraging tactic for life history are unknown, yet may be relevant to understand inter‐specific competition patterns. 2. The diving ability and activity of larvae of the main African malaria vectors, An. coluzzii and An. gambiae, at two different water depths (14 and 30 cm) were assessed. We further explored the biological relevance of diving for food harvesting by monitoring key life history traits in two species treatments (single or mixed species) and two food treatments (surface or bottom feeding). 3. Overall, An. coluzzii larvae showed more diving activity than An. gambiae. When feeding at the bottom both species, and especially An. gambiae, showed a delayed emergence and a reduced emergence rate. Moreover, An. gambiae also suffered a reduced wing length. 4. Mixed‐species rearing had a detrimental effect on the life history traits of An. gambiae but not on An. coluzzii, suggesting a competitive advantage for the latter in our experimental conditions. 5. The present results confirm that anopheline larvae are able to forage for food at the bottom of their breeding site and that An. coluzzii shows a superior diving activity than An. gambiae and this at a lower cost. These behavioural differences probably reflect specific adaptations to different aquatic habitats, and may be important in shaping species distributions and the population biology of these important vector mosquitoes.     

The influence of a parasitoid's response to temperature on the performance of a tri‐trophic food web

1. Food web interactions are complex and can respond to environmental changes in unpredictable ways that do not necessarily equate to the individual responses of each of the components of the food web. 2. Biomass can be used to evaluate the productivity of the three individual trophic levels, in the form of the Net Generational Productivity (NGP) and the performance of the entire food web with the newly developed tri‐trophic food web performance ratio (?_3t). 3. These parameters were used to evaluate the performance of nine plant‐based tri‐trophic food webs composed of: potato, Solanum tuberosum L. and two cultivars of bell pepper Capsicum annuum L; three biotypes of the aphid Macrosiphum euphorbiae Thomas (Hemiptera: Aphididae) and the parasitoid wasp Aphidius ervi (Haliday) (Hymenoptera: Braconidae). 4. The NGP showed that the thermal window for biomass productivity for each trophic level is different and is reduced by approximately 4 °C with respect to the inferior level. Aphidius ervi had the smallest thermal window for biomass productivity and development. 5. The present results showed that the performance (?_3t) of the tested food webs is influenced in a top‐down fashion, where the intra‐specific variation of the food web, namely the host plant, played a major role in the productivity of each of the subsequent trophic levels. 6. The ?_3t suggested that exposure to high and low temperatures might severely affect the effectiveness of A. ervi as a biocontrol agent of the aphid M. euphorbiae in bell pepper and potato crops.     

Impact of different acclimation temperatures and duration on the chill coma temperature and oxygen consumption in the tenebrionid beetle Alphitobius diaperinus

When the ambient temperature is lowered to an insect's lower thermal limit, the insect enters into chill coma. Chill coma temperature and chill coma recovery can vary within species as a result of thermal acclimation, although the physiological basis of the onset of chill coma remains poorly understood. The present study investigates how the temperature of acclimation (0, 5, 10, 15 and 20 °C for 2 or 7 days) affects chill coma temperature and oxygen consumption in adult Alphitobius diaperinus Panzer (Coleoptera: Tenebrionidae). It is hypothesized that the threshold decline in metabolic rate corresponds to the entry into chill coma. Oxygen consumption (as a proxy of metabolism) is measured across the chill coma temperature threshold, and a strong decline in oxygen consumption is expected at entry into chill coma. The acclimation decreases the chill coma temperature significantly from 6.6 ± 1.1 °C in control insects to 3.1 ± 0.7 °C in those acclimated to 10 °C. The change in metabolic rate (Q₁₀) after acclimation to temperatures ranging from 10 to 20 °C is 3.7. Despite acclimation, the metabolic rate of A. diaperinus conforms to Arrhenius kinetics, suggesting that the response of this beetle does not show metabolic compensation. The data suggest the existence of a threshold decline in metabolic rate during cooling that coincides with the temperature at which an insect goes into chill coma.     

Delayed setting of the photoperiodic response in recombinant clones of the aphid species Sitobion avenae

1. To explore the possible causes of apparent changes in reproductive mode from obligate to cyclical parthenogenesis over time in recombinant clones of the aphid Sitobion avenae Fabricius, all F1 progenies from various crosses were tested for several consecutive years for sexual morph production, after several weeks' exposure to a short photoperiod. 2. Variable proportions of the F1 progenies from selfing and outcrossing holocyclic clones did not produce mating females when induction was attempted in the year of hatching, but only after further induction, the following year or after. This ‘delayed setting of the photoperiodic response’ (DSPR) was much stronger in recombinants from crosses involving only clones from oceanic regions than in those involving one clone from a region with a continental climate. 3. F1 progenies resulting from crosses between one holocyclic and one intermediate clone did not show DSPR. It appeared again in the F2. 4. DSPR preferentially affected the latest hatched clones in a given progeny. 5. This phenomenon is neither an experimental artefact nor as a result of clone contamination. It appears to be because of a genetically controlled quantitative trait affecting the length of the ‘interval timer’, and may represent an adaptation of holocyclic aphid clones from oceanic regions to unpredictable winter climates.     

Inter‐individual variation in movement: is there a mobility syndrome in the large white butterfly Pieris brassicae?

1. One of the main drivers of the genesis and maintenance of biodiversity is mobility, i.e. the net result of the interaction between physiological performances (movement capacity) and behavioural decisions (movement decisions). Although several previous studies have found personality traits related to mobility, it is not yet clear whether mobility involves a real syndrome, i.e. whether individuals showing good movement capacity are also more likely to decide to move, and whether these inter‐individual differences are consistent across time. 2. The aim of the present study was therefore to disentangle the mechanisms underlying the maintenance of inter‐individual variation in mobility by measuring three traits related to mobility under experimental conditions in a butterfly species, and to test the existence of correlations between these traits. These measures implied movement capacity and movement decision. 3. It was shown that mobility‐related traits were (i) consistent across time, (ii) inter‐correlated, and (iii) dependent upon sex and morphology. 4. These results therefore suggest the existence of a mobility syndrome in a butterfly. Such findings highlight the necessity to accurately integrate inter‐individual variation (behavioural syndrome) in our comprehension of the evolution of movement strategies.