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.     

G Protein-Coupled Receptor-Mediated ERK1/2 Phosphorylation: Towards a Generic Sensor of GPCR Activation

The development of new analytical methods, aimed at profiling G protein-coupled receptor (GPCR) ligands, regardless of the G protein-coupling pattern of their respective receptor, remains a key goal in drug discovery. Considerable evidence has recently revived the central role that could be played by extracellular-signal-regulated kinase (ERK), the cornerstone protein kinase of the first tyrosine kinase receptor-mediated pathway identified, in response to the activation of various types of GPCRs. Here we reveal a conceptual study in which the potential of ERK phosphorylation is evaluated as a generic readout in response to three different receptors activating three main classes of G proteins: Gα_s, Gα_i and Gα _q. GPCR-mediated ERK phosphorylation was compared with different readouts such as GTPγ S, CAMP, or Ca^{2 +}. We propose the measurement of GPCR-activated ERK phosphorylation as an alternative assay to better understand the molecular pharmacology of ligands of promiscuous GPCRs.     

The impact of patch encounter rate on patch residence time of female parasitoids increases with patch quality

Abstract.  1. For animal species that forage on patchily distributed resources, patch time allocation is of prime importance to their reproductive success. According to Charnov's marginal value theorem (MVT), the rate of patch encounter should influence negatively the patch residence time: as the rate of patch encounter decreases, the patch residence time increases. Moreover, the MVT predicts that animals should stay longer in high quality patches.
2. Using the aphid parasitoid Aphidius rhopalosiphi (Hymenoptera: Aphidiinae), the effects of these two factors (patch encounter rate and host density) were combined in order to test if the increment in patch residence time for a given decrease in patch encounter rate was larger for high quality patches than for low quality patches.
3. The results show a significant effect of the interaction between the two factors. In high host density patches, parasitoids spent more time if they experienced a low patch encounter rate, while in low host density patches, patch encounter rate had no significant effect on the patch residence time. This suggests that the response of A. rhopalosiphi females to patch encounter rate varied with host density in the patch. Moreover, the same interaction effect was observed for the number of ovipositor contacts on aphids.
4. Parasitoid females can use patch encounter rate to estimate patch density in the habitat but the effect of this estimate on their patch residence time is modulated by patch quality. Staying longer in a patch when patches are rare is more advantageous when the fitness gained by doing so is large. In low quality patches, the expected fitness gain is small and the female may gain more by leaving and taking her chance at finding another patch.     

Epiphallus anatomy in the Arion hortensis species aggregate (Mollusca, Pulmonata)

A SEM study of the structure associated with the outlet of the epiphallus in the atrium genitale of three arionid species ( Arion hortensis s.s., A. distinctus and A. owenii ) is presented. The structures are described and compared, and the specific differences are outlined. Preliminary notes on the same structure in A. intermedius , as well as on the spermatophores of A. hortensis s.s. and A. distinctus , are also provided. It is concluded that A. owenii stands somewhat apart in relation to the latter two species, since it may be more related to A. intermedius. Although it is generally accepted that the genus Arion is characterized by the absence of a penis, it is suggested here that the described structure at the outlet of the epiphallus is nothing but a remnant of an ancestral penis; anyhow, it is at least functionally allied to a penis.     

Comparative host tissue Réactions of Musa acuminate (AAA group) cvs Poyo and Gros Michel roots to three banana-parasitic nématodes

In a comparative histopathological investigation, Poyo and Gros Michel cul-tivars of Musa acuminata (AAA triploid) were inoculated with Radopholus similis, Helicotylenchus multicinctus or Hoplolaimus pararobustus and were grown in a greenhouse under tropical conditions. R. similis infected all the cortical parenchyma layers of the roots, reaching the vascular cylinder, but it stayed more superficial in Gros Michel roots. Red-brown cytoplasmic globules appeared in the cortical parenchyma cells of Gros Michel only. H. multicinctus infected much of the outer cortical parenchyma in roots of both cultivars with a few phenolic cells occurring around the superficial lesions. H. pararobustus penetrated only the immediate sub-epidermal tissues in both cultivars. The differences observed between nématodes and cultivars reflect specific host-nematode interactions on bananas.     

MICRODIALECT AND GROUP SIGNATURE IN THE SONG OF THE SKYLARK ALAUDA ARVENSIS

ABSTRACT

The Skylark Alauda arvensis is a territorial species of open landscape in which pairs settle in stable and adjacent territories during the breeding season. Due to the heterogeneity of the habitat, territories are gathered in patches spaced by a few kilometres, in which each male produces very long and complex flight songs as a part of the territorial behaviour. We showed that, in a given patch, all the males (neighbours) share some particular sequences of syllables in their songs, whereas males settled in different patches (strangers) have almost no sequences in common. Such a phenomenon is known as microdialect. To test the hypothesis that these shared sequences support a group signature, we made playback experiments with “chimeric” signals: songs of strangers where the sequences shared by neighbours were artificially inserted. Behavioural responses to playbacks indicated a neighbour-stranger discrimination consistent with the dear enemy phenomenon, i.e. a reduced aggression toward neighbours compared to strangers. Furthermore, the same level of responses, observed when a “chimeric” song and a neighbour song were broadcast, indicated that shared sequences are recognised and identified as markers of the neighbourhood identity.