Intra-syllabic acoustic signatures used by the king penguin in parent-chick recognition: an experimental approach.

In king penguin colonies, several studies have shown that both parent-chick recognition and mate-pair recognition are achieved by acoustic signals. The call of king penguins consists of strong frequency modulations with added beats of varying amplitude induced by the two-voice generating process. Both the frequency modulation pattern and the two-voice system could play a role in the identification of the calling bird. We investigated the potential role of these features in individual discrimination. Experiments were conducted by playing back altered or reconstructed parental signals to the corresponding chick. The results proved that the king penguin performs a complex analysis of the call, using both frequency modulation and the two-voice system. Reversed or frequency-modulation-suppressed signals do not elicit any responses. Modifying the shape of the frequency modulation by 30 % also impairs the recognition process. Moreover, we have demonstrated for the first time that birds perform an analysis of the beat amplitude induced by the two-voice system to assess individual identity. These two features, which are well preserved during the propagation of the signal, seem to be a reliable strategy to ensure the accurate transmission of individual information in a noisy colonial environment.

Perceptual salience of individually distinctive features in the calls of adult king penguins.

In the king penguin, Aptenodytes patagonicus, incubation and brooding duties are undertaken alternately by both partners of a pair. Birds returning from foraging at sea find their mate in the crowded colony using acoustic signals. Acoustic recognition of the mate maintains and strengthens the mate's fidelity and favors synchronization in the different stages of reproduction. In this study it was found that the king penguin vocalizes in response to the mate's playback calls, but not to those of neighbors or unfamiliar conspecific individuals. To study individual features used by the birds for individual recognition of mates, various experimental signals consisting of synthesized modifications of the mate' s call were played back to the incubating bird. Results indicated that birds attend to the FM profile of the call, in particular its initial inflexion. The frequency modulation shape of the syllable can be assimilated to a vocal signature repeated though the different syllables of the call. King penguins pay little attention to the call' s AM envelope or its absolute frequency.

A method of independent time and frequency decomposition of bioacoustic signals: inter-individual recognition in four species of penguins.

The aim of this paper is to introduce a method for analyzing acoustic signals capable of assessing the potential for individual coding information. Signals are analysed both in the time domain (rhythm of emission of the song independent of its frequency content) and in the spectral domain (spectral content of the song independent of the rhythm of emission). The method is then applied to a comparative study of four penguin species, where the problem posed by inter-individual recognition differs from species to species. A direct relationship was shown between the potential of individual coding and the difficulty in partner identification.

Artificial neural networks as a classification method in the behavioural sciences.

The classification and recognition of individual characteristics and behaviours constitute a preliminary step and is an important objective in the behavioural sciences. Current statistical methods do not always give satisfactory results. To improve performance in this area, we present a methodology based on one of the principles of artificial neural networks: the backpropagation gradient. After summarizing the theoretical construction of the model, we describe how to parameterize a neural network using the example of the individual recognition of vocalizations of four fallow deer (Dama dama). With 100% recognition and 90% prediction success, the results are very promising.

Effects of the antithrombotic drug suloctidil on low density lipoprotein processing and cholesterol metabolism in cultured human fibroblasts.

Human foetal lung fibroblasts were pretreated for 24 h with the antithrombotic drug, suloctidil (1 to 10 mumol/l), which induced a dose-dependent increase in LDL binding, uptake and degradation. At 10 mumol/l suloctidil, the respective increases in these parameters were 40%, 80% and 50%. The same treatment also resulted in increases of 1.5 to 2-fold in the synthesis of sterols, fatty acids and triacylglycerols from sodium acetate. In contrast, the esterification of cholesterol with oleic acid was specifically decreased by 35% by 24 h pretreatment of fibroblasts with 10 mumol/l suloctidil. A similar decrease of cholesterol esterification was observed in cholesterol-laden fibroblasts. It is suggested that these effects of suloctidil on LDL processing and cholesterol metabolism are related to the amphiphilic characteristics of the drug and to its calcium-blocking properties.