Parasitoid vibrations as potential releasing stimulus of evasive behaviour in a leafminer

Abstract. The aim of this study was to characterize the vibratory signals produced by the parasitoid Sympiesis sericeicornis Nees (Hymenoptera: Eulophidae) while foraging on apple leaves infested by one of its hosts, the spotted tentiform leafminer Phyllonorycter malella (Ger.) (Lepidoptera: Gracillariidae).This leafminer changes its behaviour as a function of the parasitoid's behaviour to escape parasitization.We propose that the leafminer uses vibrations triggered by the parasitoid to detect the presence of its enemy.We measured vibrations produced by a foraging parasitoid on a mine with a laser vibrometer.By recording concurrently the behaviour of the parasitoid on video, vibrations could be assigned to particular behaviours.Subsequently, vibrations were characterized by their dominant frequencies and intensities.The behaviours Landing and Take-off both produced strong impact-like vibrations characterized by an initial irregular phase during which frequencies up to 25 kHz occurred followed by a slow decaying regular phase.Vibrations elicited by Moving, Standing and Probing showed no clear temporal pattern.During Probing , dominant frequencies of up to 5.6 kHz were observed frequently at intensities well above the background noise (>10 dB).During Moving and Standing , vibrations were more scarce and of lower frequencies and intensities.Due to their impact-like nature, vibrations produced by Landing and Take-off are probably not specific to the parasitoid.Vibrations produced by Moving and Standing are difficult to detect and not reliable because of their non-specificity.Therefore, only Probing provides a reliable and detectable source of information for the host.The vibrations elicited during Probing could account for the evasive behaviour that is observed in this and other leafminers.     

FOSSIL WOODS IN INTERGLACIAL SEDIMENTS FROM THE CARBONIFEROUS HOYADA VERDE FORMATION, SAN JUAN PROVINCE, ARGENTINA

Abstract:  Fossil woods are described and assigned to Cuyoxylon multipunctatus gen. et sp. nov. The woods were deposited in shales from an interglacial period, and are the first to be described in detail from the Carboniferous glaciation of western Gondwana. They have the primitive characters of Early Carboniferous woods, such as mesarch protoxylem and numerous contiguous pits in an alternate arrangement. They are the oldest fossil woods to have been described from South America. The growth ring characteristics are consistent with a seasonal cool climate.     

CONTENT AND ULTRASTRUCTURAL LOCALIZATION OF TRANSITIONAL METALS IN ASCIDIAN OVARY

The content of some transitional metals (Ti, V, Cr. Mn. Fe, Cu) in the ovary of Ascidia malaca and Ciona intestinalis and in the gonads of Polycarpa gracilis has been reported. The metals were localized histospectrographically and ultrastructurally. In the ovaries of C. intestinalis . the quantitative analysis shows a variable content of metals related to the ovary maturative cycle. The iron is localized in the electron dense cytoplasmic granules of A. malaca oocytcs and in the cytoplasmic dense formation of P. gracilis test cells. Cl, S, Si and P are present in the test, follicles and inierovarian cells of all examined species.
The results are discussed in relation to the zoological position of these species. The presence of metals and Ascidiacee phylogenesis might be correlated.