Larval development of Plagioscion squamosissimus (Heckel) (Perciformes, Sciaenidae) of Itaipu reservoir (Paraná river, Brazil)

The aim of the present study was to characterize the larval development of Plagioscion squamosissimus (Heckel, 1840) morphometrically, collected at Itaipu reservoir from March 1988 to April 1990. It was obtained the samples monthly, with a conic-cylindrical plankton net with 0.5mm mesh. The morphological description of the larvae of P. squamosissimus was based on different stages of development. The specimens less than 6mm long present a moderate sized head and those that are larger than this length, present a large head. The pectoral fins are in an elevated position, near the operculum bones, and the ventral fins are in thoracic positions, the body has a moderate height, the eyes are small to moderate and the mouth is large with caniniform teeth. This species presents a proportional growth among the different parts of the body, as can be seen by the high correlation coefficient values (r>0.98; p<0.001)

Acoustic correlates of stress in central Catalan and Castilian Spanish

The general literature on the phonetic correlates of stress agrees that duration, and in stress accent languages, F0 are consistent correlates of stress. However, the role of amplitude changes in the speech signal is more controversial. In particular, the conflicting results of spectral tilt as a correlate of stress have been attributed to the effects of vowel reduction. We examined the stress correlates of duration, overall intensity and spectral tilt in Catalan and Spanish in both accented and unaccented contexts while controlling for formant frequency differences between morphologically corresponding vowels in stressed and unstressed environments by comparing vowels that maintain the same quality across stress contexts with those that do not. Duration was a consistent stress correlate in all vowels in both languages, regardless of their formant frequency differences across stress contexts and of the absence of pitch accents. In fact, stressrelated formant frequency differences between corresponding vowels amplify the duration cues to the stress contrast. On the other hand, the use speakers made of intensity was not as pervasive as that of duration. Specifically, changes in spectral tilt were significant only in Catalan and in those vowels that alternate a more open and peripheral realization in stressed syllables with a mid-central realization in unstressed syllables, indicating that spectral tilt is related to the formant frequency differences linked to the centralization processes rather than to the stress contrast.We would like to thank the audience at the 2005 PaPI Conference, and also Barbara Bullock, Megan Crowhurst, Sónia Frota, José Ignacio Hualde, Scott Myers, Jacqueline Toribio, Daniel Recasens, and Marina Vigário for very useful feedback. We are also grateful to the 20 informants who kindly participated in the production experiment. Thanks to Tim Mills who kindly sent us the script that measures spectral tilt. Special thanks to John Coleman and two anonymous reviewers, whose insightful comments greatly improved the quality of this article. This research has been funded by grant 2005SGR-00753, awarded by the Generalitat de Catalunya, and by grants HUM2006-01758/FILO “Estructura prosódica y adquisición de la prosodia en catalán y español”, CONSOLIDER-INGENIO 2010 “Bilingüismo y Neurociencia Cognitiva CSD2007-00012” awarded by the Spanish Ministerio de Educación y Ciencia, and URA Program awarded by the College of Liberal Arts, University of Texas