A new automatic video multitracking system able to follow a large school.

Poster (2005)

Evolution des populations de tétras lyres (Tetrao tetrix) sur le plateau des Hautes-Fagnes en regard des modifications des paramètres écologiques du milieu.

in AVES (2005), 42/1-2

Morphological changes of the nucleolus during oogenesis in oviparous teleost fish, Barbus barbus (L.).

in Journal of Structural Biology (2005), 152(1), 1-13

In fishes, like in amphibians, it is well established that variations in rRNA activity occur during oogenesis. Contrary to amphibians, however, little is known about the ultrastructural changes of the ... [more ▼]

In fishes, like in amphibians, it is well established that variations in rRNA activity occur during oogenesis. Contrary to amphibians, however, little is known about the ultrastructural changes of the nucleolus during fish oogenesis. Evolution of the nucleolus has been followed during oogenesis in the teleost fish Barbus barbus (L.) using light and transmission electron microscopies. We show that the behaviour of the nucleolus during B. barbus oogenesis resembles that reported in amphibians but also presents several peculiarities. The most striking feature is the marked vacuolization of nucleoli occurs at the beginning of the growth during previtellogenesis. The results obtained by means of the in situ terminal deoxynucleotidyl transferase-immunogold method for detecting DNA seem further to indicate that the chromatin cap becomes integrated into developing nucleoli during previtellogenesis and then segregate at the periphery of nucleoli at the end of glycoproteinic vitellogenesis. Our study also shows that the nucleoli of germ cells, like that of follicle cells, are devoid of fibrillar centre but comprise a fibrillar and a granular component whatever the oogenetic stage. Ultrastructural detection of DNA and nucleolar proteins (AgNOR proteins, fibrillarin, and pp135) supports further the view that the Barbus nucleolus is a bipartite structure. [less ▲]

A new automatic video multitracking system able to follow a large school

in Noldus, L.P.P.J.; Grieco, F.; Loijens, L. W. S. (Eds.) et al Proceedings of Measuring Behavior 2005 (2005)

The study of shoaling behaviours is tackled by scientists by three approaches: the field, laboratory and computer modelling approach. The field studies are complicated and permit rarely an analysis of ... [more ▼]

The study of shoaling behaviours is tackled by scientists by three approaches: the field, laboratory and computer modelling approach. The field studies are complicated and permit rarely an analysis of individual positions. The third approach, consisting of development of mathematic models, is artificial. It requires a comparison with empiric results to validate and to determine the explications’ degree of each model. Thanks to the developments of digital imaging techniques, the laboratory studies on fish are able to measure the behavioural parameters with precision, impossible to realize with manual recording. Multitracking systems are rare and of recent development. These are insufficient to study the real size of shoals, often composed of hundreds of .shes. We have developed a new system of multitracking thanks to collaboration with the G.R.A.S.P. The G.R.A.S.P. has before realised other multitracking systems to follow some hundreds physical objects. Our video multitracking system is able to detect and to track more than a hundred unmarked fishes by gray scaling technique during some minutes. It permits an analysis as well at the group level as at the individual level. The multitraking program is able to attribute a number at each fish and to follow each one during the whole duration of the track. Our system permits the analysis of the movement of each individual, even if the trajectories of two fishes cross each other. It is possible thanks to the theoretical estimation of trajectory of each fish, compared with the real trajectory (analysis with feedback). The human eye is always necessary to detect the errors in identification but reediting is possible. However, if the fishes don’t move too rapidly, a rate of 25 images /s gives very good results, without too much visual expertise from the experimenter. If the fishes are too fast (i.e. escape response), it is better to use a high speed camera. [less ▲]

Poissons migrateurs : objectif Meuse. Film. Supervision scientifique de l'Unité de Biologie du Comportement.

Learning material (2005)

Préface

in Philippart, Jean-Claude (Ed.) « Le voyage périlleux des poissons grands migrateurs dans la Meuse » (2005)

Courtship behaviour at low and high water temperatures in the Alpine newt

Poster (2005)

Environmental factors are known to have a major effect on behavioral patterns of organisms. Among these factors, temperature particularly affects ectotherms. However, although many studies focused on ... [more ▼]

Environmental factors are known to have a major effect on behavioral patterns of organisms. Among these factors, temperature particularly affects ectotherms. However, although many studies focused on acoustic communication, the effect of environmental temperature on visual courtship displays and sexual performance has been little explored. The aim of this work was to determine the effect of temperature on the sexual behaviour of the Alpine newt Triturus alpestris in controlled laboratory conditions. Temperature had a major effect on the two sexes: at low temperatures, the frequencies of several displays, including sperm deposition, is lowered. This variation is in fact caused by the female responsiveness, which is temperature-dependent. However, some other behaviours, such as the fanning movement of the male’s tail (i.e., the main courtship display) are directly dependent on temperature: at lower temperatures, the tail beats at a lower rate but for a longer time. The similar reproductive success at the two temperatures indicates that breeding in cold water is not necessarily costly. It allows males and females to mate early in the season. This is particularly adaptive because, in many habitats, the reproductive period is shortened by drying or freezing conditions which may impair survival of branchiate offspring. [less ▲]

Measuring the ontogeny of swimming behaviour with a computerised video tracking system: development of spontaneous activity at the embryonic and early juvenile periods in the mouthbrooder Nile tilapia

Poster (2004, August 28)

Etablissement d’un modèle comportemental, social, populationnel du tétras lyre dans son habitat spécialement dans les Hautes-Fagnes.

Report (2004)

L'outil: une invention humaine?

in Bulletin de la Société Royale des Sciences de Liège (2004), 4