Social responses to variation in food supply and nest suitability in ants (Tapinoma erraticum)

The social organization of Tapinoma erraticum colonies has been studied in two environmental contexts: those of mild starvation and of disturbance inducing a complete change of nest site. Trophallactic activity was compared with brood transport behaviour in tests performed repeatedly on the same group of insects. Workers were individually marked enabling interactions to be analysed within the group. An age-dependent difference in behaviour exists during feeding. However, when the colony changed its location, certain workers were found to be transport specialists, whereas others remained inactive: the transport behaviour of T. erraticum workers does not appear to be agedependent, unlike feeding behaviour. A principal components analysis of the results indicated no link between these two types of activities at the individual level. This study indicates the existence of types of social organization which are specific to each of the activities performed.     

Characteristic alatoid ‘cineole cassette’ monoterpene synthase present in Nicotiana noctiflora

Nicotiana species of the section Alatae emit a characteristic floral scent comprising the? cineole cassette’ monoterpenes 1,8-cineole, limonene, myrcene, β-pinene, α-pinene, sabinene and α-terpineol. All previously isolated ‘cineole cassette’-monoterpene synthase genes are multi product enzymes that synthesize the seven compounds of the ‘cineole cassette’. Interestingly, so far this ‘alatoid’ trait was only shared with the eponymous species Nicotiana suaveolens of the sister section Suaveolentes. To determine the origin of the ‘cineole cassette’ monoterpene phenotype other potential parent species of section Noctiflorae or Petunoides as well as of the distantly related section Trigonophyllae were analysed. A monoterpene synthase producing the set of ‘cineole cassette’ compounds was isolated from N. noctiflorae. N. obtusifolia emitted solely 1,8-cineole and no monoterpenes were found in floral scents of N. petunoides and N. palmeri. Interestingly, the phylogenetic analysis clustered the new gene of N. noctiflora closely to the terpineol synthase genes of e.g. N. alata rather than to cineole synthase genes of e.g. N. forgetiana.     

Activité de la pars intermedia de l'hypophyse autotransplantée chez l'Anguille

Résumé Chez l'Anguille dont l'hypophyse est autotransplantée dans la musculature dorsale depuis 2 mois, la pigmentation est assez variable, mais généralement plus sombre que celle des animaux hypophysectomisés. De plus, une tache foncée apparaît au voisinage du greffon, indiquant une sécrétion d'intermédine ou MSH (melanocyte-stimulating hormone). Il existe une corrélation entre l'intensité de la pigmentation, le diamètre de cette tache noire et le degré de conservation de la pars intermedia dans les 13 cas où celle-ci est identifiée dans le greffon; le tissu intermédiaire est absent chez les 3 Anguilles aussi pâles que celles hypophysectomisées.La pars intermedia contient normalement 2 catégories cellulaires; seule celle colorable par l'hématoxyline au plomb (H-Pb) est encore présente dans les transplants: elle apparaît donc responsable de la sécrétion de l'intermédine; l'autre catégorie PAS (acide periodique-fuchsine de Schiff) positive, moins abondante, régresse fortement et peut même disparaître. Il s'agit donc bien de deux types cellulaires distincts, avec une évolution propre. Cependant, aucun caractère histologique ne permet de penser que les cellules hématoxylinophiles de la pars intermedia sont hyperactives, et ce fait, joint à l'absence d'une mélano-dispersion permanente n'autorise pas à conclure à la présence d'un facteur hypothalamique inhibant la décharge de MSH ou MSH-IF chez cette espèce, similaire à celui décrit chez les Amphibiens; l'hypothèse inverse de l'existence d'un MSH-RF, ou facteur de décharge de MSH, apparaît plus probable, bien que la pars intermedia jouisse d'une autonomie importante chez l'Anguille. Ces observations sont discutées à la lumière des données publiées chez d'autres Vertébrés.L'hormone de type prolactinique sécrétée par les cellules érythrosinophiles de l'hypophyse, présentes dans les 15 greffons viables, ne semble pas jouer de rôle primordial dans le contrôle de la pigmentation, elle apparaît même incapable de reproduire l'effet mélano-dispersant de la prolactine ovine. Les cellules corticotropes, identifiées dans les 15 greffons, ne paraissent pas intervenir dans le maintien de la pigmentation, mais il reste à préciser leur activité fonctionnelle.

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Activity of the pars intermedia of the autotransplanted pituitary gland in the European eel

Summary The pituitary gland was autotransplanted in the dorsal muscle of 16 eels; 2 months later, the pigmentation is quite variable, but generally darker than that of hypophysectomized animals. Also, a dark spot appears close to the graft, indicating intermedin (MSH) secretion. There is a correlation between the intensity of the pigmentation, the diameter of the black spot, and the degree of maintenance of the pars intermedia in the 13 cases where it was identified in the transplant. The intermediate lobe tissue is absent in the 3 eels which are as pale as the hypophysectomized ones.The pars intermedia normally contains 2 cell types: only the cell stainable with the leadhaematoxylin technique (H-Pb) is still present in the grafts: then, it appears responsible for the elaboration of intermedin. The other cell type, PAS positive, less abundant, is strongly regressed and can even disappear. It seems obvious that there are two distinct cell types with their own development. However, no histological criteria suggest that the H-Pb positive cells are hyperactive. As there is no permanent melano-dispersion in the grafted animals, it does not seem evident that the hypothalamus of the eel secretes a MSH-inhibiting factor (MSH-IF) similar to that described in Amphibians. Conversely, the hypothesis of a MSH-releasing factor (MSH-RF) would appear more probable despite a large degree of autonomy of the pars intermedia. These observations are compared with data published on various Vertebrates.The prolactin-like hormone secreted by the erythrosinophilic cells of the pituitary gland, identified in the 15 healthy grafts, does not seem to play an important role in the control of the pigmentation. It appears even unable to mimic the melanophoro-dispersing effect of the ovine prolactin. The corticotrophic cells present in the 15 transplants do not seem to act on the maintenance of the pigmentation, but their functional activity remains to be evaluated.

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Nous remercions bien vivement le Dr. Anastasija Dimovska pour l'aide amicale qu'elle nous a apportée au cours de cette expérience lors de son séjour en France rendu possible grâce à une bourse du Gouvernement Yougoslave. Nous remercions Mme Cuvier pour sa participation aux hypophysectomies et aux greffes et Melle J. Olivereau du CNRS pour sa collaboration histologique.     

Modifications des cellules corticotropes de l'hypophyse chez l'anguille radiothyroïdectomisée

Résumé Chez les Anguilles dont la destruction totale ou sub-totale de la glande thyroïde a été réalisée avec des injections répétées de fortes doses d'iode radioactif ¹³¹I, l'interrénal présente un aspect histologique indiquant un hypofonctionnement traduit par une atrophie cellulaire et nucléaire. De même, après 2 à 8 mois d'expérience, les cellules corticotropes de l'hypophyse sont plus petites, moins granulées à l'apex qui devient finement vacuolisé, le diamètre nucléaire est significativement réduit. La réponse de l'interrénal à la thyroïdectomie est donc contrôlée en partie par l'hypophyse. Comme l'apport de thyroxine stimule l'axe hypophyso-corticosurrénalien de l'Anguille, et la réduction ou la disparition des hormones thyroïdiennes le déprime, il semble exister chez ce Téléostéen une synergie entre les activités de la thyroïde et de l'interrénal ayant l'hypophyse comme intermédiaire.

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Modifications of the Corticotrophic Cells of the hypophysis of the radiothyroidectomized eel

Summary Eels were completely or sub-totally radiothyroidectomized with repeated injections of high doses of radioiodine ¹³¹I. After 2 to 8 months, the histological picture of the interrenal suggests a hypoactivity, indicated by a nuclear and nucleolar atrophy. Simultaneously, in the pituitary gland, the corticotrophic cells are smaller, less granulated with a finely vacuolated apical cytoplasm. The diameter of their nuclei is significantly reduced. It then appears that the adrenal response to thyroidectomy is, at least partly, mediated by the pituitary gland. As thyroxine treatment induces a stimulation of the hypophyso-adrenocortical system in the eel, and a decrease or disappearance of thyroidal hormones exerts a depressing effect, it seems that there is a synergy between the activity of the thyroid gland and the interrenal in this species, the hypophysis playing a role of mediator in these responses.

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Ce travail a été réalisé avec la collaboration technique de Mademoiselle Jacqueline Olivereau, du CNRS, que nous remercions bien vivement.     

Pattern and pace of morphological change due to variable human impact: the case of Japanese macaques

Primates - Human impact influences morphological variation in animals, as documented in many captive and domestic animal populations. However, there are different levels of human impact, and their...     

Assessing the contribution of bacteria to the heat tolerance of experimentally evolved coral photosymbionts

Coral reefs are extremely vulnerable to ocean warming, which triggers coral bleaching—the loss of endosymbiotic microalgae (Symbiodiniaceae) from coral tissues, often leading to death. To enhance coral climate resilience, the symbiont, Cladocopium proliferum was experimentally evolved for >10 years under elevated temperatures resulting in increased heat tolerance. Bacterial 16S rRNA gene metabarcoding showed the composition of intra- and extracellular bacterial communities of heat-evolved strains was significantly different from that of wild-type strains, suggesting bacteria responded to elevated temperatures, and may even play a role in C. proliferum thermal tolerance. To assess whether microbiome transplantation could enhance heat tolerance of the sensitive wild-type C. proliferum, we transplanted bacterial communities from heat-evolved to the wild-type strain and subjected it to acute heat stress. Microbiome transplantation resulted in the incorporation of only 30 low-abundance strains into the microbiome of wild-type cultures, while the relative abundance of 14 pre-existing strains doubled in inoculated versus uninoculated samples. Inoculation with either wild-type or heat-evolved bacterial communities boosted C. proliferum growth, although no difference in heat tolerance was observed between the two inoculation treatments. This study provides evidence that Symbiodiniaceae-associated bacterial communities respond to heat selection and may contribute to coral adaptation to climate change.