Advances in tropical aquaculture

If warmwater finfish protein requirements as level in diet is low, absolute intake per day is similar to those of coldwater species. But relation to this requirement with specific growth rate differs for strictly warmwater fishes as tilapia. Analysis of partition between protein and non-protein energy provided and consequently improve their protein retention. Better carbohydrate digestibility and metabolism are propunded as part of the exploration. (Résumé d'auteur

Diel cycles in Hoplosternum littorale (Teleostei) : entrainment of feeding activity by low intensity colored light

Low intensity colored light is very often used to observe or manipulate fish during the scotophase. According to data on fish vision, most species can perceive these wavelengths of light since their cone pigments have maximum absorption peaks around 455, 530 and 625 nm. To test whether #Hoplosternum littorale$ can detect low intensity red or blue light, we attempted to entrain feeding activity, known to be nocturnal and synchronized by the circadian light/dark alternation, to such light. Feeding activity was entrained with either red or blue light, indicating that these fish can perceive these lights. In all cases, the fish fed during the darker phase of the light cycle. (Résumé d'auteur

Entrainment of the circadian rythm of food demand by infradian cycles of light-dark alternation in Hoplosternum littorale (Teleostei)

#Hoplosternum littorale$ (Hancock, 1828) shows a marked circadium rhythm of food demand. Feeding activity is mainly nocturnal, with two peaks, and is synchronized whith the diel light cycle. We tested the effect of infradian (period > 28h) light dark cycles on this rhythm in fish with demand-feeders : fish subjected to a 13.5 L/22.5 D light dark cycle for 8 days and a 25.5 L/10.5 D cycle for a further 8 days showed a strictly nocturnal feeding activity a response that only passively reflected the cycle alternation of light and dark. (Résumé d'auteur

Деловое общение и манипуляция

Trois niveaux trophiques ont été expérimentalement étudiés chez le silure africain Heterobranchus longifilis. Au cours d'un 1er essai, des poissons d'un poids moyen initial de 60 g ont été rationnés (1 % du poids vif) pendant trois semaines puis alimentés pendant 3 semaines soit ad libitum soit à 3 % du poids vif. Leur croissance a été comparée à celle de poissons nourris en permanence soit en excès soit à raison de 3 % du poids vif. Si le poids vif final des lots ayant subi une restriction est inférieur à celui de leurs homologues alimentés à taux constant, les résultats indiquent que la restriction alimentaire induit ultérieurement une croissance spécifique significativement supérieure, et un indice de consommation meilleur. Cette croissance compensatrice est due à la fois à une hyperphagie et à une amélioration du métabolisme. Un effet positif de l'hyperphagie est encore noté pendant les deux semaines suivantes. Lors de la 2e expérience, des silures d'un poids moyen initial de 141 g ont été nourris pendant 10 semaines soit à un taux constant de 4 % du poids vif, soit alternativement à un taux de 2 % du poids vif pendant une semaine, puis alimentés pendant une semaine à raison de 4 ou 5 % du poids vif. Au terme de l'essai, les poids moyens ne sont pas significativement différents. Les indices de consommation les meilleurs (1,79) sont notés pour les poissons ayant subi l'alternance avec un niveau haut analogue au témoin (45 %). Lors d'une 3e expérience, des silures, d'un poids moyen initial de 340 g ont été nourris pendant 5 mois, soit au taux constant de 3 % du poids vif, soit de façon alternée à 2 et 4 % du poids vif sur la base d'un pas de 15 jours en tenant compte des phases lunaires. Au terme de l'expérience, les poids moyens finaux ont varié de 977 à 1 127 g, tandis que les indices de consommation variaient de 2,1 à 2,5. Les meilleures performances, pour l'ensemble des critères utilisés sont notées pour les lots nourris à 2 % du poids vif en lune descendante, puis à 4 % en lune montante. Chez les poissons nourris de façon restreinte, en période de lune montante, la croissance est minimale. Pour valoriser le phénomène de croissance compensatrice ainsi mis en évidence chez le silure on peut recommander une restriction alimentaire, durant des périodes de 1 semaine. En revanche, tirer bénéfice de l'hyperphagie ne semble pas profitable

Utilization of the principal nutrients for routine metabolism in atipa (Hoplosternum littorale) on starvation

Atipa (#Hoplosternum littorale$), a tropical fish from South Africa, was starved for 50 days. Changes in whole body composition (dry matter, proteins, amino acids, minerals, fats, and energy) were studied in order to assess the utilization of such nutrients for routine metabolism. The intensity of catabolism decreased with the duration of the fast. During the first ten days the daily losses amounted to 0.55 g. 0.29 g. and 0.14 g. respectively for fresh body weight, dry water, and proteins per 100 g initial body weight. During the following forty days, daily losses were on average half of the previous values. There was remarkable conservation of certain nutrients including mineral and lipid reserves and amino acids. There were two very distinct phases in energy utilization. Lipids played an important role in energy supply during the first phase but, in the long term, routine energy requirements are met mainly by proteins mobilization. (Résumé d'auteur

Postprandial utilization of energy susbtrates by a tropical catfish, Holosternum littorale : indirect calorimetry analysis

Indirect calorimetry method was used to measure postprandial utilization of energy substrates by atipa, #Hoplosternum littorale (#Callichthyidae, Siluriform). A model was adjusted to the data on respiratory exchanges and nitrogen excretion for this purpose. As for other fish species, protein was actively catabolized after feeding during the 60 hr measurement time. As long as carbohydrates were available, atipa was also able to use these substrates for its energy metabolism. A gradual increase of contribution of lipids was then noticed. Over a 24 hr period following the food intake, a 30 g fish catabolized 90 mg of proteins and 43 mg of carbohydrates. At the same time, the results led to a synthesis of 3.7 mg of fat. An estimation of the increase of the global metabolism associated to food intake was obtained from integration of the exponential terms of the models. (Résumé d'auteur

Invasiveness of an introduced species: the role of hybridization and ecological constraints

International audienceIntroduced species are confronted with new environments to which they need to adapt. However, the ecological success of an introduced species is generally difficult to predict, especially when hybridizations may be involved in the invasion success. In western Europe, the lake frog Pelophylax ridibundus appears to be particularly successful. A reason for this species' success might be the presence of the invader's genetic material prior to the introduction in the form of a hybrid between P. ridibundus and a second indigenous water frog species. These hybrids reproduce by hybridogenesis, only transmitting the ridibundus genome to gametes and backcrossing with the indigenous species (i.e. P. lessonae). This reproductive system allows the hybrid to be independent from P. ridibundus, and allows the ridibundus genome to be more widely spread than the species itself. Matings among hybrids produce newly formed P. ridibundus offspring (N), if the genomes are compatible. Therefore, we hypothesize that hybridogenesis increases the invasiveness of P. ridibundus (1) by enhancing propagule pressure through N individuals, and/or (2) by increasing adaptation of invaders to the native water frogs' habitat through hybrid-derived ridibundus genomes that are locally adapted. We find support for the first hypothesis because a notable fraction of N tadpoles is viable. However, in our semi-natural experiments they did not outperform ridibundus tadpoles in the native water frogs' habitat, nor did they differ physiologically. This does not support the second hypothesis and highlights ecological constraints on the invasion. However, we cannot rule out that these constraints may fall with ongoing selection, making a replacement of indigenous species highly probable in the future

Dual role of striatal astrocytes in behavioral flexibility and metabolism in the context of obesity

Brain circuits involved in metabolic control and reward-associated behaviors are potent drivers of feeding behavior and are both dramatically altered in obesity, a multifactorial disease resulting from genetic and environmental factors. In both mice and human, exposure to calorie-dense food has been associated with increased astrocyte reactivity and pro-inflammatory response in the brain. Although our understanding of how astrocytes regulate brain circuits has recently flourish, whether and how striatal astrocytes contribute in regulating food-related behaviors and whole-body metabolism is still unknown. In this study, we show that exposure to enriched food leads to profound changes in neuronal activity and synchrony. Chemogenetic manipulation of astrocytes activity in the dorsal striatum was sufficient to restore the cognitive defect in flexible behaviors induced by obesity, while manipulation of astrocyte in the nucleus accumbens led to acute change in whole-body substrate utilization and energy expenditure. Altogether, this work reveals a yet unappreciated role for striatal astrocyte as a direct operator of reward-driven behavior and metabolic control

The CADM1 tumor suppressor gene is a major candidate gene in MDS with deletion of the long arm of chromosome 11.

Myelodysplastic syndromes (MDS) represent a heterogeneous group of clonal hematopoietic stem cell disorders characterized by ineffective hematopoiesis leading to peripheral cytopenias and in a substantial proportion of cases to acute myeloid leukemia. The deletion of the long arm of chromosome 11, del(11q), is a rare but recurrent clonal event in MDS. Here, we detail the largest series of 113 cases of MDS and myelodysplastic syndromes/myeloproliferative neoplasms (MDS/MPN) harboring a del(11q) analyzed at clinical, cytological, cytogenetic, and molecular levels. Female predominance, a survival prognosis similar to other MDS, a low monocyte count, and dysmegakaryopoiesis were the specific clinical and cytological features of del(11q) MDS. In most cases, del(11q) was isolated, primary and interstitial encompassing the 11q22-23 region containing ATM, KMT2A, and CBL genes. The common deleted region at 11q23.2 is centered on an intergenic region between CADM1 (also known as Tumor Suppressor in Lung Cancer 1) and NXPE2. CADM1 was expressed in all myeloid cells analyzed in contrast to NXPE2. At the functional level, the deletion of Cadm1 in murine Lineage-Sca1+Kit+ cells modifies the lymphoid-to-myeloid ratio in bone marrow, although not altering their multilineage hematopoietic reconstitution potential after syngenic transplantation. Together with the frequent simultaneous deletions of KMT2A, ATM, and CBL and mutations of ASXL1, SF3B1, and CBL, we show that CADM1 may be important in the physiopathology of the del(11q) MDS, extending its role as tumor-suppressor gene from solid tumors to hematopoietic malignancies