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Resume Reproductive cycle and fecundity in Hoplostemum littorale (Siluriforme), reared in French Guiana. The timing of the reproductive cycle of the atipa, Hoplosternum littorale (Hancock, 1828), in ponds (batches of fishes) or in cages (isolated couples), is similar to that obsewed under natural conditions. Recordings of nests and spawning show a reproductive cycle extending from early November to the end of May. The reunion of spawners dunng the second part of the breeding season does not extend the reproductive cycle. The high density of fry in the ponds, a few months after the first spawnings, might lead to the interruption of reproduction. The breeding of isolated couples shows : a decrease in the spawn weight from the first to the third spawning to a stable value (28.5 to 23.9 g for females of average weight 89 g, and 66.7 to 21.9 g for females with average weight 207 g). The number of spawnings for a female can reach 14 over the complete reproductive cycle. The mass of eggs laid in one annual cycle by a single female, can be 180 g (48 600 eggs) for one weighing 89 g and 340 g (91 900 eggs) for one of 207 g weight. These estimations for the number of eggs, founded on the weight of an egg of 3.7 mg established in the present paper, are far beyond what had been previously mentioned. The average loss of weight of males (0.4 % of initial weight for 185 g and 9 % for 292 g males) and females (10% of initial weight for 89 g and 23 % for 207 g females) over a complete reproductive cycle shows the extent of the investment of both sexes in reproduction. In ponds, 48 % of the nests are not used for spawning. The high proportion of nests without spawn is observed during the periods preceding and following the period of maximum spawning activity (JanuaryFebmary). There is no relation between the proportion of nests without spawn and rainfall. 49% of the nests hold eggs laid by at least 2 females. Five or more females can spawn in the sarne nest. The conclusion attempts to integrate the presents results in a general view of the reproductive strategy of the atipa. It points out the need for detailed ethological studies in order to reach a better understanding of the reproductive biology of this species.

Deux series d'experiences ont ete menees, les unes en etang de pisciculture, les autres en laboratoire, pour determiner la relation entre conditions thermiques et duree de l'incubation chez l'Atipa [Hoplosternum littorale (Hancock, 1828)]. En milieu controle, 36 °C constituerait la limite superieure de la temperature d'incubation permettant la survie des œufs. La temperature minimum testee, 24 °C, ne constitue pas la limite inferieure permettant la survie des œufs. La duree minimale d'incubation, evaluee a 36 heures, serait obtenue pour une temperature d'incubation de 33,6 °C. La quantite minimum d'energie fournie par l'environnement pour obtenir l'eclosion est exprimee en degres-heures et s'eleverait a 1 201 °C × h pour la temperature d'incubation de 31,3 °C. Une typologie du developpement embryonnaire de l'espece, directement inspiree de celle de Ballantyne (1930), a ete calee sur une echelle exprimee en °C × h. En etangs, les conditions de temperature au sein de la ponte, plus elevees que celles de l'air, sont sensiblement identiques a celles de l'eau environnante et relativement stables d'une experience a l'autre (27 a 29 °C en moyenne). Le temps d'incubation observe sur l'ensemble des 9 nids equipes de capteurs varie de 47 a 54 heures. A temps d'incubation egal, le nombre de degres-heures necessaires pour obtenir l'eclosion est plus important en etang qu'en milieu controle. La discussion porte sur le role du nid dans la reproduction de l'espece.

L'evolution ponderale de jeunes Pitymys duodecimcostatus issus de primipares (50 femelles et 39 mâles) ou de multipares (74 femelles et 45 mâles) ont ete suivie entre la naissance et l'âge de 180 jours. Elle depend de l'effectif de la portee et est independante du numero d'ordre du part. Le poids a la naissance d'un campagnol provencal (2,4 g) represente un fort pourcentage de son poids adulte (10,6%). Sa vitesse de croissance moyenne (ne tenant pas compte de l'effectif de la portee) entre la naissance et 21 jours s'eleve a 0,39±0,01 g/j. Elle est fortement deprimee a l'âge de 15 jours, au moment du sevrage

International audience; During winter, gathering of starlings is studied in 3 very different sites in western France. A positive correlation is found between the size of starling flocks and the time of the day.

International audience