Cycle de reproduction et fecondité de l'atipa, Hoplosternum littorale (Siluriforme) en Guyane française

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.