REPRODUCTIVE-CYCLE AND FECUNDITY IN HOPLO STERNUM-LITTORALE (SILURIFORME), REARED IN FRENCH-GUIANA

The timing of the reproductive cycle of the atipa, Hoplosternum littor ale (Hancock, 1828), in ponds (batches of fishes) or in cages (isolate d couples), is similar to that observed under natural conditions. Reco rdings of nests and spawning show a reproductive cycle ex;tending from early November to the end of May. The reunion of spawners during the second part of the breeding season does not extend the reproductive cy cle. The high density of fry in the ponds, a few months after the firs t spawnings, might lead to the interruption of reproduction. The breed ing of isolated couples shows : a decrease in the spawn weight from th e first to the third spawning to a stable value (28.5 to 23.9 g for fe males of average weight 89 g, and 66.7 to 21.9 g for females with aver age weight 207 g). The number of spawnings for a female can reach 14 o ver the complete reproductive cycle. The mass of eggs laid in one annu al cycle by a single female, can be 180 g (48 600 eggs) for one weighi ng 89 g and 340 g (91 900 eggs) for one of 207 g weight. These estimat ions for the number of eggs, founded on die weight of an egg of 3.7 mg established in the present paper, are far beyond what had been previo usly 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 reproduct ive cycle shows the extent of the investment of both sexes in reproduc tion. In ponds, 48 % of the nests are not used for spawning. The high proportion of nests without spawn is observed during the periods prece ding and following the period of maximum spawning activity (January-Fe bruary). There is no relation between the proportion of nests without spawn and rainfall. 49 % of the nests hold eggs laid by at least 2 fem ales. Five or more females can spawn in the same nest. The conclusion attempts to integrate the presents results in a general view of the re productive strategy of the atipa. It points out the need for detailed ethological studies in order to reach a better understanding of the re productive biology of this species.