Spermatophore production and sperm quality of the river prawn Macrobrachium americanum Spence Bate, 1868 fed with different diets

The effects of different diets on spermatophore production and sperm quality were investigated in the river prawn Macrobrachium americanum. River prawns were cultured and fed with three diets for 244 days: fresh food (50% squid meat, Dosidicus gigas and 50% sardine muscle, Sardinops sagax); commercial pellets (35 Purina (R)); and a 50:50 mixture of both diets. Spermatophore production was recorded every 24 days on average as the percentage of spermatophores produced per extraction per diet, weight and biochemical composition. Sperm quality was measured as the total number of sperm, the proportion of live/dead sperm and normal/abnormal sperm morphology. There were no significant differences in the mean biochemical composition of M. americanum spermatophores for any of the diets. Biochemical composition was 36.3% protein, 25.8% carbohydrate and 4.6% lipids for all data pooled. The weight of spermatophores and sperm counts was not significantly different among diets, nor were there any differences as a function of the male initial total length (p > .05). Male river prawn reproductive exhaustion was observed as a decline in spermatophore production, weight of the spermatophores and the number of sperm cells per spermatophore, with an increasing proportion of dead and abnormal sperm seen throughout the experiment. The recommended period of maintenance in captivity for male broodstock is less than 115 days. It is recommended to feed broodstock males of M. americanum with commercial pellets because no significant differences were detected with the diets tested; pellets are easier to use, ensuring the same spermatophore production and sperm quality that was obtained with fresh food.