Gonodal development of the peacock bass <i> Cichla monoculus</i> (Perciformes: Cichlidae) in the Middle Solimões

Abstract

The common peacock bass, Cichla monoculus Spix; Agassiz, 1831, is a Neotropical cichlid native to the Amazon basin. Although it is highly valued for the quality of its flesh and intensely exploited by commercial fishing, representing the fourth most sold fish along the middle Solimões River in terms of landing statistics, little is known of the reproductive characteristics of this species in its natural habitat. The objective of this work was to reveal some morphological and histological aspects of gonadal development for this species. We also wanted to verify the gonadosomatic relation and allometric condition factor, and assess their use as reproductive indicators. Finally, we intended to reveal the fecundity and spawning type for some individuals of this species living in natural environments. In this study 73 females and 72 males of C. monoculus were utilized, from whom data were collected on total weight and total individual length. The gonads were later removed, weighed and macroscopically analyzed. To confirm this analysis tissue slices were taken from tissue cuts from 41 of the gonads. Based on the results of macroscopic and histological analyses five stages of development for females and four for males were identified. The ovaries were classified as immature, maturing, mature, spawned and at rest. The testicles were classified as immature, maturing, mature and spermiated. The females were found to be larger than the males, but the males were heavier. The gonadosomatic relation and the allometric condition factor were not considered good indicators of the reproductive status for this species. The spawning observed was of the total type, presenting an absolute average fecundity of 8,624 mature oocytes. Diameters of the vitellogenic oocytes varied from 1,210 μm to 3,000 μm. The total spawn, which is accompanied by oocytes with large diameters that have a large reserve of vitellus, is a factor that may favor the reproductive success of C. monoculus on the middle Solimões.