Reproduction of invasive Loricariichthys platymetopon Isbrücker & Nijssen, 1979 (Actinopterygii, Loricariidae) on the upper Paraná River floodplain

Abstract

Loricariichthys platymetopon originally occurred in the Uruguay, Paraguay and lower Paraná rivers. With the formation of Itaipu Reservoir in 1982, it invaded and colonized the upper Paraná River. Using the data obtained quarterly at nine sampling sites on the upper Paraná River floodplain, the reproductive phases and the germ cells of L. platymetopon females were characterized. Variation in oocyte diameter, batch fecundity, and relative batch fecundity by standard length and total weight was also verified, as well as the reproduction sites on the upper Paraná River floodplain. The following stages were recorded: single oogonia, oogonial and oocytes cysts, initial, intermediate and final primary growth oocytes, full-grown oocytes and maturation oocytes. The reproductive phases were validated by the germ cell attributes and females were recorded in the following phases: developing, spawning-capable, regression and regeneration. Oocyte diameters varied from 100 to 4100 µm. Batch fecundity varied from 372 to 1392 oocytes.g-1 and the relative batch fecundity estimate by length was 16 to 49 oocytes.cm-1 and by weight was 3.6 to 6.4 oocytes.g-1. The reproductive patterns of L. platymetopon on the upper Paraná River floodplain showed the sites where reproductive activity is more intense (Guaraná, Garças and Fechada lagoons and the Baía River) and sites where it is less intense (Ivinheima and Paraná rivers). Thus, the biotic resistance of the Ivinheima River, due to the integrity of these environments in this area, which is part of the Environmental Protection Area of the Islands and Marshes of the Paraná River, has prevented the reproductive success of this invader.