Abundância e aspectos reprodutivos de Loricariichthys platymetopon (Siluriformes, Loricariidae) em quatro trechos da represa Capivara, médio rio Paranapanema

Abstract

ABSTRACT. Abundance and reproductive aspects of Loricariichthys platymetopon (Siluriformes, Loricariidae) in four sections of the Capivara reservoir, river Paranapanema. The armored catfish Loricariichthys platymetopon was recently caught by the first time in the middle region of river Paranapanema. It has quickly become one of the most abundant species. This study evaluated reproductive aspects of 1,044 specimens collected in the Capivara reservoir. Abundance, sex ratio, RGS, IAR and oocyte diameter were evaluated. Sites far away from the dam showed higher abundances than the one next to it. Breeding occurred when temperature was higher, with moderate intensity. Mean absolute fecundity and mean relative fecundity were 663.95 ± 141.99 oocytes and 4.9 ± 1.24 oocytes.gr -1 respectively. Spawning occurred in batches. Mean diameter of mature oocytes was 3.67 mm. KEYWORDS.Neotropical, Upper Rio Paraná, armored catfish, reproduction, fecundity. RESUMO. O cascudoLoricariichthys platymetopon foi capturado pela primeira vez recentemente na região média do rio Paranapanema, tornando-se uma espécie abundante desde então. Aspectos reprodutivos dessa espécie foram analisados neste estudo, com base numa amostra de 1.044 exemplares provenientes do reservatório de Capivara. Foram avaliados a abundância, proporção sexual, RGS, IAR e o diâmetro dos ovócitos. Locais distantes da barragem apresentaram as maiores abundâncias, as fêmeas atingiram maiores tamanhos que os machos e a proporção sexual variou entre os trechos de coleta. A reprodução ocorreu principalmente nos meses quentes, com intensidade moderada; as médias da fecundidade absoluta e da relativa foram de 663,95 ± 141,99 ovócitos e 4,9 ± 1,24 ovócitos/g, respectivamente. A desova ocorreu de modo parcelado e o diâmetro máximo médio do ovócito maduro foi de 3,67 mm. Os dados foram relacionados com o sucesso da espécie na ocupação da região.

Population structure and reproductive biology of Loricariichthys melanocheilus Reis & Pereira, 2000 (Siluriformes: Loricariidae) in the rio Ibicuí, Brazil

“…The values for GSI also began to rise in August/September, peaking in October/November for females and August/September for males. Similar results were found in other Loricariidae in various regions of Brazil, for example, Rhinelepis aspera (Agostinho et al, 1990), Hypostomus commersonii (Agostinho et al, 1991), H. ancistroides (Viana et al, 2008), Rineloricaria latirostris (Barbieri, 1994), Loricariichthys platymetopon (Bailly et al, 2011;Marcucci et al, 2005), L. spixii (Duarte et al, 2007), among others. Males showed distinctly greater condition factor than that of females throughout the study period, probably because of higher energy expenditure of females during the maturation process (Cantanhêde et al, 2007), a feature also reported by Agostinho et al (1990) for Rhinelepis aspera in the rio Paranapanema (state of Paraná).…”

“…In other studies with species of the genus Loricariichthys, e.g. L. platymetopon in the Paranapanema and the Paraná rivers (Marcucci et al, 2005;Bailly et al, 2011) and L. spixii in the Lajes reservoir (Duarte et al, 2007) this pattern also were observed. Although registered for some species, the 1:1 ratio is seldom found.…”

“…According to these researchers, in species of the family Loricariidae, where the behavior of males is that of protecting their offspring in the nest, males are usually larger than females because they may have to face situations of struggle; this behavior is mainly observed for species of the genus Hypostomus (Agostinho et al, 1991). However, this does not seem to be the case for species of the genus Loricariichthys, because as already observed by some researchers (Tos et al, 1997;Marcucci et al, 2005;Duarte et al, 2007), the males of these species carry the eggs, protecting them with a welldeveloped labial expansion; in a state of disorder, males abandon the egg mass with no defense behavior, and return to it as soon as the situation of stress or disturbance ends (Tos et al, 1997). For Loricariichthys melanocheilus, males had smaller sizes than females and in some cases, it was possible to observe this lip expansion; thus, it is assumed that this behavior is similar to that of the other species of Loricariichthys cited above.…”

“…This pattern was also found by other researchers working with species of the same genus. Marcucci et al (2005), working with Loricariichthys platymetopon in the rio Paranapanema, found a larger number of males in the classes below 20 cm, and there was greater collection of females in the following classes: 20 to 28 cm SL. Tos et al (1997) also reported that females of Loricariichthys platymetopon were larger than males.…”

“…Studies conducted on the genus Loricariichthys have focused primarily on L. anus (Valenciennes, 1835), L. platymetopon Isbrücker & Nijssen, 1979(Tos et al, 1997Querol et al, 2002;Marcucci et al, 2005;Bailly et al, 2011) and L. spixii (Steindachner 1881) (Duarte & Araújo, 2001). So far, there is no record in the literature of studies addressing aspects of the biology of Loricariichthys melanocheilus, probably because it is a recently described species and is not widely distributed along several Brazilian basins, but rather, restricted only to the southern region of Brazil.…”