Reproductive plasticity of Hypostomus affinis (Siluriformes: Loricariidae) as a mechanism to adapt to a reservoir with poor habitat complexity

Abstract

ABSTRACT. In this work we describe the gonad morphology and spawning season of Hypostomus affinis (Steindachner, 1877) in a tropical reservoir based on 55 males and 125 females. Our aim was to assess eventual adaptations in reproductive tactics developed by this riverine species inhabiting an oligotrophic reservoir with low habitat complexity, few rocks and few other preferred consolidated substrata. We described the stages of cells of reproductive lineage, gonadal development and some reproductive traits which were compared with information in the available literature. Cells from the spermatogenic lineage were spermatogonia, spermatocytes, spermatids and spermatozoa, and cells from the oocytarian lineage were primary oocytes, previtelogenic oocytes, cortical vesicle oocytes and yolk globules or vitellogenic.Five stages were described for the males/females according to the distribution of oocytes and spermatogenic lineage cells: resting; initial maturation; advanced maturation; partially spent/spawned; totally spent/spawn. Females outnumbered males and reached larger size. Synchronic ovary development in two groups was found with diameter of mature oocytes ranging from 2 to 3.35 mm. Indication of early maturation, a longer reproductive period and the production of smaller eggs in small clutches seems to be features of the reservoir population not found in riverine systems. Such changes in tactics may indicate a shift to an opportunistic strategy, helping the population to withstand environmental constraints and to succeed in this oligotrophic and poorly structured reservoir.

Biological variables of Hypostomus francisci (Siluriformes: Loricariidae) from Itapecerica River, Minas Gerais State, Brazil

“…However, compared with other species of the genus Hypostomus with equilibrium strategy (Gomes et al 2015), H. francisci showed small eggs and high fecundity. Whereas, if compared with armored fish opportunistic strategy (Duarte andAraujo 2002, Duarte et al 2011), it showed low fecundity and oocytes with similar size.…”

“…However, the number of females was significantly greater for larger specimens above 331 mm. Sexual dimorphism in relation to size also occurs in Loricariichthys castaneus (Gomes et al 2011) and Hypostomus affinis (Duarte et al 2011), with females reaching larger sizes than males. This observation can be re- lated to the fecundity, since larger fish produce more eggs increasing the population number (Murua and Saborydo-Rey 2003).…”

“…The genus Hypostomus Lacépède is the largest genus within the family Loricariidae, with approximately 130 species recognized (Zawadzki et al 2010). This genus habits clear running water on the rocky-bottom of South American Rivers (Garavello and Garavello 2004), as well as, muddy water with soft bottoms and can withstand the barrage events by adapting to reservoirs (Duarte et al 2011). Due to their iliophagous feeding habits, they play an important role in accelerating the recycling of nutrients.…”

Ecomorphological relationships among four Characiformes fish species in a tropical reservoir in South-eastern Brazil

“…This approach has been taken to study fish species inhabiting reservoirs, and which possess morphological and reproductive plasticity to adapt to modified environmental conditions (DUARTE et al 2011). Moreover, impoundments can cause changes in the feeding strategies of species (HAHN & FUGI 2007) …”

Phosphorus body content in an herbivorous fish in environments with different trophic state

“…The habitat characteristics in this site (e.g. presence of shelter, mesohabitat heterogeneity and substrates) could be allowing fish to have better body conditions, since these characteristics directly influence the availability of food and reproduction success (Duarte et al, 2011;Mazzoni et al, 2010). Catfishes are very often associated with rocky substrates, both favouring feeding and reproduction (Casatti et al, 2005;Duarte et al, 2011).…”