Biology and population features of a rare species of Pseudopimelodidae from the Upper Paraná River Basin

Abstract

Streams contain an expressive fraction of the South American fish diversity, mostly composed of smallsized, endemic, and rare species. Populational, reproductive, and diet aspects of Microglanis garavelloi were studied, aiming to make a wide characterization of this species of bumblebee catfish. This is an endemic species of the Upper Paraná River Basin, and the only representative of the genus in the watershed. It is a littoral-dweller of small rivers, with asymptotic length of 34.1 mm and a population mostly composed of individuals with 20-30 mm of standard length. This species presents high fecundity and mortality rate, and low longevity and growth rate. It is a total spawner, October to February being the spawning period, and probably has brood care behavior, as has been already observed for some Heptapteridae species. The species can be considered an active predator, probably presenting benthic life like most siluriforms, having a diet uniquely composed of aquatic insect larvae. This species occurs as small populations patchily distributed in the Upper Paraná River Basin. This population characteristic, combined with the progressive environmental degradation of its habitats, points to a situation of constant threat that could lead to an irreversible extinction process. Resumo: Rios de pequeno porte abrigam uma importante fração da diversidade ictiofaunística sul-americana, caracterizada principalmente por espécies endêmicas, raras e de pequeno porte. Com o objetivo de realizar uma ampla caracterização da espécie Microglanis garavelloi, encontrada em pequenos corpos d'água da Bacia do Alto Rio Paraná, foram estudados alguns de seus aspectos populacionais, reprodutivos e alimentares. Essa espécie é endêmica do Alto Rio Paraná, sendo a única representante do gênero nessa bacia. Ela ocupa principalmente a região litorânea de pequenos rios, apresenta comprimento assintótico de 34,1 mm, e população composta principalmente por indivíduos com comprimento padrão entre 20 e 30 mm. Esta espécie apresenta alta fecundidade, alta taxa de mortalidade, baixa longevidade e baixa taxa de crescimento. Além disso, apresenta desova total, que ocorre de outubro a fevereiro e, provavelmente, apresenta comportamento de cuidado com a prole, como já observado em algumas espécies de Heptapteridae. Sua dieta é baseada unicamente em larvas de insetos aquáticos, podendo ser considerada uma predadora com comportamento alimentar ativo e, provavelmente, apresenta vida bentônica, como a maioria dos Siluriformes. Esta espécie ocorre como populações pequenas com distribuição fragmentada na bacia do Alto Rio Paraná. Esta característica populacional, acrescida da constante degradação ambiental em seus hábitats, indica uma situação de constante ameaça que pode levar a um irreversível processo de extinção. Palavras-chave: siluriformes, conservação, estrutura populacional, dinâmica reprodutiva, dieta. Biota Neotrop., vol. 10, no. 3 This study aimed to add information on the endemic and rare M. garavelloi, a bumblebee catfish. We prese...

Ontogeny of the brain of Microglanis garavelloi Shibatta and Benine 2005 (Teleostei: Siluriformes: Pseudopimelodidae)

“…These regions are integrative centres of sensory and motor signals, processing information from the lateral line, vestibular, somatosensory, auditory, visual, olfactory, and hormonal systems (Meek & Nieuwenhuys, 1998). It is known that males of M. garavelloi also reach sexual maturity earlier than females (♂ L 50 = 22.7 and ♀ L 50 = 30.1 mm SL, Esguícero & Arcifa, 2010), an aspect that may be related to the differential brain growth rate, as an early sexual maturity may demand faster growth rates of key integrative regions responsible for specific behavioural responses.…”

“…It inhabits the Paranapanema and Tietê river basins, living mainly among riparian vegetation roots (Shibatta and Benine, 2005). Like most members of the genus, M. garavelloi has nocturnal activity (Esguícero & Arcifa, 2010), and adults exhibit subtle external sexual dimorphism (males slender than females vs. females with expanded belly; Silva, 2013). Males are already mature at 22.7 mm SL, and females at 30.1 mm SL (Esguícero & Arcifa, 2010), and older females reach larger sizes than older males (Silva, 2013).…”

“…Like most members of the genus, M. garavelloi has nocturnal activity (Esguícero & Arcifa, 2010), and adults exhibit subtle external sexual dimorphism (males slender than females vs. females with expanded belly; Silva, 2013). Males are already mature at 22.7 mm SL, and females at 30.1 mm SL (Esguícero & Arcifa, 2010), and older females reach larger sizes than older males (Silva, 2013). This taxon becomes of interest due to the availability of feeding and reproductive behaviour studies (Esguícero & Arcifa, 2010; Silva, 2013), that is, data that may be useful when compared to brain modifications across ontogeny.…”

“…Males are already mature at 22.7 mm SL, and females at 30.1 mm SL (Esguícero & Arcifa, 2010), and older females reach larger sizes than older males (Silva, 2013). This taxon becomes of interest due to the availability of feeding and reproductive behaviour studies (Esguícero & Arcifa, 2010; Silva, 2013), that is, data that may be useful when compared to brain modifications across ontogeny. The present paper provides a detailed investigation of the gross morphology of the brain and olfactory organ of M. garavelloi .…”