Diet of four annual killifishes: an intra and interspecific comparison

Abstract

We examined the diet of 4 annual fishes, Austrolebias viarius, Austrolebias cheradophilus, Austrolebias luteoflammulatus and Cynopoecilus melanotaenia inhabiting temporal ponds of southeastern Uruguay, by analysis of stomach contents. Fishes were captured from fifty ephemeral ponds of Castillos Lagoon basin, in the region of the Humedales del Este. We identified 13099 individual prey items extracted from 669 stomachs of the four captured species. In the studied system, annual killifishes represents the most abundant and conspicuous top predators. Killifishes are generalist key predators at the ephemeral ponds of the studied system, consuming mostly aquatic items. Zooplancton represented the bulk of the diet in the four analyzed species, followed by eggs, algae and diatoms. Insects are the next group in prey number, as follows: Diptera larvae (especially Chironomidae and Cullicidae), Ephemeroptera (especially Betidae), and coleopteran larvae (especially Dytiscidae). Acari are also important prey in number. The four fish species differ in diet composition and in diet richness. A general pattern of differences in diet richness among killifish species and demographic groups could be related to variations in body sizes. As top predators annual killifishes are an important component of the temporal pond ecosystems. Understanding the natural history of this species and their communities is necessary in order to conserve them. Nós examinamos a dieta de 4 peixes anuais, Austrolebias viarius, Austrolebias cheradophilus, Austrolebias luteoflammulatuse Cynopoecilus melanotaenia, que habitam poças temporárias do sudeste do Uruguai, através da análise de conteúdo estomacal. Os peixes foram capturados em cinco poças temporárias da bacia da lagoa Castillos, na região de Humedales del Este. Nós identificamos 13099 itens de presas estraídos de 669 estômagos das quatro espécies. No sistema estudado, peixes anuais representam os predadores de topo mais abundantes e conspícuos. Os rivulídeos são predadores generalistas nas poças temporaries estudadas, consumindo principalmente itens aquáticos. Zooplâncton representou o item principal da dieta para as quatro espécies, seguido de ovos, algas e diatomáceas. Insetos compoem o próximo grupo em número de presas, como segue: larvas de Diptera (especialmente Chironomidae e Cullicidae), Ephemeroptera (especialmente Betidae), e larvas de Coleoptera (especialmente Dytiscidae). Ácaros foram também presas importantes em número. As quatro espécies de peixes diferem na composição e riqueza das dietas. O padrão geral de diferenciação da dieta entre espécies e grupos demográficos de rivulídeos pode ser relacionado à variação do tamanho corporal. Como predadores de topo, os rivulídeos anuais são um componente importante dos ecossistemas de poças temporárias. A compreensão da história natural destas espécies e de suas comunidades é necessária a sua conservação.

Estrategias reproductivas de dos especies de rivulidos Neotropicales Austrolebias vandenbergi y Neofundulus ornatipinnis (Cyprinodontiformes: Rivulidae) en el Gran Chaco Boliviano

“…in this study, the A. vandengerbi had an equal adult sex ratio (i.e., 1:1), but there was a slight non significant female biased ratio for N. ornatipinnis. These values were similar to Laufer et al (2009) who found a ratio of 1:1 (males:females) for Austrolebias spp. and C. melanotaenia in ephemeral ponds in Uruguay; but differed from Gonçalves et al (2011) whom observed a ratio of 2:1 for C. melanotaenia in ephemeral ponds Southern Brazil, and from Calviño (2005) who reported a sex ratio of 1:4 for N. ornatipinnis from Argentina.…”

“…Males of both species exhibited a larger body size than females in regards to both standard length and body depth. This trend has been observed in other species of tropical annual rivulids including Cynopoecilus melanotaenia (Regan, 1912) and several species of Austrolebias (Laufer, Arim, Loureiro, Piñeiro-Guerra, Clavijo-Baquet & Fagúndez, 2009). These differences in body size play an important role in sexual selection (Garcia et al, 2008).…”

Effect of temperature on growth of the threatened annual fish Austrolebias nigrofasciatus Costa & Cheffe 2001

“…Independently of temperature effect, the higher length of males in rivulids was also observed for several species (e.g. Walford & Liu 1965, Liu et al 1975, Laufer et al 2009, Arenzon et al 2001) and is considered a pattern of Austrolebias species (Costa 2006).…”

The opportunistic feeding and reproduction strategies of the annual fish Cynopoecilus melanotaenia (Cyprinodontiformes: Rivulidae) inhabiting ephemeral habitats on southern Brazil

“…However, few biological studies have been conducted so far (Arenzon et al, 1999(Arenzon et al, , 2001Errea & Danulat, 2001;Shibatta & Rocha 2001;Shibatta & Bennemann, 2003;Laufer et al, 2009;Arim et al, 2010;Polaèik & Reichard, 2010), despite of the great diversity of the family (Costa, 2008) and the extreme vulnerability of some species (Costa, 2002b;Reis et al, 2003;Rosa & Lima, 2008). The lack of basic information on annual fishes is due, in part, by few ichthyological surveys in environments where these species are exclusively found (Rosa et al, 2003).…”

“…At the time they were conducted, the specimens were identified as Cynopoecilus melanotaenia (Regan, 1912), however, after a taxonomic revision made by Costa (2002) and in accordance with their geographic range, this species is now defined as Cynopoecilus multipapillatus Costa, 2002. Two recent studies focused on the diet (Laufer et al, 2009), and the relationships between food web structure and body size (Arim et al, 2010) of C. melanotaenia and three other rivulids. No previous study aimed to analyze reproductive aspects of C. melanotaenia and this study represents the first investigation about reproductive biology of this species.…”