Matheus Vieira Volcan

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

Most Rivulidae fishes are popularly known as annual fishes which live in ephemeral environments such as pools, that obligatorily dry out seasonally causing the death of adult individuals. They have unique biological characteristics such as small body size, early sexual maturation, continuous reproduction, an elaborated courtship behavior, and a great reproductive capacity among fishes. The rivulids are widely distributed in North, Central and South America. In this study, the diet and reproductive biology of Cynopoecilus melanotaenia was analyzed. A total of 263 specimens were collected and the analysis of 233 gastrointestinal contents revealed an invertivorous diet composed mainly of small crustaceans (Cladocera, Amphipoda, and Ostracoda) and immature insects (Chaoboridae, Culicidae, Syrphidae, but mainly Chironomidae larvae). Lepidophagy on male’s diet was also registered. Fecundity was estimated by analyzing 59 pairs of mature ovaries and ranged from 2 to 157 oocytes (mean, 19 ± 26[SD]). The species has fractional spawning, a strategy to increase the chance of survival to prolonged depletions. This study is the first to investigate the reproductive biology of C. melanotaenia. The results confirmed the opportunistic character of the rivulid C. melanotaenia and provided unreported reproductive information that may aid conservation of the species. A maioria dos peixes da familia Rivulidae sao popularmente conhecidos como anuais por completarem todo seu ciclo biologico em pequenos corpos de agua temporarios que secam obrigatoriamente em determinados periodos do ano causando a morte dos individuos adultos. Possuem caracteristicas biologicas peculiares como pequeno porte, maturacao sexual precoce, reproducao continua, um elaborado padrao de corte e uma grande capacidade reprodutiva entre os peixes. Os rivulideos se encontram amplamente distribuidos nas Americas do Norte, Central e Sul. Este trabalho analisou a dieta e a biologia reprodutiva de Cynopoecilus melanotaenia. Foram coletados 263 exemplares e a analise de 233 conteudos gastrointestinais revelou uma dieta invertivora composta principalmente por microcrustaceos (Cladocera, Amphipoda e Ostracoda) e insetos imaturos (Chaoboridae, Culicidae, Syrphidae, mas principalmente larvas de Chironomidae). Foi registrada a lepidofagia na dieta dos machos. A fecundidade foi estimada pela analise de 59 pares de ovarios maduros e variou entre 2 a 157 ovocitos (media, 19 ± 26[DP]). A especie apresentou desova parcelada, uma estrategia para aumentar a chance de sobrevivencia a deplecoes prolongadas. Este trabalho apresenta a primeira investigacao sobre a biologia reprodutiva de C. melanotaenia. Os resultados encontrados sugerem a estrategia reprodutiva oportunista de C. melanotaenia e fornecem novas informacoes biologicas que podem contribuir para pesquisas de conservacao e manutencao da especie em seu ambiente natural.

Threatened fishes of the world: Austrolebias nigrofasciatus Costa and Cheffe 2001 (Cyprinodontiformes: Rivulidae)

Common names: Annual fish, killifish. Conservation status: “Endangered” (Fontana et al. 2003, MMA 2004). Identification: 21–26 anal-fin rays in males and 18–23 in females, 19–22 caudal-fin rays, 27–29 vertebrae. Illustration by Felipe Ribas. Coloration: Males: body’s sides metallic blue, with 6–12 dark brown to black bars. Females: body’s sides light yellowish brown, with vertical rows of elongate gray spots, sometimes forming gray bars (Costa and Cheffe 2001; Costa 2006). Distribution: Endemic to river drainages associated with the margin of São Gonçalo channel, Patos-Mirim lagoon system, Rio Grande do Sul, southern Brazil. Abundance: Relatively abundant in its restricted area of occurrence, however there is not estimation on the size of population. Habitat and ecology: Inhabits seasonal wetlands that are formed during the rainy seasons in southern Brazil and it is registered syntopic occurrence in two other species of annual fish: Cynopoecilus melanotaenia and Austrolebias wolterstorffi. Reproduction: Sexual maturity reached about a month after the hatching and presents average fertility of around 30 eggs per week (Volcan 2009). Threats: The drainage and the landfill of areas of floodplain for urban construction in restricted area of distribution of the species and the cultivation of rice in adjacent areas to the São Gonçalo channel are the main threats. Conservation action: It was theoretically protected in its type-locality, in the Pontal da Barra swamp, whose area was established as a Private Natural Heritage Reserve, but the grounding of the property for construction and negligence of local authorities with this fact, threaten the population type of the specie. Conservation recommendations: Establish some form of legal protection in the area where the species occurs, inclusion of species in genus Austrolebias in listings of IUCN and recovery and monitoring of its habitat. Environ Biol Fish (2009) 86:443–444 DOI 10.1007/s10641-009-9544-x

Threatened fishes of the world: Austrolebias univentripinnis Costa and Cheffe 2005 (Cyprinodontiformes: Rivulidae)

Common names: Annual fish, killifish. Conservation status: None. Identification: Urogenital papilla completely attached to anal fin in males, pelvic fins 75 to 90% fused. Largest male registered 35.6 mm SL and largest female 32.2 mm SL (Illustration by Felipe Ribas). Coloration: Lateral body of males with 11–18 vertical rows of brilliant blue-green pigmentation on a dark greenish gray background. Lateral body of females with elongated bars on a faint yellow-brown background (Costa and Cheffe 2005). Distribution: Endemic to Jaguarao River basin, Patos-Mirim Lagoon system, Rio Grande do Sul, Brazil. Abundance: Population estimates not available. Habitat and ecology: Inhabit shallow temporary pools that are formed generally between June to September, in the winter months, during the rainy season. Pools generally are small in surface area (<1,000 m) with maximum depth of 50 cm and high density of aquatic macrophytes. The pH was 6.6–6.8 and the water was whitish. Reproduction: Unknown; likely similar to congenera, which mature within two months after hatching and reproduce throughout his life (Errea and Danulat 2001). Threats: Greatest threat is caused by drainage and changes in physical structure and the hydrological cycle of wetlands due to rice cultivation in floodplains of the Jaguarao River and its small tributaries. The loss of habitat caused by urban progress in the city of Jaguarao and the cattle presence in all sampling sites of the species are also threats to populations of A. univentripinnis (Lanes and Cheffe 2006). Conservation action: None taken. Conservation recommendations: Establish some form of legal protection, as small conservation units, in areas of occurrence of the species; realization of studies regarding the biology and ecology; inhibit the illegal draining and use of wetlands for rice cultivation and urban construction; include it in lists of species of fauna threatened with extinction and recovery and monitoring of its habitat. Environ Biol Fish (2010) 87:319–320 DOI 10.1007/s10641-010-9605-1

Growth of Critically Endangered annual fish Austrolebias wolterstorffi (Cyprinodontiformes: Rivulidae) at different temperatures

Given the importance of knowledge of the biology of endangered species for the planning of conservation and management efforts, the aim of this study was to investigate the influence of temperature on the growth of Austrolebias wolterstorffi (Ahl, 1924). To clarify the thermal influence on the growth of the species, temperatures of 16, 20, 24 , and 28°C were tested in triplicate. The present study showed that a water temperature of 28°C is detrimental to the growth of the species. Among the other tested temperatures, it was found that the optimum temperature for growth decreases as an individual ages and is slightly lower for females. It was demonstrated here that males reach a higher weight and length, and grow faster than females, reaching sexual maturity earlier. To optimize the growth of this species in captivity, the ideal temperature of the water during the initial life period is 24°C, until after puberty when the temperature should decrease to about 21°C.

Pisces, Cyprinodontiformes, Rivulidae, Austrolebias periodicus (Costa, 1999): Distribution extension in state of Rio Grande do Sul, southern Brazil

The present note extends the distribution of annual killifish Austrolebias periodicus , a endangered species, endemic of the Pampas region, in Ibicui River basin, state of Rio Grande do Sul, southern Brazil. This information is needed to develop conservation strategies for this species and its habitat, which are at high risk due to the expansion of rice production and exotic forests in southern Brazil.

Pisces, Perciformes, Eleotridae, Dormitator maculatus (Bloch, 1792): distribution extension for Patos-Mirim lagoon system, state of Rio Grande do Sul, Brazil

We present here the record of Dormitator maculatus (Bloch, 1792) to the Patos-Mirim lagoon system, Rio Grande do Sul, Brazil. This is also the southernmost occurrence in South America, extending species range ca. 150 km from the previously known localities.

Pisces, Perciformes, Gobiidae, Evorthodus lyricus (Girard, 1858): new record from Patos-Mirim Lagoon System, state of Rio Grande do Sul, southern Brazil

The present note records for the first time the tropical gobiid fish Evorthodus lyricus (Girard, 1858) from Patos- Mirim Lagoon System, state of Rio Grande do Sul, southern Brazil. Considering the known distribution of the species, and unpublished data obtained from fish collections, the present record widens the distribution of E. lyricus in 300 km southwards, and is the first occurrence of the species for freshwater conditions in southern Brazil.

Incubation media affect the survival, pathway and time of embryo development in Neotropical annual fish Austrolebias nigrofasciatus (Rivulidae): incubation media in embryo a. nigrofasciatus

To analyse the survival, pathway and time of embryo development in the annual fish Austrolebias nigrofasciatus eggs were monitored in four liquid media and two damp media under experimental conditions for 130 days until their development was complete. Eggs kept in the same breeding water from oviposition remained in diapause I (DI) during all experiments. In constrast, up to the stage prior to entering diapause II (DII), the other media had no influence on development. Embryos at this stage (DII), however, show longer development time when treated in medium with water and powdered coconut shell so that about 80% of embryos remained in DII at 100 days. In contrast, all other treatments had a significantly lower proportion of embryos remaining in DII. When treated with Yamamotos solution in humid media, embryos showed the fastest development. The first fully developed embryos (DIII) were seen at 27 days after oviposition. It took an average of 46-58 days for 50% of eggs in each treatment to reach DIII. Compared with other studies, survival in all incubation media was high at between 70 and 98%. Taken together, it can be concluded that all incubation media were found to be viable for maintaining embryos. Altering developmental trajectories through the manipulation of diapauses in different media makes this species a potential model organism for laboratory studies.

Body size and population dynamics of annual fishes from temporary wetlands in Southern Brazil

Annual fishes live exclusively in temporary wetlands where several species coexist. Understanding how annual fishes cohabit in small and isolated pools is still a challenge. In this study, we aimed to examine the prediction that annual fish assemblages in temporary pools in Southern Brazil are structured by temporal differences in body size, specific growth rate and density. Two–three fish species coexisted in each pool. The most abundant and frequent species were Cynopoecilus melanotaenia and Austrolebias nigrofasciatus, while A. wolterstorffi was less abundant and rare. The species differed significantly in body size throughout the flooding phase and showed similar growth patterns, with higher specific growth rates in the first months of flooding and a reduction in growth rate thereafter. The monthly average densities of A. nigrofasciatus and C. melanotaenia did not differ over time, but they were higher than values observed for A. wolterstorffi. Our results provide evidence for hatching synchrony, similar specific growth rates and densities among the most abundant species and differences in body sizes among all species that are more evident after adulthood, suggesting that differences in body size mediate the coexistence of annual fishes in temporary pools.

Phylogeography of the critically endangered neotropical annual fish, Austrolebias wolterstorffi (Cyprinodontiformes: Aplocheilidae): genetic and morphometric evidence of a new species complex

Austrolebias wolterstorffi is a critically endangered annual fish, occurring in temporary ponds in a restricted area of Southern Brazil and Uruguay. Here, we evaluate the levels of genetic diversity and morphometric differentiation presented by A. wolterstorffi, attempting to reconstruct the spatiotemporal scenario by which this species reached their current distribution. Part of the mitochondrial cytochrome b and nuclear rhodopsin genes were characterized and analysed for a set of 122 and 110 specimens, respectively, collected along the entire distribution range of the species. Additionally, shape variations were evaluated for 92 individuals (43 males and 49 females) through geometric morphometric methods. Our analyses demonstrated several cases of significantly high levels of genetic differentiation among individual populations, in an isolation-by-distance pattern of divergence, with at least six different population groups along the Patos-Mirim lagoon. These groups differed by a minimum of 0.9% and a maximum of 2.6% of corrected cyt b nucleotide distances and did not share any mitochondrial haplotype. Such a pattern, added to the slight morphometric differentiation detected for most of the groups, suggests the occurrence of incipient speciation as consequence of allopatric fragmentation. The chronophylogenetic tree performed with the concatenated dataset supported independent oriental and occidental colonization routes, with the population located in the northwest part of the Rio Grande do Sul coastal plain presenting the most ancient divergence. In general, the recovered biogeographic patterns are highly consistent with the records of Quaternary climatic changes and depositional events that have occurred along the area inhabited by the studied species. This allowed us to establish a molecular clock calibration system for Neotropical annual fish. Thus, although the taxonomic status of each of the detected population units needs further study, it is clear that independent conservation strategies must be taken in each of the major areas covered by this study, most of which are located in Brazil.