Biogeography and Breeding in Gymnotiformes from Uruguay (original) (raw)
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The reproductive biology and feeding habits of the electric fish Brachyhypopomus gauderio were studied. The species has seasonal reproductive behavior, with breeding occurring during the Southern Hemisphere spring and summer, and having a positive relation with the photoperiod variation. Brachyhypopomus gauderio was defined as a fractional spawner, with low relative fecundity and high first maturation size. Sexual dimorphism was registered, males undergoing hypertrophy of the distal portion of caudal filament. The results on reproductive biology herein obtained are in agreement with data concerning gymnotiforms from Southern Brazil and Uruguay, pointing to an ecological pattern for the species from high latitudes, differing from species with tropical distribution. According to the analysis of the food items, B. gauderio feed mainly on autochthonous insects, likewise the other gymnotiforms previously investigated, leading to conclude that there is no variation on the diet of the species of the order related to climatic conditions or even to habitat of occurrence.
The reproductive biology and feeding habits of the hypopomid Brachyhypopomus bombilla were studied. The species has seasonal behavior, with breeding and feeding activity occurring mostly during the Southern Hemisphere spring and summer. We defined fractional spawning for the species and a relative fecundity similar to those previously reported for other gymnotiform species. According to the analysis of the food items, B. bombilla was included in the trophic category invertivorous, feeding mainly on autochthonous insects. The reproductive periods of males and females as well as female feeding activity were significantly related to the photoperiod. During a period of 5 months, when the lowest water temperatures and shortest photoperiod were recorded, all the specimens of B. bombilla were found buried in the muddy bottom of the creek, with lower electric organ discharge activity, empty stomachs, and gonads in early stages of the maturation process. This period, herein defined as a dormancy period, is reported here for the first time for a species of the Gymnotiformes order.
ENVIRONMENTAL BIOLOGY OF FISHES, 2016
The present study describes the life history of Gymnotus refugio, a species classified as Endangered in the last published list of threatened species of the Brazilian fauna. The study was conducted at a conservation unity that protect one of the last remaining semideciduous forests in the region. The reproductive period was estimated as occurring from the end of winter to the last summer months. Gymnotus refugio exibited fractional spawning, the lowest relative fecundity registered among the Gymnotifomes species studied at the present, and male parental care behavior. The analyses showed a seasonal pattern on the species diet, associating different food categories to winter, autumn, and spring. According to food items analysis and estimated intestinal quotient, G. refugio was classified as invertivorous, feeding mainly on autochthonous insects. The results obtained herein suggest that the position of G. refugio as an Endangered species might be influenced by its territoriality, habitat specificity, parental care behavior, and low fecundity, reinforcing the importance of swampy forest environment conservation as the only means of the species maintenance.
The reproductive biology of a population of the weakly electric fish Brachyhypopomus draco from southern Brazil is described. Information is provided on the establishment of the reproductive period in this species and its relations with environmental and feeding factors, as well as on the absolute and relative fecundities, spawning type, sex ratio and sexual dimorphism. The species exhibits a relatively long reproductive period, a relative fecundity of 0.173 oocytes per mg of female total weight, and fractional spawning. The sex ratio did not differ from 1:1 during all sampled months. Sexual dimorphism related to hypertrophy of the male's distal portion of caudal filament was observed and males grew to greater lengths than females. Male gonadosomatic index (GSI) was significantly related to water depth, oxygen saturation and temperature. Female GSI was significantly related to water depth and hepatosomatic index.
A New Species of Brachyhypopomus (Gymnotiformes, Hypopomidae) from Northeast Uruguay
Copeia, 2006
A new species of Brachyhypopomus from north and northeast Uruguay is described. The new species is found in tributaries of the Uruguay River and southern Los Patos-Merín system. Brachyhypopomus bombilla can be distinguished from all other species of the genus by the following combination of characters: pigmentation pattern of body consisting of scattered dark brown pigmentation over a brown background, more dense on the dorsal half of the body, epidermal laterosensory canals not depigmented, head depth 61.8-76.4% of HL, caudal filament 6.5-16.6% of TL, anal-fin rays 155-190, fourth supraorbital pore dorsal and halfway between posterior nares and anterior margin of orbit, upper jaw slightly longer than lower jaw, mesocoracoid bone not ossified, maxilla anterodorsal process slender, all branchiostegal rays of equal size, none hook-like. Like many other species of the genus Brachyhypopomus, B. bombilla generates a pulse-type biphasic EOD, with a head-positive phase followed by a headnegative phase. The EOD duration of the new species was significantly lower than the EOD duration of the sympatric B. pinnicaudatus, whereas the EOD rate was significantly higher, thus suggesting that duration and frequency are conspicuous electrophysiological parameters that greatly aid in the description of electric fish species.
Brachyhypopomus gauderio n. sp. is described here from the central, southern and coastal regions of the Rio Grande do Sul state, Brazil, from Uruguay, and from Paraguay. It is diagnosed from the congeners on the basis of body coloration, meristic and morphometric characters, such as the number of anal-fin rays, the position of anal-fin origin in relation to pectoral-fin, the morphology of the distal portion of caudal filament of mature males, and body proportions. The new species has been formerly identified as B. pinnicaudatus and is herein distinguished from it.
Gymnotus paraguensis, a Good Example of Phenotypic Plasticity in the Pantanal Biome, Brazil
Zebrafish, 2021
Gymnotus is the most studied genus of the order Gymnotiformes, but the morphological similarities of the different species make it difficult to identify taxa reliably. The present study is a continuation of the ongoing research into the taxonomic diversity of the stocks of Gymnotus sold as live bait in the Pantanal, Brazil. These studies have been based on cytogenetic analyses, DNA barcoding, and the analysis of coloration patterns. The results of the cytogenetic analysis confirmed the presence of three distinct strains, recognized as Gymnotus paraguensis, G. sylvius, and G. pantanal. However, the results revealed that the molecular operational taxonomic units identified as G. paraguensis actually include a relatively diverse set of fish, separated by considerable genetic distances. As the G. paraguensis specimens also presented considerable variation in coloration patterns, further genetic diversity analyses were conducted on these individuals, to test the hypothesis that more than one species is present in this cytotaxonomic unit. The haplotype network revealed a regional pattern in the distribution of this species. The results indicate that the observed variation in coloration patterns is associated with a high degree of phenotypic plasticity in G. paraguensis. These findings emphasize the importance of using an integrative approach for a more accurate diagnosis of Gymnotus, in particular, the species marketed as live bait for the fisheries of the upper Paraguay River basin in the Brazilian Pantanal.
Iheringia. Série Zoologia, 2011
This work describes the reproduction of Gymnogeophagus labiatus (Hensel, 1870) from an upper stretch of Sinos river, southern Brazil, based on the analysis of 174 males and 132 females captured in monthly samples taken from January to December 2007. Results showed that reproductive activity occur in spring and summer although ripe males were found along the year. The standard length of the smallest ripe male was 104.74 mm (Lt) and the smallest ripe female was 55.00 mm (Lt). There was a significant difference in total sex ratio, with 1.32 males to each female (χ2 = 5.76). Males were much more abundant in March (1.75 males: 1 female) and December (5 males: 1 female). Females were more abundant in the 62├77 mm interval (1 male: 2.36 female) while males were more abundant in the 77├92 mm size interval (2.57 males: 1 female). The largest length intervals were composed of only males. Mean absolute fecundity was 113.4 (± 31.24 sd) and mean relative fecundity was 0.0125 (± 0.0026 sd) oocyte...