Lethal Temperatures of a Neotropical Fish Relic in Patagonia, the Scale-Less Characinid Gymnocharacinus-Bergi

Fil: Ortubay, Silvia G.. Dirección de Pesca. Ministerio de Economía de la Provincia de Río Negro; ArgentinaFil: Gómez, Sergio E.. Instituto de Limnología Dr. Raúl A. Ringuelet (ILPLA). Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Cussac, Víctor E.. Centro Regional Universitario Bariloche. Universidad Nacional del Comahue. Bariloche. Río Negro; Argentin

The adaptation of rainbow trout to warmer water: oxidative damage in the germinal line

Contemporary evolution was observed in a feral rainbow trout (Oncorhynchus mykiss) population of a thermal stream (Valcheta) in Northern Patagonia, in terms of juvenile thermal tolerance and preferred temperature. Other authors showed that high-temperature treatment applied to male rainbow trout juveniles increased the thermal tolerance in the next generation. This implies a high mutation rate and/or a modified epigenetic inheritance. Comparisons were made among a) a rainbow trout strain adapted in terms of upper thermal tolerance and higher preferred temperature (Valcheta stream), b) a wild temperate stream population (Guillelmo stream), and c) two temperate farmed strains. We examined: Oxidative damage (lipid peroxidation) and activities of antioxidant enzymes; Catalase (CAT), Glutathione S-Transferases (GST), and Superoxide Dismutase (SOD), in liver, testicle, and spermatozoa. Semen fatty acid composition, sperm morphology, sperm motility, and fertilization performance in samples before and after the application of cryopreservation procedures were also evaluated. The observed responses, mainly related to the sperm membrane, reinforces the idea that ROS can affect the germinal line of male rainbow trout juveniles subjected to high water temperature. Our results suggest that the acquired thermal tolerance traits may be part of a wide spectrum of novel characteristics produced as a consequence of an enhanced mutation rate and/or a different DNA methylation pattern, induced by higher temperatures and mediated by ROS.Centro de Investigación y Desarrollo en Criotecnología de Alimento

LAGUNA BLANCA: RESTAURACIÓN ECOLÓGICA, USO RACIONAL Y PESCA ARTESANA

A partir de la introducción ilegal de peces en la Laguna Blanca (sitio Ramsar) del Parque Nacional homónimo en Neuquén, se ha registrado en los últimos años una disminución notoria de las aves acuáticas (particularmente de los cisnes de cuello negro, flamencos y patos) y una importante modificación del hábitat (desaparición de vegetación acuática, alteración de la red trófica y de la calidad del agua), en desmedro de las condiciones de refugio y dieta de las aves. Este trabajo realiza una propuesta de recuperación ambiental a través del desarrollo de una pesquería artesanal

Populations of Odontesthes (Teleostei: Atheriniformes) in the Andean region of Southern South America: body shape and hybrid individuals

The original distribution area of the Patagonian 'pejerrey' Odontesthes hatcheri has been subjected to the introduction of a related species; the Bonaerensean 'pejerrey' Odontesthes bonariensis. This species currently coexists with O. hatcheri in lakes and reservoirs, and can interbreed and produce fertile hybrid offspring. The purposes of this study were; a) the extensive sampling of Patagonian and Andean-Cuyan populations of pejerrey, b) the species identification according to taxonomic key, c) validation of taxonomic results on the basis of mitochondrial DNA composition, and d) applying morphometric analysis to explore the effects of hybridization and environmental conditions on body shape. Cytochrome b sequence analysis showed a high degree of genetic divergence between species and low intraspecific variation in O. hatcheri. Geometric Morphometric Analyses detected shape differences in agreement with diagnostic characteristics of each species. Putative hybrids exhibiting intermediate diagnostic characteristics were identified by Geometric Morphometric Analysis. Significant regressions between body shape and total phosphorus and altitude were found, suggesting a dependence on trophic web structure. This multi-level approach suggests the introgression of O. bonariensis into several O. hatcheri populations throughout Patagonia. Managers should take this into account when considering further exotic introductions into regions where non-native fishes have not yet become established

Populations of Odontesthes (Teleostei: Atheriniformes) in the Andean region of Southern South America: body shape and hybrid individuals

The original distribution area of the Patagonian 'pejerrey' Odontesthes hatcheri has been subjected to the introduction of a related species; the Bonaerensean 'pejerrey' Odontesthes bonariensis. This species currently coexists with O. hatcheri in lakes and reservoirs, and can interbreed and produce fertile hybrid offspring. The purposes of this study were; a) the extensive sampling of Patagonian and Andean-Cuyan populations of pejerrey, b) the species identification according to taxonomic key, c) validation of taxonomic results on the basis of mitochondrial DNA composition, and d) applying morphometric analysis to explore the effects of hybridization and environmental conditions on body shape. Cytochrome b sequence analysis showed a high degree of genetic divergence between species and low intraspecific variation in O. hatcheri. Geometric Morphometric Analyses detected shape differences in agreement with diagnostic characteristics of each species. Putative hybrids exhibiting intermediate diagnostic characteristics were identified by Geometric Morphometric Analysis. Significant regressions between body shape and total phosphorus and altitude were found, suggesting a dependence on trophic web structure. This multi-level approach suggests the introgression of O. bonariensis into several O. hatcheri populations throughout Patagonia. Managers should take this into account when considering further exotic introductions into regions where non-native fishes have not yet become established

Early morphological variation and induction of phenotypic plasticity in Patagonian pejerrey

The aim of this work was to study two aspects of phenotypic plasticity in the Patagonian pejerrey Odontesthes hatcheri (Teleostei: Atherinopsidae) the dependence of the early morphology on developmental time and temperature, and the induction of morphological changes by controlled feeding in juveniles. Newly hatched free embryos, incubated at two different temperatures (13 and 18oC), and juveniles were used for the study and induction of phenotypic plasticity. Body and head shapes were analyzed with geometric morphometrics and linear measurements. Our results showed that shape variation at hatching was related to the bending of the embryo head on the yolk sac, increasing the head-trunk angle due to progressive straightening of the embryo. The head-trunk angle was related with temperature at incubation, with embryos incubated at higher temperature being more bent. Embryos that hatched earlier had bigger yolk sacs than those that hatched later. In juveniles, controlled feeding experiments added new morphological variation to that of wild juveniles. In all comparisons, the slenderness of the head, the size of premaxilla and jaw, and the position of the eye showed an enlarged variation due to controlled feeding. These results will contribute to comprehending the complexity of the morphological variation of O. hatcheri

The effect of rearing temperature in larval development of pejerrey, Odontesthes bonariensis: morphological indicators of development

It is well known that in pejerrey water temperature not only affects growth rates but also directs the sexual differentiation process. This fact rise the question of how different the development of pejerrey larvae of the same age is when reared at different temperatures. A description of developmental stages for the embryonic and larval periods of the pejerrey, Odontesthes bonariensis, and the influence of rearing temperature on larval development are presented. Then, larval development was studied at three rearing temperatures, and changes in general morphology, fin morphology, and caudal fin structure have been taken into consideration within the thermal range involved in the temperature sex determination of this species. Fin fold reabsorption, caudal fin formation, and body shape were selected to follow the events leading to the acquisition of the juvenile morphology. The juvenile phenotype was defined when the fin fold was reabsorpted and the caudal fin acquired its definitive homocercal structure. The moment at which the juvenile phenotype was achieved, was evaluated in relation to larval age, size and, shape. The size resulted as the best indicator of development in pejerrey

Native and exotic fishes in a Patagonian reservoir with rainbow trout cage culture: spatial and trophic resource use

Although the interactions of exotic salmonids with native Patagonian fishes are well known, little is known about the ecology and impact of farmed fish escapees. Salmonid production in Argentina is largely concentrated in the Alicurá reservoir in north Patagonia, where fish community studies have been scarce. Here, we assess and compare the spatial distribution, body size–condition and diet of the different fish species in this reservoir. Strong vertical segregation was observed between exotic rainbow trout Oncorhynchus mykiss (both escapees and wild), dominating the littoral zone, and native Percichthys trucha which dominate the medium and deep strata. Low piscivory–benthivory and high zooplanktivory were observed for rainbow trout, both traits being uncommon at a regional scale. Escaped farmed rainbow trout (ERT) diet included abundant indigestible items along with wild prey. Higher body condition of P. trucha close to farms, as well as the regionally unprecedented high incidence of Daphnia sp. in the guts of all the species suggest that farm nutrient discharges have had significant impacts. Finally, the high body condition of ERT, together with their wild food diet and the long dispersal distance observed, demonstrate post-escape success, drawing our attention to potential upstream dispersion affecting the biodiversity and fisheries of Patagonian rivers and lakes