Within-species differentiation in phenotypic characters related to resource use (resource polymor... more Within-species differentiation in phenotypic characters related to resource use (resource polymorphism) is frequently thought to result from divergent natural selection in a heterogeneous environment with 'open niches'. In this study we found consistent resource-based polymorphism within three different populations of Percichthys trucha , a lake-dwelling fish native to the southern Andes. In each of three lakes we found two morphotypes that could be clearly distinguished by differences in gill raker length. However, the magnitude of the polymorphism, and the suite of phenotypic characteristics associated with the polymorphism, differed between lakes. Patterns of divergence were more similar between the two northern lakes which ultimately drain into a common river, than between these two lakes and a more southern, unconnected lake. The southern population, which had the largest divergence in gill raker length (32% vs. 16% and 19%), also showed substantial differences in diet. Evidence from the southern population suggests that polymorphism in P. trucha is present early during ontogeny. We conclude that while there are some strong parallels among lakes in the development of a trophic polymorphism, differences in environmental conditions and/or colonization history have led to substantial differences in the evolutionary history, resulting in different ecological roles of common morphotypes within different lakes. Lake Rivadavia Limay river Nahuel Huapi Lake Lake Futalaufquen CHILE ARGENTINA Aluminé river Collón Curá river 70°4 0°L ake Quillén S. Pacific Ocean S. Atlantic Ocean 100 km 500 D. E. RUZZANTE ET AL .
The aim of this work was to study two aspects of phenotypic plasticity in the Patagonian pejerrey... more 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.
It is well known that in pejerrey water temperature not only affects growth rates but also direct... more 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.
The introduction of salmonids in Patagonia has resulted in significant impacts on its lakes, as w... more The introduction of salmonids in Patagonia has resulted in significant impacts on its lakes, as well as a major impact on streams, in which native fishes seem to have been displaced almost completely by rainbow trout (Oncorhynchus mykiss). Another perspective is that the introduced salmonid species have resulted in wild fish populations that sustain an economically important sport fishery. The wide distribution and high abundance of escaped farmed rainbow trout, and a clear decrease in the abundance of native and successfully introduced salmonid species in Alicura Reservoir were all observed, based on comparison of recent data and data from 1993 to 1995 corresponding to littoral gillnet captures. Thus, both native fish and introduced salmonid populations seem to have been drastically reduced in the presence of farmed fish escapees. The results of the present study regarding fish escapes deserve major consideration when making decisions about fish cage culture activities for other Patagonian reservoirs.
Gymnocharacinus bergi (Pisces, Characidae) is classified as 'endangered' . It has been given part... more Gymnocharacinus bergi (Pisces, Characidae) is classified as 'endangered' . It has been given particular attention among Patagonian fishes due to the reduction of some of its morphological structures, particularly scales, its extreme southern distribution among the Characiformes and its strong adaptation to a thermal environment in northeastern Patagonia. This paper describes the main aspects of gametogenesis, induced breeding, spawning and development of G. bergi, whose life history traits are related to the peculiar characteristics of its restricted environment. The temperature and flow stability of the Valcheta Stream make many of the environmental variables predictable. Other variables related to photoperiod undergo predictable fluctuation during the year. Gymnocharacinus bergi has synchronous gametogenesis and a rather short breeding season, which is earlier than for Paranensean characids. Its reproductive mode, courtship and spawning behaviour, and the absence of sexual dimorphism are common to other small characins from lotic environments. Gymnocharacinus bergi is a sedentary species with precocial characters, such as low fecundity and slightly adhesive, yolk-rich oocytes which are large in relation to the small size of the female. Larvae are robust, development is indirect and adulthood prolonged. These peculiar characteristics indicate a reproductive style very different from that of the main groups of Patagonian fish fauna.
Phymaturus zapalensis inhabits harsh thermal environments in the steppe of Patagonia, Argentina, ... more Phymaturus zapalensis inhabits harsh thermal environments in the steppe of Patagonia, Argentina, characterized by climate conditions that impose constraints on reproduction, providing an appealing model to study the role of steroid hormones in the regulation of seasonal reproductive events. Males of P. zapalensis exhibited a postnuptial spermatogenic cycle with spermiation in mid-spring in synchrony with female ovulation time when mating occurs, followed by testicular recrudescence, but do not show sperm reservoir during hibernation period in winter. Females of P. zapalensis can reproduce annually or biennially. Here, we studied the steroidogenic functions of testicular compartments of P. zapalensis by analysing serum testosterone and ultrastructure related to steroidogenic activity in Sertoli and Leydig cells, as a possible mechanism for the synchronization of male and female reproductive cycles. The testosterone cycle resembles the gonadal cycle in P. zapalensis previously described by morphology and histology of testes. Testosterone concentration is highest in mid-spring and lowest in early summer, with an initial recovery at the beginning of a new spermatogenic cycle in late summer and early autumn. Ultrastructural morphological features indicative of steroidogenic activity in Leydig and Sertoli cells were observed during the spermatogenic cycle. Evidence of temporal asynchrony in steroidogenic activity between compartments were found in males captured in summer and autumn, while synchronous activity was found during mating in spring. Temporal separation of steroidogenic activity serves to synchronize male and female cycles in P. zapalensis and assures the adjustment of reproductive activity to physiological and environmental constraints.
ABSTRACT In this study, body shape of hybrid and presumptive introgressed South American silversi... more ABSTRACT In this study, body shape of hybrid and presumptive introgressed South American silversides was studied. Body shape of O. bonariensis and O. hatcheri from wild populations and farmed stocks was compared to provide basic information on the effects of fish farming on morphometric parameters. Subsequently, wild presumptive introgressed individuals and artificially hybridized farmed individuals were morphologically analysed to assess the effects of hybridization on the same parameters. Most farmed purebred individuals were shorter and higher than their wild counterparts, which is probably due to the favourable growth conditions compared to the wild habitat. However, the results evidenced that purebred individuals were more slender than both hybrid (farmed) fish and introgressed (wild) fish. Further studies on the growth performance of hybrid Odontesthes will be required in order to assess whether the combination of hybridization and sterilization could produce, under farming conditions, growth performances which satisfy the requirements of aquaculture.
Zoologischer Anzeiger - A Journal of Comparative Zoology, 2014
The South American fish genus Percichthys, due to its great morphological variation, has included... more The South American fish genus Percichthys, due to its great morphological variation, has included several nominal species throughout a long history. However, current genetic analyses signal the existence of only two extant species, Percichthys melanops Girard in Chile (west of the Andes) and P. trucha (Valenciennes) in Chile and Argentina (west and east of the Andes). Here the morphological variation of free embryos, larvae, and juveniles of P. trucha was analyzed using linear measurements and geometric morphometrics. Early morphological variation and compensatory growth were examined using sibling free embryos and larva. Morphological consequences of experimentally controlled food treatments were explored in juveniles. Our results showed individual variation in the size of the yolk-sac of free embryos and in the duration of the mixed feeding period. Phenotypic convergence of the upper jaw length from larva to juveniles and adults, and the causal relationship between diet and head shape was found to change as a consequence of controlled feeding. Embryonic, larval, and juvenile morphological variation and phenotypic plasticity observed in P. trucha pinpoint a possible cause for the shape variation observed in the wild. Phenotypic plasticity allows P. trucha to exploit different trophic resources and to occupy different habitats in low biodiversity lakes of Patagonia, being a major factor taking part in the past and present success of P. trucha.
The interaction between native fishes and salmonids introduced in Patagonia at the beginning of t... more The interaction between native fishes and salmonids introduced in Patagonia at the beginning of the 20th Century, developed at the same time as the environmental change. The phenomenon of global warming has led to the formulation of predictions in relation to changes in the distribution of species, in the latitudinal dimension, both at intralacustrine, or small streams levels. The aim of the present work includes three main objectives: a) to compose a Historical changes such as southward dispersion, relative abundance changes, and geographical patterns for relative abundance and diversity are basic concepts needed not only in future research but also in management design for Patagonian fish populations.
New Zealand Journal of Marine and Freshwater Research, 2002
Abstract Galaxiids are present in many of the Andean lakes in southern South America. We studied ... more Abstract Galaxiids are present in many of the Andean lakes in southern South America. We studied landlocked Galaxias maculatus (Jenyns) and Galaxias platei Steindachner populations in a deep oligotrophic lake (Lake Gutiérrez, Patagonia, Argentina). Their ...
The catfish family Diplomystidae is one of the earliest branching lineages within the diverse ord... more The catfish family Diplomystidae is one of the earliest branching lineages within the diverse order Siluriformes and shows a deep phylogenetic split from all other extant and extinct major catfish groups. Despite its relevance in the evolution of siluriforms, phylogenetic relationships within the Diplomystidae are poorly understood, and prior to this study, no phylogenetic hypotheses using molecular data had been published. By conducting a phylogeographic study across the entire distribution of the family, that encompasses river systems from Central-South Chile and Argentina, we provide the first molecular phylogenetic hypothesis among all known species of Diplomystidae, and in addition, investigate how their evolutionary history relates to major historical events that took place in southern South America. Our phylogenetic analyses show four main lineages and nine sub-lineages strongly structured geographically. All Pacific basin populations, with one exception (those found in the Baker basin) clustered within three of the four main lineages (clades I-III), while all populations from Atlantic basins and those from the Baker basin clustered in a single main clade (clade IV). There was a tendency for genetic diversity to decrease from north to south for Pacific basins consistent with an increasing north-south ice coverage during the last glacial maximum. However, we did not find a statistically significant correlation between genetic diversity and latitude. Analysis of molecular variance (AMOVA) showed that river basins and the barrier created by the Andes Mountains explained a high percentage of the genetic variation. Interestingly, most of the genetic variation among drainages was explained among Pacific basins. Molecular phylogenetic analyses agree only partially with current systematics. The geographical distribution of main lineages did not match species distribution and suggests a new taxonomic hypothesis with support for four species of Diplomystes, three species distributed allopatrically from the Rapel to the Valdivia basin, and only one species distributed in Baker and Atlantic basins. High genetic differentiation among river basins suggests that conservation efforts should focus on protecting populations in each basin in order to preserve the genetic diversity of one of the oldest groups of catfishes on the earth today.
Ten polymorphic microsatellite markers (five tetra-, one compound tetra-, one octa-and three dinu... more Ten polymorphic microsatellite markers (five tetra-, one compound tetra-, one octa-and three dinucleotides) were isolated and characterized for Galaxias maculatus, a fish species widely distributed in the Southern Hemisphere. Markers were tested in 89 individual samples from a single location and the number of alleles ranged between 2 and 28. Observed and expected heterozygosities ranged from 0.103 to 0.910 and 0.098 to 0.935 respectively. No evidence was detected for either linkage disequilibrium (P-values > 0.05 for each locus pair) or deviations from HWE (P-values > 0.05 for every loci).
We used molecular evidence to examine the roles that vicariance mechanisms (mountainbuilding and ... more We used molecular evidence to examine the roles that vicariance mechanisms (mountainbuilding and drainage changes during the Pleistocene) have played in producing phylogeographical structure within and among South American fish species of the temperate perch family Percichthyidae. The percichthyids include two South American genera, Percichthys and Percilia , each containing several species, all of which are endemic to southern Argentina and Chile (Patagonia). Maximum-likelihood phylogenies constructed using mitochondrial DNA (mtDNA) control region haplotypes and nuclear GnRH3-2 intron allele sequences support the current taxonomy at the genus level (both Percichthys and Percilia form strongly supported, monophyletic clades) but indicate that species-level designations need revision. Phylogeographical patterns at the mtDNA support the hypothesis that the Andes have been a major barrier to gene flow. Most species diversity occurs in watersheds to the west of the Andes, together with some ancient divergences among conspecific populations. In contrast, only one species ( Percichthys trucha ) is found east of the Andes, and little to no phylogeographical structure occurs among populations in this region. Mismatch analyses of mtDNA sequences suggest that eastern populations last went through a major bottleneck c . 188 000 BP , a date consistent with the onset of the penultimate and largest Pleistocene glaciation in Patagonia. We suggest that eastern populations have undergone repeated founder-flush events as a consequence of glacial cycles, and that the shallow phylogeny is due to mixing during recolonization periods. The area of greater diversity west of the Andes lies outside the northern limit of the glaciers. mtDNA mismatch analysis of the genus Percilia which is restricted to this area suggests a long-established population at equilibrium. We conclude that patterns of genetic diversity in these South American genera have been primarily influenced by barriers to gene flow (Andean orogeny, and to a lesser extent, isolation in river drainages), and by glacial cycles, which have resulted in population contraction, re-arrangement of some watersheds, and the temporary breakdown of dispersal barriers among eastern river systems. Unrooted minimum spanning network of mtDNA control region haplotypes for (a) Percichthys trucha and (b) Percilia spp. Circles represent unique haplotypes scaled according to their frequency in the overall sample for each genus. Small black circles on branches connecting nodes represent inferred missing haplotypes. Grey curved branches represent alternative connections between haplotypes. For (a), asterisks next to haplotypes 57 and 58 indicate the two potential connections found between the highly divergent Itata haplotypes and all others, east and west of the Andes.
Changes in lake and stream habitats during the growth and retreat of Pleistocene glaciers repeate... more Changes in lake and stream habitats during the growth and retreat of Pleistocene glaciers repeatedly altered the spatial distributions and population sizes of the aquatic fauna of the southern Andes. Here, we use variation in mtDNA control region sequences to infer the temporal dynamics of two species of southern Andean fish during the past few million years. At least five important climate events were associated with major demographic changes: (i) the widespread glaciations of the mid-Pliocene (c. 3.5 Ma); (ii) the largest Patagonian glaciation (1.1 Ma); (iii) the coldest Pleistocene glaciation as indicated by stacked marine d 18 O (c. 0.7 Ma); (iv) the last southern Patagonian glaciation to reach the Atlantic coast (180 ka); and (v) the last glacial maximum (LGM, 23-25 000 years ago). The colder-water inhabitant, Galaxias platei, underwent a strong bottleneck during the LGM and its haplotype diversity coalesces c. 0.7 Ma. In contrast, the more warm-adapted and widely distributed Percichthys trucha showed continuous growth through the last two glacial cycles but went through an important bottleneck c. 180 000 years ago, at which time populations east of the Andes may have been eliminated. Haplotype diversity of the most divergent P. trucha populations, found west of the Andes, coalesces c. 3.2 Ma. The demographic timelines obtained for the two species thus illustrate the continent-wide response of aquatic life in Patagonia to climate change during the Pleistocene, but also show how differing ecological traits and distributions led to distinctive responses.
Liolaemus elongatus (Liolaemidae) is a viviparous, mainly lecithotrophic species with placental s... more Liolaemus elongatus (Liolaemidae) is a viviparous, mainly lecithotrophic species with placental structures specialized for uptake of oxygen and inorganic nutrient transport. An allantoplacenta and an omphaloplacenta are present during early embryonic stages (25-28) and there is a moderate distension of the uterine wall and major glandular activity in the uterine mucosa and submucosa compared with nonpregnant females. The uterine epithelium increases in height, first as a growth in the height of some dispersed cells localized in all regions of the placenta, and later as groups of cells localized in the periembryonic and central-abembryonic regions. At embryonic stage 39, the allantoplacenta reaches its maximum extension around the yolk sac. Omphaloplacenta is restricted to the abembryonic zone, the yolk cleft limiting the newly formed isolated vitelline mass. At more advanced embryonic stages (39-42), the blood supply to the allantoplacenta's periembryonic zone increases, matching the profuse allantoic vascularization. At embryonic stage 42, a secondary cleft opens in the main vitelline mass, above the first yolk cleft, and allantoic blood vessels enter into this secondary cleft. This secondary cleft subdivides the vitelline mass into a large embryonic region connected to a much smaller abembryonic region. In L. elongatus most nutritional resources seem to be provided by the yolk that remains attached to the newborn for 2 or 3 days as an external supply. The embryo's wet weight doubles the weight of the decrease observed in vitelline mass. But the dry wet diminishes, evidencing the importance of the exchange of water and inorganic nutrients. J. Reptiles provide an excellent model for the evolution of viviparity because both oviparous and viviparous sister taxa can be studied. The amniote egg allowed the embryo's independence from aquatic environments. The extraembryonic membranes of these eggs generate elaborate vascular systems for transferring oxygen, water, and nutrients to the embryo, while eliminating metabolic wastes. These vascular systems support the development of reptilian and mammalian placentas, with their wide range of structural arrangements .
Within-species differentiation in phenotypic characters related to resource use (resource polymor... more Within-species differentiation in phenotypic characters related to resource use (resource polymorphism) is frequently thought to result from divergent natural selection in a heterogeneous environment with 'open niches'. In this study we found consistent resource-based polymorphism within three different populations of Percichthys trucha , a lake-dwelling fish native to the southern Andes. In each of three lakes we found two morphotypes that could be clearly distinguished by differences in gill raker length. However, the magnitude of the polymorphism, and the suite of phenotypic characteristics associated with the polymorphism, differed between lakes. Patterns of divergence were more similar between the two northern lakes which ultimately drain into a common river, than between these two lakes and a more southern, unconnected lake. The southern population, which had the largest divergence in gill raker length (32% vs. 16% and 19%), also showed substantial differences in diet. Evidence from the southern population suggests that polymorphism in P. trucha is present early during ontogeny. We conclude that while there are some strong parallels among lakes in the development of a trophic polymorphism, differences in environmental conditions and/or colonization history have led to substantial differences in the evolutionary history, resulting in different ecological roles of common morphotypes within different lakes. Lake Rivadavia Limay river Nahuel Huapi Lake Lake Futalaufquen CHILE ARGENTINA Aluminé river Collón Curá river 70°4 0°L ake Quillén S. Pacific Ocean S. Atlantic Ocean 100 km 500 D. E. RUZZANTE ET AL .
The aim of this work was to study two aspects of phenotypic plasticity in the Patagonian pejerrey... more 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.
It is well known that in pejerrey water temperature not only affects growth rates but also direct... more 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.
The introduction of salmonids in Patagonia has resulted in significant impacts on its lakes, as w... more The introduction of salmonids in Patagonia has resulted in significant impacts on its lakes, as well as a major impact on streams, in which native fishes seem to have been displaced almost completely by rainbow trout (Oncorhynchus mykiss). Another perspective is that the introduced salmonid species have resulted in wild fish populations that sustain an economically important sport fishery. The wide distribution and high abundance of escaped farmed rainbow trout, and a clear decrease in the abundance of native and successfully introduced salmonid species in Alicura Reservoir were all observed, based on comparison of recent data and data from 1993 to 1995 corresponding to littoral gillnet captures. Thus, both native fish and introduced salmonid populations seem to have been drastically reduced in the presence of farmed fish escapees. The results of the present study regarding fish escapes deserve major consideration when making decisions about fish cage culture activities for other Patagonian reservoirs.
Gymnocharacinus bergi (Pisces, Characidae) is classified as 'endangered' . It has been given part... more Gymnocharacinus bergi (Pisces, Characidae) is classified as 'endangered' . It has been given particular attention among Patagonian fishes due to the reduction of some of its morphological structures, particularly scales, its extreme southern distribution among the Characiformes and its strong adaptation to a thermal environment in northeastern Patagonia. This paper describes the main aspects of gametogenesis, induced breeding, spawning and development of G. bergi, whose life history traits are related to the peculiar characteristics of its restricted environment. The temperature and flow stability of the Valcheta Stream make many of the environmental variables predictable. Other variables related to photoperiod undergo predictable fluctuation during the year. Gymnocharacinus bergi has synchronous gametogenesis and a rather short breeding season, which is earlier than for Paranensean characids. Its reproductive mode, courtship and spawning behaviour, and the absence of sexual dimorphism are common to other small characins from lotic environments. Gymnocharacinus bergi is a sedentary species with precocial characters, such as low fecundity and slightly adhesive, yolk-rich oocytes which are large in relation to the small size of the female. Larvae are robust, development is indirect and adulthood prolonged. These peculiar characteristics indicate a reproductive style very different from that of the main groups of Patagonian fish fauna.
Phymaturus zapalensis inhabits harsh thermal environments in the steppe of Patagonia, Argentina, ... more Phymaturus zapalensis inhabits harsh thermal environments in the steppe of Patagonia, Argentina, characterized by climate conditions that impose constraints on reproduction, providing an appealing model to study the role of steroid hormones in the regulation of seasonal reproductive events. Males of P. zapalensis exhibited a postnuptial spermatogenic cycle with spermiation in mid-spring in synchrony with female ovulation time when mating occurs, followed by testicular recrudescence, but do not show sperm reservoir during hibernation period in winter. Females of P. zapalensis can reproduce annually or biennially. Here, we studied the steroidogenic functions of testicular compartments of P. zapalensis by analysing serum testosterone and ultrastructure related to steroidogenic activity in Sertoli and Leydig cells, as a possible mechanism for the synchronization of male and female reproductive cycles. The testosterone cycle resembles the gonadal cycle in P. zapalensis previously described by morphology and histology of testes. Testosterone concentration is highest in mid-spring and lowest in early summer, with an initial recovery at the beginning of a new spermatogenic cycle in late summer and early autumn. Ultrastructural morphological features indicative of steroidogenic activity in Leydig and Sertoli cells were observed during the spermatogenic cycle. Evidence of temporal asynchrony in steroidogenic activity between compartments were found in males captured in summer and autumn, while synchronous activity was found during mating in spring. Temporal separation of steroidogenic activity serves to synchronize male and female cycles in P. zapalensis and assures the adjustment of reproductive activity to physiological and environmental constraints.
ABSTRACT In this study, body shape of hybrid and presumptive introgressed South American silversi... more ABSTRACT In this study, body shape of hybrid and presumptive introgressed South American silversides was studied. Body shape of O. bonariensis and O. hatcheri from wild populations and farmed stocks was compared to provide basic information on the effects of fish farming on morphometric parameters. Subsequently, wild presumptive introgressed individuals and artificially hybridized farmed individuals were morphologically analysed to assess the effects of hybridization on the same parameters. Most farmed purebred individuals were shorter and higher than their wild counterparts, which is probably due to the favourable growth conditions compared to the wild habitat. However, the results evidenced that purebred individuals were more slender than both hybrid (farmed) fish and introgressed (wild) fish. Further studies on the growth performance of hybrid Odontesthes will be required in order to assess whether the combination of hybridization and sterilization could produce, under farming conditions, growth performances which satisfy the requirements of aquaculture.
Zoologischer Anzeiger - A Journal of Comparative Zoology, 2014
The South American fish genus Percichthys, due to its great morphological variation, has included... more The South American fish genus Percichthys, due to its great morphological variation, has included several nominal species throughout a long history. However, current genetic analyses signal the existence of only two extant species, Percichthys melanops Girard in Chile (west of the Andes) and P. trucha (Valenciennes) in Chile and Argentina (west and east of the Andes). Here the morphological variation of free embryos, larvae, and juveniles of P. trucha was analyzed using linear measurements and geometric morphometrics. Early morphological variation and compensatory growth were examined using sibling free embryos and larva. Morphological consequences of experimentally controlled food treatments were explored in juveniles. Our results showed individual variation in the size of the yolk-sac of free embryos and in the duration of the mixed feeding period. Phenotypic convergence of the upper jaw length from larva to juveniles and adults, and the causal relationship between diet and head shape was found to change as a consequence of controlled feeding. Embryonic, larval, and juvenile morphological variation and phenotypic plasticity observed in P. trucha pinpoint a possible cause for the shape variation observed in the wild. Phenotypic plasticity allows P. trucha to exploit different trophic resources and to occupy different habitats in low biodiversity lakes of Patagonia, being a major factor taking part in the past and present success of P. trucha.
The interaction between native fishes and salmonids introduced in Patagonia at the beginning of t... more The interaction between native fishes and salmonids introduced in Patagonia at the beginning of the 20th Century, developed at the same time as the environmental change. The phenomenon of global warming has led to the formulation of predictions in relation to changes in the distribution of species, in the latitudinal dimension, both at intralacustrine, or small streams levels. The aim of the present work includes three main objectives: a) to compose a Historical changes such as southward dispersion, relative abundance changes, and geographical patterns for relative abundance and diversity are basic concepts needed not only in future research but also in management design for Patagonian fish populations.
New Zealand Journal of Marine and Freshwater Research, 2002
Abstract Galaxiids are present in many of the Andean lakes in southern South America. We studied ... more Abstract Galaxiids are present in many of the Andean lakes in southern South America. We studied landlocked Galaxias maculatus (Jenyns) and Galaxias platei Steindachner populations in a deep oligotrophic lake (Lake Gutiérrez, Patagonia, Argentina). Their ...
The catfish family Diplomystidae is one of the earliest branching lineages within the diverse ord... more The catfish family Diplomystidae is one of the earliest branching lineages within the diverse order Siluriformes and shows a deep phylogenetic split from all other extant and extinct major catfish groups. Despite its relevance in the evolution of siluriforms, phylogenetic relationships within the Diplomystidae are poorly understood, and prior to this study, no phylogenetic hypotheses using molecular data had been published. By conducting a phylogeographic study across the entire distribution of the family, that encompasses river systems from Central-South Chile and Argentina, we provide the first molecular phylogenetic hypothesis among all known species of Diplomystidae, and in addition, investigate how their evolutionary history relates to major historical events that took place in southern South America. Our phylogenetic analyses show four main lineages and nine sub-lineages strongly structured geographically. All Pacific basin populations, with one exception (those found in the Baker basin) clustered within three of the four main lineages (clades I-III), while all populations from Atlantic basins and those from the Baker basin clustered in a single main clade (clade IV). There was a tendency for genetic diversity to decrease from north to south for Pacific basins consistent with an increasing north-south ice coverage during the last glacial maximum. However, we did not find a statistically significant correlation between genetic diversity and latitude. Analysis of molecular variance (AMOVA) showed that river basins and the barrier created by the Andes Mountains explained a high percentage of the genetic variation. Interestingly, most of the genetic variation among drainages was explained among Pacific basins. Molecular phylogenetic analyses agree only partially with current systematics. The geographical distribution of main lineages did not match species distribution and suggests a new taxonomic hypothesis with support for four species of Diplomystes, three species distributed allopatrically from the Rapel to the Valdivia basin, and only one species distributed in Baker and Atlantic basins. High genetic differentiation among river basins suggests that conservation efforts should focus on protecting populations in each basin in order to preserve the genetic diversity of one of the oldest groups of catfishes on the earth today.
Ten polymorphic microsatellite markers (five tetra-, one compound tetra-, one octa-and three dinu... more Ten polymorphic microsatellite markers (five tetra-, one compound tetra-, one octa-and three dinucleotides) were isolated and characterized for Galaxias maculatus, a fish species widely distributed in the Southern Hemisphere. Markers were tested in 89 individual samples from a single location and the number of alleles ranged between 2 and 28. Observed and expected heterozygosities ranged from 0.103 to 0.910 and 0.098 to 0.935 respectively. No evidence was detected for either linkage disequilibrium (P-values > 0.05 for each locus pair) or deviations from HWE (P-values > 0.05 for every loci).
We used molecular evidence to examine the roles that vicariance mechanisms (mountainbuilding and ... more We used molecular evidence to examine the roles that vicariance mechanisms (mountainbuilding and drainage changes during the Pleistocene) have played in producing phylogeographical structure within and among South American fish species of the temperate perch family Percichthyidae. The percichthyids include two South American genera, Percichthys and Percilia , each containing several species, all of which are endemic to southern Argentina and Chile (Patagonia). Maximum-likelihood phylogenies constructed using mitochondrial DNA (mtDNA) control region haplotypes and nuclear GnRH3-2 intron allele sequences support the current taxonomy at the genus level (both Percichthys and Percilia form strongly supported, monophyletic clades) but indicate that species-level designations need revision. Phylogeographical patterns at the mtDNA support the hypothesis that the Andes have been a major barrier to gene flow. Most species diversity occurs in watersheds to the west of the Andes, together with some ancient divergences among conspecific populations. In contrast, only one species ( Percichthys trucha ) is found east of the Andes, and little to no phylogeographical structure occurs among populations in this region. Mismatch analyses of mtDNA sequences suggest that eastern populations last went through a major bottleneck c . 188 000 BP , a date consistent with the onset of the penultimate and largest Pleistocene glaciation in Patagonia. We suggest that eastern populations have undergone repeated founder-flush events as a consequence of glacial cycles, and that the shallow phylogeny is due to mixing during recolonization periods. The area of greater diversity west of the Andes lies outside the northern limit of the glaciers. mtDNA mismatch analysis of the genus Percilia which is restricted to this area suggests a long-established population at equilibrium. We conclude that patterns of genetic diversity in these South American genera have been primarily influenced by barriers to gene flow (Andean orogeny, and to a lesser extent, isolation in river drainages), and by glacial cycles, which have resulted in population contraction, re-arrangement of some watersheds, and the temporary breakdown of dispersal barriers among eastern river systems. Unrooted minimum spanning network of mtDNA control region haplotypes for (a) Percichthys trucha and (b) Percilia spp. Circles represent unique haplotypes scaled according to their frequency in the overall sample for each genus. Small black circles on branches connecting nodes represent inferred missing haplotypes. Grey curved branches represent alternative connections between haplotypes. For (a), asterisks next to haplotypes 57 and 58 indicate the two potential connections found between the highly divergent Itata haplotypes and all others, east and west of the Andes.
Changes in lake and stream habitats during the growth and retreat of Pleistocene glaciers repeate... more Changes in lake and stream habitats during the growth and retreat of Pleistocene glaciers repeatedly altered the spatial distributions and population sizes of the aquatic fauna of the southern Andes. Here, we use variation in mtDNA control region sequences to infer the temporal dynamics of two species of southern Andean fish during the past few million years. At least five important climate events were associated with major demographic changes: (i) the widespread glaciations of the mid-Pliocene (c. 3.5 Ma); (ii) the largest Patagonian glaciation (1.1 Ma); (iii) the coldest Pleistocene glaciation as indicated by stacked marine d 18 O (c. 0.7 Ma); (iv) the last southern Patagonian glaciation to reach the Atlantic coast (180 ka); and (v) the last glacial maximum (LGM, 23-25 000 years ago). The colder-water inhabitant, Galaxias platei, underwent a strong bottleneck during the LGM and its haplotype diversity coalesces c. 0.7 Ma. In contrast, the more warm-adapted and widely distributed Percichthys trucha showed continuous growth through the last two glacial cycles but went through an important bottleneck c. 180 000 years ago, at which time populations east of the Andes may have been eliminated. Haplotype diversity of the most divergent P. trucha populations, found west of the Andes, coalesces c. 3.2 Ma. The demographic timelines obtained for the two species thus illustrate the continent-wide response of aquatic life in Patagonia to climate change during the Pleistocene, but also show how differing ecological traits and distributions led to distinctive responses.
Liolaemus elongatus (Liolaemidae) is a viviparous, mainly lecithotrophic species with placental s... more Liolaemus elongatus (Liolaemidae) is a viviparous, mainly lecithotrophic species with placental structures specialized for uptake of oxygen and inorganic nutrient transport. An allantoplacenta and an omphaloplacenta are present during early embryonic stages (25-28) and there is a moderate distension of the uterine wall and major glandular activity in the uterine mucosa and submucosa compared with nonpregnant females. The uterine epithelium increases in height, first as a growth in the height of some dispersed cells localized in all regions of the placenta, and later as groups of cells localized in the periembryonic and central-abembryonic regions. At embryonic stage 39, the allantoplacenta reaches its maximum extension around the yolk sac. Omphaloplacenta is restricted to the abembryonic zone, the yolk cleft limiting the newly formed isolated vitelline mass. At more advanced embryonic stages (39-42), the blood supply to the allantoplacenta's periembryonic zone increases, matching the profuse allantoic vascularization. At embryonic stage 42, a secondary cleft opens in the main vitelline mass, above the first yolk cleft, and allantoic blood vessels enter into this secondary cleft. This secondary cleft subdivides the vitelline mass into a large embryonic region connected to a much smaller abembryonic region. In L. elongatus most nutritional resources seem to be provided by the yolk that remains attached to the newborn for 2 or 3 days as an external supply. The embryo's wet weight doubles the weight of the decrease observed in vitelline mass. But the dry wet diminishes, evidencing the importance of the exchange of water and inorganic nutrients. J. Reptiles provide an excellent model for the evolution of viviparity because both oviparous and viviparous sister taxa can be studied. The amniote egg allowed the embryo's independence from aquatic environments. The extraembryonic membranes of these eggs generate elaborate vascular systems for transferring oxygen, water, and nutrients to the embryo, while eliminating metabolic wastes. These vascular systems support the development of reptilian and mammalian placentas, with their wide range of structural arrangements .
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