The Experts below are selected from a list of 1185 Experts worldwide ranked by ideXlab platform
Emily M. Standen - One of the best experts on this subject based on the ideXlab platform.
-
Terrestrial acclimation and exercise lead to bone functional response in Polypterus senegalus pectoral fins.
The Journal of experimental biology, 2020Co-Authors: Emily M. StandenAbstract:The ability of bones to sense and respond to mechanical loading is a central feature of vertebrate skeletons. However, the functional demands imposed on terrestrial and aquatic animals differ vastly. The pectoral girdle of the basal actinopterygian fish Polypterus senegalus was previously shown to exhibit plasticity following terrestrial acclimation, but the pectoral fin itself has yet to be examined. We investigated skeletal plasticity in the pectoral fins of P. senegalus after exposure to terrestrial loading. Juvenile fish were divided into three groups: a control group was kept under aquatic conditions without intervention, an exercised group was also kept in water but received daily exercise on land, and a terrestrial group was kept in a chronic semi-terrestrial condition. After 5 weeks, the pectoral fins were cleared and stained with Alcian Blue and Alizarin Red to visualize cartilage and bone, allowing measurements of bone length, bone width, ossification and curvature to be taken for the endochondral radial bones. Polypterus senegalus fin bones responded most strongly to chronic loading in the terrestrial condition. Fish that were reared in a terrestrial environment had significantly longer bones compared with those of aquatic controls, wider propterygia and metapterygia, and more ossified metapterygia and medial radials, and they showed changes in propterygial curvature. Exercised fish also had longer and more ossified medial radials compared with those of controls. Polypterus senegalus fin bones exhibit plasticity in response to novel terrestrial loading. Such plasticity could be relevant for transitions between water and land on evolutionary scales, but key differences between fish and tetrapod bone make direct comparisons challenging.
-
phenotypic plasticity of muscle fiber type in the pectoral fins of Polypterus senegalus reared in a terrestrial environment
The Journal of Experimental Biology, 2017Co-Authors: Trina Y Du, Emily M. StandenAbstract:ABSTRACT Muscle fiber types in the pectoral fins of fishes have rarely been examined, despite their morphological and functional diversity. Here, we describe the distribution of fast and slow muscle fibers in the pectoral fins of Polypterus senegalus , an amphibious, basal actinopterygian. Each of the four muscle groups examined using mATPase staining showed distinct fiber-type regionalization. Comparison between fish raised in aquatic and terrestrial environments revealed terrestrially reared fish possess 28% more fast muscle compared with aquatically reared fish. The pattern of proximal–distal variation in the abductors differed, with a relative decrease in fast muscle fibers near the pectoral girdle in aquatic fish compared with an increase in terrestrial fish. Terrestrially reared fish also possess a greater proportion of very small diameter fibers, suggesting that they undergo more growth via hyperplasia. These observations may be a further example of adaptive plasticity in Polypterus , allowing for greater bursts of power during terrestrial locomotion.
-
Observations of terrestrial locomotion in wild Polypterus senegalus from Lake Albert, Uganda
African Journal of Aquatic Science, 2016Co-Authors: Hce Larsson, Emily M. StandenAbstract:Polypterids, the most basal actinopterygians, are a group of fish long-considered living fossils and holding a key position for understanding fish and tetrapod evolution. Knowledge of the natural history of Polypterus is limited, their having been studied in little detail since the early 1900s. The locomotory habits of wild Polypterus senegalus from Lake Albert, Uganda, were investigated in 2014. High-speed videography demonstrated the capability of large Polypterus to move overland successfully. Contrary to previous evidence, field observations found that terrestrial locomotion in Polypterus is not inherently restricted by body size. Evidence that Polypterus exhibit this behaviour as part of their natural life history can be found in the existence of environmental challenges and the presence of adaptations for amphibious life.
-
Polypterus and the evolution of fish pectoral musculature
Journal of anatomy, 2015Co-Authors: Benjamin C. Wilhelm, Emily M. Standen, Hans C. E. LarssonAbstract:Polypterus, a member of the most primitive living group of ray-finned fishes, has demonstrated the ability to perform fin-assisted terrestrial locomotion, a behavior that indicates a complex pectoral musculoskeletal system. Review of the literature reveals that many aspects of the pectoral muscular anatomy of Polypterus are still unclear, with a number of conflicting descriptions. We provide a new interpretation of the pectoral musculature using soft tissue-enhanced microCT scanning and gross anatomical dissection. The results demonstrate a complex musculature, with six independent muscles crossing the glenoid-fin joint. Comparisons with other bony-fish (Osteichthyes), including both ray-finned (Actinopterygii) and lobed-fin (Sarcopterygii) fish, indicate the presence of novel muscles within Polypterus: coracometapterygialis I+II and the zonopropterygialis medialis. Examination of these muscular additions in the context of osteichthyan phylogeny indicates that this represents a previously unrecognized event in the evolution of pectoral musculature in Osteichthyes. Despite its phylogenetic position as a basal actinopterygian, the musculature of Polypterus has more similarities both anatomically and functionally with that of sarcopterygians. This anatomy, along with other features of Polypterus anatomy such as lobed fins, ventral paired lungs, and a large spiracle, may make it a good model for inferences of stem tetrapod locomotion.
-
Developmental plasticity and the origin of tetrapods.
Nature, 2014Co-Authors: Emily M. Standen, Hans C. E. LarssonAbstract:The origin of tetrapods from their fish antecedents, approximately 400 million years ago, was coupled with the origin of terrestrial locomotion and the evolution of supporting limbs. Polypterus is a member of the basal-most group of ray-finned fish (actinopterygians) and has many plesiomorphic morphologies that are comparable to elpistostegid fishes, which are stem tetrapods. Polypterus therefore serves as an extant analogue of stem tetrapods, allowing us to examine how developmental plasticity affects the ‘terrestrialization’ of fish. We measured the developmental plasticity of anatomical and biomechanical responses in Polypterus reared on land. Here we show the remarkable correspondence between the environmentally induced phenotypes of terrestrialized Polypterus and the ancient anatomical changes in stem tetrapods, and we provide insight into stem tetrapod behavioural evolution. Our results raise the possibility that environmentally induced developmental plasticity facilitated the origin of the terrestrial traits that led to tetrapods. The most primitive extant bony fish, Polypterus, exhibits adaptive plasticity for life on land when raised on land rather than in water, suggesting that environmentally induced phenotypic plasticity might have facilitated the macroevolutionary transition to life on land. Bichirs (genus Polypterus) are primitive ray-finned fish found in Africa — and sometimes in home aquaria — that have functional lungs derived from the swim bladder and powerful pectoral fins that provide support during occasional forays ashore. This study takes Polypterus senegalus as a model for the immediate ancestors of tetrapods and quantifies the anatomical and behavioural changes that occur when these fish are 'terrestrialized'. When raised on land, bichirs lift their heads higher off the ground, deploy their forelimbs closer to the midline and slip around much less often than those raised underwater and prompted to walk ashore for the first time. These observations, together with changes in bone structure and musculature, suggest that some of the postural changes seen in the earliest tetrapods, or rather their immediate antecedents, might have been made in response to the environment and assimilated by developmental plasticity.
Arne Ludwig - One of the best experts on this subject based on the ideXlab platform.
-
Unusual Intraindividual Variation of the Nuclear 18S rRNA Gene is Widespread Within the Acipenseridae
2013Co-Authors: Jeannette Krieger, V. J. Birstein, Paul A Fuerst, Anne Kathrin Hett, Arne LudwigAbstract:Significant intraindividual variation in the sequence of the 18S rRNA gene is unusual in animal genomes. In a previous study, multiple 18S rRNA gene sequences were observed within individuals of eight species of sturgeon from North America but not in the North American paddlefish, Polyodon spathula, in two species of Polypterus (Polypterus delhezi and Polypterus senegalus), in other primitive fishes (Erpetoichthys calabaricus, Lepisosteus osseus, Amia calva) or in a lungfish (Protopterus sp.). These observations led to the hypothesis that this unusual genetic characteristic arose within the Acipenseriformes after the presumed divergence of the sturgeon and paddlefish families. In the present study, a survey of nearly all Eurasian acipenseriform species was conducted to examine 18S rDNA variation. Intraindividual variation was not found in the polyodontid species, the Chinese paddlefish, Psephurus gladius, but variation was detected in all Eurasian acipenserid species. The comparison of sequences from two major segments of the 18S rRNA gene and identification of sites where insertion/deletion events have occurred are placed in the context of evolutionary relationships within the Acipenseriformes and the evolution of rDNA variation in this group. Sturgeons (Acipenseridae) and paddlefishes (Polyodontidae) are members of the order Acipenseriformes, a group of approximatel
-
Unusual Intraindividual Variation of the Nuclear 18S rRNA Gene is Widespread Within the Acipenseridae
Journal of Heredity, 2006Co-Authors: Jeannette Krieger, V. J. Birstein, Paul A Fuerst, Anne Kathrin Hett, Arne LudwigAbstract:Significant intraindividual variation in the sequence of the 18S rRNA gene is unusual in animal genomes. In a previous study, multiple 18S rRNA gene sequences were observed within individuals of eight species of sturgeon from NorthAmerica but not in the North American paddlefish, Polyodon spathula, in two species of Polypterus (Polypterus delhezi and Polypterus senegalus), in other primitive fishes (Erpetoichthys calabaricus, Lepisosteus osseus, Amia calva) or in a lungfish (Protopterus sp.). These observations led to the hypothesis that this unusual genetic characteristic arose within the Acipenseriformes after the presumed divergence of the sturgeon and paddlefish families. In the present study, a survey of nearly all Eurasian acipenseriform species was conducted to examine 18S rDNA variation. Intraindividual variation was not found in the polyodontid species, the Chinese paddlefish, Psephurus gladius, but variation was detected in all Eurasian acipenserid species. The comparison of sequences from twomajorsegmentsofthe18SrRNAgeneandidentificationofsiteswhereinsertion/deletioneventshaveoccurredareplacedin the context of evolutionary relationships within the Acipenseriformes and the evolution of rDNA variation in this group.
Hans C. E. Larsson - One of the best experts on this subject based on the ideXlab platform.
-
Polypterus and the evolution of fish pectoral musculature
Journal of anatomy, 2015Co-Authors: Benjamin C. Wilhelm, Emily M. Standen, Hans C. E. LarssonAbstract:Polypterus, a member of the most primitive living group of ray-finned fishes, has demonstrated the ability to perform fin-assisted terrestrial locomotion, a behavior that indicates a complex pectoral musculoskeletal system. Review of the literature reveals that many aspects of the pectoral muscular anatomy of Polypterus are still unclear, with a number of conflicting descriptions. We provide a new interpretation of the pectoral musculature using soft tissue-enhanced microCT scanning and gross anatomical dissection. The results demonstrate a complex musculature, with six independent muscles crossing the glenoid-fin joint. Comparisons with other bony-fish (Osteichthyes), including both ray-finned (Actinopterygii) and lobed-fin (Sarcopterygii) fish, indicate the presence of novel muscles within Polypterus: coracometapterygialis I+II and the zonopropterygialis medialis. Examination of these muscular additions in the context of osteichthyan phylogeny indicates that this represents a previously unrecognized event in the evolution of pectoral musculature in Osteichthyes. Despite its phylogenetic position as a basal actinopterygian, the musculature of Polypterus has more similarities both anatomically and functionally with that of sarcopterygians. This anatomy, along with other features of Polypterus anatomy such as lobed fins, ventral paired lungs, and a large spiracle, may make it a good model for inferences of stem tetrapod locomotion.
-
Developmental plasticity and the origin of tetrapods.
Nature, 2014Co-Authors: Emily M. Standen, Hans C. E. LarssonAbstract:The origin of tetrapods from their fish antecedents, approximately 400 million years ago, was coupled with the origin of terrestrial locomotion and the evolution of supporting limbs. Polypterus is a member of the basal-most group of ray-finned fish (actinopterygians) and has many plesiomorphic morphologies that are comparable to elpistostegid fishes, which are stem tetrapods. Polypterus therefore serves as an extant analogue of stem tetrapods, allowing us to examine how developmental plasticity affects the ‘terrestrialization’ of fish. We measured the developmental plasticity of anatomical and biomechanical responses in Polypterus reared on land. Here we show the remarkable correspondence between the environmentally induced phenotypes of terrestrialized Polypterus and the ancient anatomical changes in stem tetrapods, and we provide insight into stem tetrapod behavioural evolution. Our results raise the possibility that environmentally induced developmental plasticity facilitated the origin of the terrestrial traits that led to tetrapods. The most primitive extant bony fish, Polypterus, exhibits adaptive plasticity for life on land when raised on land rather than in water, suggesting that environmentally induced phenotypic plasticity might have facilitated the macroevolutionary transition to life on land. Bichirs (genus Polypterus) are primitive ray-finned fish found in Africa — and sometimes in home aquaria — that have functional lungs derived from the swim bladder and powerful pectoral fins that provide support during occasional forays ashore. This study takes Polypterus senegalus as a model for the immediate ancestors of tetrapods and quantifies the anatomical and behavioural changes that occur when these fish are 'terrestrialized'. When raised on land, bichirs lift their heads higher off the ground, deploy their forelimbs closer to the midline and slip around much less often than those raised underwater and prompted to walk ashore for the first time. These observations, together with changes in bone structure and musculature, suggest that some of the postural changes seen in the earliest tetrapods, or rather their immediate antecedents, might have been made in response to the environment and assimilated by developmental plasticity.
Jeannette Krieger - One of the best experts on this subject based on the ideXlab platform.
-
Unusual Intraindividual Variation of the Nuclear 18S rRNA Gene is Widespread Within the Acipenseridae
2013Co-Authors: Jeannette Krieger, V. J. Birstein, Paul A Fuerst, Anne Kathrin Hett, Arne LudwigAbstract:Significant intraindividual variation in the sequence of the 18S rRNA gene is unusual in animal genomes. In a previous study, multiple 18S rRNA gene sequences were observed within individuals of eight species of sturgeon from North America but not in the North American paddlefish, Polyodon spathula, in two species of Polypterus (Polypterus delhezi and Polypterus senegalus), in other primitive fishes (Erpetoichthys calabaricus, Lepisosteus osseus, Amia calva) or in a lungfish (Protopterus sp.). These observations led to the hypothesis that this unusual genetic characteristic arose within the Acipenseriformes after the presumed divergence of the sturgeon and paddlefish families. In the present study, a survey of nearly all Eurasian acipenseriform species was conducted to examine 18S rDNA variation. Intraindividual variation was not found in the polyodontid species, the Chinese paddlefish, Psephurus gladius, but variation was detected in all Eurasian acipenserid species. The comparison of sequences from two major segments of the 18S rRNA gene and identification of sites where insertion/deletion events have occurred are placed in the context of evolutionary relationships within the Acipenseriformes and the evolution of rDNA variation in this group. Sturgeons (Acipenseridae) and paddlefishes (Polyodontidae) are members of the order Acipenseriformes, a group of approximatel
-
Unusual Intraindividual Variation of the Nuclear 18S rRNA Gene is Widespread Within the Acipenseridae
Journal of Heredity, 2006Co-Authors: Jeannette Krieger, V. J. Birstein, Paul A Fuerst, Anne Kathrin Hett, Arne LudwigAbstract:Significant intraindividual variation in the sequence of the 18S rRNA gene is unusual in animal genomes. In a previous study, multiple 18S rRNA gene sequences were observed within individuals of eight species of sturgeon from NorthAmerica but not in the North American paddlefish, Polyodon spathula, in two species of Polypterus (Polypterus delhezi and Polypterus senegalus), in other primitive fishes (Erpetoichthys calabaricus, Lepisosteus osseus, Amia calva) or in a lungfish (Protopterus sp.). These observations led to the hypothesis that this unusual genetic characteristic arose within the Acipenseriformes after the presumed divergence of the sturgeon and paddlefish families. In the present study, a survey of nearly all Eurasian acipenseriform species was conducted to examine 18S rDNA variation. Intraindividual variation was not found in the polyodontid species, the Chinese paddlefish, Psephurus gladius, but variation was detected in all Eurasian acipenserid species. The comparison of sequences from twomajorsegmentsofthe18SrRNAgeneandidentificationofsiteswhereinsertion/deletioneventshaveoccurredareplacedin the context of evolutionary relationships within the Acipenseriformes and the evolution of rDNA variation in this group.
R. Glenn Northcutt - One of the best experts on this subject based on the ideXlab platform.
-
An immunohistochemical study of the telencephalon of the senegal bichir (Polypterus senegalus).
The Journal of comparative neurology, 1992Co-Authors: Anton Reiner, R. Glenn NorthcuttAbstract:The telencephalon in ray-finned fish (actinopterygians) is everted, in contrast to the evaginated telencephalic hemispheres in all other vertebrates. In the more derived ray-finned fish, the teleosts, proliferation of neurons and their migration from the ependymal zone of the pallium renders comparisons between telencephalic cell groups of the teleosts and members of other vertebrate groups extremely difficult. The telencephalon of Polypterus (a primitive living ray-finned fish), although everted, is cytoarchitecturally much simpler than that of teleosts. We have thus applied immunohistochemical techniques to the study of the telencephalon of Polypterus to help clarify the evolution of the telencephalon in teleosts and facilitate comparisons between the telencephalon in ray-finned fish and other vertebrates. Antisera against the following neuroactive substances were used: 1) serotonin (5HT), 2) tyrosine hydroxylase (TH), 3) substance P (SP), 4) leucine-enkephalin (ENK), 5) neuropeptide Y (NPY), and 6) the neurotensin-related hexapeptide LANT6. Several features of the labeling patterns obtained suggested that the dorsal and ventral subdivisions of the area ventralis are homologous as a field to the basal ganglia and septum plus other basal telencephalic regions of land vertebrates, sharks and lungfish: 1) an abundance of SP +, NPY +, and ENK+ fibers; 2) an abundance of TH+ fibers, possibly of posterior tubercle/tegmental origin; 3) the presence of an SP + fiber bundle that appeared to descend from basal telencephalic levels and terminate in the posterior tubercle/tegmentum, which contain TH + (possibly dopaminergic) neurons; and 4) an abundance of 5HT+ fibers, presumably of posterior tubercle/tegmental origin. It was not possible, however, to recognize distinct pallidal and striatal subdivisions within the area ventralis of Polypterus. The olfactory pallium (Pl) was generally poor in most of the substances examined, except for the presence of LANT6+ fibers. The P3 pallid field was conspicuously rich in SP+ and ENK+ fibers throughout its extent, and the caudal and lateral parts of the P2 field were rich in SP+ fibers and ENK+ fibers. Since this is characteristic of the medial pallial and/or dorsomedial pallial walls of the telencephalon in lungfish, sharks, frogs, and reptiles, the P3 field and caudolateral part of the P2 field may be homologous to these portions of the telencephalon in other vertebrates. More rostromedial parts of P2 may correspond to those parts of the pallium in land vertebrates that are in receipt of specific sensory input from the thalamus, since low neuropeptide levels are characteristic of these regions. These results indicate that the dorsal part of the ventral area of the telencephalon in ray-finned fish may be homologous to the basal ganglia in other vertebrates. These results also suggest that the pallial portions of the telencephalon in Polypterus may include a region comparable to part of the isocortex or its homologues in amniotes. o 1992 Wiley-Liss, Inc.