Background: Bone fracture frequencies and survival rates are essential parameters in skeleton evolution, but information on the functional consequences of naturally healed fractures is scarce. No leg bone fracture hea...Background: Bone fracture frequencies and survival rates are essential parameters in skeleton evolution, but information on the functional consequences of naturally healed fractures is scarce. No leg bone fracture healing in the wild has been reported so far from long-legged Charadriiformes(waders), which depend on bipedal locomotion for feeding.Methods: We documented a healed but malaligned tarsometatarsus fracture in a wild Willet(Tringa [Catoptrophorus]semipalmata), and a malaligned tibiotarsus fracture in a Curlew(Numenius arquata) skeleton from a museum collection. Functional consequences of the malalignments were evaluated by kinematic analyses of videos(Willet) and in silico 3D modeling(Curlew).Results: The Willet's left tarsometatarsus exhibited an angular malalignment of 70°, resulting in a limping gait that was less pronounced at high than at low walking speed. The bird seemed unable to club the toes of the left foot together, apparently a secondary effect of the deformity. The Curlew's tibiotarsus showed an angular and an axial malalignment, causing the foot to rotate outwards when the intertarsal joint was flexed. Despite the severe effects of their injuries, the birds had survived at least long enough for the fractures to heal completely.Conclusions: Somewhat unexpectedly, leg fractures are not necessarily fatal in long-legged waders, even if deformities occur in the healing process. Bipedal locomotion on vegetated grounds must have been impeded due to the bone malalignments in both analyzed cases. The birds probably alleviated the impact of their handicaps by shifting a larger proportion of their activities to vegetation-free habitats.展开更多
In the 192os, the German forestry scientist Ernst M{Jnch postulated that photo-assimilate transport is a mass flow driven by osmotically induced pressure gradients between source organs （high turgot） and sink organs...In the 192os, the German forestry scientist Ernst M{Jnch postulated that photo-assimilate transport is a mass flow driven by osmotically induced pressure gradients between source organs （high turgot） and sink organs （lower turgor）. Two crucial components of MOnch＇s hypothesis, the translocation by mass flow from sources to sinks and the osmotic mechanism of pressure flow, were established notions at the time, but had been developed by two institutionally separated groups of scholars. A conceptual separation of wholepplant biology from cellular physiology had followed the institutional separation of forestry science from botany in German-speaking central Europe during the so-called Humboldtian reforms, and was reinforced by the delayed institutionalization of plant physiology as an academic discipline. Munch did not invent a novel concept, but accomplished an integration of the organism-focused and the cell-focused research traditions, reducing the polarization that had evolved when research universities emerged in central Europe. Post-Munch debates about the validity of his hypothesis focused increasingly on the suitability of available research methodologies, especially the electron microscope and the proper interpretation of the results it produced. The present work reconstructs the influence of the dynamic scientific and non-scientific context on the history of the Munch hypothesis.展开更多
The effects of the variability of individual prey locomotory performance on the vulnerability to predation are poorly understood,partly because individual performance is difficult to determine in natural habitats.To g...The effects of the variability of individual prey locomotory performance on the vulnerability to predation are poorly understood,partly because individual performance is difficult to determine in natural habitats.To gain insights into the role(s)of individual variation in predatory relationships,we study a convenient model system,the neotropical sandy beach gastropod Olivella semistriata and its main predator,the carnivorous snail Agaronia propatula.The largest size class of O.semistriata is known to be missing from A.propatula's spectrum of subdued prey,although the predator regularly captures much larger individuals of other taxa.To resolve this conundrum,we analyzed predation attempts in the wild.While A.propatula attacked O.semistriata of all sizes,large prey specimens usually escaped by'sculling',an accelerated,stepping mode of locomotion.Olivella semistriata performed sculling locomotion regardless of size,but sculling velocities determined in the natural environment increased strongly with size.Thus,growth in size as such does not establish a prey size refuge in which O.semistriata is safe from predation.Rather,a behaviorally mediated size refuge is created through the size-dependence of sculling performance.Taken together,this work presents a rare quantitative characterization in the natural habitat of the causal sequence from the size-dependence of individual performance,to the prey size-dependent outcome of predation attempts,to the size bias in the predator's prey spectrum.展开更多
文摘Background: Bone fracture frequencies and survival rates are essential parameters in skeleton evolution, but information on the functional consequences of naturally healed fractures is scarce. No leg bone fracture healing in the wild has been reported so far from long-legged Charadriiformes(waders), which depend on bipedal locomotion for feeding.Methods: We documented a healed but malaligned tarsometatarsus fracture in a wild Willet(Tringa [Catoptrophorus]semipalmata), and a malaligned tibiotarsus fracture in a Curlew(Numenius arquata) skeleton from a museum collection. Functional consequences of the malalignments were evaluated by kinematic analyses of videos(Willet) and in silico 3D modeling(Curlew).Results: The Willet's left tarsometatarsus exhibited an angular malalignment of 70°, resulting in a limping gait that was less pronounced at high than at low walking speed. The bird seemed unable to club the toes of the left foot together, apparently a secondary effect of the deformity. The Curlew's tibiotarsus showed an angular and an axial malalignment, causing the foot to rotate outwards when the intertarsal joint was flexed. Despite the severe effects of their injuries, the birds had survived at least long enough for the fractures to heal completely.Conclusions: Somewhat unexpectedly, leg fractures are not necessarily fatal in long-legged waders, even if deformities occur in the healing process. Bipedal locomotion on vegetated grounds must have been impeded due to the bone malalignments in both analyzed cases. The birds probably alleviated the impact of their handicaps by shifting a larger proportion of their activities to vegetation-free habitats.
文摘In the 192os, the German forestry scientist Ernst M{Jnch postulated that photo-assimilate transport is a mass flow driven by osmotically induced pressure gradients between source organs （high turgot） and sink organs （lower turgor）. Two crucial components of MOnch＇s hypothesis, the translocation by mass flow from sources to sinks and the osmotic mechanism of pressure flow, were established notions at the time, but had been developed by two institutionally separated groups of scholars. A conceptual separation of wholepplant biology from cellular physiology had followed the institutional separation of forestry science from botany in German-speaking central Europe during the so-called Humboldtian reforms, and was reinforced by the delayed institutionalization of plant physiology as an academic discipline. Munch did not invent a novel concept, but accomplished an integration of the organism-focused and the cell-focused research traditions, reducing the polarization that had evolved when research universities emerged in central Europe. Post-Munch debates about the validity of his hypothesis focused increasingly on the suitability of available research methodologies, especially the electron microscope and the proper interpretation of the results it produced. The present work reconstructs the influence of the dynamic scientific and non-scientific context on the history of the Munch hypothesis.
文摘The effects of the variability of individual prey locomotory performance on the vulnerability to predation are poorly understood,partly because individual performance is difficult to determine in natural habitats.To gain insights into the role(s)of individual variation in predatory relationships,we study a convenient model system,the neotropical sandy beach gastropod Olivella semistriata and its main predator,the carnivorous snail Agaronia propatula.The largest size class of O.semistriata is known to be missing from A.propatula's spectrum of subdued prey,although the predator regularly captures much larger individuals of other taxa.To resolve this conundrum,we analyzed predation attempts in the wild.While A.propatula attacked O.semistriata of all sizes,large prey specimens usually escaped by'sculling',an accelerated,stepping mode of locomotion.Olivella semistriata performed sculling locomotion regardless of size,but sculling velocities determined in the natural environment increased strongly with size.Thus,growth in size as such does not establish a prey size refuge in which O.semistriata is safe from predation.Rather,a behaviorally mediated size refuge is created through the size-dependence of sculling performance.Taken together,this work presents a rare quantitative characterization in the natural habitat of the causal sequence from the size-dependence of individual performance,to the prey size-dependent outcome of predation attempts,to the size bias in the predator's prey spectrum.
