Numbers of successfully metamorphosing juvenile amphibians were tabulated at three wetlands in South Carolina, U.S.A. using terrestrial drift fences with pitfall traps. A relatively undisturbed Carolina bay was studied for eight years, a partially drained Carolina bay for four years, and a man-made borrow pit for three years. Annual production of juveniles at the undisturbed Carolina bay ranged from zero to 75,644 individuals of 15 species. Fewer individuals of fewer species typically metamorphosed at the borrow pit than at the undisturbed bay, with the least numbers at the partially drained Carolina bay. Both total number and species diversity of metamorphosing juveniles at each site each year showed a strong positive correlation with hydroperiod, i.e., the number of days a site contained standing water that year. Data for one common anuran species and the most common salamander species were analyzed separately by multiple regression, in addition to the community analyses. For the mole salamander, Ambystoma talpoideum, hydroperiod was a significant predictor of the number of metamorphosing juveniles, but the number of breeding females was not. For the ornate chorus frog, Pseudacris ornata, the number of breeding females was a significant predictor of the number of metamorphosing juveniles, but hydroperiod was not. Variation in the dates of wetland filling and drying interacts with other factors to determine amphibian community structure and diversity. Either increasing or decreasing the number of days a wetland holds water could increase or decrease the number and species diversity of amphibians in and around a wetland.
metamorphosing
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In the present study we examined the effect of developmental temperature on the swimming performance of Gilthead seabream metamorphosing larvae. In contrary to previous relevant studies in other fish species, where temperature was applied during a relatively long ontogenetic period (embryonic and larval stages)20,26, in our study, the application of the different thermal treatments was limited to the short period of the embryonic and yolk-sac larval stages (Fig. 1). Body-shape and heart morphometry, important features for swimming speed20,39 were also analysed in an attempt to explain swimming performance results. Additionally, we examined the effect of temperature during this short ontogenetic period on the development of skeletal abnormalities.
In the present paper, we found that water temperature during early development influences the swimming performance of metamorphosing seabream larvae. To our knowledge, this is the first study demonstrating the programming of swimming performance by the temperature which was experienced by the fish during the relatively short embryonic and yolk-sac period. Previous relevant studies on the thermally induced programming of fish swimming performance, targeted the wider ontogenetic period from the embryonic stage to metamorphosis, in European sea bass26 and zebrafish20. Interestingly, and independent of the tested species and ontogenetic stage, all studies concluded that low developmental temperature results in higher fish swimming performance in the following developmental stages (present and previous20,26 studies).
Body shape is tightly associated with the swimming performance of fishes40. In the present paper, fish with the highest critical swimming speed (17 C DT group) were characterized by a comparatively slender body, terminal mouth and ventrally transposed pectoral fins. Similar responses to low developmental temperature have been reported in European seabass metamorphosing larvae41 and in Gilthead seabream juveniles38. A streamline body form serves in reducing drag during prolonged swimming, whereas a lower orientation of the pectoral fins serves in improving hovering and manoeuvrability42,43,44. Whether the observed body shape plasticity of metamorphosing seabream larvae (present study) is reversible or not during the following development, remains unknown. In European seabass, thermally induced plasticity of body shape decreased during the metamorphosis period41. In Gilthead seabream, Loizides et al.38 showed that the plastic responses of juvenile body shape decreased as different thermal treatments were applied during shorter and earlier ontogenetic windows.
As the first and sometimes only skeletal tissue to appear, cartilage plays a fundamental role in the development and evolution of vertebrate body shapes. This is especially true for amphibians whose largely cartilaginous feeding skeleton exhibits unparalleled ontogenetic and phylogenetic diversification as a consequence of metamorphosis. Fully understanding the evolutionary history, evolvability and regenerative potential of cartilage requires in-depth analysis of how chondrocytes drive growth and shape change. This study is a cell-level description of the larval growth and postembryonic shape change of major cartilages of the feeding skeleton of a metamorphosing amphibian. Histology and immunohistochemistry are used to describe and quantify patterns and trends in chondrocyte size, shape, division, death, and arrangement, and in percent matrix from hatchling to froglet for the lower jaw, hyoid and branchial arch cartilages of Xenopus laevis. The results are interpreted and integrated into programs of cell behaviors that account for the larval growth and histology, and metamorphic remodeling of each element. These programs provide a baseline for investigating hormone-mediated remodeling, cartilage regeneration, and intrinsic shape regulating mechanisms. These programs also contain four features not previously described in vertebrates: hypertrophied chondrocytes being rejuvenated by rapid cell cycling to a prechondrogenic size and shape; chondrocytes dividing and rearranging to reshape a cartilage; cartilage that lacks a perichondrium and grows at single-cell dimensions; and an adult cartilage forming de novo in the center of a resorbing larval one. Also, the unexpected superimposition of cell behaviors for shape change onto ones for larval growth and the unprecedented exploitation of very large and small cell sizes provide new directions for investigating the development and evolution of skeletal shape and metamorphic ontogenies.
Of the three programs proposed by Rose (2009, 2014) to account for cartilage shape changes in metamorphosing amphibians, this study finds no evidence of the first, cells condensing and chondrifying next to a larval cartilage, in the ceratohyal, and only a minor role for it in the lower jaw. This program likely accounts for formation of the paired alar and thyroid processes in the space previously occupied by the branchial basket (Fig 1) [42, 51], and for the additions of juvenile cartilage to the hyale in early postmetamorphosis [51] and elastic cartilage to the male larynx in sexual maturation [90]. The lower jaw and ceratohyal conform with the proposed second and third programs only to the extent that cell behaviors are more uniformly distributed in the former cartilage than the latter, and the perichondrium does not remain intact in the latter. The lower jaw exhibits more spatially localized behaviors than expected, including cell condensation and apposition at the ends and the earlier emergence of cell clusters on the outer side of the cartilage. The spatial patterning predicted for the ceratohyal, cell death peripherally and cell division centrally, is also incorrect as cell death and cell division occur in both regions.
That the cell behavior programs exhibited by Xenopus can be exploited for much greater ontogenetic divergence and for significant phylogenetic diversification is evidenced by the wide array of larval and adult shapes that have evolved in frog viscerocranial skeletons [12, 45]. Some frogs have tiny lower jaws as tadpoles and huge ones as adults, others lose the ceratohyal at metamorphosis, and some have very simple branchial arch skeletons. This high diversity could be tied to cell behaviors for shape change being superimposed onto ones for growth, and to chondrocytes undergoing dramatic reductions in size, as these factors allow for significant shape change without the functional and energetic costs of cartilage replacement. Whether salamanders, lampreys and other metamorphosing vertebrates evolved the same flexibility in their cartilage remodeling programs remains to be seen. Unravelling the rules and limits that the repertoire of cell behaviors available to chondrocytes imposes on skeletal evolution awaits more comparative study of how they grow and remake cartilages.
In 2013, gopher frog tadpoles were found in 32 ponds, including 11 new ponds. The first gopher frog vouchers were recorded in Liberty and Suwannee counties. This metamorphosing tadpole was found during the 2014 survey period. As you can see, it's in a transitional period and entering into the juvenile stage of its life.
Lynn M. Riddiford, James W. Truman, Aljoscha Nern; Juvenile hormone reveals mosaic developmental programs in the metamorphosing optic lobe of Drosophila melanogaster. Biol Open 15 April 2018; 7 (4): bio034025. doi:
Turning into frogs: asymmetry in forelimb emergence and escape direction in metamorphosing anurans : Lateralised forelimb emergence and turning. / Walsh, Patrick; Zechini, Luigi; Waddell, Emily et al.
N2 - There is considerable debate about the pattern and origin of laterality in forelimb emergence and turning behaviour within amphibians, with the latter being poorly investigated in tadpoles around metamorphic climax. Using six species of metamorphosing anurans, we investigated the effect of asymmetrical spiracle location, and disturbance at the time of forelimb emergence, on the pattern of forelimb emergence. Turning behaviour was observed to assess whether motor lateralisation occurred in non-neobatrachian anurans and was linked to patterns of forelimb emergence. Biases in forelimb emergence differed among species, supporting the hypothesis that asymmetrical spiracle position results in the same asymmetry in forelimb emergence. However, this pattern only occurred when individuals were undisturbed. Therefore, context at the time of the emergence of the forelimbs may be important, and might explain some discrepancies in the literature. Turning biases, unconnected to forelimb emergence, were found in Pipidae and Bombinatoridae, confirming the basal origin of lateralised behaviour among anurans. Turning direction in our metamorphs differed from the left-ward bias commonly observed in tadpoles, but may be analogous to the prevalent right-"handedness" among adult anurans. Therefore, the transitions occurring during metamorphosis may affect lateralised behaviour and metamorphosis may be fruitful for understanding the development of lateralisation. 2ff7e9595c
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