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Karen M. Warkentin – One of the best experts on this subject based on the ideXlab platform.

  • Egg clutch dehydration induces early hatching in red-eyed treefrogs, Agalychnis callidryas
    PeerJ, 2017
    Co-Authors: María José Salica, James R. Vonesh, Karen M. Warkentin

    Abstract:

    Terrestrial eggs have evolved repeatedly in tropical anurans exposing embryos to the new threat of dehydration. Red-eyed treefrogs, Agalychnis callidryas, lay eggs on plants over water. Maternally provided water allows shaded eggs in humid sites to develop to hatching without rainfall, but unshaded eggs and those in less humid sites can die from dehydration. Hatching responses of amphibian eggs to dry conditions are known from two lineages with independent origins of terrestrial eggs. Here, we experimentally tested for dehydration-induced early hatching in another lineage (Agalychnis callidryas, Phyllomedusidae), representing a third independent origin of terrestrial eggs. We also investigated how dehydration affected egg and clutch structure, and egg mortality. We collected clutches from a pond in Gamboa, Panama, and randomly allocated them to wet or dry treatments at age 1 day. Embryos hatched earlier from dry clutches than from wet clutches, accelerating hatching by ∼11%. Clutch thickness and egg diameter were affected by dehydration, diverging between treatments over time. Meanwhile, mortality in dry clutches was six-fold higher than in control clutches. With this study, early hatching responses to escape mortality from egg dehydration are now known from three anuran lineages with independent origins of terrestrial eggs, suggesting they may be widespread. Further studies are needed to understand how terrestrial amphibian eggs can respond to, or will be affected by, rapid changes in climate over the next decades.

  • How embryos escape from danger: the mechanism of rapid, plastic hatching in red-eyed treefrogs.
    The Journal of experimental biology, 2016
    Co-Authors: Kristina L Cohen, Marc A Seid, Karen M. Warkentin

    Abstract:

    Environmentally cued hatching allows embryos to escape dangers and exploit new opportunities. Such adaptive responses require a flexibly regulated hatching mechanism sufficiently fast to meet relevant challenges. Anurans show widespread, diverse cued hatching responses, but their described hatching mechanisms are slow, and regulation of timing is unknown. Arboreal embryos of red-eyed treefrogs, Agalychnis callidryas, escape from snake attacks and other threats by very rapid premature hatching. We used videography, manipulation of hatching embryos and electron microscopy to investigate their hatching mechanism. High-speed video revealed three stages of the hatching process: pre-rupture shaking and gaping, vitelline membrane rupture near the snout, and muscular thrashing to exit through the hole. Hatching took 6.5-49 s. We hypothesized membrane rupture to be enzymatic, with hatching enzyme released from the snout during shaking. To test this, we displaced hatching embryos to move their snout from its location during shaking. The membrane ruptured at the original snout position and embryos became trapped in collapsed capsules; they either moved repeatedly to relocate the hole or shook again and made a second hole to exit. Electron microscopy revealed that hatching glands are densely concentrated on the snout and absent elsewhere. They are full of vesicles in embryos and release most of their contents rapidly at hatching. Agalychnis callidryas’ hatching mechanism contrasts with the slow process described in anurans to date and exemplifies one way in which embryos can achieve rapid, flexibly timed hatching to escape from acute threats. Other amphibians with cued hatching may also have novel hatching mechanisms.

  • Appendix E. Examples of egg clutches of phyllomedusine hylid frogs, Agalychnis and Pachymedusa, showing differences between highly gelatinous and minimally gelatinous clutches.
    , 2016
    Co-Authors: Ivan Gomez-mestre, John J. Wiens, Karen M. Warkentin

    Abstract:

    Examples of egg clutches of phyllomedusine hylid frogs, Agalychnis and Pachymedusa, showing differences between highly gelatinous and minimally gelatinous clutches

Ivan Gomez-mestre – One of the best experts on this subject based on the ideXlab platform.

  • Appendix F. Differences in size and developmental stage between early induced hatchlings and modal spontaneous hatchlings in six phyllomedusine treefrogs (Agalychnis and Pachymedusa).
    , 2016
    Co-Authors: Ivan Gomez-mestre, John J. Wiens, Karen M. Warkentin

    Abstract:

    Differences in size and developmental stage between early induced hatchlings and modal spontaneous hatchlings in six phyllomedusine treefrogs (Agalychnis and Pachymedusa)

  • Appendix E. Examples of egg clutches of phyllomedusine hylid frogs, Agalychnis and Pachymedusa, showing differences between highly gelatinous and minimally gelatinous clutches.
    , 2016
    Co-Authors: Ivan Gomez-mestre, John J. Wiens, Karen M. Warkentin

    Abstract:

    Examples of egg clutches of phyllomedusine hylid frogs, Agalychnis and Pachymedusa, showing differences between highly gelatinous and minimally gelatinous clutches

  • EVOLUTION OF ADAPTIVE PLASTICITY: RISK‐SENSITIVE HATCHING IN NEOTROPICAL LEAF‐BREEDING TREEFROGS
    Ecological Monographs, 2008
    Co-Authors: Ivan Gomez-mestre, John J. Wiens, Karen M. Warkentin

    Abstract:

    Adaptive plasticity at switch points in complex life cycles (e.g., hatching, metamorphosis) is well known, but the evolutionary history of such plasticity is not. Particularly unclear is how a single plastic response (e.g., shifts in hatching timing) evolves to respond to different threats and cues (e.g., abiotic and biotic). We conducted a comparative phylogenetic study of hatching plasticity in a group of frogs with arboreal embryos to determine when risk-accelerated hatching evolved in the clade, whether responses to two common egg-stage risks (snake predation and flooding) evolved independently, and whether the overall capacity for hatching plasticity was evolutionarily more conservative than responses to specific cues. Red-eyed treefrogs (Agalychnis callidryas) hatch early to escape from several egg-stage risks but otherwise hatch later, improving larval survival with predators. We reconstructed a phylogeny for Agalychnis and related genera based on three mitochondrial and four nuclear genes. We quantified onset of hatching competence, spontaneous hatching timing, responses to egg-stage risks, and costs of premature hatching in Agalychnis and Pachymedusa. We also assessed hatching plasticity in a basal phyllomedusine, Cruziohyla calcarifer. The capacity to hatch ;30% before the spontaneous hatching age appears ancestral for phyllomedusines, with little change over ;34-50 million years among the species examined. A strong hatching response to flooding, with no mortality of hatching-competent eggs, is similarly ancient and conserved. Premature hatchlings of Agalychnis and Pachymedusa are more vulnerable to fish predation than are full-term hatchlings, indicating a conserved risk trade-off across hatching that would make plasticity advantageous. In contrast, the hatching response to snake attack has undergone major changes at least twice in the Agalychnis-Pachymedusa clade, with two species showing substantially lower escape success than the others. Responses to different threats have thus evolved independently. The capacity for switch point plasticity may be evolutionarily more stable than the response to individual stage-specific threats.

C. Shaw – One of the best experts on this subject based on the ideXlab platform.

  • identification of a new myotropic decapeptide from the skin secretion of the red eyed leaf frog Agalychnis callidryas
    PLOS ONE, 2020
    Co-Authors: Lei Wang, Mei Zhou, Tianbao Chen, Yitian Gao, Wenqing Yang, C. Shaw

    Abstract:

    Bradykinin-related peptides (BRPs) family is one of the most significant myotropic peptide families derived from frog skin secretions. Here, a novel BRP callitide was isolated and identified from the red-eyed leaf frog, Agalychnis callidryas, with atypical primary structure FRPAILVRPK-NH2. The mature peptide was cleaved N-terminally at a classic propeptide convertase cleavage site (-KR-) and at the C-terminus an unusual -GKGKGK sequence was removed using the first G residue as an amide donor for the C-terminally-located K residue. Thereafter, the synthetic replicates of callitide were assessed the myotropic activity and showed a significant contraction of balder, with the 0.63 nM EC50 value, more potent than most discovered myotropic peptides. The binding mode was further speculated by molecular docking and stimulation. The result indicated that the C-terminal of callitide might selectively bind to bradykinin receptor B2 (BKRB2). Further investigation of the callitide needs to be done in the future to be exploited as potential future drug leads.

  • unravelling the skin secretion peptides of the gliding leaf frog Agalychnis spurrelli hylidae
    Biomolecules, 2019
    Co-Authors: Carolina Proanobolanos, Ailin Blascozuniga, Jose Rafael Almeida, Lei Wang, Miguel Angel Llumiquinga, Miryan Rivera, Mei Zhou, Tianbao Chen, C. Shaw

    Abstract:

    Frog skin secretions contain medically-valuable molecules, which are useful for the discovery of new biopharmaceuticals. The peptide profile of the skin secretion of Agalychnis spurrelli has not been investigated; therefore, the structural and biological characterization of its compounds signify an inestimable opportunity to acquire new biologically-active chemical scaffolds. In this work, skin secretion from this amphibian was analysed by molecular cloning and tandem mass spectrometry. Although the extent of this work was not exhaustive, eleven skin secretion peptides belonging to five peptide families were identified. Among these, we report the occurrence of two phyllokinins, and one medusin-SP which were previously reported in other related species. In addition, eight novel peptides were identified, including four dermaseptins, DRS-SP2 to DRS-SP5, one phylloseptin-SP1, and three orphan peptides. Phylloseptin-SP1 and dermaseptins-SP2 were identified in HPLC fractions based on their molecular masses determined by MALDI-TOF MS. Among the antimicrobial peptides, dermaseptin-SP2 was the most potent, inhibiting Escherichia coli, Staphylococcus aureus, and ORSA with a minimum inhibitory concentration (MIC) of 2.68 μM, and Candida albicans with an MIC of 10.71 μM, without haemolytic effects. The peptides described in this study represent but a superficial glance at the considerable structural diversity of bioactive peptides produced in the skin secretion of A. spurrelli.