Hatching of Amphibian Embryos: The Physiological Trigger

Petranka, James W.; Just, John J.; Crawford, Eugene C.

doi:10.1126/science.7089563

Cited by 98 publications

(49 citation statements)

References 28 publications

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“…Oxygen stress is known to induce or accelerate hatching in amphibians and fish (DiMichele & Taylor 1980;Petranka et al 1982;Bradford & Seymour 1988), and may be the stimulus for early hatching of flooded eggs. It could also play a role in fungus-induced hatching.…”

Section: Cues To Mortality Risk and Embryonic Decision Makingmentioning

confidence: 99%

Wasp predation and wasp-induced hatching of red-eyed treefrog eggs

2000

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Section: Cues To Mortality Risk and Embryonic Decision Makingmentioning

confidence: 99%

Wasp predation and wasp-induced hatching of red-eyed treefrog eggs

2000

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“…Second, the fungus could reduce oxygen availability to embryos either by reducing the exposed egg surface area available for oxygen diffusion, or by directly competing with embryos for oxygen within egg capsules. In several species of amphibians and fish, oxygen stress accelerates or induces hatching (DiMichele and Taylor 1980, Petranka et al 1982, Bradford and Seymour 1988. Once capable of hatching, Agalychnis callidryas eggs hatch rapidly if exposed to hypoxic gas mixtures or if submerged in water, which reduces oxygen diffusion (K. M. Warkentin, unpublished data).…”

Section: Embryonic Response To Fungusmentioning

confidence: 99%

Egg-Killing Fungus Induces Early Hatching of Red-Eyed Treefrog Eggs

Warkentin¹,

Currie²,

Rehner³

2001

Ecology

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Abstract. Pathogens can cause substantial mortality of amphibian eggs. If the timing of hatching is phenotypically plastic, embryos could escape from otherwise lethal infections by hatching early. We tested this with the arboreal eggs of red-eyed treefrogs, Agalychnis callidryas. A filamentous ascomycete (Dothideales: Phaeosphaeriaceae) was present on ϳ7% of egg clutches collected from a pond in the rain forest in Panama and, when present, killed 40% of the eggs, on average. Inoculation experiments confirmed that the fungus attacked and killed healthy embryos, establishing that this fungus is a pathogen of A. callidryas eggs. As predicted from life history theory, embryos hatched earlier from both naturally infected and inoculated clutches than from fungus-free control clutches. Within infected clutches, live embryos in contact with fungal hyphae hatched before those embryos not in contact with the fungus. Accelerated hatching allowed embryos to survive that otherwise would have been killed, and tadpoles hatched from infected clutches were themselves uninfected. Red-eyed treefrog embryos also hatch early if attacked by predators, apparently in response to vibratory cues. Because fungal infection provides no vibratory stimuli, embryos must respond to different cues in fungus-induced hatching than in predatorinduced hatching. The behavioral decision of when to hatch is complex and merits further investigation. Our study indicates that pathogens can influence the timing of life history transitions, as do other stage-specific risks.

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“…Hatching frees animals from the diffusion barrier of the egg and can be induced prematurely by hypoxia in many taxa (Petranka et al, 1982;Warkentin, 2007). In some species, hatching is both advanced by hypoxia and delayed by hyperoxia, suggesting that it occurs at a respiratory threshold (Latham and Just, 1989).…”

Section: Introductionmentioning

confidence: 99%

External gills and adaptive embryo behavior facilitate synchronous development and hatching plasticity under respiratory constraint

Rogge

Warkentin

2008

Journal of Experimental Biology

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SUMMARYPlasticity in hatching timing allows embryos to balance egg-and larval-stage risks, and depends on the ability of hatchingcompetent embryos to continue developing in the egg. Hypoxia can slow development, kill embryos and induce premature hatching. For terrestrial eggs of red-eyed treefrogs, the embryonic period can extend ~50% longer than development to hatching competence, and development is synchronous across perivitelline oxygen levels (P O 2) ranging from 0.5-16.5 kPa. Embryos maintain large external gills until hatching, then gills regress rapidly. We assessed the respiratory value of external gills using gill manipulations and closed-system respirometry. Embryos without external gills were oxygen limited in air and hatched at an external P O 2 of 17 kPa, whereas embryos with gills regulated their metabolism and remained in the egg at substantially lower P O 2. By contrast, tadpoles gained no respiratory benefit from external gills. We videotaped behavior and manipulated embryos to test if they position gills near the air-exposed portion of the egg surface, where P O 2 is highest. Active embryos remained stationary for minutes in gills-at-surface positions. After manipulations and spontaneous movements that positioned gills in the O 2 -poor region of the egg, however, they returned their gills to the air-exposed surface within seconds. Even neural tube stage embryos, capable only of ciliary rotation, positioned their developing head in the region of highest P O 2. Such behavior may be critical both to delay hatching after hatching competence and to obtain sufficient oxygen for normal, synchronous development at earlier stages.

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Hatching of Amphibian Embryos: The Physiological Trigger

Cited by 98 publications

References 28 publications

Wasp predation and wasp-induced hatching of red-eyed treefrog eggs

Wasp predation and wasp-induced hatching of red-eyed treefrog eggs

Egg-Killing Fungus Induces Early Hatching of Red-Eyed Treefrog Eggs

External gills and adaptive embryo behavior facilitate synchronous development and hatching plasticity under respiratory constraint

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