larval amphibian ecology

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Larval Amphibian Ecology. Materials produced by:. Jennifer Pramuk, Ph.D. Curator of Herpetology Bronx Zoo/Wildlife Conservation Society Michael McFadden. Amphibian Larvae. Have hatched Are morphologically distinct Are non-reproductive Passes through metamorphosis - PowerPoint PPT Presentation

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  • Larval Amphibian EcologyJennifer Pramuk, Ph.D.Curator of HerpetologyBronx Zoo/Wildlife Conservation Society

    Michael McFaddenMaterials produced by:

  • Amphibian LarvaeHave hatchedAre morphologically distinctAre non-reproductivePasses through metamorphosisUsually are aquatic and feeding (with exceptions)

    Direct developing Eleutherodactylus eggsPhytotelm breeders:e.g., Dendrobates pumilio

  • SalamandersMorphology: conserved Elongated, salamander-like appearance from early on in developmentExternal gills, tail fin, large heads, no eyelidsSkeleton contains bone, teeth in jaws

    Ambystoma maculatum

  • Salamanders: Larval typesLarviformBody shape varies with habitatTerrestrialPond typeStream typeMountain-brook type

    Pond typeStream type

  • Salamanders: MetamorphosisMore gradual than in anuransTail fin reduces (resorbed)Skin becomes thickerGills resorbed, gill slits closeLungs developPalate restructuringTeeth become pedicellate

    Pedicellate teeth

  • SalamandersLarviform (i.e. neotenic or paedomorphic): Adults that look like larvae (failure to metamorphose completely)Some obligate, others facultative

    Hi, ImLarviform

  • Larval salamander ecologyDevelopmental modes:Eggs laid: aquatic eggs, aquatic larvae (most spp.)Non aquatic eggs and aquatic larvaeNon aquatic eggs and direct development (e.g., Plethodon, Ensatina, Aneides + Bolitoglossini)Viviparity (e.g., salamandrids)

    Plethodon vandykei

  • Salamanders: DietsAlmost all are carnivorousSuction feedingPond dwellers: small prey (e.g., zooplankton)Stream dwellers: larger preyCannibalism is common

    Zooplankton

  • SalamandersLarval period: varies between 40 days (e.g., Hemidactylium scutatum) to 5 years (Cryptobranchus alleganiensis and Necturus maculosus). Development time dependent on food availability and water temp.

    Cryptobranchus alleganiensis

  • Frogs

  • Frogs: Tadpole MorphologyLimbs appear relatively late as larvaeGills quickly covered with operculum (front legs develop behind operculum first)

  • Frogs: Tadpole MorphologyOral disc (jaw sheaths, labial teeth, lobes and papillae)Keratinized mouthparts (jaw sheaths and labial teeth)Variable number of tooth rows & papillae

  • Frogs: Tadpole TypesGrace OrtonType 1: Pipidae + RhynophrynidaeType 2: MicrohylidaeType 3: Ascaphus, Leiopelma, Bombinatoridae, + DiscoglossidaeType 4: all other frogs

    Type 1Type 2Type 3Type 4

  • Frogs: Internal MorphologyPath of digestion: Branchial basket>esophagus>manicotto glandulare (secretes HCl, enzymes)Mid and hindguts (elongated)Nitrogenous wastes excreted by kidneys as ammoniaReproductive organs begin to differentiate midway through developmentCutaneous respiration primary

  • Frogs: Functional MorphologyFeeding and respiratory systems:Water taken in through mouthPasses across gillsExits through spiracle

  • Tadpole Habitats and microhabitats

    Benthic, midwater, surface feedersBurrow in substrate of streamsSuctorial mouthparts, belly suckers

    Amolops sp.

  • Tadpole Habitats and microhabitats

    Some primarily predator (e.g., fish) freePhytotelmsTree holes, bamboo stalksSeed husksSelected based on abiotic factors: Dissolved O2Water depth, flow rateSubstrate texture and qualityEphemeralityTemperature

  • Tadpole FeedingFilter feedingCarnivorous (e.g., Hymenochirus, Ceratophrys)Cannibalistic (e.g., Rhinophrynus)Cannibalistic morphs in Scaphiopus and SpeaMutualist nematodes in hindguts of Rana catesbeiana

    Rhinophrynus dorsalisRhinophrynus dorsalis tadpoleScaphiopus multiplicatus

  • Frog life cycleAs little as 8 days (Scaphiopus couchii)As long as 23 years (some high altitude Rana, leptodactylids) or up to 5 years (Ascaphus)Determining factors (other than phylogeny): food availability, temperatures, density of conspecifics, competitors, predatorsHigh density retards development because of proteinaceous compound

    Scaphiopus couchii

  • EcomorphologyTremendous adaptive radiationBody shape etc., determined by:1) Source of energy2) Type of aquatic environment3) Feeding biology Rana palmipes (slow waters)Megophrys montana (slow waters)Hyla rivularis (stream dweller)Hyla bromeliacia (bromeliad dwelling)

  • Staging larvae: Gosner stages

  • Frogs: MetamorphosisMetamorphosis: relatively abrupt Drastic morphological changes:Digestive gut shortens; stomach formsTadpole mouthparts disappear; replaced by teeth, etc.Movable eyelidsLungs formCartilaginous skeleton replaced with boneTail resorbedLimbs form

  • CaeciliansVery poorly knownMost (70%) are oviparous; mostly with aquatic larvaeDirect development occurs in CaeciliidaeViviparity occurs in African and S. American species of Caeciliidae, all Typhlonectidae, and Scolecomorphus

    Boulengerula taitanus

  • Caecilian larvaeHatched at relatively advanced stageLungs well developedLarvae lack tentaclesLateral line developedAmpullary (electroreceptive) organs prominent on head

    Ichthyophis embryo

  • Caecilian larval ecologyMostly unknownIchthyophis and Epicrinops: found in mud or under objects at waters edge; larval development up to a yearLikely nocturnalSubterranean during day, forage at surface at night? WHO KNOWS??

  • Caecilians: MetamorphosisRelatively gradualExternal gills lost within days of hatchingLateral line, tail fins lost at metamorphosisScaled species gain scalesColor change

  • Frogs, salamanders, and caecilians comparedCaecilians and salamanders: General morphological resemblance to adultMetamorphosis is gradualPredaceous, functional teeth and jawsAnurans: Larvae dramatically different from adultsLack true teeth, long digestive tractMetamorphosis is dramatic

  • Behavior and Physiology of Larval AmphibiansAbiotic factors:Light (mostly averse to light=negatively phototaxic)O2 content: TemperatureSalt tolerance

    LenticLoticPhytotelm

  • Behavior and Physiology of Larval AmphibiansParental care:Egg attendanceFeeding unfertilized eggs to offspring

    Osteocephalus oophagusDendrobates pumilioAnotheca spinosa

  • Behavior and Physiology of Larval AmphibiansParental care:Carrying tadpoles Nest chamber (e.g., Plethodontohyla inguinalis)Transporting tadpoles to more favorable environment

    Alytes obstetricansColostethus subpunctatusHemiphractus johnsoniGastrotheca cornuta

  • Behavior and Physiology of Larval AmphibiansSocial interactionsAggregations in response to abiotic factorsPredator avoidance Thermoregulation (e.g., Bufo tads)Schooling polarized or not

    Bufo tadpole schoolDragon fly larva vs. frog larva

  • MetamorphosisUnder hormonal controlGrowth regulated by prolactin (pituitary gland), thyroid stimulating hormone (pituitary gland), corticotrophin releasing hormone (hypothalamus)Obligate = metamorphosis always takes placeFacultative= may or may not occur

  • Metamorphosis: Biochemical changeHormonesBlood: hemoglobin with higher O2 affinityLiver: Ammonotelism > ureotelismSkin: Osmoregulation improvesEye: eye pigments change

    Hyla chrysoscelismetamorph

  • Metamorphosis: Morphological changeSkeleton: e.g., development of limbs; increased ossificationSkin: becomes thickerMusculature: e.g., degeneration of tailDigestive system: In frogs, drastic; metamorphs nonfeedingUrogenital system: pronephric kidney> to adult (varies)Sensory systems: Lateral lines degenerate; tentacle (caec.) develops

    Tadpole chondrocrania

  • MetamorphosisPlasticity Rate of metamorphosis modulated by environmental cuesE.g.,: drying pond will increase hormones which stimulate growthDownside: often metamorphose at smaller size

  • Larval husbandryLittle known about many taxaAll husbandry information gathered on various taxa should be recorded and made available.

  • Larval husbandryCaecilians (Viviparous spp.)Viviparous, miniature adultsSome evidence that viviparous offspring may be better kept with parentsLower water depth for gravid mothers

    Typhlonectes natans

  • Larval husbandryCaecilians (Oviparous spp.)Some direct developing (larvae treated as viviparous spp.)Egg clutches found in moist ground, never in waterLarvae amphibiousCarnivorousMaternal attendance (why?)

  • Larval husbandryCaudatesAll carnivorous, some cannibalisticMaintain in low densities to limit intraspecific competitionWill feed on animal-based foods (e.g., small worms, daphnia, brine shrimp, chopped fish, mosquito larvae, etc.)

    Ambystoma maculatum larvae

  • Larval husbandryAnuransMuch more to consider re. diversityMost tadpoles are herbivorous or omnivorousPotential foods: commercial fish flakes, tabs, Sera Micron (filter feeders), Zippy flakesVary foods as much as possibleWater quality!

  • Stocking DensityThe stocking density of tadpoles will largely depend on the water quality and the amount of water flowing through.Increased density may cause:Increased competitionDecreased water qualitySmaller metamorph sizeLonger larval periodLower survivorship

  • Water QualityWater should be tested frequently to determine the quality of the water.Appropriate filtration or water changes should be carried out to maintain quality.This will largely depend on the stocking density and the quality of source water.

  • FeedingLargely dependant on the species.The diet should be varied if possible.Commercial foods, including Sera micron, algal flakes, spirulina flakes, various fish flakes.Frozen endive or lettuce.Naturally growing algae.For omnivorous species, bloodworm and shrimp may also be added.

  • Water TemperatureAttempt to replicate the temperature in the natural habitat of t