Bio of Vertebrates - Exam 3 Part 2

Ch 12 (Lissamphibia) and Ch 14 (Endo and Ectothermy)

Lissamphibia

-All extant amphibians
-Moist, scaleless skin with many mucus glands
-Skin is important for physiological exchange with environment, respiratory gases, water, solutes
-Cutaneous respiration
-Moist skin readily loses water via evaporation, limits activity to moist microhabitats and times
-Skins contains granular glands, which produce toxins/poisons to deter predators
-Highly toxic species often have bright aposematic coloration; warning coloration
-All carnivores as adults.

Cutaneous Respiration

Requires skin to be moist

Granular glands

Toxins/poisons to deter predators

Aposematic Coloration

Warning coloration

Lissamphibia 3 clades

-Caudata (or Urodela) = Salamanders
-Anura = frogs and toads
-Gymnophiona = caecilians

Caudata/Urodela

-Salamanders
-Four limbs (in most)
-Locomotion via primitive walking-trot or swimming via lateral undulation
-Terrestrial or aquatic as adults
-Terrestrial forms often have aquatic larvae, that lose gills and metamorphose into terrestrial adults
-Many aquatic forms are paedomorphic (retains larval characteristics as adults)
-Gills present in aquatic larvae and paedomorphic adults
-Lungs and skin used for respiration in adults
-All carnivorous as adults

Plethodontidae

Lungless salamanders; respiration entirely cutaneous
-Loss of lungs allowed specialization of the hyobranchial (hyoid) apparatus for tongue protrusion
-Tongue with sticky end, protudes from mouth to capture insect prey
-Eyes placed more anterior on head

Paedomorphic

Retains larval characteristics as adults

Lunged salamanders use the hyobranchial apparatus in _ _ to ventilate the lungs

buccal pumping

Aquatic salamander larvae use the hyobranchial apparatus for _ _, not compatible with protrusible tongue development

suction feeding

Nasolabial grooves

Pick up scents from substrate and transmit them (capillary action) to the vomeronasal organ

Vomeronasal organ

Chemosensory organ for detecting pheromones.

Pheromone

Chemical signal produced by an individual to affect the behavior of other individuals of the same species. 

Many plethodontids have _ _ eggs, do not have free-living larvae and young hatch as a miniature versions of adult

direct developing

Plethodontidae nesting

Nest terrestrially, not dependent on standing water for reproduction

Plethodontidae territoriality

-Uses pheromones to mark their territories, identify neighbors and intruders
-Neighbor recognition
-Aggression can be fierce, with severe consequecnes as bites can be directed at tail or nasolabial grooves.

Neighbor Recognition

Resident males recognize the scent cues of territorial neighbors and respond less aggressively than they do to unfamiliar intruders. 

Salamander/Caudata Reproduction

-Most have internal fertilization but lack intromittent organs
-Males deposit spermatophores (sperm cap on gelatinous base),which males deposit and females pick up with their cloacas
-Mating involves elaborate courtship behavior and pheromones

Caudata Courtship

-Many are sexually dimorphic, with males possessing secondary sexual characters and courtship displays
-Courtship behavior, sexual characters, and pheromones of males are important for species recognition (prevents hybrid matings)
-Males rub/chin tap females to physically stimulate and to transfer pheromones
-Terrestrial = male transfer pheromones to via direct physical contact to nostrils/nasolabial groove or to skin (often bite to allow pheromones to absorb)
-Aquatic = males waft a current of pheromones with their tail

All of Caudata are oviparous (minus ~4 species)

-Breed and oviposit in water or terrestrially
-Aquatic breeders lay eggs in water, aquatic larvae
-Terrestrial breeders nest on land, direct development

Viviparous species are… or ….

lecithotrophic or matrotrophic (embryos feed on oviducal secretions/lining, other ova, or siblings)

Anura

-Frogs and toads
-No tail
-Big head/mouth and robust body
-Four well-developed limbs, with hind limbs larger
-Locomotion via jumping or hopping (some walking)
-Powerful hindlimbs launch frog upward/forward
-Axial skeleton modified for saltatory locomotion
-Terrestrial, aquatic, arboreal, or fossorial (burrowing) as adults
-Arboreal species (tree frogs) have enlarged disks on toes - allow adhesion to smooth surface of foliage.
-Usually have free-living aquatic larvae (tadpoles), that lose gills and metamorphose into adult frogs.
-Gills present in aquatic larvae. Lungs present in adults.
-Lungs and skin used for respiration in adults
-All are carnivorous as adults
-Tadpoles = suction feeding
-Adults flip out their sticky tongue to catch and ingest prey.

Anuran Body Form (Primitive wise)…

-Ancestors walked much like salamanders
-Short pelvic girdle
-Flexible trunk vertebrae

Modern Anurans Have…

-Long, strong hindlimbs for launching upward and forward
-Elongated pelvic girdle and urostyle (fused vertebrae) make posterior trunk rigid
-Pre-sacral vertebrae have large zygapophyses that restrict flexing.
-Robust forelimbs and pectoral girdle for landing

Anuran body forms and locomotor mode

-Long hindlimbs = jumper, swimmer
-Short hindlimbs = walker, hopper, burrower
-Long forelimbs = walker
-Long forelimbs and hindlimbs = arboreal walker-jumper

Reproductive modes in Anurans

-Exhibits more diversity of reproductive modes than any group except fishes
-Almost all species are oviparous.
-Most have external fertilization
-Amplexus = male clasps female with his forelimbs and releases sperm over ova as they are released
-Mating usually involves territoriality and vocalizations by males
-Eggs laid in water or on land

Parental Care in Anurans

-Some adult anurans carry the eggs on/in their bodies
-Eggs hatch into aquatic larvae or small versions of adults (direct development)
-Larvae undergo metamorphosis, transforming to adult form 
-Viviparous species are lecithotrophic or matrotrophic (embryos feed on oviducal secretions)
-Most exhibit no parental care of eggs or young
-Guard eggs/tadpoles/hatchlings
-Carry tadpoles/hatchlings from terrestrial nest to water
-Feed tadpoles (unfertilized ova)

Vocalization by male anurans

-Males establish territories at breeding sites, and emit frequent advertisement calls to attract females and defend territory from other males
-Often call in choruses of multiple males, all competing for mating opportunities.
-Territorial intrusion often leads to aggression/combat.
-Males have vocal sacs (gular sacs that are inflated with air to amplify calls)
-Sound is produced by air expelled from lungs, across vocal cords
-Vocalization is energetically expensive and increases risk of predation

Tadpoles

-Free-living aquatic larvae
-Feed, grow and ultimately metamorphose into adult form
-Herbivorous, some carnivorous + cannibalistic
-Suction feeders and filter feeders
-Many have rasping mouth-parts to scrape algae or plant material free
-Metamorphosis involves major physical and physiological changes to many body systems and structures.
-Larval salamanders much more closely resemble the adult body form, but still undergo radical changes to internal structure and physiology. 

Gymnophiona

-Caecilians
-Limbless, worm-like body form
-Burrowing (terrestrial or aquatic)
-Circular folds of skin form annuli (rings) on body
-Eyes covered by skin or absent entirely
-Pair of protrusible (nasolacrimal) tentacles between eyes and nostrils; chemosensory
-Carnivorous (Feed on earthworms, insects, etc.)
-Skull much more robust than in Anura and Caudata

Chemosensory

Picks up and transfer molecules to vomeronasal organ

Reproduction in Gymnophiona

-All have internal fertilization. Males have an intromittent organ (transfers sperm to female’s cloaca)
-Oviparous or viviparous

Oviparity in Gymnophiona

-Aquatic larvae or direct development

-Many brood or guard their eggs

Viviparity in Gymnophiona

-Have large young.
-Lecithotrophic early in development
-Matrotrophic later. Embryos consume oviducal secretions “uterine milk”. Some feed on lipid fortified stratum corneum from the mother after birth (Dermatophagy)
-Gas exchange via close contact between fetal gills and uterine lining
-Embryos ahve gills, but lose them prior to birth/hatching

Amphibians’ Intermediate and Facultative Hearts

-Gills and skin used for respiration by larvae and aquatic (paedomorphic) adults
-Gills and lungs used for respiration by post-metamorphic adults
-Lungs used more as body temperature and/or activity level rises

Water Balance of Anurans

-Don’t drink water orally, osmosis through the skin is the primary water uptake mechanism
-Behavioral adjustments = avoids hot/dry
-Morphological adaptations 

Aestivation

Some amphibians and reptiles seek refuge (usually underground) and remain dormant during dry or excessively hot periods

Cocoon

During dry periods, some anurans and sirens aestivate underground and form an impermeable cocoon from multiple sloughed layers of stratum corneum, impermeable sac open only at the nares

Amphibian Skin has two types of glands

-Mucus glands
-Granular glands

Mucus glands

Secrete mucus (water and mucopolysaccharides) to moisten and lubricate skin
-Moisture keeps skin from drying and being damaged, faciliates trans-cutaneous exchange including respiration, also prone to evaporation

Granular glands

Secretes noxious and/or toxic substances to deter predators
-Some highly toxic species exhibit aposematic coloration to warn would be predators
-Even non-toxic ones are foul tasting and/or cause nausea/vomiting

Ectotherms have much lower….

mass-specific energy needs

Endotherms expend how much of their energy intake just to maintain high body temperature?

90%

Ecotherms are able to… much more of the energy they consume

convert to biomass

Endotherm’s mass specific energy needs _ with smaller body size; higher surface area/volume leads to rapid heat loss

increase; so an elephant needs to consume/conserve more energy than a mouse to preserve its temperature

Implications of Ectothermy

-Smaller size allows for occpuation niches that endotherms can’t fill
-Greater efficiency allows for survival and reproduction in habitats where energy is in short supply.
-Better to tolerate harsh and less predictable envirionments
-Can limit daily activity or aestivate during harsh seasons

Energy exchange and thermoregulation

Thermal environment on land varies considerably, over short spatial and temporal scales, due to low specific heat and heat conductivity of air. 

Infrared radiation

Gain or loss; objects and animals radiate IWavelengths corresponding to their temperature

Convection 

Gain or loss; heat transfer by motion of air, from local heating or forced convection (wind)

Behavioral Thermoregulatory Mechanisms

-Movement (shuttling) between warmer/cooler microhabitats, such as sun to shade.
-Changing orientation to sun, posture, skin color to increase or decrease solar heating
-Changing posture to increase or decrease surface area of body or contact with substrate
-Limiting time of activity, choosing appropriate refugia while inactive.

Physiological Thermoregulatory Mechanism

-Constrict or dilate blood vessels to aid warming or cooling via skin surface.
-Panting rapidly dissipates heat but loses water, usually only used to avoid overheating

Uric acid

Excretion. Semi-solid. Minimizes water loss from waste excretion

Salt Glands

-Excrete salt ions with less water loss than urine
-Nasal, lingual, or lacrimal glands
-Marine lepidosaurs, turtles, crocodilians, and birds

Keratinized epidermis

limits evaporative loss