Amphibian Physiology

Mucous gland location

Embedded in stratum spongiosum with ducts to epidermis.

Functions of mucous glands

Moisture retention, respiration, thermoregulation, antifungal defense, predator escape.

Slimy Salamander defense

Extremely sticky mucus gums predator jaws.

Granular glands

Produce defensive secretions; hormonally or nervously activated.

Granular gland locations

Head, tail, dorsolateral folds, warts, parotoid glands.

Granular secretions

Colorless to milky; mixtures of peptides and alkaloids.

Amphibian toxin diversity

About 200 known toxic substances.

Highly toxic families

Salamandridae, Dendrobatidae, Bufonidae.

Tarichatoxin

Newt toxin nearly identical to tetrodotoxin.

Tetrodotoxin effect

Causes paralysis by blocking sodium channels.

Human risk from newts

Toxin must enter bloodstream to be dangerous.

Batrachotoxins

General term for frog skin poisons.

Dendrobatid toxin source

Derived from diet, especially insects.

Captive dart frogs

Lose toxicity when diet changes.

Phyllobates terribilis

Extremely toxic poison dart frog.

Batrachotoxin mechanism

Prevents sodium channel closure causing paralysis.

Medical interest in toxins

Epidobatidine studied as painkiller.

Bufotoxins

Cardiotoxic steroids produced by toads.

Toad egg toxicity

Eggs and tadpoles are also toxic.

Sonoran Desert Toad

Produces hallucinogenic secretions.

Cane Toad invasive impacts

Toxic to predators and domestic animals.

Toad specialists

Hog-nosed snakes feed on toads.

Garter snake resistance

Immune to toad and newt toxins.

Coevolutionary arms race

Newts and garter snakes evolve toxicity and resistance.

Aposematic coloration

Bright colors warning predators of toxicity.

Unken reflex

Defensive posture exposing bright ventral colors.

Bombina defense

Bright belly display with toxin secretion.

Red eft toxicity

More toxic juvenile stage of eastern newt.

Tail-lashing defense

Salamanders release toxins while lashing tail.

Mimicry definition

One species resembles another for defense.

Batesian mimicry

Harmless species mimics toxic species.

Müllerian mimicry

Both model and mimic are toxic.

Plethodon cinereus mimicry

May mimic red eft coloration.

Pseudotriton ruber toxicity

Intermediate toxicity and strong mimicry.

Predator-directed displays

Postures exposing poison glands or eye spots.

Thanatosis

Playing dead to deter predators.

Inflation defense

Toads inflate body to avoid being swallowed.

Autotomy

Tail loss to escape predators.

Cost of tail loss

Reduced speed and energy reserves.

Tadpole tail coloration

Directs predator attacks away from body.

Distress calls

Frogs scream when seized by predators.

Predator-specific responses

Behavior varies depending on predator type.

Snake tongue-flick response

Run when tongue-flicked; freeze when touched.

Adaptive freezing

Reduces detection by motion-oriented predators.