Reproduction in Amphibians

Flashcards about amphibian reproduction.

Amphibian Egg Characteristics

Amphibian eggs are non-cleidoic and lack a shell, requiring them to be laid in moist environments.

Modified Amphibian Reproduction: Loss of Larval Stage

Some amphibians, like the Whistling frog (Eleutherodactylus martinicensis), exhibit a loss of the larval stage.

Modified Amphibian Reproduction: Neoteny/Paedomorphosis

Some amphibians, like the Axolotl (Ambystoma mexicanum), exhibit loss of the adult stage, also known as neoteny or paedomorphosis, and is almost exclusively seen in salamanders.

Modified Amphibian Reproduction: Non-Reproductive Terrestrial Stage

Some amphibians, like the red-spotted newt (Notophthalmus viridescens), have an eft (terrestrial) stage that may or may not occur.

Amphibian Egg Placement: Aquatic Eggs

Amphibians lay eggs in various aquatic environments, including freshwater (e.g., leopard frog Rana sphenocephala), brackish water (e.g., green toad Bufo viridis), and flowing water (e.g., tailed frog Ascaphus).

Amphibian Egg Placement: Eggs on Land

Amphibians lay eggs in terrestrial environments under stones or cover, with tadpole nutrition provided by yolk or direct development.

Foam Nests

Some amphibians create foam nests over water (e.g., Asian brown tree frog Polypedates leucomystax) or in burrows (e.g., Leptodactylus) for their eggs.

Reproductive Mode Plasticity

Some frogs, like the hourglass treefrog (Dendropsophus ebraccatus), can lay eggs both on land and in water.

Variable Hatch Times

Red-eyed tree frog (Agalychnis callidryas) larvae sense vibrations from egg predators and hatch prematurely.

Eggs in Oviducts: Ovoviviparous

Nutrition provided by yolk (e.g. some salamanders, a few anurans).

Eggs in Oviducts: Viviparous

Nutrition provided by oviducal secretions (e.g., African toad Nectophrynoides spp.).

Viviparity in Amphibians

Viviparity has evolved at least 4 times in caecilians, is rare in anurans, and rare in salamanders (Salamandridae only).

Temperate Breeding Stimulus

Involves seasonal hypertrophy of gonads, rise in temperature in spring stimulates anterior pituitary gland to release hormone that stimulates gonads.

Tropical Seasonal/Dry Breeding Stimulus

The occurrence of rain annually or erratically.

Tropical Moist Breeding Stimulus

Breeding may be continuous, with peak at wettest time of year.

Caecilian Mate Location

Use chemical cues (solitary, fossorial, blind and deaf but with good sense of smell).

Newt Mate Location

Use olfactory cues (e.g., smell of decomposing pond veg).

Anuran Mate Location

Olfactory, auditory (calling), and sometimes visual cues (e.g., foot-flagging).

Newt Courtship

Visual, tactile, and chemical cues. Amplexus in a few only.

Frog Courtship

Auditory (exclusive to anurans). Amplexus important, during which tactile, olfactory, auditory cues operate.

Amplexus

A mating behavior in anurans during which tactile, olfactory, auditory cues operate

Caecilian Fertilization

Internal fertilization with aid of phallodeum. Few yolky eggs. Aquatic eggs and larvae, terrestrial eggs and direct dev., or retain eggs in oviducts.

Newt Fertilization

Internal fertilization with spermatophore in most. Some primitive groups have external fertilization. Eggs laid singly or in small groups. Larvae similar to adults in morphology and diet.

Frog Fertilization

Vast majority with external fertilisation. A few exceptions are ovoviviparous. Full range of developmental options. Where present, larvae very different to adults. Undergo complete re-organisation of body plan on metamorphosis.

Parental Care

Any behaviour by a parent towards its offspring that increases the offspring’s chances of survival.

Egg Attendance

Usually by female, facultative, includes defence, cleaning, moistening.

Egg & Tadpole Carrying

Both sexes but usually male, facultative and obligate. Associated with increased terrestriality, smaller clutches, and less frequent reproduction.

Extreme Parental Care

Examples include the Rheobatrachus silus (Southern Gastric Brooding Frog) and Rhinoderma spp. (Darwin’s Frogs).

Extreme Parental Care: Caecilians

e.g., Boulengerula taitana: Oviparous, direct development. Female guards young. Feed on skin of female.