Urodele & Gymnophiona

I. General Amphibian CharacteristicsII. Salamanders

A. CharacteristicsB. Ecological Role of Salamanders

• Diverse Life Histories

C. CourtshipD. Variation among larval salamandersE. Defensive behavior

III. Gymnophiona – Caecilians– Characteristics

I. General Amphibian characteristics:

1) Ectotherms

2) Four limbs

3) Two occipital condyles

II. Salamanders - Urodela (Caudata)

1) 4 limbed animals

2) Trunk superficially segmented

3) Size varies from 30mm to 2m

4) rather have an opercular apparatus

A. Characteristicshttp://video.google.com/videoplay?docid=2058128235852512799&q=salamander&hl=en

the Salamanders

~515 species, 24 Genera, 9 Families (8.5% of all amphibians)-date back to middle Jurassic

Chinese giant salamander (Andrias davidianus)

Del Norte Salamander (Plethodon elongatus)

Hemidactylium scutatum

B. Ecological Role of Salamanders:

Play role in organizing communities– Mole salamander larvae influence abundance

and diversity of invertebrates in vernal ponds– Giant salamanders reach high densities &

biomass in small streams lacking fish

Diverse Life Histories:

1. Many species have biphasic life cycle

3. Paedomorphesis – Some deviate and retain the larval form,

particularly where the terrestrial habitat is unfavorable for survival

Larval form

Adult Form (Ambystoma)

Biphasic lifestyle

Ambistoma mexicanum (Axolotl)Paedomorphic!

C. Courtship• Well-defined breeding season (usually triggered by

seasonal changes)

Courtship/mating behavior:• Male spermatophore & internal fertilization

• spermatophores vary in size, shape & composition – most consist of a gelatinous base that tapers toward the top & supports an apical sperm mass

• male deposits one or more in front of a female, the female then moves forward, aligns her vent above the spermatophore and removes all or a portion of the sperm mass from the top

• External fertilization• Pheromones –

http://www.clayoquotbiosphere.org/images/CSRimg.jpg

D. Variation among larval salamanders:

• Morphological adaptations that correlate with their environment

1) “pond-type” –

2) “stream-type” –

http://fwie.fw.vt.edu/VHS/Eastern%20Tiger%20Salamander%20(Ambystoma%20%20tigrinum%20tigrinum)larvae002.jpg

Larval Salamanders (cont.)

• Predators of aquatic invertebrates, some cannibalistic or feed on heterospecific larvae

a) Vernal ponds =

b) Streams =

Pseudotriton ruber

Ambystoma maculatum

On rainy nights, Marbled salamanders (Ambystoma opacum) emerge from their hiding places beneath leaves and logs, traveling to low-lying areas that will become pools when they are soaked with spring rains, to lay their eggs; in the spring, aquatic larva hatch from the eggs and develop into salamanders.

Salamander Migration:

Terrestrial Salamanders

• Active at night on ground surface

• Usually restrict activity to moist microhabitats,

• Dry conditions =

• Territorial =

Plethodon cinereus – Red backed Salamander

Adults mark territories

Defensive posture the cave salamander (Eurycea lucifuga) assumes when attacked by a predator such as a bird. Note that the salamander closes its eyes and raises and wiggles its tail above its lower head.

E. Defensive Behavior:1) Posturing2) Toxins3) Aposmatic coloration

http://www.livingunderworld.org/amphibianArticles/article0011.shtml

III. Gymnophiona - Caecilians

Known from the early Jurassic – Earliest fossil = Eocacilia (had limbs)

Gymnophiona: 6 Families, 160 species

Caeciliaidae.--is the largest family, with about 22 genera in Mexico, Central and South America, subsaharan Africa, India, SE Asia and the Seychelles. Many are small, but the largest reach 1.5 m. Some are viviparous; others have direct development

Typhlonectidae.-- are truly aquatic caecilians, with four genera in South America, some to 75 cm. The posterior body is laterally compressed, and there is no tail. They are also viviparous.

Characteristics of Caecilians

• Occur worldwide in the tropics & look like earthworms…

• Annulated bodies = • Tail is very short or absent • Teeth are curved and relatively long

compared to other amphibians • Chemosensory structure (tentacle)

Characteristics cont.

• Skull is very solid, with extensive suturing of cranial elements,

• Operculum absent (no ear openings)• Dermal scales often present• All caecilians have internal fertilization• Males – • Offspring may develop internally or externally

Cloaca