Amphibian Life History

1. Amphibian Life History

2. Amphibian Life History • What is an amphibian? • Amphibian evolution • Ecological importance • Feeding behavior • Vocalizations

3. What is an Amphibian? • From the Greek - Amphibios - leads two lives • Ectothermic vertebrates with aquatic, gilled larval stage and terrestrial adult stage. All possess glandular skin and lack nails or claws. Kingdom - Animalia Phylum - Chordata Subphylum - Vertebrata Class - Amphibia Order Caudata – Salamanders 390 spp Order Anura – Frogs and Toads 4000 spp Order Apoda – Caecilians 163 spp

7. Evolution • Evolved from Lobe-finned fishes common in Devonian Period - 400 mya • During Devonian, sea levels rise and fall repeatedly; coastal area swamps flood and dry many times. • Characteristics • Lungs • Some possessed true internal nares • Fins supported by bony elements

8. Geological Time

10. Evolution • Amphibians diverse by close of Devonian – 345 mya • Key evolutionary traits/adaptations • Most return to water to breed – aquatic larvae have gills • Moist skin aids in respiration • Improved circulatory system • Toxic skin glands offer protection • Sensory regions of brain processing vision,hearing,balance expanded compared to fishes • Locomotion - salamanders less efficient; anurans capable of hopping, jumping, become most successful group

11. Ecological Importance • In many moist, terrestrial habitats, amphibians may be the most important links in the food chain • Amphibians may exceed in numbers and biomass each of other vertebrates • Annual production of new tissue exceeds birds, mammals • Salamanders in NE had densities of 7-10/sq m; 2X biomass of breeding birds, same as small mammals • In Michigan marsh, amphibians most important 2nd and 3rd level consumers in food chain • In Texas, standing crop of Lesser Siren greater than that of total of 7 species of fish in same habitat

12. Ecological Importance • Amphibians are the primary vertebrate predators on small invertebrates in many freshwater and moist terrestrial environments • A small pond population of cricket frogs (Acris crepitans) estimated to consume ~ 4.8 million arthropods/yr • Amphibians are major conveyor belt of energy transfer from arthropods to other vertebrates • Amphibians have low metabolic rates, slow maturation and are relatively long-lived, thus serving as energy reservoir for ecosystems

13. Food Habits • Most adults are carnivorous, feeding on a variety of live animals – anything they can swallow! • Larvae mostly herbivorous – algae, plant material, debris • Tongues of many species can be extended well beyond opening of mouth • Sticky pad impacts on, adheres to and pulls in prey • Action is so fast—10 msec—as to be nearly undetectable by human eye

14. Vocalizations • Male anurans use ADVERTISEMENT CALLS to attract females • Vocal sac(s) modify, amplify sound as air forced from lungs over larynx • Call intensity varies with species – audible from several yards to over a mile. SPL: 90-120 dB • Energetically expensive - O2 consumption up 4-7X • Intensity may be related to spacing of local males

15. Anuran Distended Vocal Sacs Pseudacris Bufo Rana

16. Vocalizations • Chorus Formation • Advertisement calls first attract other males, then females • Calls often alternated when males close to each other • Tendency to call in groups of 2-4 with “choir master” always initiating, each with noticeably different quality • Dominant males call louder, longer, lower pitched - may reflect age, size, vigor - all factors in female selection

17. Vocalizations • Warning Calls/Release Calls • Vocalizations cease or are modified under threat of predation • Fright calls often given before jumping into water • Release, distress calls given if anuran grabbed by wrong sex or if captured by predator

18. Amplexus