Heying lect 4a-FTTS Fall 2004 (H5)1Introduction to Amphibians1. Amphibians: what are they, and what do they want with us?2. Introduction to three major groups of amphibians3. Riparian Forests: amphibian habitat, nutrient cycling, and effects of management1. Amphibians: some basic facts• Amphibian literally means “both lives” (amphi: both or all; bios: life)• First colonized the land in the mid-Devonian, 350 mya.• Transitional between fully aquatic lobe-finned fishes (Sarcopterygians) and terrestrialamniotes. As such, many (but not all) amphibians experience metamorphosis.• Adaptive radiations in many groups of amphibians have resulted in more life historystrategies than among any other group of tetrapods.Amphibians have it hard• Susceptible to pollutants and other drastic changes in both aquatic and terrestrialecosystems• Taste great (they are “the major conveyor belt that provides for transfer of invertebrateenergy sources to predatory animals higher up the food chain”)• In 1758, Linneaus had this to say about amphibians: “These foul and loathsome animalsare abhorrent because of their cold body, pale color, cartilaginous skeleton, filthy skin,fierce aspect, calculating eye, offensive smell, harsh voice, squalid habitation, and terriblevenom; and so their Creator has not exerted his powers to make many of them.”(Actually, There are upwards of 4,500 species of amphibians (more than mammals).Some diagnostic characters of “modern amphibians”• Glandular skin that contains both mucous and poison glands (but no epidermalstructures--no scales, feathers, or fur)• Three-chambered heart (two atria, one ventricle)• Cutaneous respiration (most species also have lungs, but the three-chambered heart doesnot provide enough pressure to fully inflate the lungs on its own, so amphibian lungs arenot as efficient as ours)• Complex inner ear anatomy, including a membrane that allows amphibians to hearacoustic signals of less than 1,000 Hz (very low “bass” sounds).• Highly variable chromosome number, genome size, and ploidy.2a. Major groups: caecilians (Gymnophiona)• Limbless, burrowing, tropical amphibians that nobody ever sees• Circumtropical (except Madagascar)• Adults are almost entirely subterranean (and therefore mostly blind)• Internal fertilization• Some very interesting parental care and reproductive modes exhibited, includingviviparity, and egg and larval attendance2b. The salamanders (Caudata)• Caudata: salamanders (and newts, which are just a small group of often aquaticsalamanders within the family Salamandridae)• The only major group of amphibians with both tails and limbs• Most diverse in SE U.S.—adaptive radiation spread them to most of North America andsome of Central America, plus a few in Europe and east Asia.Heying lect 4a-FTTS Fall 2004 (H5)2Salamander life histories• Most common life history: aquatic larvae, terrestrial adults, internal fertilization viaspermataphore, eggs laid in water. (True amphibious lifestyle)• Alternate life histories: paedomorphosis. Reproductive adults retain larval characteristics,typically those associated with an aquatic lifestyle (these individuals live their entire livesin water). Adaptations include retention of external gills and dorsal fins. Species mayhave obligate or facultative paedomorphosis.• Notophthalmus viridescens (“Eastern Newt”; eastern US). 3 part life history: Aquatic larvaemetamorphose into terrestrial, non-reproductive efts, which stay on land for severalyears before metamorphosing again into aquatic, reproductive adults.How do salamanders breathe? How does anything breathe? Or: What is respiration?Now that we know what respiration is: how do salamanders do it? Put another way: What arethe respiratory organs of salamanders?Weird salamanders: One family is lungless: Plethodontidae, including Ensatina and Plethodon inW. Washington. What ramifications does lunglessness have?Being lungless, plethodontids have evolved long, thin bodies, yielding high surface area:volumeratios for increased efficiency of cutaneous respiration. What is the downside of this bodyshape?Rhyacotriton olympicus (Olympic torrent salamander)• Diagnostic features: Up to 10cm total length. Large eyes. Bright yellow underbelly. Maleshave squared lobes of their cloacas. Lungs are reduced to reduce buoyancy in fast-moving streams.• Habitat: In and around clear, headwater streams, especially where water is cool and clear,and substrate is gravelly.• Defense mechanism: unken reflex (displaying bright underbelly)• Conservation status: At risk from siltation and increasing water temp—results of logging.Dicamptodon copei (Cope’s giant salamander)• Diagnostic features: Up to 20 cm total length. Most adults retain external gills.• Habitat: Similar though not identical to that for torrent ‘manders.• Development: Most individuals are paedomorphic: they retain larval characters (e.g. gills,tail fin, toe-webbing) as reproductive adults. Rare individuals may undergometamorphosis, however, so paedomorphosis is facultative, not obligate.• Importance: Can comprise over 95 percent of the predator biomass in small streams3c. Diagnostic features of Anura: What makes a frog a frog?• Anurans are defined as the tailless amphibians (there is one apparent, although notactual, exception). Postsacral vertebrae are fused into a single element: the coccyx, orHeying lect 4a-FTTS Fall 2004 (H5)3“tailbone”.• Have elongated hind limbs (relative to their forelimbs) that are fused (ours our unfused),an adaptation for jumping.• Most frogs have no ribs.• More geographically widespread than Gymnophiona or Caudata, but still moreprevalent in the tropics than elsewhere.• Adaptations for jumping: Long hind limb bones; long feet bones; elongate pelvic girdle;shortened, but strong, spine.Also:• Most are nocturnal.• Almost all anurans have external fertilization.• Almost all are oviparous.• Most anurans mate in a posture called amplexus, in which the male grasps the female inthe armpits or at the waist. In some species, amplexus can last for months.• Length of breeding season is often limited by climate, or seasonal availability of breedingsites (such as ephemeral pools). Temporal patterns of reproduction can be roughlydivided into two types: explosive breeding and prolonged breeding. What generalities arelikely to be true regarding which frogs