Salamanders, Anurans and Cealians

1. Salamanders, Anurans and Cealians Chapter 10

2. Lissamphibia • Monophyletic • 3 lineages of Amphibians considered orders of this class • Varying body lengths

3. Lissamphibia • Salamanders/Urodela • Elongated animals, terrestrial, usually with four legs; Have tails as adults • Frogs (Anurans): Frogs, toads, tree frogs • Short bodies, no tails as adults; Large heads • Large hind legs (walking, jumping, climbing) • Caecilians(Gymniophiona) = no legs • are an order of legless amphibian. • most have no tail, also called rubber eels • Burrowing animals

4. General Characteristics • Skin: • Smooth; thin;permeable; no scales; moist; & modified for gas exchange • All forms are carnivorous as adults • Will eat whatever comes within range, that is not to long • Non-amniotes • No extra embryonic membranes • Eggs lack amnion, chorion, and allantois • Lungs present in all terrestrial forms except Plenthodontid salamanders • Lungs are simple with relatively small surface area

5. General Characteristics • Generally two –phase life history • Aquatic tadpole • Terrestrial adult • Double circulatory system • Systemic one to body generally and • Pulmocutaneous one to lungs and skin

6. Salamanders: Urodela • Order =Urodela • 10 families & ~ 515 spp • See figure 10-1 • Elongate body, 4 limbs of equal size • Walking trot gain coupled with anquilliform motion of body while moving legs forward • Mostly in N America & Central America • Tennessee has largest no of spp

7. Salamanders • Hind legs only slightly larger than front legs • Many are paedomorphic • Larva attains sexual maturity before attaining adult body form • Due to progenesis • Rapid devpt of reproductive organs relative to somatic tissue • (Neoteny = retention of larval embryonic traits past reproductive maturity)

8. Salamanders • Paedomorphs retain such larval characteristics as external gills, lateral line system, no eyelids & larval tooth patterns • Several salamanders adapted to life in caves due to their constant Temperature & moisture

9. Salamanders • Largest living Salamanders include • Japanese & Chinese giant Salamanders - > 1m long • Mudpuppies (necturus) • Paedomorphic spp that retain external gills • Occurs in lakes and streams in eastern North America • All salamanders lack ribs • Use buccal pumping to get air into lungs • Uses a lot of muscles attached to the tongue

10. Plenthodontid Salamanders • Well known, interesting specializations • Lung less, terrestrial, aquatic • Respiration wholly thru skin • Protrusible tongue used to capture even moving prey • Seen a grp called the Bolitoglossines • Can hit moving targets by projecting their tongues the length of their trunk..

11. Plenthodontid Salamanders • Presence of Nasolabial Groove • From external nares to the upper lip • (figure 10.4) • Liquids from substrates drawn into the NG which then passes it into the nose and then the vomeronasal (Jacobsen) organ which is used for chemoreception • Thus NG & vomeronasal organ used for olfaction and chemoreception

12. Plenthodontid Salamanders • Produce unique pheromones • Used for marking territories for feeding and mating • Neighbors are able to detect each other’s pheromones and use the smell to fight off intruders

13. Plenthodontid Salamanders • Reproduction • Mostly internal by use of a spermatophore (a pkt of sperms) • Males deposit a spermatophore on substrate • No intromittent organ, thus no direct deposit of sperm into female • See fig. 10-14 • Spermatophores vary in shape

14. Plenthodontid Salamanders • Females may • Pick it up with cloaca • Deposit egg sacs on spermatophore • Some males deposit spermatophore on top of the female & use their feet to insert the spermatophore into her cloaca • Males clasp females during courtship to deposit pheromones onto the skin of the females. Female must give positive feedback to the male for him to deposit the spermatophore • Read page 236

15. Plenthodontid Salamanders • Eggs hatch into gilled larval forms • Will undergo metamorphosis into an adult • Paedomorphosis occurs in which the larvae becomes sexually mature without metamorphosis into adult form • Viviparity • Only a few spp are viviparous • Give birth to live young • Eggs maybe retained until hatching and get all their nutrients from yolk • Young born as larvae

16. Plenthodontid Salamanders • Terrestrial spp lay masses of eggs under logs or in holes of soft dirt • Many spp remain near eggs to guard them • Some go to the aquatic life in larval forms • Others bypass larval forms & hatch as miniature adults

17. ANURANS: Frogs & Toads • 29 families • > 4800 spp • In all continents but Antarctica • Specialized for jumping • hind limbs greatly enlarged for swimming or jumping • Tibia and fibula are fused into one solid bone

18. ANURANS: Frogs & Toads • Pelvic girdle enlarged and anchored to vertebral column • Ilium is elongate • Caudal vertebra are fused into a solid rod the urostyle • Spinal column is short and inflexible with 9 or fewer (usually 5) pre sacral vertebrae • Lacks a visible neck; appear neckless

19. ANURANS: Frogs & Toads • Ribs are gradually reduced, usually fused to the vertebral column • Form distinctive transverse processes • See figure 10-7 • Pectoral girdle and forelimbs absorb the impact of landing • Eyes are large, placed forward on the head giving binocular vision

20. ANURANS: Frogs & Toads • Largest frog is the West African : Gigantorana goliath: • > 30cm body length • Weighs 7.5 lbs, eats rats, or ducks • Largest American frog is the bull frog (Rana catesbiana): ~ 20 cm body length

21. ANURANS: Frogs & Toads • Body forms reflect specializations for different habitats • Frogs have • long legs • Move by jumping • Webbed feet as seen in semi aquatic frogs • Toads • Stout bodied, compact • Make short hops • Thicker skin; shorter hind limbs, little to no webbing between toes.

22. ANURANS: Frogs & Toads • Horned frogs • Extremely large heads and mouths • Feed on small vertebrates including birds, frogs and mammals • Arboreal Frogs • Large heads & eyes • Slim waists • Long legs, walk, climb & leap with all legs • Many spp have enlarged toe discs for clinging to vertical surfaces. Produce a viscous substance for sticking to wet surfaces

23. ANURANS: Frogs & Toads • These frogs are able to stick to vertical & even to the underside of leaves • Adhesion and detachment alternate as the frog walks across a leaf • Because of the mechanism by which the toes can cling to the surface, a tree frog must orient with its head facing up for its toes to remain pointed upwards & clinging to surface • Descending a vertical surface, move backward inorder to keep the toes facing upward

24. Frogs & Toads:Mating systems • Explosive Breeding • Short breeding season, even a few days • Common in toads & some anurans • Males and females gather together in large numbers

25. Frogs & Toads:Mating systems • Prolonged Breeding • Long breeding season • Maybe several months long • Males are first to arrive at breeding sites • Green frogs establish territories, spend months defending territories • Females join later & leave after breeding • Males compete for females thru vocalizations

26. Frogs & Toads: Vocalizations • Frogs & toads very vocal • Calls are species specific • Serve as a premating,isolating mechanism for many species • Mostly calls are used for mating & territorial defense • Called Advertisement calls • Affected by body size, spp • In most spp, only males call, spp respond only to their own unique call types • Response is hormone triggered

27. Frogs and Toads:Cost of Calls • Require energy • More energy from one if many are calling at each time, trying to outcompete each other • Increase rate of predation

28. Frogs & Toads: Reproduction • Reproduction is external in most spp • Males & females engage in Amplexus • Male on back of female, grasps female with his forelegs • Axillary amplexus: Clasping on pectoral region • Inguinal amplexus: clasping on pelvic region • Amplexus maintained for several hours/days before female lay eggs

29. Frogs & Toads: Reproduction • Anurans exhibit a variety of larval dvpt • Many lay eggs in water • Some exceptions • Some tropical forms deposit eggs on leaves overhanging water so that the as eggs hatch, the larva drops into the water • Some use pools of water in bromeliads • Epiphytic plants growing on trees in tropical rain forest

30. Frogs & Toads: Reproduction • Some encase in a frothy protective foam mass consisting of air, sperms, eggs, cloacal secretions, and some water • Other anurans posses dorsal pouches on their backs in which eggs are incubated or eggs maybe attached in some other manner to the back of the parent where they remain until hatching • See figure 10-21

31. Frogs & Toads: Parental Care • Direct development • No larval or tadpole stage • Eggs deposited in moist sites are guarded by male parent • Males Chilean Rhinoderma darwini pick up eggs & incubate them in his vocal pouch until young complete metamorphosis and emerge as miniature adults • Australian Rheabatrachus: Gastric brooder. Carries eggs in stomach and tadpoles dvpt into miniature adults in stomach.. The mothers then eject baby frogs out of their mouths.

32. Frogs & Toads: Parental Care • Parental care ranges from several days to as long as four months • May be in the form of transport of eggs and or larva • Tadpoles maybe carried on back of adults for a week • Some tadpoles hatch on land, attach to adult & transported into water • Some tadpoles follow mother in water • African bull frog males guard both eggs and tadpoles

33. Ecology of tadpoles • Aquatic • Gill bearing larva hatched (tadpoles) in aquatic environments • Morphological variations related to feeding habits and methods • Tadpole stage maybe 7-10 days in spadefoof frogs or as long as 2-3 yrs in bull frogs • Generally filter feeders • Species that graze/eat from surfaces have small keratinized beaks for scrapping algae • Only a few are predators and these have larger horny beaks for attacking prey (other tadpoles)

34. Metamorphosis (See table 10.15) • Complete reorganization of the body plan: tadpole to adult • Includes • Growth of legs, loss of tail, loss of gills, development of lungs, and reorganization of the skull as modes of feeding • Process controlled by thyroxin which in turn is controlled by thyroid stimulating hormone (from pituitary gland)

35. Metamorphosis: 3 stages • Pre-metamorphosis • Growth phase, tadpoles increase in size, no change in form • Prometamorphosis • Hind legs appear • Growth continues • Metamorphic climax: see • Fore legs appear, tail disappears • Very rapid-only a few days

36. Metamorphosis: 3 stages • Metamorphic Climax • Animals most vulnerable due to predation by snakes • In water snakes capture • 30% of tadpoles • 67% of transforming ones • On land snakes capture • 45% of transformed frogs • 90% of transforming ones

37. Skin of all amphibians • Glandular skin • No external scales • Highly permeable to gases & water • Mucus glands distribute all over the body-keep skin moist & permeable • Dry skin reduces oxygen uptake • Both water and gas pass readily thru skin • Facilitates cutaneous respiration • Skin also retains urea and active take Na ions

38. Blood Circulatory system • Left and right atrium divided by a septum • Ventricle undivided but has a complex structure that keeps blood separated • No mixing of poor with rich oxygen blood • Spiral valve is a structure in the ventricles used to separate blood

39. Blood Flow • O2 rich blood from pulmonary veins • Left atrium and then left side of common ventricle • Ventricle contracts, pushes blood into the left side of the ventral portion of spirally divided conus • Blood is thus selectively distributed to the tissues of the head

40. Blood Flow • O2 poor blood from body enters the right atrium and then the dorsal half of the spiral valve conus • Goes to the pulmocutaneous arch, then to • lungs for oxygen on land or to • Skin for oxygenation when frog is in water • Thus frogs can switch among gas exchange modes (lungs vs. skin) depending on whether animal is in water or on land.