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Salamanders, Anurans and Cealians Chapter 10. Lissamphibia Monophyletic 3 lineages of Amphibians considered orders of this class Varying body lengths.

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Presentation on theme: "Salamanders, Anurans and Cealians Chapter 10. Lissamphibia Monophyletic 3 lineages of Amphibians considered orders of this class Varying body lengths."— Presentation transcript:

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 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.


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