Amphibians: “double lifers”PART I

VERTEBRATE ZOOLOGY (VZ Lecture12 – Fall 2012 Althoff - reference PJH Chapter 10)

Recall that….

• Only remaining ____________ tetrapods were the lineages still present today:

caeciliansfrogs

salamandersSIGHTLESS HEAD SMOOTH SKIN

Caecilia nigncans

spri

ng

pee

pe

rtig

er

sala

ma

nde

r

Evolutionary Relationship of Amphibiansto other TETRAPODS

SYNAPSIDA(mammals)

SAUROPSIDS(turtles, lizards, snakes,

crocodiles, & birds)

TETRAPODS

AMNIOTES

Classification of Amphibia

CLASS Amphibia

SUBCLASS Labryinthodonotia*

Leposondyl*

Lissamphibia

ORDER Urodela

Anura

Gymnophiona

* = extinct

(salamanders)

(frogs)

(caecilians)

Shared Derived Characters(summarized from Table 10.1 pg221 PJH)

_________: structure and importance to gas exchange.

A) all have mucus glands that keep the skin moistB) substantial part of an amphibian’s CO2 and O2 exchange thru skinC) all have poison (granular) glands in skin (some more potent than others)

_______________________: special sensoryarea in wall of sacculus of the inner ear

A) area sensitive to frequencies <1000 Hz (cycles per second)B) Papilla basilaris (2nd area)

sensitive to frequencies >1000 Hz

Shared Derived Characters(summarized from Table 10.1 pg221 PJH)

__________________________ COMPLEX: most have 2 bones involved in

transmitting sound. Columella derived from hyoid arch which is found in salamanders, caecilians, and most frogs. Operculum associated with fenestra ovalis of the inner ear

_____________: Salamanders and frogs havedistinctive green rods (retinal cells). Caecilians appear to lack them but their eyes are greatly reduced anyway (may have had them at one time)

Shared Derived Characters(summarized from Table 10.1 pg221 PJH)

__________________ TEETH: Most modern species have teeth in which crown and

base (pedicel) are composed of dentine, separated by a narrow layer of uncalcified dentine or fibrous connective tissue.

STRUCTURE OF THE _________________ MUSCLE: this muscle is a thin sheet in the floor

of the orbit (eye socket) that is innervated by the 5th cranial nerve. It causes the eyes to

bulge outwardenlarging the buccal cavity.All salamanders and anurans…modified

form in caecilians

Anterior

outer margin of jaw

crown

pedicel

PEDICELLATE TEETH

Teeth tend to “______” back into the mouth where the crown and pedicel are separated by the fibrous tissue

Other generalities concerning amphibian ….• All are __________________. Mouth sizes vary

in sympatric species (comparable to what you might recall from Darwin finches example of differentiation in beak sizes/morphology).

• As noted, permeable skin, a shared characteristicis a key feature. Even though it may seem “primitive” (starting _____ MYA), it clearly

still “works” in some of today’s ecosystems

• For other categories, much ________—especially in the areas of a) reproduction

b) locomotionc) defense

• Ectotherms

• 3-chambered heart (2 atria, 1 ventricle)

Focus on SALAMANDERS• ORDER: _________ (may see “Caudata” in older

listings/references = “bearing a tail”)

• 10 families, ~515 species

• Most species found in northern hemisphere; some down to northern South America. Greatest diversity in North America-Central America

• Body form is elongate. Most have 4 functional limbs. Moves with lateral bending & leg movements

• Largest > 1m (Japanese & Chinese giant salamanders) In NA, largest is hellbender (<60 cm)

• _______________: common trait…larva becomes sexually mature without attaining adult body form

The mudpuppy is paedomorphic.

Also with respect to other salamander species, it retains its external gills as a reproductive adult

Congo Eels• 3 species in North America (lower Mississippi Valley

& coastal plains)

• Have well-developed lungs….atypical for this taxon

• Can survive in mud of dried ponds for up to 2 years…sort of like the LUNGFISH we’ve already studied (recall: estivation/aestivation)

• 3-toed

• 2-toed

• 1-toed

Salamanders con’t….

• Some species are blind (i.e. Texas blind salamander)

• Many are cave-dwellers

• Some are fully terrestrial (i.e., no aquatic larval stage ________________ salamanders

• Major family of fully terrestrial salamanders are the Plethodontidae (common: Plethondontids)

….example of no aquatic larval stage as young hatch from eggs as miniature

adults

Batrachoseps

“fully terrestrial”life cycle

Most salamander species have aquatic larvae that lose their external gills when they reach adulthood

(Mabee’s salamander Ambystoma mabeei)

Aqu

atic

larv

ae

Adu

lt

Closer Look….Feeding Specializationsof Plethodontids

• Being lungless “frees up” the ______________ _________ to do “something else.” In “lunged” salamanders, hyobranchial apparatus is essential part of respiratory system

In this case, plethodontids use it to help protrude the tongue a considerable distance from the mouth

• Bolitoglossine plethodontids known as the “dart tongues” (bola is Greek for “dart”, glossa is “tongue”)

Position of eyes differs for those capable of extended tongue protrusion. To “hit” prey, it takes accurate projection of the tongue. Eyes positioned ______________ (i.e., not to side of head) and __________ more help in accuracy.

Feeding Specializationsof Plethodontids…con’t

VS.

Social Behavior of Plethodontids:SCENTING & TERRITORIALITY

• Good sense of smell. Key feature is the external _________________ that extends from the external nare to around down to the mouth on each side

• Animal obtains fluid (moisture) on the groove that enters external nares nasal chamber over epithelial lining of ____________ organ

Fig. 10-4 p225 PJH

Remember this for ungulate/bison—Flehman behavior

during rut???

Many territorial species

• Good evidence males, at least, are very territorial. Mark territories with pheromones

• Neighboring males get used to each other—scent may elicit marking but not aggressive, direct confrontations. But transient males and females bring out strong responses

• Experiment by Jaeger et al. 1983 with red- backed salamanders resulted in some very interesting behavioral responses

Jaeger, R.G. et al. 1983. Foraging tactics of a terrestrial salamander: costs of territorial defense. Animal Behaviour 31:191-193.

Observations of red-backed salamanders in lab cages (by Jaeger and colleagues)

Male resident bites the male intruder…less aggressively if neighbor

Resident bites the intruder’s tail region…intruder’s autotomizes its tail to escape. Consequence: takes up to year to regrow tail and delays sexual maturity/activity

Resident bites intruder on snout injuring intruder’s nasolabial groove (NLG)

Fig.10-5 pg227 PJH

1

2

3

no scar NLG with scar

Additional observations…lab and field on red-backed salamanders

• Lab: those with bitten snouts captured average of 5.8 fruit flies in a 2-hour period vs. 18.6 flies for salamanders not bitten on snout

• Field: sample of 144 red-backed salamanders in Shenandoah National Forest revealed 11.8 % had been bitten on nasolabial grooves. Those so bitten weighed less, on average likely do to reduced foraging success.

• Advantage of recognizing neighboring? a) b) for attacks

R.G. Jaeger website

spotted salamander

R.G. Jaeger website

tiger salamander

R.G. Jaeger website

slimy salamander