Amphibians: “double lifers” PART I

1. VERTEBRATE ZOOLOGY (VZ Lecture12 – Fall 2012 Althoff - reference PJH Chapter 10) Amphibians: “double lifers”PART I

2. Recall that…. • Only remaining ____________ tetrapods were the lineages still present today: caeciliansfrogs salamanders SIGHTLESS HEAD SMOOTH SKIN tiger salamander Caecilia nigncans spring peeper

3. Evolutionary Relationship of Amphibians to other TETRAPODS SAUROPSIDS (turtles, lizards, snakes, crocodiles, & birds) SYNAPSIDA (mammals) AMNIOTES TETRAPODS

4. Classification of Amphibia CLASS Amphibia SUBCLASS Labryinthodonotia* Leposondyl* Lissamphibia Urodela (salamanders) ORDER (frogs) Anura Gymnophiona (caecilians) * = extinct

5. 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 moist B) substantial part of an amphibian’s CO2 and O2 exchange thru skin C) all have poison (granular) glands in skin (some more potent than others) • _______________________: special sensory area 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

6. 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 have distinctive green rods (retinal cells). Caecilians appear to lack them but their eyes are greatly reduced anyway (may have had them at one time)

7. 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 outwardenlarging the buccal cavity. All salamanders and anurans…modified form in caecilians

8. PEDICELLATE TEETH Anterior  crown outer margin of jaw pedicel Teeth tend to “______” back into the mouth where the crown and pedicel are separated by the fibrous tissue

9. 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 characteristic is 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) locomotion c) defense • Ectotherms • 3-chambered heart (2 atria, 1 ventricle)

10. 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

11. The mudpuppy is paedomorphic. Also with respect to other salamander species, it retains its external gills as a reproductive adult

12. 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

13. 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

14. “fully terrestrial” life cycle Batrachoseps

15. Most salamander species have aquatic larvae that lose their external gills when they reach adulthood (Mabee’s salamander Ambystoma mabeei) Aquatic larvae Adult

16. 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

17. Feeding Specializationsof Plethodontids…con’t • 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. VS.

18. 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???

19. 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.

20. Observations of red-backed salamandersin 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)

21. 1 2 3 no scar NLG with scar Fig.10-5 pg227 PJH

22. 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

23. spotted salamander R.G. Jaeger website

24. tiger salamander R.G. Jaeger website

25. slimy salamander R.G. Jaeger website