Lab Quiz 2~Salamander Diversity

Question 1

How many families are within Caudata? (Salamanders)

How many species?

Answer 1

9 families, ~640 species

Question 2

Where are Caudata usually found?

Answer 2

Essentially all in Northern Hemisphere (Laurasian), generally in cool, wet temperate regions, some Plethodontids extend to lower Central America and South America

• usually absent from oceanic islands
• 4 ‘familes’ restricted to New World, with only Hynobiidae endemic to Old World

Question 3

What is the typical generalized body form of the Caudata?

What are some deviations seen from this and in what groups?

Answer 3

short body, with four functional limbs

~deviations include elongated body, with reduced limbs (Amphiuma, Siren, Pseudobranchus)

Question 4

What is the body size range for Caudata?

Answer 4

30 mm (Thorius) to 1.5-1.8 m (Andrais)

Question 5

Typically, what type of breeders are Caudata?

Answer 5

~most are terrestrial, but some are aquatic

~exhibit internal fertilization but no intromittent organ (via spermatophores instead)

Question 6

What is a spermatophore?

Answer 6

~a sperm cap on a gelatinous base
~the male deposits this following a courtship ritual and the female pics it up with cloacal lips for internal fertilization.

Question 7

How do the ‘basal’ salamanders reproduce? (Sirenidae & Cryptobranchoidea)

Answer 7

~external fertilization and no courtship behavior (Sirenid courtship unknown, but no cloacal glands or spermatotheca so looks like no internal fertilization)
~have aquatic eggs and larvae

Question 8

What are the different reproductive modes found within the Caudata?

Answer 8

1. Generalized pattern ~ aquatic eggs and larvae
2. Terrestrial eggs, aquatic larvae
3. Terrestrial eggs & larvae, non-feeding larvae
4. Terrestrial eggs with direct development
5. Eggs retained in oviducts (viviparous)

Question 9

What are some characteristics of Caudata larvae?

Answer 9

~more like adults than are tadpoles of anurans (limbs appear early)
~all carnivorous (none herbivores like tadpoles)
~they have ecomorphs (like tadpoles); in ponds and slow moving water they have large bushy gills, prominent tail fins, and laterally compressed bodies; fast moving water they have smaller gills, less prominent fins, depressed bodies, and calloused toes for gripping the bottom

Question 10

What is paedomorphism?

Answer 10

retention of larval characters; ex. larval teeth, bone patterns or structure, absence of eyelids, the lateral line system, or external gills.

Question 11

Which Caudata usually have paedomorphic forms?

Answer 11

Sirenidae, Amphuimidae, Proteidae, and Cryptobranchidae all generally aquatic and are paedomorphic.

Question 12

What is paedomorphism the result of in salamanders?

Answer 12

neotony~somatic development terminates early

~can be facultative (depends on environmental cues) or obligatory (cannot transform)

Question 13

What is heterochrony?

Answer 13

Changes in developmental timing

Question 14

What are the different ecomorphs seen in Caudata?

Answer 14

Terrestrial, Scansorial, Fossorial, Aquatic, Aquatic burrower, Aquatic bottom-walker, Troglobitic

Question 15

What are Caudate synapormophies?

Answer 15

1. Operculum fused to ear capsule leaving only free columella
2. Quadratojugals absent
3. Angular bone fused with prearticular
4. Second ceratobranchials lost at metamorphosis
5. Palate remodeled at metamorphosis
6. Late appearance of maxillae in ontogeny

Question 16

What is the stem-based name of the Caudates? How far do the fossils in this group date back?

Answer 16

Urodeles & date back to at least mid-Jurassic (~170 mya).~Karaurus sharovi
In mid Jurassic there were “standard” salamander neotonic forms, long-bodied, and small present, with most ecomorphs represented, probably all families present throughout Laurasia

Question 17

What group is sister taxa to all remaining salamanders? What families does this group consist of?

Answer 17

Cryptobranchoidei, composed of 2 families; Cryptobranchidae and Hynobiidae

Question 18

Cryptobranchidae

Answer 18

2 genera, 3 species
~Cryptobranchus in E. US, retains one pair of gill slits, males construct nest under rocks in streams
~ Andrais in E. Asia, can reach up to 2 m, males construct nests in tunnels in river bar
They are the largest salamanders
Have incomplete metamorphosis, lack eyelids, retain lateral line, body and head dorsoventrally compressed, aquatic bottom-walkers in cold mountain streams and skin heavily folded, external fertilization, feed on crayfish, worms, insects captured via unique suction mechanism.

Question 19

Hynobiidae

Answer 19

7-10 genera, ~55 species
~Temperate & subarctic regions of N. Asia with disjunct populations in mountains of S. Asia
~relatively small (100-250mm), external fertilization, free swimming larvae that undergo complete metamorphosis, most are terrestrial (ecological equivalents of the North American ambystomatids)

Question 20

Sirenidae

Answer 20

2 genera, 4 species
~Siren (can reach nearly 1 m) & Pseudobranchus (small)
~ S.E. US and extreme N.E. Mexico
~first fossil of sirenid from Cretaceous of Sudan (65-90mya), phylogenetic relationships unknown, either sister to all other salamanders or sister to proteins
~eel-like with tiny forelimbs & no hind limbs
~obligatorily neotonic; external gills present, skin histologically similar to larval skin, non-pedicellate teeth, lack eyelids, maxilla reduced or absent
~Aquatic burrowers in slow moving waters like swamps, lakes, and marshes.
~feed on crustaceans, insects, & worms via suction-feeding
~aestivation in dried mud by secreting a mucous cocoon
~probably external fertilization

Question 21

Salamandroidea

Answer 21

Group that contains all species of salamanders except Cryptobranchoids and Sirenidae; includes 6 families;
Protieidae, Salamandridae, Ambystomatidae, Rhyacotritonidae, Amphiumidae, Plethodontidae.
~extreme amount of diversity, with Plethodontidae being most diverse
~All have internal fertilization via spermatophores

Question 22

Proteidae

Answer 22

2 genera, 6 species
~Necturus (found in E. North America), inhibits lakes and streams
~Proteus (in Karst regions of NE Italy & E. coast of Adriatic Sea) (Proteus anguinus~troglobitic ecomorph that lives in limestone caves, blind, pigmentless, reduced number of digits)
~Highly aquatic and neotonic with external gills and caudal fins, also lack maxillae

Question 23

Treptobranchia

Answer 23

Consist of Ambystomatidae & Salamandridae

Question 24

Salamandridae

Answer 24

~15-22 genera, ~90 species
~has four distributional centers: E. North America (Notophthalmus), W. North America (Taricha), E. Asia, & Europe, N. Africa, W.Asia
~fossil record suggests salamandrids invaded NA across Beringia
~some terrestrial as adults, others aquatic
~deemed highly “derived”
~many with glandular skin that can produce tetrodotoxins, often with aposematic coloration and elaborate defensive displays
~courtship often highly elaborate and prolonged
~different reproductive modes, oviparous- eggs in water or viviparous-advanced larvae in water or fully developed young
~Consists of Notophthalmus & Taricha with complex life cycles

Question 25

Notophthalmus

Answer 25

Within Salamandridae, 3 species, complex life history
~some larvae transform directly into aquatic adults
~most transform into an immature eft stage and remain terrestrial from 1-14 year
~then eft transforms into a fully aquatic breeding adult

Question 26

Taricha

Answer 26

within Salamandridae, 4 species
~lack eft stage
~terrestrial adults return to water to breed (tail becomes laterally compressed during breeding period)
~California Newt is Taricha….produced tetrodotoxins

Question 27

Ambystomatidae

Answer 27

2 genera, ~37 species
Ambystoma (33 sp) & Dicamptodon (4 sp)
~occur in NA; S. Canada to Mexican Plat.
~generally transforming adults are terrestrial, neotony is pervasive, some exhibit facultative neotony, others obligate

Question 28

Ambystoma

Answer 28

Within Ambystomatidae
~courtship may involve migration of huge numbers of individuals to breeding ponds, males arrive first, and most breed in early spring; some deposit eggs on land in fall that hatch out when flooded in spring.

Question 29

Dicamptodon

Answer 29

within Ambystomatidae
~Pacific giant salamanders (Pacific NW US)
~inhabit moist coniferous forests with cold streams or cold mountain lakes
~forage at night along stream sides
~some obligatorily neotonic (Dicamptodon copei), and permanently aquatic, and others are facultatively nektonic, transformed adults are terrestrial

Question 30

Rhyacotritonidae

Answer 30

1 genus, 4 species
~NW US
~Small, fully transformed
~larvae and adults occur in cold, fast-moving streams in old-growth coniferous forest
~greatly reduced lungs are typical of stream-adapted taxa
~species difficult to distinguish morphologically, but extremely divergent biochemically

Question 31

Xenosalamandroidei

Answer 31

Consists of Amphiumidae and Plethodontidae

Question 32

Amphiumidae

Answer 32

1 genus (Amphiuma), 3 species
~SE United States
~Obligatory neotonic, fully aquatic, eel-like, lack eyelids, have pedicellate teeth, have all four limbs, & lack external gills but have single pair of gill slits
~some over 1 m (tridactylum & means), and others only reach ~0.3 m (pholeter)
~inhabit slow moving bodies of water like swamps and sluggish streams
~nocturnal and pass the day in crawfish burrows
~move overland during rain
~have internal fertilization, male places spermatophore into females cloaca, eggs then laid on land under logs & in alligator nests
~Aquatic larvae with gills
~feed on wide range of vertebrates or invertebrates
~aestivate for up to 2 years during drought conditions

Question 33

Plethodontidae

Answer 33

~25 genera, ~420 species
most speciose ‘family’
~unusual distribution, in E US, Pacific Coast, Southern to N South America; also disjunct distributed taxa found in Europe and Sardinia and recently discovered in Korea; center of origin believed to be in Appalachian Mountains in E. US
~loss of lungs
~nasolabial groove that aids in chemoreception
~Radiation was related to 2 adaptations: evolution of direct development allowed to move onto land, and loss of lungs & switch to cutaneous respiration led to extreme tongue protrusion because the loss of lung freed up the glossal skeleton to be co-opted for tongue
(this evolved 4-6 times in plethodontids)
~has 4 subfamilies within; Bolitoglossinae (12 genera), Hemidactyliinae (1 genus), Plethodontinae (8 genera), and Spelerpinae (5 genera).
~only known phylogenetic relationship is Plethodontinae is sister to all others, but other relationships uncertain

Question 34

Plethodontinae

Answer 34

~subfamily within Plethodontidae
~8 genera, ~ 100 species
~3 prominent NA terrestrial genera with ~ 50 species
Has Plethodon, Aneides, Ensatina, & Desmognathines
Plethodon: Extensive radiation in E US & some in W US
Aneides: Few west coast species, 1 east coast
Ensatina: coastal region of W US
Desmognathines: Appalachia & SE U.S., has 2 genera within; Desmognathus & Phaeognathus, many aquatic bottom walkers and have derived feeding mechanisms and life history modes, some with direct development
~sister taxa to all other Plethodontidae

Question 35

Spelerpinae

Answer 35

Within Plethodontidae
~5 genera, 36 species
~most are terrestrial adults with aquatic larvae
~large radiation of neotonic species if Eurycea along Balcones Encarpment of TX, most aquatic or troglodytic

Question 36

Bolitoglossinae

Answer 36

Within Plethodontidae
~12 genera, ~280 species
~US West Coast (Batrachoseps); extensive radiation into MX & Central America; reaches S America
~Wide range in size (tiny Thorius to large Pseudoeurycea)
~Extensive radiation bc of 1. direct development and 2. derived tongue projection mechanism and 3. heterogenous montane tropical environments

Question 37

Hemidactyliinae

Answer 37

Within Plethodontidae
1 genus, 1 species~Hemidactylium scutatum
~small species
~widespread, but fragmented distribution in E. US
~4 hind toes
~basal tail constriction
~Terrestrial adults and aquatic larvae