Frog Taxonomy (with a focus on Georgia frogs)

Georgia currently has 30 native frog species and two introduced frog species that fall into six different families.

The most distinct of these families is Bufonidae or the true toads. All toads will be found in this family. All toads are frogs but not all frogs are toads. Toads are a specialized group of frogs who typically have warty dry skin, are short and stubby, and large glands on the sides of their heads that kind of look like shoulder pads and are called parotoid glands.  Toads can actually aim these glands at predators. The glands release a toxin, called bufo. That’s why it’s common to see toads hopping around during the day. The eggs are typically laid in long strands. Toads also have no teeth. Worldwide there are 604 species in this family.  In Georgia we have 4 species; American Toad (Anaxyrus americanus), Fowler’s Toad (Anasyrus fowleri), the Oak Toad (Anaxyrus quercicus), and the Southern Toad (Anaxyrus terrestris). In the Metro Atlanta area, it’s common to hear both American and Fowler’s toads calling. The Ameican toad sounds like a long musically thrill that lasts between 6 and 30 seconds. The Fowler’s Toad sounds like a harsh thrill, kind of like a nasally WAAAHHHH.

 

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Red-spotted toad (Anaxyrus punctatus, formerly Bufo punctatus), captured by Lauren Schramm

 

The largest family of frogs in Georgia is Hylidae or the tree frogs, chorus frogs, and cricket frogs. Worldwide the family has 710 species. They all shared a claw-shaped finger which is found at the end of their toe pad. The toe pads function not like suction cups, but via wet adhesion, similar to 2 pieces of wet glass sticking together. In Georgia we have the Northern Cricket Frog (Acris crepitans), Southern Cricket Frog (Acris gryllus), Bird-voiced Treefrog (Hyla avivoca), Cope’s Gray Treefrog (Hyla chrysoscelis), Green Treefrog (Hyla cinerea), Pine Woods Treefrog (Hyla femoralis), Barking Treefrog (Hyla gratiosa), Squirrel Treefrog (Hyla squirella), Cuban Treefrog (Osteopilis septentrionalis), Mountian Chorus Frog (Pseudacris brachyphona), BRimley’s Chorus Frog (Pseudacris brimleyi), Spring Pepper (Pseudacris cruicifer), Upland Chorus Frog (Pseudacris feriarum), Southern Chorus Frog (Pseudacris nigrita), Little Grass Frog (Pseudacris ocularis), and finally the Ornate Chorus Frog (Pseudacris ornata). The Cuban Treefrog is actually an invasive species that is twice as large as our native treefrogs and it consumes them! It’s really hard to find because it’s a treefrog and so there is not much we can do about it’s invasion. The upland chorus frog (sounds like running your finger along a comb), spring pepper (sounds like bird-like peeps), Cope’s gray treefrog (harsh, high pitched trill), green treefrog (nasally and duck-like), bird-voiced treefrog (like a bird call whit-whit-whit), squirrel treefrog (harsh repetitive, squirrel-like call), and northern cricket frog (sounds like two marbles being tapped together) can all be found in the Metro Atlanta area.

 

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Cope’s Grey Treefrog, captured by Lauren Schramm

 

The family Ranidae contains true frogs who have smooth and wet skin. Worldwide they have a large range. Generally, they are aquatic or live close to water. This family is probably what comes to mind when most people think of frogs. In Georgia you can find Gopher Frogs (Lithobates capito), Bullfrogs (Lithobates catesbeinanus), Green Frogs (Lithobates clamitans), Pig Frogs (Lithobates grylio), River Frogs (Lithobates heckscheri), Pickeral Frogs (Lithobates palustris), SOuthern Leopard Frogs (Lithobates sphenocephalus), Wood Frogs (Lithobates sylvaticus), and Carpenter Frogs (Lithobates virgatipes). Bullfrogs, green frogs, pickerel frogs, and Southern leopard frogs all have calls that can be heard in the metro Atlanta area. Respectively the calls sound like a repeated jug-o-ruummmm, like a banjo pluckling, a snoring person, and the sound of squeezing a balloon.

 

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Pickeral Frog, captured by Lauren Schramm

 

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How will climate change and impact Chytridiomycosis and amphibians?

Chytridiomycosis is a disease that is killing amphibians worldwide at alarming rates. To read more about amphibians see this blog post. The disease is caused by Batrachochytrium dendrobatidis or Bd for short. Bd is a fungus that is specific to amphibians. Currently, the disease is responsible for the greatest disease-caused loss of biodiversity in recorded history. Species have had massive drops in populations and seem to have disappeared overnight.Bd occurs inside the cells of the outer skin layer. It causes microscopic changes in the skin and enlarges this layer. This is deadly because amphibians absorb water and salts through the skin. In the family of lungless salamanders, and one lungless species of caecilian Bd causes them to suffocate. Bd travels into the mouthparts of tadpoles or other larval amphibians. When tadpoles change into adults the infection spreads to the skin. Spores, which are the reproductive part of the fungus, cause the skin to become enlarged. This reduces osmotic regulation and electrolyte blood levels drop which leads to cardiac arrest. Chytridiomycosis has almost a 100 percent mortality rate.

 

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Cells infected with Batrachochytrium dendrobatidis 

 

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Class Amphibia

The class Amphibia contains amphibians which are some of my favorite animals. There are three major types which are frogs & toads (order Anura), salamanders (order Caudata), and caecilians (order Apoda). All these orders share certain characteristic including being endothermic, meaning they are unable to regulate their own body temperature. They have both lungs and gills, typically they have gills in the larvae stage but then develop lungs in the adult stage. Their eggs are anamniotic, meaning they are covered by a gelatinous mass that protects the eggs and prevents them from drying out. The warmer and moister an area the more likely it is that they will have more species of Amphibia.

The order Anura contains both frogs and toads, and over 3,400 species! They have longer hind legs than front legs which gives them the ability to hop. The tail is lost in the adult stage and adult males are typically the only ones that vocalize, and they do so to attract mates. Within the order, there are a few distinct families which include the tailed-frog (Ascaphidae),  spadefoot toads (Pelobatidae), narrow-toed toads (Leptodactylidae), true toads (Bufonidae), and true frogs (Ranidae). These are only 5 families. I will post later but this is a good start. If you learned the basic characteristic of each family it will greatly improve the speed and accuracy with which you can identify species.

  • tailed-frog (Ascaphidae)
    • this family only has one species (Ascaphus truei) that lives in the Pacific Northwest
    • ascaphus_truei_web
  • spadefoot toads (Pelobatidae)
    • mostly live underground and come out at night
    • have a horny digger on their hind feet and help them dig
    • breed in temporary pools, and therefore their eggs and larval can develop as quickly as 12 days
    • scaphiopus_couchii_anra
  • narrow-toed toads (Leptodactylidae)
    • most species are tropical and lay eggs on land
    • found in the Southern US to South America
    • there are over 800 species, so characteristics vary widely
    • eleutherodactylus_guttilatus
  • true toads (Bufonidae)
    • over 350 species, 17 species in the US
    • skins very warty with parotid glands behind the eyes
    • shorter legs than frogs as they are designed for hopping, not leaping
    • usually burrow during the day, hunt insects at night
    • a toad light can be set up for their observation See this link by Michigan DNR
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Red-Spotted Toad (Bufo punctatus), captured by Lauren Schramm, Lajitas, Texas
  • true frogs (Ranidae)
    • long legs and slim waist
    • have a very distinct eardrum
    • webbed feet, usually have distinct ridges down the back
    • aquatic larvae, aquatic and terrestrial adults

 

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Green frog (Rana clamitans)  Inlet, NY- captured by Lauren Schramm, photo credit- Peter Spawn

Going back to the salamanders, order Caudata, they are distinct by a long slender body, four limbs, and tail. There are 340 species worldwide. They almost call have smooth skin and glands that promote poison. Salamanders can be found in soil, leaf litter, or in water bodies. They have internal fertilization via spermatophores, which means that the male gives a packet of sperm to the female which she absorbs into her body to fertilize eggs. Breeding occurs in the early spring, often with the 1st warm rain. Salamanders start to migrate to the breeding location, in this process road present a huge barrier to them. Some states even have groups that go out during this time and act as crossing guards for the salamanders. If you are interested I found groups in New Hampshire and Vermont. Sexual dimorphism is common in salamanders meaning that the males and females have different physical characters. The 5 families I will talk about in this blog post are giant salamanders (Cryptobranchidae), mole salamanders (Ambystomatidae), Conger eels (Amphiumidae), lungless salamanders (Plethodontidae), and newts (Salamandridae).

  • giant salamanders (Cryptobranchidae)
    • largest living salamanders
    • fully aquatic
    • the largest species is the giant salamander (Cryptobranchus alleganiensis) which can be almost 6 feet long and lives in Japan
    • one species, the Hellbender (Cryptobranchus alleganiensis), lives in the US but is near threatened
    • 4739185259_6e3f628337_b
  • mole salamanders (Ambystomatidae)
    • characterized by their stout bodies
    • found in the US and Canada
    • there are 30 species of this burrowing salamander
    • named after the fact that they only emerge to breed

    eastern_tiger_salamander_28ambystoma_tigrinum29_282552238976229

  • Conger eels (Amphiumidae)
    • only 3 species
    • named the overall body shape
    • found in the southern US
    • named for the number of toes they have; One-toed amphiuma (Amphiuma pholeter), Two-toed amphiuma (Amphiuma means), Three-toed amphiuma (Amphiuma tridactylum)
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  • lungless salamanders (Plethodontidae)
    • breathe through the skin and the mouth
    • there are over 250 species, making it the most diverse family of salamanders
    • most are found in the Americas but a few are found in Europe
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      Red-backed salamander (Plethodon cinereus)- captured by Lauren Schramm, Norcross, GA
  • newts and salamanders (Salamandridae)
    • has the largest geographic distribution of any salamander family
    • has two subgroups that contain true salamanders (genera ChioglossaMertensiella, and Salamandra) and newts (other genera)
    • most adults are smaller and rarely longer than 20 cm
    • notophthalmus_viridescenspcca20040816-3983a

Finally, the last order, Apoda, contains caecilians, which are the lesser known group of amphibians and for good reasons. Caecilians is latin for blind onesThey are basically salamanders without legs, although some do have very tiny legs. They live underground and very little is known about them. There are 160 species. THeir eyes may be covered with bone or skin. They hunt prey underground using their head as a sensor. My old biology professor called them nightmare material. vivipary is common among them, meaning that the young develop inside the mother and then they are born. They are found in the tropics in of South and Central America, Africa, and southern Asia. Their skin contains calcite scales which led scientists to originally think they were related to Stegocephalia which is a salamander/ lizard-like creature that lived 350 million years ago.

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