Posts Tagged ‘amphibians’

The Plot “Thickens”

Tuesday, May 17th, 2011

If you have ever had the misfortune of turning over a log or rock in eastern Oklahoma and grabbing a black salamander with white spots, you know that washing off the thick, sticky liquid that they secrete from their skin in defense is no easy matter. Imagine being a small predator like a snake, biting the salamander, getting a mouthful of that sticky stuff, and then trying to rub it off in the leaf litter ending up with a mouthful of leaves stuck to your mouth! These salamanders, which look pretty much the same from mountain ridge to mountain ridge, and even resemble a lowland salamander, form a complex of species whose identities and relationships are just beginning to be understood. To the layman, these are known as the “slimy” salamanders.

The salamander Plethodon ouachitae, occurs along several ridges in the Ouachita Mountains and is commonly known as the Rich Mountain Salamander.

The Rich Mountain Salamander (P. ouachitae) occurs along several ridges in the Ouachita Mountains.

Dr. Don Shepard, a former graduate student from the University of Oklahoma, has combined field studies with DNA sequence data to unravel relationships among these species. Until recently, these salamanders have been considered as four species. One, Plethodon albagula, appears to be widespread in lowlands and the Ozark foothills of eastern Oklahoma, extending up into Missouri. Three other species, P. caddoensis, P. fourchensis, and P. ouachitae, each occur on their own mountain ridges in the Ouachita Mountains of southeastern Oklahoma and southwestern Arkansas. If only it were that simple!

By combining DNA sequence data with known rates of evolutionary change for specific genes, Don has discovered that not only have some of these “species” experienced divergence into genetically different populations, the causes of divergence differ among species. For P. ouachitae and P. fourchensis, genetically different populations are associated with mountain ridges, indicating that populations were isolated on mountain tops as the climate slowly changed over geologic time. Why would they become isolated? The answer is that these salamanders require a specific set of environmental conditions to survive. These include relatively cool temperatures and high humidity, usually associated with mountain tops. The salamanders appear unable to adapt to warmer and drier conditions so they simply live in the same kind of microhabitats that they lived in historically. This inability to adapt is referred to by scientists as “niche conservatism.”

For P. caddoensis, diversification is associated with stream drainages. Four distinct lineages within P. caddoensis have been identified from each of the following four streams; lower Caddo River, Upper Caddo River, Brushy Creek, and Cossatot and Little Missouri Rivers. Diversification in this “species” appears tied to more recent climatic change and specialized niche characteristics of the salamanders, primarily related to thermal and humidity variables associated with stream drainages.

The Western Slimy Salamander, Plethodon albagula, occurs from Missouri south to extreme southeastern Oklahoma and into Texas.

The Western Slimy Salamander (P. albagula) occurs from Missouri south to extreme southeastern Oklahoma and into Texas.

Dr. Shepard is now beginning to examine the lowland and widespread “species” P. albagula. No doubt this species has undergone some interesting divergences in the past, but what the pattern is and how it occurred remains a mystery to be unraveled. So, the next time you pick up one of these so-called “slimy salamanders,” reflect on their evolutionary history and what they tell us about past events underscoring the remarkable diversity that we see today in eastern Oklahoma. Oh, and if you have been slimed, try WD-40 followed by soap and water. WD-40 seems to be a universal solvent and will clean many things!

Slimy Salamanders and Bigfoot

Tuesday, June 15th, 2010

Southeastern Oklahoma harbors an interesting set of reptiles and amphibians, dominated by species typical of southeastern deciduous forests. However, a small group of related salamanders are endemic to the east to west chain of mountains collectively known as the Ouachita Mountains. Also known as the Interior Highlands, these are the only mountains between the Appalachian Mountains to the east and the Rocky Mountains to the West. Each mountain has a name (e.g., Kiamichi Mountains, Winding Stair, Boktuklos, Rich Mountain), and almost all have their own endemic salamander species. The salamanders have been collectively called “slimy salamanders” and are in a large group of salamanders known as lungless salamaders (Family Plethodontidae). They are “slimy” because they produce a viscous liquid from glands in the skin that is first slimy, but then sticky. They are “lungless” because they do not have lungs, but rather breath entirely through their skin!

The lungless salamander, Plethodon sequoia

The lungless salamander, Plethodon sequoyah

Slimy salamanders of the Ouachita Mountains have recently been studied in detail by Dr. Don Shepard, formerly a graduate student at the University of Oklahoma and here in the Sam Noble Museum. One of the salamanders is shown above and a future blog will detail what Don has discovered about these interesting salamanders.

Another interesting point about southeastern Oklahoma is a growing interest in Bigfoot, the large, hairy, man-like beast that purportedly runs wild in the forests near the tiny town of Honobia. A fall festival (the Bigfoot Festival) occurs each year in which various groups attempting to gather evidence of Bigfoot’s existence meet and discuss their findings. Honobia is remote and located equidistant from Oklahoma City, Dallas, and Shreveport. Limited lodging is available at Dancing Rain Ranch and the Honobia Creek Country Store, with additional lodging in Talihina. Each year, Bigfoot researchers claim to have gathered additional evidence, but firm verifiable physical evidence that Bigfoot exists has still not been presented to the public. Perhaps in the next few years, Bigfoot will step on a slimy salamander and lose some hair so that DNA can be collected and analyzed—but please, don’t hold your breath, unless you are a slimy salamander!

Mole salamanders

Wednesday, April 21st, 2010

In an earlier blog, we mentioned that Spotted salamanders (Ambystoma maculatum) were making their way into ponds to breed. We thought that we might tell you about not only Spotted salamanders but also about the family of salamanders that they belong to, the Ambystomatidae. These amphibians are collectively known as “mole” salamanders because they spend much of the year underground. This family is distributed throughout most of North America and contains 37 species. Oklahoma has six species.

Four of the six species of mole salamanders in Oklahoma

Four of the six species of mole salamanders in Oklahoma

Among the Oklahoma species of mole salamanders, some breed in late winter, like the Spotted salamander and the Small-mouthed salamander (A. texanum), some breed in fall, like the Marbled and Ringed salamanders (A. opacum and A. annulatum, respectively), and some breed in spring, like the Tiger and Mole salamanders (A. tigrinum and A. talpoideum, respectively). When they are breeding, many hundreds seem to appear from nowhere. Considering how many arrive at the breeding ponds, it seems that they could be found any time during the remainder of the year—not so! After adults breed in ponds, they leave the ponds and go underground, not to be seen until the next breeding event. Obviously, they must feed while underground in order to grow and save energy to reproduce next time, but very little is known about their underground activity. Some, like Tiger salamanders, are known to live in gopher burrows, often in large numbers, but for the rest, we know very little.

After the breeding events, eggs hatch in ponds, and thousands of tiny salamander larvae emerge. Larvae of all species of mole salamanders look superficially alike, and a bit of skill is required to identify the different species in larval form. They have external gills, a laterally compressed tail that aids in swimming, and when not slowly walking on the pond bottom, they swim with an undulating motion, similar to that of alligators. Temporary ponds are filled with tiny invertebrates, collectively called microinvertebrates, such as ostracods, copepods, and Daphnia (a genus of cladocerans). Larvae of mole salamanders vacuum up these tiny invertebrates by opening the mouth and expanding the throat at the same time. They close the mouth and expel the water out through the gill slits, but retain the prey items. Their diet includes nearly every kind of pond organism small enough to fit into their mouths.

Larvae of Mole salamanders grow rapidly, but should rain be scarce, their pond might dry up before they are large enough to transform into adults. Ponds are also filled with predators that eat salamander larvae, including watersnakes, bullfrogs, giant waterbugs, and larvae of dragonflies and predaceous diving beetles. Some species of birds also visit ponds and capture salamander larvae. As salamander larvae grow, it is less likely that they will be captured and eaten by an insect. Large larvae are particularly attractive to birds and snakes. Life in the pond is risky for salamander larvae, and the best thing to do is grow fast and leave the pond as quickly as possible.  Of the thousands of eggs that are deposited each year, some will survive to become adults and breed, and most won’t. Variation among individual offspring sets the stage for natural selection.

Larva of a Tiger salamander

Larva of a Tiger salamander

The First Spring Rains Bring Out Frogs and Salamanders

Wednesday, April 21st, 2010

Rains that occurred several weeks ago in southeastern Oklahoma brought out all of the early spring frogs, including Spring peepers (Pseudacris crucifer), Cajun chorus frogs (Pseudacris fouquettei), Pickerel frogs (Lithobates palustris), and Southern crawfish frogs (Lithobates areolata). Even Southern leopard frogs (Lithobates sphenocephala) and American toads (Anaxyrus americanus) were active. In addition to running our traps at our primary research site in Le Flore County, we spent time driving roads at night in both Le Flore and McCurtain Counties. Nearly every roadside pond contained some mix of the above frog species. The only two that did not occur together were Pickerel and Crawfish frogs.

An adult Cajon chorus frog

An adult Cajun chorus frog

A number of amphibian species in Oklahoma breed during late winter and early spring, and their nearly deafening choruses can be easily experienced by driving around in rural areas at night. Males congregate in ponds when rains first begin, and their calls attract females that have spent the fall and winter converting energy that they stored from spring, summer, and fall activity into eggs. Examination of ponds during the daytime usually reveals many egg masses attached to vegetation or floating on the pond surfaces.

In addition to frogs that reveal their presence by calling, salamanders are moving into ponds to breed. We found large numbers of Spotted salamanders (Ambystoma maculatum) moving across roads heading for ponds during rains, and we captured some in our traps. Unlike frogs, salamanders do not vocalize. Whereas female frogs are attracted to individual males by the quality of the call, female salamanders are attracted to individual males by the quality of their courtship behavior.

An adult Spotted salamander

An adult Spotted salamander

So, for those of you are interested in amphibians, drive around in rural areas when it begins to rain and listen for frog choruses.  With the windows cracked, you can hear choruses in breeding ponds along the roads.  If you find a chorus on public property, put on your boots, turn on your good flashlight or headlight (preferred), and see if you can locate individual frogs that are calling. Chorus frogs are tiny and usually call inside grass clumps at the surface of the water. A Chorus frog calling right at your feet can be difficult to locate and requires persistence. If you are lucky enough to hear the low snoring calls of Pickerel or Crawfish frogs, you will need to move slowly without sloshing the water.  Even slight movement of the water caused these wary frogs to stop calling and dive below the surface. If you stand quietly for ten minutes or so, males will reappear and begin calling.

Sirens galore!

Tuesday, April 20th, 2010

Several weeks ago, a group from the museum visited the ODWC’s Red Slough in search of some salamanders that only occur in swamps of the southeastern part of Oklahoma. We were able to trap more than 20 sirens, which are elongate, eel-shaped salamanders that live their lives in water. They are in their own family, the Sirenidae, and the species that occurs in Oklahoma is the Western lesser siren, Siren intermedia.

Adult Lesser siren

Adult Western lesser siren

Unlike eels, sirens have external gills and a pair of tiny front legs, that on first glance, appear useless. Believe it or not, they use these legs on rainy nights when they move short distances across land. These sirens can reach eight inches in length, but most are slightly smaller. In most salamanders that have aquatic larvae, external gills used for respiration in water are lost when the salamanders metamorphose into terrestrial adults. In sirens, no obvious metamorphosis takes place, with the adults looking exactly like the “larvae,” just larger in size. However, close examination of the internal morphology reveals that reproductive organs develop as the “larvae” increase in size and age. Consequently, they do “metamorphose” but retain some larval characteristics (external gills).

Sirens reach sexual maturity in about two years. They deposit from 100–200 eggs in cavities in mud at the bottom of swamps. One of the most interesting aspects of the biology of sirens is their ability to form a cocoon around their body when swamps dry up. They burrow into the mud and secrete mucous that forms the cocoon, the function of which is to prevent them from drying up. Sirens can remain inactive for as much as eight months in their cocoon until rains fill the swamps that they live in.

Although sirens are difficult to observe because they are under water, they can be easily trapped with minnow traps, and no bait is needed. If you should trap one to observe, be sure to keep it in water that contains oxygen and is not chlorinated. It might also be useful to drop a few dried pine needles or oak leaves into the aquarium as tannins released from needles and leaves can keep mold from attacking the skin of sirens and other aquatic amphibians and reptiles.

Head of Lesser siren showing external gills

Head of Western lesser siren showing external gills

Blog Readers, we are back!

Tuesday, April 20th, 2010

Just after our last blog, rains brought frogs and salamanders out all over the place, which sent us racing around different parts of southeastern Oklahoma. We also ran our drift fence traps at our field site in Le Flore County, trying to keep up with movements of amphibians. A brief trip to Florida to present a talk to one of the Florida herpetological societies in Gainesville interrupted our amphibian and reptile excursions in Oklahoma, but only for about a week. As a result, we have been so busy that we have not been able to keep up with our blog. However, as the title says, we are back, and we will try to catch you up on what we have been doing in the following series of blogs. We hope you will all stick with us, and many thanks for all of your kind comments.