NASA launches a frog, and experimental biogeograhy

September 13, 2013 • 9:07 am

by Greg Mayer

On Sept. 6, NASA launched the Lunar Atmosphere and Dust Environment Explorer (LADEE) towards the moon, where it will go into orbit to gather data on the thin lunar atmosphere. But along with the rocket, a frog, apparently resting on the rocket or launch pad, was taken spaceward, before being thrown free.

An unidentified frog is launched along with the LADEE rocket (NASA photo).
An unidentified frog is launched along with the LADEE spacecraft on Sept. 6, 2013 (NASA photo).

NASA’s dry caption is priceless:

A still camera on a sound trigger captured this intriguing photo of an airborne frog as NASA’s LADEE spacecraft lifts off from Pad 0B at Wallops Flight Facility in Virginia. The photo team confirms the frog is real and was captured in a single frame by one of the remote cameras used to photograph the launch. The condition of the frog, however, is uncertain.

The photo reminded me immediately of a famous biogeographic experiment performed by Thomas Barbour (1884-1946) and Philip Darlington (1904-1983), who differed over the importance of land bridges (favored by Barbour) versus overwater dispersal (favored by Darlington) in the distribution of animals on islands. The experiment and its results are handed down from one generation of graduate students to the next by a well-known oral tradition at the Museum of Comparative Zoology, but the only published account I know of is by Bob O’Hara (1988):

A how-possibly experiment performed by Philip Darlington and Thomas Barbour at the Museum of Comparative Zoology has become legendary. Darlington and Barbour were disputing the possibility of frogs being dispersed in the West Indies by hurricanes. Darlington, who believed such dispersal was possible, took a bucket of live frogs up to the roof of the Museum, and, with Barbour standing on the lawn below, proceeded to throw the frogs to the ground, one by one. As each one hit the ground, Barbour examined it and called up “That one’s dead,” “So’s that one,” and so on. But after a few minutes, much to Barbour’s disappointment, the frogs all revived and started to hop away. Darlington had thus shown that hurricane dispersal was possible, or at least had removed one of Barbour’s objections to it, namely that it would be too rough on the frogs.

To Bob’s account I would add that the MCZ is 5 stories tall, which gives you some idea how far the frogs fell in their journey to the courtyard below. Bob used the experiment to illustrate his notion of a “how possibly” experiment, which demonstrates the possibility, though not the actual occurrence, of a phenomenon.

I thought of the experiment because I wondered about the “uncertain” fate of the frog. The frog appears to be outside the plume of hot gas escaping form the rocket engine. If so, and if the clear air around it has not been super-heated, the frog could well survive the fall. Many tree frogs are adept at jumping long distances, bodies flattened and limbs spread, so that they reach a terminal velocity more dependent on aerial friction than gravity. The so-called “flying frogs” are ones that have gotten very good at this, usually with both morphological and behavioral specialiazations (see Wallace’s flying frog, an apt example for Wallace Year).

I’m not sure about the identity of the frog. My guess is that it’s a tree frog of some sort. [Note: I’d originally guessed it was a  Cuban tree frog (Osteopilus septentrionalis), a large, introduced species in Florida, but that’s before I realized the rocket was launched from a facility at Wallops Island, Virginia, on the Delmarva Peninsula, and not from NASA’s more usual Florida launchpads.]

h/t Christian Science Monitor

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O’Hara, R.J. 1988. Homage to Clio, or, toward an historical philosophy for evolutionary biology. Systematic Zoology 37:142–155. pdf

Frogs!

June 30, 2011 • 5:31 am

by Greg Mayer

As an Everton supporter, I am loath to praise anything Mancunian, but Andrew Johnson, a Manchester zoology graduate, has a marvelous website on the Amphibians of Borneo, which was brought to my attention by Matthew (yet another praiseworthy Mancunian).

Ansonia leptopus (Bufonidae) by Andrew Johnson

The site contains excellent photographs of many species of Bornean frogs. What struck me most is the resemblance of many of the depicted species to Central American frogs, especially the Costa Rican ones with which I am most familiar. Our toad friend above reminds me of the gracile-limbed Central American toads of the genus Atelopus. (Superb photos of the various Costa Rican frogs mentioned can be found in Jay Savage’s magisterial The Amphibians and Reptiles of Costa Rica [see references] and at Costa Rican Frogs, a site I just discovered.). The following one is a more typical-looking toad, resembling various Central American Bufo.

Duttaphrynus melanostictus (Bufonidae) by Andrew Johnson

The following species resembles the Central American toad Bufo haematiticus in its cryptic forest-floor dress, but is in fact not a true toad, but a member of a different family.

Kalophrynus baluensis (Microhylidae) by Andrew Johnson

The resemblances between the Bornean and Central American frogs is a mixture of convergence (in this case, adaptation to the varied niches of tropical rain forest) and common ancestry (in some cases, a toad is a toad is a toad). Convergence is indicated when similar species are in different families, but it’s also possible within families. Both American Atelopus and Bornean Ansonia are members of the family Bufonidae (true toads), but their gracile form may have evolved independently from more squat ancestors (that’s why phylogenetic studies are so important for elucidating evolutionary phenomena– we need to know who’s related to who, and what the likely ancestral conditions were).

Here are several other of my favorites. The first resembles Central American Leptodactylus, especially pentadactylus.

Limnonectes ingeri (Dicroglossidae) by Andrew Johnson

Our friend above is named in honor of my esteemed colleague Robert Inger of the Field Museum, the dean of Bornean amphibian studies (see references below). The following species, in the same genus, Limnonectes, resembles various Central American Eleutherodactylus, a very species-rich genus with more than 40 Costa Rican species.

Limnonectes laticeps (Dicroglossidae) by Andrew Johnson

We’ll finish with some treefrogs, none of which are in the “true” treefrog family, Hylidae (which has many genera and species in Central America), but rather the Old World Rhacophoridae. The first resembles some of the the Central American Smilisca.

Rhacophorus cyanopunctatus (Rhacophoridae) by Andrew Johnson

The next resembles various Hyla.

Rhacophorus dulitensis (Rhacophoridae) by Andrew Johnson

And finally, a flying (actually gliding) frog; note the large webs. Some Costa Rican hylid treefrogs of the genus Agalychnis are capable of gliding, too.

Rhacophorus nigropalmatus (Rhacophoridae) by Andrew Johnson

A more academic site devoted to Bornean frogs, also beautifully illustrated and with a great range of useful information, is Frogs of Borneo, by Alexander Haas and Indraneil Das. The American Museum of Natural History is currently hosting a traveling exhibition entitled Frogs: a Chorus of Colors, featuring live (not preserved) frogs, which I saw when it was at the Milwaukee Public Museum, and is worth seeing if you’re in the New York area.

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Behler, J. and D. Behler. 2005. Frogs: A Chorus of Colors. Sterling Publishing, New York. (book to accompany the exhibition)

Inger, R.F. 1966. The systematics and zoogeography of the amphibia of Borneo. Fieldiana Zoology 52:1-402. (downloadable as pdf)

Inger, R.F. and R.B. Stuebing. 2005. A Field Guide to the Frogs of Borneo. 2nd ed. Natural History Publications (Borneo), Kota Kinabalu, Sabah, Malaysia. (available here)

Inger, R.F.  and F.L. Tan. 1996. Checklist of the frogs of Borneo. Raffles Bulletin of Zoology 44(2): 551-574. (pdf)

Savage, J.M. 2002. The Amphibians and Reptiles of Costa Rica | A Herpetofauna between Two Continents, between Two Seas. University of Chicago Press, Chicago.

… breeding mulleins out of the dead land.

April 11, 2010 • 12:43 am

by Greg Mayer

March continued its cruelty, and less than two weeks after they emerged in Virginia, mulleins emerged from the dead land of Wisconsin as well.

Mullein, Saukville, Wisconsin, 23 March 2010. Photo by Eric Hileman.

The above was one of a number of mulleins Eric Hileman and I found and photographed while reconnoitering his Butler’s garter snake (Thamnophis butleri) study site at the University of Wisconsin-Milwaukee Field Station. The plywood board against which the mullein nestles is one of several hundred in a 15m mesh grid that the snakes use as cover, enabling Eric to find them and track their numbers and movements.

Eric Hileman and a snake cover board amidst the dead land, Saukville, Wisconsin, 23 March 2010.

The progress of spring continues apace. Earlier tonight, in Franskville, Wisconsin, I passed a chorus of chorus frogs (Pseudacris triseriata) in wet fields and sloughs calling so loudly that I could hear them in my car with the radio on and the windows closed at 45 mph!

Polymorphism in vertebrates

March 26, 2010 • 1:04 pm

by Greg Mayer

Darwin’s theory of evolution (and ours), unlike that of Lamarck, is variational, rather than transformational: the process of evolution is a change in frequency of different variants within a population, not a transformation of the individuals.  Darwin thus made the origin, nature, and inheritance of variation key problems for biology; indeed, for much of the 20th century, evolution and genetics were often taught as a single course at universities.

One of the most distinctive sorts of variation is polymorphism, in which two or more discontinuous forms are found in a single species (this is distinct from sexual or age related variation). Darwin himself pioneered the study of polymorphisms. Such discontinuous variation often has a simple genetic basis, with allelic variation at one genetic locus accounting for all (or most) of the variability.The color polymorphism in peppered moths (Biston betularia) is a well known and well studied case involving industrial melanism, in which light and dark forms are adapted to polluted and unpolluted environments, respectively. A well known case of polymorphism in vertebrates are the two color phases of Cuban sparrow hawk (Falco sparverius sparverioides). This case is not well studied, though, and we know nothing about the genetics, nor the adaptive significance (if any) of the polymorphism.

Light and rufous phase male Cuban sparrow hawks (Falco sparverius sparverioides).

A polymorphism in vertebrates that many Americans and Canadians are familiar with are the melanistic and gray forms of the gray squirrel (Sciurus carolinensis). The most frequent color form is gray, but blackish or dark brownish individuals are widely distributed, and in places quite frequent. I have seen them in Illinois (Cook County), Wisconsin (Racine and Kenosha Cos.) and Michigan (Ingham Co.), and also on the campus of Princeton University. (I was told at Princeton that, during football season, black squirrels are captured, and orange stripes applied to them, so that they resemble diminutive arboreal tigers, the tiger being Princeton’s mascot.)

A demonic gray squirrel (locally known as 'yard dogs'), Annapolis, MD, 23 June 2008.

A much less common color morph is the leucistic or albinistic form, which is whitish, cream or yellowish. They are famously common in Olney, Illinois (due to an introduction of two albinistic individuals to an area previously lacking any gray squirrels at all), and also occur regularly in Stevens Point, Wisconsin, but I had never seen one before my recent trip to Washington, DC, where I saw one on the tree right across from the steps on the Mall entrance to the USNM.  (The picture was taken through a bus window.)

Leucistic or albinistic gray squirrel, Washington, DC, 16 March 2010.

Vertebrate polymorphisms are often less well understood than those of invertebrates, because their generally greater size and longer generation times make experimental study more difficult. Melanism in squirrels, for example, has been related to thermoregulation and fire frequency, but no thoroughly compelling explanation has been found. One exception to this is coat color variation in mice of the genus Peromyscus, where coat color seems to be an adaptation for camouflage in varying environments.

Light and dark forms of Peromyscus polionotus from sandy and dark soils (P. p. leucocephalus on the left, P. p. polionotus on the right, I think).

In the 1930s, F.B. Sumner conducted classic field and lab studies on light colored mice living on sandy soils and dark mice on dark soils. Unlike the melanistic and albinistic squirrels, which are variant individuals within a populations, there is an element of geographic variation in the mice, which live in distinct, though adjacent, places. Sumner’s studies showed that there were several (not just one) genetic loci involved in coat color, and the color forms intergrade where their habitats meet and they interbreed. Hopi Hoekstra of the Museum of Comparative Zoology is currently conducting exciting studies of some of the same species studied by Sumner.

Although the mice occur in distinct modal forms (white vs. brown), the intergradation where they meet shows an underlying continuous variation. The frogs below show that although we can pick out distinctly different individuals, the range of pattern from plain to mottled to striped makes it difficult to recognize a small number of discrete color morphs, and the variation approaches a continuous dictribution. Such continuous variations were thought by Darwin, and most biologists today as well, to be important raw material for the evolutionary process.

Leotpdactylus albilabris from Isla Vieques.

March is the cruelest month…

March 21, 2010 • 2:48 pm

by Greg Mayer

…breeding mulleins out of the dead land.

Mullein along railroad track, Arlington, Virginia, March 12, 2010.

During a visit to the Washington, DC, area last weekend I made a point of looking at how advanced the spring greening was. Despite  the east coast’s hard winter, and the mild winter in the midwest (and 2010 in general is starting off quite warm), things are much more alive (as I expected) in the east, but still pretty gray-brown. In addition to the mulleins above (the greenish ground rosettes, with last year’s meter high flowering stalks still standing in many), a number of flowers (all in cultivation) had also emerged.

Washington, DC, March 17, 2010.
Washington, DC, March 17, 2010.

Suitland, Maryland, March 16, 2010.

Early emergence is a key adaptation for many plants, especially those of the forest understory. Later in the season, the forest floor will be in deep shade from the trees, so many herbaceous and small woody plants take advantage of the photosynthetic opportunities provided by the early spring. The animals were also active– fish crows and mockingbirds on the Mall in DC–, but most noticeably large and loud choruses of spring peepers (Pseudacris crucifer, a tree frog) in many places in Prince William and northern Stafford Counties, Virginia. I attempted to record a chorus in Dumfries, Virginia, and thought I had, but the file came up blank, so you’ll just have to imagine hundreds of little frogs, all saying “peep” at the same time (or listen here). When I lived in the DC area, peepers began calling around the same time redwinged blackbirds did, February 15, so they’ve probably been calling for around a month already. No frog calls yet in Wisconsin.

What frogs go through for their tadpoles

September 4, 2009 • 2:30 pm

by Greg Mayer

Matthew has once again given me a hot tip: the BBC has a video of a mountain chicken, Leptodactylus fallax, feeding its developing tadpoles with unfertilized eggs. (I am unable to embed the video– do click through to watch). The mountain chicken is actually a large frog (so named because they are good eating– many years ago an attempt was made to establish the species in Puerto Rico as a food source) that is found on the eastern Caribbean islands of Montserrat and Dominica, and formerly Martinique.

Leptodactylus melanonotus, a smaller relative of the mountain chicken

Feeding unfertilized eggs to tadpoles may seem like a bizarre and exotic way to take care of your offspring (the BBC labeled it an “alien scene”), but it’s actually sort of mundane in the world of amphibians. Amphibians have the most diverse set of modes of reproduction and nutrition of juveniles of all the land vertebrates. Laurie Vitt and Janalee Caldwell, in their superb herpetology textbook, list 40 different reproductive modes for frogs. Its hard to pick a strangest amphibian reproductive mode, but I’d go with either the gastric-brooding frog, Rheobatrachus silus, in which the female swallows her eggs, which develop in her stomach, or histophagy, practiced by several amphibians, in which the fetuses feed upon the mother’s hypertrophied oviductal lining (i.e. while still inside of her).

Dendrobates auratus with tadpole, Est. Biol. La Suerte, Costa Rica

The poison dart frog, Dendrobates auratus, above is a male, carrying a single tadpole in the lower middle of its back, which it will transport to some wet spot, such as a puddle or tree hole. The female of its relative Dendrobatus pumilio (featured in a previous post) places its tadpoles in the axils of bromeliads or other arboreal plants, and then returns, like the mountain chicken, to feed them with unfertilized eggs.

DSCN3789The pair of tree frogs, Hyla phlebodes, above was found in amplexus (that’s what mating is called in frogs); the male is the smaller one. Unlike the other frogs mentioned in this post, this species has the typical, un-exotic reproductive mode for frogs: eggs are laid in the water, which hatch into tadpoles, which metamorphose into froglets. It’s a pretty wondrous way of life, too, it just seems a bit un-exotic because we’ve been jaded by its familiarity.

Many amphibians have recently undergone significant population declines, and a number of species, including the gastric-brooding frog are now extinct. A fungal disease called chytridiomycosis has been implicated in causing the decline of many species, including the mountain chicken. The BBC video was made as part of a captive breeding conservation effort involving the Jersey Zoo, founded by the late naturalist and author Gerald Durrell,and the London Zoo.

Poison dart frogs: poison, yes; dart, not so much

August 21, 2009 • 10:07 pm

by Greg Mayer

The brightly colored, poisonous frogs of the family Dendrobatidae are usually called poison dart frogs, but the name is a bit of a misnomer. While they do have toxic alkaloids in their skins, only three species are definitely known to be used for poisoning blowgun darts– Phyllobates aurotaenia, Phyllobates bicolor, and Phyllobates terribilis— all by the Noanama and Embera Choco Indians of western Colombia. The most toxic of these, and the most toxic of all dendrobatids, is the very bright yellow, and appropriately named, Phyllobates terribilis.

PhyllobatesterribilisWilfriedBerns
Phyllobates terribilis, photo by Wilfried Berns, via Wikipedia

The foremost students of these frogs have been Chuck Myers of the American Museum of Natural History, and his colleague John Daly. During a visit to the Museum some years ago, Chuck kindly showed me the terribilis he kept in his office, but I did not take any pictures, hence the Wiki photo. Their studies have shown that there is considerable individual, geographic, and interspecific variation in the poisons present in the frogs, and that individual frogs may contain multiple toxic compounds. Some of this variation results from the fact that the frogs obtain the alkaloids, at least in part, by uptake from arthropod prey.

The American Museum has made all the back issues of its scientific publications available as pdf’s, and many of  Myers and Daly’s papers, including quality color plates, are available there.  I would recommend

1976. Preliminary evaluation of skin toxins and vocalizations in taxonomic and evolutionary studies of poison-dart frogs (Dendrobatidae). Bulletin of the AMNH 157:175-262;

1978. A dangerously toxic new frog (Phyllobates) used by Emberá Indians of western Colombia, with discussion of blowgun fabrication and dart poisoning. Bulletin of the AMNH 161:309-365 (with Borys Malkin);

1995. Discovery of the Costa Rican poison frog Dendrobates granuliferus in sympatry with Dendrobates pumilio, and comments on taxonomic use of skin alkaloids. AM Novitates 3144:1-21 (with H.M. Garrafo, A. Wisnieski, and J.F. Cover).