Wednesday, June 25, 2014

Amphibious Brain Freeze

Amphibious Brain Freeze

What does a tiny frog called the “Spring Peeper” have in common the 7-11 Slurpee marketed as “The Brain Freeze?” They both come frozen. Pseudacris crucifer is known by gardeners from the mid-Atlantic northward to be the auditory harbinger of spring – time to get planting! This nickel-sized amphibian is one of the first hibernating animals to wake up after a cold winter, and the males wake up singing for you-know-what. The amazing thing about the northern spring peeper is that it can wake up from a frozen state. P. crucifer is one of a few species in the animal kingdom capable of surviving several weeks as a frog popsicle. Its southern cousin, Pseudacris crucifer bartramiana, may share this amazing ability with the northern spring peeper, but Florida winters evidently haven’t put it to the test.

North of “The Land of the Flowers” frogs generally hibernate in areas protected from all but the harshest freezes: lake bottoms or deep under the ground. By contrast, northern spring peepers spend the winter on the forest floor camouflaged underneath moist leaf litter. When temperatures hover around freezing, stage one of the peeper’s hypothermic response kicks into gear. Reacting to near-freezing temperatures, the frog’s liver changes stored glycol into glucose, a form of sugar. By introducing glucose into the organs and circulatory system, the freezing point of the frog’s bodily fluids is lowered by several degrees. Remember our Brain Freeze Slurpee? The sugar in the beverage allows the drink to be super-cooled while not freezing solid (it helps that the liquid is constantly moving like cement in a mixer). When we drink this hyperchilled beverage, some of us experience the pain of a too-sudden exposure to its freezing temperatures, the famous Slurpee Brain Freeze. Prolonged exposure to freezing temperatures can harm and even kill humans.

But not so given the peeper’s hypothermic survival response: stage one prevents ice crystals from forming in the frog’s essential organs by pumping them full of glucose. That protects the frog down to about 27 degrees F. What happens then temperatures continue to fall? The second stage of the peeper response is to allow its body to freeze – but to do so in a controlled manner, doing the least potential damage to vital organs. As temperatures drop, the frog’s body adopts a triage strategy to its freezing process. It draws water out of the most vital organs and supercools the remaining fluids by absorbing solutes into the cell structures. Both measures minimize the formation of ice crystals that could rupture cells and organs. Less vital structures are allowed to freeze solid. After the frog has effectively been frozen, the heart stops. Any necessary energy consumption is performed anaerobically.

This controlled freeze-out is amazing, even weird. But even more remarkable is the thaw. The peeper must survive, indeed, return to life as a result of the process. So its meltdown can’t simply return the ice crystals in its body to a liquid state. The whole process must unwind itself precisely, starting by activating the vital organs simultaneously and ending with the glucose being converted back to glycol and returned to the liver. There are limits to this hypothermic response and reversal mechanism. External temperature drops must not be too dramatic; the frog needs time to engage the hypothermic response. Conversely, the heat up time cannot occur too quickly for the frog to reverse the chemistry it set into motion. A frog cannot remain in cryogenic suspension too long; the adaptation has a shelf life. And at super cold subzero temperatures, the response is ineffective – too many ice crystals will form and damage essential organs. Therefore, peepers cannot inhabit arctic or subarctic areas. The peeper’s freezing response is energy consumptive; harsh or prolonged winters even in temperate climes can be its demise. A frog can only mount so many hypothermic responses in one season before energy reserves give out. Hopefully, the spring thaw arrives before that happens.

Early spring imposes new demands on spring peepers. At least for males itching to mate, the demand is to peep. Females are listening for the loudest peeper that can also peep the most quickly. She can assess his fitness by these two qualities alone. The loudest peeps come from the biggest vocal sacs that only the heftiest individuals can sport. And a superfast peeper has to have remarkable breath control – fit enough to keep peeping long and fast without pausing to provide himself with oxygen. Once she has made her choice, the peepers dip into the lake for an intimate moment. Then they go their separate ways. She, to lay her eggs on a stem or twig underneath the water. He, to begin peeping another fair maiden.

Even though our southern spring peeper is not called upon to perform cryogenic feats, the male must still outdo his competitors in the chorus line. Whether north or south, the mechanics are the same. The frog fills its lungs with air, seals its nose and mouth and passes that air back and forth from the lungs over the larynx (that produces the sound) and into the vocal membrane. This membrane vibrates and acts like an amplifier. And size counts. The larger the frog, the larger the membrane. The larger the membrane, the louder the sound. Louder is better. In the spring the peeps of these frogs can be so loud, one wonders if an alien ship has landed near some body of water. Unlike the nocturnal northern peeper, all a southern fella needs to start peeping, day or night, is a good soaking rain. A healthy Florida rain can evoke a long and strong peeping behavior in P.c. bartramiana that predictably arouses the female.

When the last peep is peeped and the last egg deposited, northern peepers retire to woodland locales to lounge on lower branches, eat small insects, and await the coming winter. The randier southern peepers are better climbers. This subspecies spends its time in higher limbs catching flies, spiders, and other small insects, and vocalizing when the situation arises. Both peepers used to be classified as tree frogs, Hyla, until biologists posited them into the Pseudacris (false cricket) family of chorus frogs. Fertilized peeper eggs hatch into tadpoles in just under two weeks. After a few weeks of grazing in their aquatic environment, both northern and southern peeper tadpoles mature into adults, acquiring the brown “x” (crucifer) on their backs. The northerners join the other grown-ups in wooded areas, stocking up on proteins for the coming winter. In three years’ time, northern and southern males will be tuning up their vocal sacs in the hopes of gaining a lady’s favor.

Every July 11th, participating 7-11 stores offer free Slurpee (Brain Freeze) drinks to their customers. Maybe you’ll want to quaff one down to celebrate the northern spring peeper, the plucky amphibian with the big winter survival adaptation. Just don’t ask the store clerk for one in frog-flavor.

Last Saturday’s Pollinator Celebration was fun and informative. Mark your calendar for next year! In the meantime, if you want to continue your celebration of native pollinators, why not sign up as a monthly butterfly monitoring volunteer? And please do feed the pollinators! See the Unsung Heroes of Pollination article for tips on how to start a pollinator-friendly garden.

Wednesday, June 18, 2014

To the Unsung Heroes of Pollination

To the Unsung Heroes of Pollination

As part of our lead up to Pollinator Day this Saturday, Weird Animal Wednesday has spotlighted a particular pollinator species from the butterfly, moth, bee, bat, and bird families – our salute to the important work these creatures do in keeping countless species of plants from becoming extinct. We have one more Wednesday left before 6/21. What other pollinator types remain unnamed? Several, it turns out.

In 2006, the U.S. Senate created a National Pollinator Week to “recognize the importance of pollinators to ecosystem health and agriculture in the United States.” So, we’d be remiss if we failed to acknowledge these lesser-known pollinators. The heretofore unmentioned heroes of pollination include many types of flies, wasps, and beetles. And some would also add the ant. OK, it’s a big tent, or more precisely, a big plant kingdom. And these little creatures are the unsung pollinator heroes of that world. In some cases their pollination is an essential, not just an incidental benefit.

Let’s review some aspects of the pollination “relationship”. First of all, it is a relationship. Except in the case of self-pollination or wind pollination, two different representatives, each from distinct biological kingdoms, are involved. What brings this “odd couple” together? One motivational factor is reciprocal benefit. The flower attracts a pollinator using several means at its disposal: color and accessibility (for instance, shape), scent in some cases, and nutrition (nectar, and possibly pollen or wax) or subterfuge.

Nutrition or subterfuge. Well, nutrition is straightforward; almost all of our better-known pollinators – bees, butterflies, moths, bats, and birds – derive nutritional benefits. Most of the lesser-known animals – flies, wasps, and beetles – also utilize plant nectar for energy. But some plants are deceptive, promising what they don’t deliver. For instance, some orchid species imitate female wasps. The male attempts (unsuccessfully) to “mate” with the orchid; the orchid receives a pollination benefit. Pollination is about sex, after all – and sometimes it’s not confined to plant sex, even if the insect sex is just a fantasy. This is a case where the benefits are not exactly reciprocal, but hope springs eternal, so it’s a “sure thing” to the orchids’ benefit that these male wasps will get fooled again.

Sometimes the subterfuge involves a promise of a meal the plant can’t deliver. But the insect doesn’t know it. Many flies and beetles are “adventurous diners”, and plants that specialize in attracting these species don’t just rely on their good looks and nectar sources; they also beckon beneficial insects by mimicking the rotten meat these insects consume. A suitably stinky aroma combined with a color the shade of decomposing flesh is a powerful attractant. The mammoth Titum arum, affectionately known as the Corpse Flower, is a huge case in point. Its 6-8 foot inflorescence is short-lived, but makes a powerful putrid statement. The first night is when the female flowers are open for business, the tall central spadix actually heats up to 98 degrees Fahrenheit, just below normal living human body temperature – the better to disburse it’s scent to passing flies that, hopefully, have just finished a visit to another Corpse Flower and have a little of its pollen to dispense. To the human eye it is a repulsive shade of purple-brown/maroon, and phosphorescent green. When one bloomed in 2005 at the National Arboretum, the building stayed open into the wee hours to accommodate the flood of (human) visitors wishing to witness a floral rarity. Unfortunately, the Titum arum chose to bloom just before Christmas in Washington, DC. It is unlikely any of its visitors included flies that had recently paid call to another blooming member of its species.

If the insect is sometimes the loser in the pollination relationship, the plant can also lose. Consider the wasp. Some species, like the great black wasp is a straightforward pollinator. Others, like the bee wolf wasp linger on the flowers that its prey visits; its meal consists of the pollinator, and any pollination that occurs because of the encounter is strictly random. But some species are truly the black sheep of the plant-insect relationship. Take the western yellowjacket. It’s an outright nectar thief, robbing the plant of its biggest asset while providing no pollination services at all. It accesses the nectar by boring a hole in the flower; and that hole can be used by opportunistic ants or flies that would otherwise not be able to gain entry. A true scientist shouldn’t judge, but the rest of us can say, “Shame, shame.”

A clarification of the word “relationship” is also in order. When we said,”two different representatives, each from distinct biological kingdoms are involved,” the numerical reference to “two” was only a generalization. In truth, most flowers can be pollinated by a range of animals. And most pollinators can access many flowers. In the case of pollinating wasps, bees, and beetles, which lack the long proboscis of other animals, the ideal flower shape is relatively open or shallow, with easily accessible pistils. But that too is a general not an iron-clad rule. And then, there is the “perfect match,” where animal and plant pair is so specialized that no other creature can partake of the union. The fig wasp that pollinates only the fig, which in turn produces enough seeds to feed the wasp and to perpetuate itself, forms a mutually obligate pair. Or the yucca month. Such tight relationships are of necessity mutually beneficial. And perilous. For if either the pollinator or the plant dies, survival of the obligate partner is nil. Unless, in the case of the vanilla orchid, a human intervenes and pollinates the plant. Vanilla is such a prized spice that humans will go to these length. Last, but not least, timing is everything. Pollen and pollinator must be in the right place at the right time, or all is for naught.

If you are a robotics aficionado, perhaps you’re envisioning a world where pollination services for our “favored plant species” could be performed by drones. We have produced micro-drones. The problem is, we still don’t know enough about how many of our key plant species are pollinated. And we can’t just worry about pollinating OUR favorites while forgetting the unsung heroes of the plant world that keep our world healthy. What we do know is that countless pollinators are losing essential habitat. You don’t have to be a rocket (or robotics) scientist to be able to help keep these natural relationships going. Devote a small piece of your property to a natural pollinator sanctuary. If your neighbor does the same, you’ll have a chain of oases for creatures trying to survive an urban/suburban dessert.

So let’s celebrate our pollinators! Join us at the GTM on 6/21 for Pollinator Day. And keep the celebration (and the pollinators) going. See the Native Plant Wildlife site for creating a pollinator oasis in celebration of National Pollinator Week. And learn more about Creating a Natural Habitat for our Florida native pollinators.

Additional Links

Wednesday, June 4, 2014

He Moves in Mysterious Ways

We’re now in the last three week of our marathon celebration of pollinators, culminating in the GTM’s National Pollinator Festival on Saturday, 6/21. Weird Animal Wednesdays has covered one representative from the butterfly, moth, bat, and bee categories. Well this week, we’re going to the birds to look at that engineering marvel, the tiny hummingbird. Florida is visited by at least ten species of hummers, many of whom migrate to Central America during cold weather, traveling for distances of up to 500 miles between “rest stops”.

You’ve probably seen hummingbirds visiting a vining or bushy collection of flowers, darting from one to another in the blink of an eye. High sucrose nectar powers them. Hummingbirds drink several times their body weight daily. Their long, forked tongues can form two tubes, uncurling to immerse into the nectar, and curling up to capture it. Pollination is incidental. Hummingbirds hover when visiting a flower, much like bees or other insects. With an almost vertical feeding position, it is no surprise that these animals prefer flowers that have relatively flat vertical faces; hummingbird feeders deliver their nectar from such designs. But hummingbirds also visit flowers that hang downwards, hovering in a rather awkward position to do so. Scientists speculate that such flowers are visited because their nectars is well-protected from dilution by rain.

Hummingbirds are in the family, trochilidae, meaning “small bird”. The name might be accurate, but it hardly does this little creature justice. The hummingbird’s unique physiology and flight technique are much closer to that of insects such as bees or hawkmoths, which, as you may remember from a previous Weird Animal edition, were real speedsters. These insects fly with more efficiency because both the down stroke and the upstroke provide lift. Hovering insect wings are supremely flexible, turning inside out with the flying process. Hummingbirds’ wings don’t exhibit that much rotation but they can turn sideways during the flight stroke. Think about how you tread water when your body is vertical. The hummer’s wing movements resemble your arm strokes to keep yourself stationary and erect. This efficiency means the bird uses less energy to fly than its larger counterparts whose wings flap up and down from a shoulder-like appendage. Nonetheless, a hummingbird spends much of its time perching. Flight is reserved for obtaining nectar and catching insects to augment their protein requirements – and for mating rituals.

Mating displays and rituals are where the male hummingbird “shines”. Not only does the male of the species sport an iridescent jeweled coat, but he performs incredible acrobatic feats to prove himself the fittest and win the fair heart of the drabber female. The courtship behavior of Anna’s hummingbird (Calypte anna) has been extensively studied; other species have similar behaviors and feather structures so it seems a safe bet that they use a routine similar to Anna’s to impress a female. During breeding season, male hummingbirds will search for perching females. When he finds a likely spectator he’ll fly straight up, perhaps as high as… feet. Then the bird will tuck back its wings and dive headfirst. At the last second, the descending male fans out his tail features, stopping his fall. He then pulls back the feathers and pulls out of his dive. The sound his tail feathers make in the onrushing wind creates a distinctive chirp, which the female evaluates for its desirable qualities. What is she looking for? First of all, since each species of hummingbird produces a distinctive “tail song” she wants to be sure her potential mate is the same as she is. Then she looks for volume. The louder the sound, the faster the male was falling. It takes a strong male to achieve the highest speeds (and live through it). This is no casual trick. A descending Anna’s hummer can reach speeds over 50MPH – so fast the velocity could rip the bird’s wings off were the chest muscles not able to draw them back out of the friction zone. Measured in terms of the hummingbird’s size this descent is faster than a jet pilot. Pulling out of the fall takes tremendous strength and the ability to withstand up to10 G’s of force; 7 G’s can cause humans to black out. Hummingbirds can pull out so quickly, however, that these forces are only active for a microsecond, thus minimizing the danger to the bird.

Adult male Anna's Hummingbird. Photo taken
by Joan Gellatly, AZ Feb 2009.
If his display impresses her, she may acquiesce. Then, his job is done. On to the next death-defying maneuver to win another feminine heart. After the tryst, the female’s job begins. She builds a lichen nest lined with soft material connected with carefully harvested spiders’ webs. Two voracious chicks emerge from the eggs she lays and now she has three mouths to feed. If the nesting took place in our neck of the woods, it’s time for the family to migrate south.

If you enjoy hummingbird visits, install some of their favorite nectar plants in your yard. See the links below. While it is tempting to hang a feeder for them, your visitors will be less stressed feeding nature’s way. A bird feeder invites competition and fighting in this territorial little creature. And remember, our hummingbirds need to head south for the winter. Keeping your feeder up too long will encourage them to stay and risk freezing to death. Flowers know when to begin and to stop blooming, and that will tell your hummers to depart on time and be back with the weather is favorable.

For some cool videos and more information check out the following links: