Sharks are Better Than You

Sharks are insane. There’s no light way around it. Almost everything about their natural history, their morphology, and their adaptations seem to cross the line from typical, run-of-the-mill animal nature to completely and utterly bizarre.

Let’s start with their sensory organs. Since childhood, it is ingrained in us that there are five general categories of senses: sight, smell, taste, hearing, and touch. Each of these senses has a general organ associated with it for people: eyes for sight, nose for smell, so on and so forth. Five general sensory organs for five general senses. Pretty simple stuff, pretty well established across the animal kingdom. I mean, wouldn’t it be ridiculous for other animals to have extra senses that we don’t have? That would be utterly terrifying.

 Gulp.

Sharks don’t have five sensory organs. Not six, either. Their sensory organ count tops out at seven. Seven separate body parts, each performing a different function – usually related to food consumption, further cementing their reputation as incredibly efficient  killing machines.

Their sixth sense derives from something that all fish (including sharks) share: a lateral line. This line is a series of sensory organs running alongside the fish, giving it the sense of motion detection. This way the fish can feel potential prey moving away from it – or a fearsome predator moving towards it – before it actually sees the animal at hand. The fish in the Chondricthyes class (sharks, rays, and chimaeras) have a seventh sense as well: the ampullae of Lorenzini, a series of snout receptors that can detect electrical impulses produced by otherwise cryptic prey.

 Electric impulses are given off with muscle contractions. Yes, that includes your bicep flexing to impress the ladies.

I could go on all day about all the anatomy that we take for granted in the animal kingdom that are simply not true for sharks. Skeletons are made out of bones, right? Not for sharks – their entire skeletal structure is made out of spongy cartilage and connective tissue. It’s also pretty much common sense that fish lay eggs. Sharks can lay eggs. But for most, this egg laying occurs inside the mother’s body, where the pups are incubated, hatch, and are then born into the water. (Some species forgo the whole egg concept and give live birth.) And as for jaw placement? The whole idea that jaws are attached to something on the head just simply doesn’t apply to these guys.

Who needs cranial jaw attachment? Not goblin sharks, that’s for sure! (Photo credit Peter Halasz)

In general, sharks also have way too many of certain body parts, as the following chart suggests.

Body Part	Our Number	Shark’s Number	Because . . .
Eyelids	2 per eye (top and bottom)	3 per eye, including a clear nictitating membrane	…sharks need eye protection underwater.
Teeth	28, 32 if you still have your wisdom teeth	3,000 at a time, thousands in a lifetime	…a sea creature diet isn’t as easy on the teeth as our mushy human food.
Male reproductive organs	1 per male	2 per male	…sharks are just more manly than human men.

Last week, I encountered what some might consider the most unabashedly bizarre shark of all – a scalloped hammerhead shark. Not only does it have a detachable jaw, spew live babies like some kind of mammal wannabe, and can find electricity with it’s snout, but it also has one of the oddest shaped heads in the animal kingdom.

Don’t make fun of his head, he can’t help it. (Photo credit Barry Peters)

Scalloped hammerheads are just one of 9 species in the genus Sphyrna, which derives from the Greek word for hammer and refers to the odd head shape. This “hammer” is known as a cephalofoil, and this oddity has been around in the shark world for 20 to 25 million years.

Why the odd shape? There are many theories floating out there, but one widely accepted idea is that the odd eyeball placement enhances the animal’s binocular vision. Monocular vision, or using one eye at a time to increase the field of view, is better for animals that are primarily prey, as it helps them scan the horizon quickly for predators. Binocular vision, however, offers much more of an advantage for predatory critters. This is because the binocular vision, which creates an overlap between the two eyes, helps the animal locate and focus on specific prey items. The wider the head, the greater the binocular overlap – as long as the eyes tilt forward, as the hammerheads’ eyes do. Hammerheads also have 360 degree vision, thanks to their straight-outta-sci-fi eyeball placement. Like sharks needed something else to make them scarier.

For some reason, I don’t think human binocular vision has the same terrifying effect.

Hammerheads, like many big sharks, have built up a rather nasty, human-biting reputation. After all, most of them are primarily carnivorous beasts the length of a Lincoln Navigator, so it’s not hard to imagine where that reputation came from. This reputation however, is almost 100% unfounded, according to the International Shark Attack  File.  Since 1580, only 1 fatal hammerhead attack has been recorded. That’s right. We’re looking at a 1 per 500 year average. Overall, the grand total of fatal, unprovoked shark attacks in the last 500 years? 138, out of just barely more than 1,200 reported attacks. Those are pretty good odds.

Now I’m not suggesting that we go out and give hammerheads a big ol’ bear hug, of course. Sharks still have powerful jaws and thousands of sharp teeth. They are still creatures that have the potential to hurt us. But that’s it – just the potential.

No shark hugs. Not even the little cute ones. (Photo credit Terren Peterson)

Humans are not natural prey of sharks. Most cases of shark bites end up being “exploratory bites.” One taste usually results in the shark leaving, because people are apparently not as tasty as seals, stingrays, squids, or any one of the million other things that sharks eat.

Even trash is considered more desirable than humans by many shark species. Take that as a compliment. (Photo credit  S. Muller)

Sharks are a group of animals that people should certainly be aware of and respect. This is just a classic example of the “we leave them alone, they leave us alone” concept. So exercise caution, but don’t go thrashing about in terror like a wounded animal if you come across one. Observe, learn, and share. Because sharks may be some of the weirdest animals to grace our oceans, but they’re also some of the coolest.

Avocado Family Tree

During the blazing hot summer months in Georgia, my eating habits suddenly change. My produce bills start to go up as I toss more and more avocados in my grocery cart. I seem to be drawn to more authentic Mexican restaurants with fresh, chunky guacamole. Without realizing what I’m doing, I order menu items just because they have the word “avocado” in the description. What is it about this vegetable that inexplicably draws me to it when the temperature heats up? This cool, creamy, smooth, refreshing, heavenly—

Excuse me while I faceplant into this bowl of guacamole.

Culinarily speaking, avocados are considered vegetables. Botanically, however, the avocado is definitely a fruit. Specifically, a berry. Yes, I am aware the avocado looks nothing like a blackberry, strawberry, raspberry, or any other fruit-like object that people have slapped the “berry” label on.  Oh, and by the way – none of those are berries anyway.

Berries are fleshy fruits with seeds contained in a single ovary. If it has seeds in one fruit body from many ovaries *coughcoughblackberrycough*, then it is not a berry. It’s called an aggregate fruit. If the fruit’s so called “seeds” are actually teeny tiny individual fruits (with their own ovaries) all lumped together, then it’s an accessory fruit – meaning strawberries are not even close to true berries.

The jig is up, straw-”berry.” We know your secret.

Avocados, or Persea americana, are a widely cultivated species in the Lauraceae, or laurel, family. Laurels are known for their aromatic oils, small round flowers with spirals of stamens  (aka, boy parts), and fleshy fruits – such as enormously fleshy avocado berries.

The fleshy part of the avocado is technically the mesocarp.  I prefer it’s common name, the deliciousness.

Another cultivated member of the laurel family tree (See what I did there? Clever, eh?) is Cinnamomum, or simply, cinnamon. Rather than being cultivated for its fruits, these plants are grown for their bark and harvested to create spices and herbs.

That’s right, your morning bowl of Cinnamon Toast Crunch came courtesy of some tree bark. You’re welcome.

One member of the laurel family that is native, rather than cultivated, here in the southeast United States is the redbay, or Persea borbonia. Often outshadowed by majestic live oaks, this small tree has been gaining more than it’s fair share of attention in the last decade due to a particularly nasty strain of laurel wilt.

The wilt is caused by a fungus transmitted by the redbay ambrosia beetle (an exotic pest) and is currently wreaking havoc on Georgia’s redbay population – and is expected to keep moving along the coast. This is terrible news for turkey, bobwhite quail, songbirds and deer, which all eat various parts of the redbay plant. It’s even worse news for three species of swallowtail butterfly, which all produce larva that is dependent on redbay leaves.

I know this creeper spicebush swallowtail butterfly larva looks like he could destroy anything that tries to take his food, but he’s pretty defenseless against laurel wilt.

And if we’re not careful, it could spell doom for lovers of decently priced avocados. Redbay and avocado are not only members of the same family, but the same genus. In 2007, five years after the arrival of the laurel wilt fungus in the Southeast, Florida’s first avocado plant fell victim to the disease. It sounds devastating, and it very well could be. But there is action that can be taken. Leaving the research and policy making to the experts, there are several easy things we can do to help: avoid transporting firewood or dumping yard waste, donate money to research efforts, and simply spread knowledge of the problem to more Southeast citizens.

Please help stop the spread of the redbay ambrosia beetle. Avocados are expensive enough as it is  Save the Redbays!

The Birds and the Honey Bees

It’s a pretty well-known fact that it takes two parents to produce another living animal. One parent contributes one set of chromosomes, the other parent supplies the second set, the genes are mixed at fertilization, and POOF! Offspring capable of carrying on the line of its parents is produced. Count it a win for “genetic diversity.”

That’s the general gist of “the birds and the bees” in the animal kingdom. Except that one of these namesake creatures defies this conventional wisdom and produces an entire population segment with the, erm, input of just one parent.

S

See that one big bee in the middle? All elevendy billion of those bees around her were spawned by her.

Honey bees, or any species of bee in the genus Apis, lay eggs whether they are fertilized by a male or not. Fertilized eggs (diploid, or eggs with 32 chromosomes from two parents) will develop into female bees. Unfertilized eggs (haploid, or eggs with just 16 chromosomes from the mother only), will develop into the male bees. This is a form of asexual reproduction known as parthenogenesis. In the plant world, this phenomenon is a little more common. In the animal world, it crosses the line into bizarre, only happening in a few invertebrates species and with a few fish and reptiles under extreme circumstances.

To appreciate how incredible this is, visualize a carton of chicken eggs. Each egg is an unfertilized egg laid by the mother hen. Imagine instead of you cracking open that egg and dumping its into a cake batter, you watched in horror/surprise/feigned interest as that egg hatched into a rooster. Now imagine that EVERY rooster that ever existed came into the world this way: half-clones of their own mothers, all virtually identical, without even a full genetic code to make itself feel better.

Honey bee males, or drones, certainly do get the short end of the stick in the hives. Not only do they have half the genes (and double the “absent daddy” issues), but they don’t even have what is arguably the most bad-ass part of the bee: the stinger. Stingers are modified egg-laying organs, or ovipositors. As males, they are sorely lacking in the ability to lay eggs and, as a result, don’t even have the chance to develop this venomous barb.

 A venomous butt-sword would certainly make life in the hive more entertaining.

Drones don’t have stingers to defend themselves or the ladies of the hive. They don’t produce honey, collect nectar, construct hives, or gather pollen like the female worker bees, either. They don’t get a chance to be fed royal jelly to develop into a queen bee. Drones only appear to serve two purposes: to keep the hive warm and, most importantly, to mate with queens from other hives. (But this mating doesn’t have quite the happy ending for our down-on-their luck drones, as their reproductive organs and abdomens are ripped out in the process).

Basically, drones only exist for mating and warming the house by sitting on its rump all day. This is either the most pointless, degrading job assigned by Mother Nature – or the most incredibly awesome one. Maybe it’s nature’s version of a “Sorry You Only Have Half Your Chromosomes” Hallmark card.

Here comes Peter Cottontail, hopping down the bunny trail

In honor of Easter this weekend, this week’s post will explore that mammalian reproductive enigma that confuses children across America every spring: the egg-laying Easter Bunny! The origins of this tale (get it? get it?) of an egg-laying mammal are a little fuzzy (double pun! Oh, how I crack myself up!).

The story most likely comes from a German folktale that was introduced to American audiences by immigrants in the 18th century. The German folktale of the “Oschter Haws,” a hare that laid nests of brightly colored eggs in children’s hats and bonnets every spring, itself has pretty murky origins. The Grimm brothers made a feeble attempt to give the story a little historical credibility by attempting to link it to pre-Christianity pagan myths, but even this was a stretch. Odds are, the story is an amalgamation of historical fertility symbols with new Christian traditions. And, as we are constantly reminded by advertisers every spring, rabbits and Easter are forever intertwined.

What Easter bunny eggs look like when they hatch.

But why are rabbits and hares tied so closely with fertility, and fertility tied with Easter celebrations? Easter coincides with the beginning of spring – the time of rebirth and renewal after the long, dormant, cold winter months. And with that renewal comes lots of new baby animals. Lots and lots of baby animals. And in order to create new baby animals, that means the parent animals had to…well, you know. And what group of animals are known for copulating like bunnies?

Well, I think I just answered my own question.

Rabbits, and hares as well, are members of the Leporidae family. They closely resemble rodents, and used to be classified as such, but are now in their own category thanks to significant differences in skull, jaw, and tooth formation. One of the most famous species of this family is the Eastern Cottontail (Sylvilagus floridanus), found all the way from Canada to South America and as far west as the Great Plains. Suffice to say, it’s a pretty common rabbit. And, to put it lightly, these rabbits are “very productive” in the reproductive department.

Eastern cottontails can have anywhere from three to seven litters per year, thanks to a month-long gestation period and two-week weaning period. Each litter can have anywhere from four to seven young. That’s anywhere from 12 to nearly 50 babies for one mother per year. Considering that 80% of these litters are born from April to June, it’s pretty easy to see where the fertility-rabbit connection came from.

All in a day’s work.

Unfortunately for these proud super-rabbit-moms, there’s a reason why they need to produce so many offspring. The average mortality rates for eastern cottontail rabbits hover at around 80% per year, most of which happens during the breeding season. Predation by coyotes, bobcats, foxes, owls, and hawks make up the bulk of this mortality. Cottontails tend to prefer early forest successional habitats, meaning areas of dense shrubs and thickets. As they move out into the open from the cover of these thickets during the spring, they are more open to predation.

Don’t keep yourself up too late at night worrying about the rabbits going extinct, however. In addition to early succession habitat, many species of rabbits also take advantage of crop fields, orchards, and pastures – prime agricultural land which, coincidentally, provides a pretty easily attainable food source for these herbivorous almost-rodents.

What? I’m totally supposed to be here.

One important question to raise, however, is why rabbits move in to human agricultural fields. Could loss of natural early succession habitat be a factor? It wouldn’t be the first case of wild animals relocating to human-influenced areas thanks to loss of natural habitat. Although the rabbits are pretty adept at re-populating themselves, that’s not the case for other early succession forest-dwelling critters. Many species of birds (sparrows, songbirds, shrikes and the like) rely on this habitat to build their nests and lay their eggs. Less habitat equals fewer nests, and thus, fewer eggs. Sigh. Now, if only the Easter bunnies really did lay eggs. . .

Birds and other kinds of dinosaurs

The link between birds and dinosaurs has become increasingly apparent over the years. Although the scientific community is pretty settled on this evolutionary link, debate is sure to continue among the public regarding where this group of animals came from. I’m not here to start an argument about evolution. But, I dare you to get face-to-face with this monstrous bird and not shudder in terror, because you are looking a freaking dinosaur in the eye.

This is what nightmares are made of.

This is a cassowary. No, this is not actually a dinosaur. But, like all birds, it has an ancestral link to the dinosaurs. Whenever I see birds like this, I have a hard time denying that there is an evolutionary link between our avian friends and the “terrible lizards” of millions of years ago.

When I come across birds that look like fuzzy rodents, however, the physical kinship between dinos and birds becomes a tad less obvious. When I see this kiwi, I have a bit of a hard time believing I’m even looking at a bird and not some sort of long-nosed gopher.

Look how fuzzy!

Not only is the kiwi a bird (and most decidedly not a gopher), it is actually pretty closely related to that terrifying dino-bird, the cassowary. Both are part of a monophyletic (from the same ancestral lineage) group of flightless birds called the ratites. The word ratite comes from the Latin word for “raft,” and describes birds that have no keel on their sternum – a.k.a., no place in their chest for wing muscles to attach. Even if they had proper wings (which they don’t), this lack of a keel would prevent them from flying.

This group of birds also includes ostriches, emus, and rheas – all giant flightless birds found predominantly in the southern hemisphere. Modern science views these birds as descendants of early flying birds who evolved flightlessness and bigger bodies than their flighted counterparts.The term “ratite” doesn’t apply to all flightless birds – for example, you’d never see a penguin lumped into this group. Why? Because they are more recently descended from birds of flight, and they do have a keel in which their wing muscles are attached. If penguins were to suddenly sprout well-developed, powerful wings, they could have the ability to fly. Ratites, however, aren’t so lucky in this department.

I believe!

Kiwis, although much more similar in stature to the penguins than the ostriches, are still classified as ratites. In fact, some sources believe that the kiwi’s ancestors may have been giant birds themselves, making kiwis a tiny version of a giant bird – which itself was a large version of a smaller bird at one point in its evolutionary history.

Many studies of ratite evolutionary history have identified these birds as primitive descendants of bipedal (two-footed) dinosaurs, branching off before other groups of smaller, flighted birds did. Now, thanks to the advent of DNA-based molecular data, older theories are being tested and ratites are still trying to find their exact spot in the evolutionary tree. But whether or not these birds are closer to sparrows or velociraptors, I still find myself fascinated with their striking resemblance to dinosaurs. Because if Jurassic Park came true and dinosaurs started coming out of the woodwork, I strongly suspect they would look something like this cassowary:

I Scream, You Scream, We All Scream for Orchids in Our Ice Cream

I’ll admit, my knowledge of orchids is pretty limited. I did read Susan Orlean’s The Orchid Thief a few years back, but all I really remember about orchids from the book is that they are highly prized for their flowers, yet they are notoriously hard to grow and cultivate. Rare. Delicate. Exquisite. All these ideas come to mind when an orchid is conjured up in my mind. Not “boring-est flavor of ice cream.”

Mmm….basic and umodified traditional sweets!

That’s right, folks. Vanilla, which Urban Dictionary defines as “unexciting, normal, conventional,boring” is actually a type of orchid. A rare, delicate, exquisite orchid. Due to the difficulty of pollinating and cultivating said orchids, vanilla is the second most expensive spice in the world. Shocking, I know. But wild vanilla orchids, as the all-knowing and always-correct Wikipedia just informed me, are invested in an extremely mutualistic relationship with a Central American species of Melipona bees. These bees are the only things capable of pollinating the vine that produces the vanilla flower. The only things other than humans, that is. If you really wanted to cultivate your very own vanilla, you could painstakingly swab a small stick onto some orchids and transfer the pollen onto other orchids. One by one. By yourself. In the tropics. All the time.

Yes, this is a white orchid. No, this is not a vanilla orchid. But you get the idea.

Of course, growers do this a lot to produce pure vanilla, and this vanilla is available for a (pricey) purchase at supermarkets. Or, you could do what I do, and purchase a bottle of synthetic vanilla extract from Kroger for about a buck, and dream about the day when you can afford the real stuff. Or move to Central America and start your own vanilla orchid enterprise.