July 11 – What A Croc!

Today’s factismal: A female Nile crocodile determines the sex of her children by changing the temperature of the nest; too hot or too cold means more girls!

When Alice went to Wonderland, she recited a poem about Nile crocodiles; the poem praised their “shining scales” and “gently smiling jaws”. But what she should have praised was their ability to determine the gender of their children. As is the case with many other reptiles, the Nile crocodile can change the sex of its children simply by changing the temperature at which the eggs are incubated. If the eggs are kept between 89.1°F and 94.1°F, then the babies that hatch are male. But if the eggs stay too cold or too warm, then the babies that hatch are female.

A baby Nile crocodile hatching (Image courtesy Africa Wild Trails)

A baby Nile crocodile hatching
(Image courtesy Africa Wild Trails)

This would normally just be an interesting and somewhat puzzling phenomenon; biologists could (and have) argue for years over why such a mechanism for determining the sex of the offspring is necessary. But the world is currently undergoing something of a heat wave. The past fifteen years have been stuck on “hot” and the next few decades don’t look much better. And what that means is that the Nile crocodiles will have a harder time keeping their eggs in the temperature range needed for male hatchlings. In effect, the number of male Nile crocodiles will serve as a proxy for the temperature.

A baby American alligator. Cute little nipper, isn't he? (My camera)

A baby American alligator. Cute little nipper, isn’t he?
(My camera)

And Nile crocodiles are far from being the only critters that will change as the climate does. Trees will sprout further up on mountains, and butterflies will migrate earlier in the year. Flowers will bloom earlier or later. And even fish may change their spawning in response to changes in the climate.

The Washington Monument, peeking out from the cherry trees

How will global warming change the annual cherry tree festival?

Naturally, phenologists (scientists who study the timing of natural events) would love to record all of these changes. But Nature has the phenologists out-numbered eleventy billion to some. And that’s where you come in. If you would like to spend a little time each week observing the flowers in your backyard or the birds in your neighborhood or any other regular natural event, then the folks at the National Phenology Network would like you to become a Nature Observer! Just mark down your observations and add them to the easy-peasy web form and watch as the phenologists use your data!

July 2 – Bull Shark!

Today’s factismal: Bull sharks have been seen in Lake Michigan, more than 1,600 miles from the ocean where they live.

Imagine, if you will, that you are in Chicago trying to out-do Ferris Beuller. You’ve gone to a Cubs game. You’ve eaten in the fanciest restaurant you could find. You’ve even headed for the top of the Sears Tower (excuse me – the “Willis Tower”). And you decide to round off the day by heading out to the lake for a nice, relaxing afternoon by the lake. But what do you see when you get there but the fin of a large shark, cruising up and down the coast! Sound like another fake Discovery Channel documentary? Believe it or not, it really happened!

How would you like to meet this in a lake? (Image courtesy J E Randall)

How would you like to meet this in a lake?
(Image courtesy J E Randall)

The reason that it happened is that not all sharks live in the ocean. Though the vast majority of sharks are dedicated sea dwellers, there are about five species that live exclusively in fresh water and another ten or so that can live in both fresh and salt water. And that turns out to be a much harder trick than it sounds. The reason that it is difficult is because salt water has a lot of salt and fresh water doesn’t. And the reason that is important is because an animal, such as a shark, can only survive if it has the right amount of salt in its blood; too much or too little and it will die.

Fortunately, sharks (and people) have kidneys that have evolved to remove just the right amount of water and keep the blood at exactly the right level of saltiness. If it is a freshwater shark, then water percolates into the shark via osmosis (the movement of water through a membrane in order to balance solution strength) and the kidneys remove a lot of water to keep the shark’s blood salty enough. If you’ve got a saltwater shark, then water leaves the shark through osmosis and the kidneys remove just enough water to move wastes out. But if you put a freshwater shark into salt water, the kidneys won’t know that it is in salt water and will keep removing water until the shark dies of dehydration in the ocean. And if you put a saltwater shark into fresh water, the kidneys won’t remove enough water and the shark will die of bloating.

A bull shark caught in the Amazon (Image courtesy Teodoro Vaske)

A bull shark caught in the Amazon
(Image courtesy Teodoro Vaske)

The bull shark and its other fishy friends who move from salt to fresh water and back have kidneys that are capable of adjusting the amount of water that they remove from the shark’s blood. That allows them to live in both the salty ocean and the fresh lakes, which means that they can search for food in more places. (And food makes sharks very happy.) And that’s probably what happened in Chicago; a bull shark headed up the Mississippi River chasing after lunch, then followed the fish through the Illinois River and ended up in Lake Michigan. Though it is fairly rare to see a bull shark that far up a river, they are fairly common in the estuaries and river mouths near oceans all over the world.

But we’re still learning about the bull shark and other fish. We still don’t know for sure how common the bull shark is in shallow freshwater or how many rivers it swims up or what it likes to eat on these excursions into freshwater. If you see a bull shark (or other fish) and would like to help scientists learn more about them, why not add your information to the pile already stored over at Fish Base?


July 1 – The Green, Green, Seagrass Of Home

Today’s factismal: Seagrass absorbs more CO2 per square foot than rain forests do.

If you are an adult shark, you spend a lot of your time eating. But if you are a baby shark, you spend a lot of your time hiding from things that would like to eat you. And there are two places that sharks a(and other fish) hide best: in the roots of mangrove forests and in thick seagrass. If you’ve never heard of seagrass, don’t worry – you aren’t alone! It is one of those unsung heroes of the ecosystem that nobody (except marine biologists) notices until it is gone. And yet, seagrass is one of the most important things on Earth!

Seagrass provides a home for many fish (My camera)

Seagrass provides a home for many fish
(My camera)

It provides a hiding place and food for mollusks, small fish, crabs, and even huge dugongs and manatees! Not only does seagrass provide a sanctuary for little fish, it also helps stabilize sea floors and provides food for many animals. Seagrass grows on shallow muddy and sandy bottoms, changing them from places filled with muck to havens filled with life. Seagrass slows down the water that washes over it which causes the sediment to fall to the bottom where it is anchored by the seagrass roots. That sediment is mostly mud and fine sand that would choke the gills of small fish and cut off the light from small plants if it weren’t turned into useful sea bottom.

Seagrass helps stabilize the sea floor (My camera)

Seagrass helps stabilize the sea floor
(My camera)

And the root of that bounty is the photosynthesis that seagrass does. By living in the shallow water, it is able to take advantage of the abundant sunlight and nutrients to grow rapidly. And that rapid growth means that it also stores CO2 rapidly; some biologists estimate that seagrass absorbs more than twice as much CO2 per square foot than a rain forest would. All told, seagrass absorbs about 1/8th of the CO2 that goes into the ocean, making it one of the world’s greatest tools for fighting climate change and species loss.

Seagrass helps make oxygen (My camera)

Seagrass helps make oxygen
(My camera)

Unfortunately, we are losing seagrass. Overuse of fertilizers, soil loss from farming, and shoreline development have reduced the amount of seagrass by more than 12,000 square miles – that’s about the size of Maryland! Fortunately, there is a citizen science opportunity to help. Seagrass Watch is looking for people to report on the state of the seagrass that they see. To take part, head on over to:

June 30 – Archie Toothless

Today’s factismal: The giant squid Architeuthis (“chief squid”) isn’t the biggest squid in the ocean but it is the longest.

One of the interesting things about sharks is that even though all sharks are meat-eaters, each type of shark eats a different type of meat. Whale sharks eat plankton. Tiger sharks eat fish and seals. Great white sharks eat seals and fish. And some sharks even eat squid.Heck, some of them even eat giant squid!

There is no creature more fabled and fabulous than the giant squid. Mentioned in literature from the time of the Bible and featured in books as diverse as 20,000 Leagues Under The Sea and Moby Dick, it is known more by rumor than by fact. That’s because old Architeuthis (Archie to his friends) is a shy critter who prefers hiding in the deep water (the better to nab his favorite snack of other squids) to gamboling about where people can see him. Until very recently, Archie was known more by implication than by actual fact.

Architeuthis sucker scars on sperm whale skin (Image courtesy Magell Inc)

Architeuthis sucker scars on sperm whale skin
(Image courtesy McMillan Company)

What sort of implication? Consider the sperm whale. These behemoths love to munch on fish and squid, and (given their size-driven appetite) the bigger, the better. So it is only natural that sperm whales would chase down big squid like Archie and ask them to dinner. And it is only natural that Archie would vigorously decline the invitation, leaving giant sucker marks on the whale. Of course, when the whale would win the argument, there’d be the beak (the part that proves a squid to be a mollusc) left as an undigestible lump in its stomach which would be found when whalers insisted on the sperm whale joining them for a bite.

Until 2004, this was the only way we found giant squid (Image courtesy Enrique Talledo)

Until 2004, this was the only way we found giant squid
(Image courtesy Enrique Talledo)

And then there were the rare sightings. Originally taken for nothing more than sailor stories, they acquired a great deal more importance once the sailors started backing up their tales with something more than scrimshaw. By the mid 1800s, we knew that there was a giant squid living in the ocean. But that was about all that we knew. It wasn’t until 2004 that images of a giant squid swimming around and chasing other squid surfaced. Since then, there have been many more sightings, but we continue to learn more about Archie.

Why they named it "Middle clawed" (Image courtesy Theudericus)

Why they named it “Middle clawed”
(Image courtesy Theudericus)

Including the fact that though Archie is the longest squid out there (a whopping 43 ft long from tip to tail for the women and 33 ft for the men), it is not the most massive squid in the oceans (“just” 606 lbs for the lady squids and a mere 303 lbs for the gents). Instead, the colossal squid known as Mesonychoteuthis hamiltoni (“Hamilton’s middle clawed squid”) that lives in the waters near Antarctica outweighs it by a large margin; the largest recorded specimen of Hamie weighed 1,091 lbs! (Imagine half a ton of angry squid headed toward you…) However, though old Hamie is fat, he isn’t very long; they are only about 33 ft from tip to tail when grown (so they are shorter than a city bus).

So what can we learn from these not-so-gentle giants? First and foremost, there are plenty of exciting things still left to discover. From bigger-than-giant squids to smaller than a pin microbes, life is amazingly diverse and new discoveries lurk around every corner. Second, most of the sightings of Archie and Hamie happened when ordinary folks (that’s you and me) happened to see something and reported it to researchers. If you’d like to help, then why not join the Washington NatureMappers or start a project like that in your area?

June 29 – Walk The Plankter

Today’s factismal: “Plankton” means “a lot of floating critters”; “plankter” means “just one floating critter”.

One of the coolest things about sharks is that the largest shark, which also happens to be the largest fish in the world, is the whale shark and it feeds off of some of the smallest critters in the ocean. And the feeding is good; there are about one million bacteria and ten million viruses in every teaspoon of sea water. While a whale shark might call them dinner and you and I might call them disgusting, what a biologist calls them is plankton (from the Greek planktos for “drifter”) if there are a lot of them. If there is just one, a biologist calls it a plankter.

Four tiny plankton; the largest is about the size of a grain of rice (Image courtesy John R. Dolan, NOAA)

Four tiny plankton; the largest is about the size of a grain of rice
(Image courtesy John R. Dolan, NOAA)

Plankton are little critters that are too small and weak to swim against the tide so instead they drift with it going wherever the currents take them. As is the case on land, most plankton get their energy from sunlight; these are known as phytoplankton because they act just like plants (phytos if you are Greek or a geek). The zooplankton are animals that nibble on other plankton and whatever else they can get their jaws around; interestingly, a lot of bigger animals spend at least a little time as zooplankton. These meroplankton include starfish, crustaceans, worms, and lots and lots of fish (who still don’t get out of the water to go to the bathroom). And then there are the bacteriaoplankton, little bugs that eat the leftovers of the other two groups which sometimes includes the dead members of the other two groups.

A small zooplankton, drifting along (Image courtesy Mikhail Matz, NOAA)

A small zooplankton, drifting along
(Image courtesy Mikhail Matz, NOAA)

And that leads us to what may the most interesting and slightly disgusting fact of all: we still don’t know where most of the plankton in the ocean live! Until recently, we thought that they were mostly confined to the near surface where the phytoplankton could get lots of sunlight and the zooplankton could get lots of phytoplankton. But that may not be true. As we have learned more about the types of places that life thrives, we have learned that life thrives in unexpected places. And the Plankton Portal wants your help to identify some of those places. By looking at pictures taken of sea water from different places in different oceans, you can see plankton floating around. And by identifying each plankter, you can help the oceanographers understand how nutrients and energy move around in the ocean, which will help them understand how life actually is lived here on planet Earth. To learn more about the project, swim to:

June 28 – Sailing the Seventy Seas

Today’s factismal: There are at least 140 different seas on Earth.

Where do sharks live? Why in the seven seas, of course. But what are the seven seas? And why are they called that? As usual, there is a modern answer, an ancient answer, and the right answer.

The Aegean Sea was known to the ancients (My camera)

The Aegean Sea was known to the ancients
(My camera)

The ancient answer comes from the Greeks. They were great seafarers and sailed all over the “known world”. In doing so, they encountered many different bodies of water and called the largest and most important of them “seas”. To a Greek sailor of 300 BC or so, they seven seas would be the Aegean Sea between Greece and what was Troy and is Turkey, the Adriatic Sea between what was Rome and now is Italy and what was Illyria and now is Croatia, the Mediterranean Sea, the Black Sea between Turkey and the Ukraine, the Red Sea between Egypt and Saudi Arabia, the Persian Sea (now known as the Persian Gulf) between what was Persia and what is Saudi Arabia and what was Persia and what is Iran, and the Caspian Sea between what was wasteland and now is Russia and what was Persia and now is Iran. When a Greek sailor said he had sailed the seven seas, he was bragging that he had been all across the known world; he’d been everywhere, done everything, and gotten the toga.

The Atlantic Ocean, anotehr ancient "sea" (My camera)

The Atlantic Ocean, anotehr ancient “sea”
(My camera)

The modern answer is both the same and different from the ancient answer. The modern description of the seven seas includes the Arctic Sea, the North Atlantic Ocean, the South Atlantic Ocean, the North Pacific Ocean, the South Pacific Ocean, the Indian Ocean, and the Southern Ocean (also known as teh Antarctic Ocean). Though the seas are different, they idea is still the same. For someone to say that they have sailed the seven seas today means that they’ve been everywhere, done everything, and have the T-shirt to prove it.

The Coral Sea (My camera)

The Coral Sea
(My camera)

So what is the right answer? The right answer is that there is no actual answer. There are at least 140 different regions on Earth that are described as seas. Some of them are large bodies of salt water, like the North Atlantic. Some of them are tiny, little freshwater ponds, like the Caspian. (Tiny being a relative term; the Caspian Sea is literally half the size of Texas.) Some of them have clearly defined borders, like the North Pacific. Some of them have no real borders at all, like the Sargasso Sea. (The Sargasso Sea does, however, have plenty of boarders.) So pick any seven to sail and those can be your own, personal seven seas.

The Antarctic Ocean, one of the modern "seven seas" (My camera)

The Antarctic Ocean, one of the modern “seven seas”
(My camera)

And while you are sailing, why not do some science along the way? To learn more about coral reefs and how they form oases in the oceans, then head on over to the Coral Reef Monitoring Program!

June 27 – By Neptune’s Beard!

Today’s factismal: A mermaid’s purse is the case that protects a shark egg.

Shark week starts today and so does my annual set of posts about all things in the ocean. Our first post is about how sharks give birth. In many shark species (e.g., the whale shark and the basking shark), the fertilized egg actually hatches inside the mother; the pups continue to live inside her for a while before being “born”. This is known as ovovivipary (“egg live birth”). But other sharks, like the bullhead shark and the small-spotted catshark, are oviparous (“egg birth”); a protective case forms around the eggs which are then placed in the ocean. Specialized flanges and coverings on the protective cases help to anchor the egg cases, but they often wash ashore where collectors refer to them as “mermaid’s purses”.

The egg case of a catshark (Image courtesy Adolphe Millot)

The egg case of a catshark
(Image courtesy Adolphe Millot)

The egg case of a bullnose shark (Image courtesy Adolphe Millot)

The egg case of a bullnose shark
(Image courtesy Adolphe Millot)

Of course, the number of mermaid’s purses that you see on a shore is directly related to the number of sharks that you may not see in the ocean offshore. So by collecting purses, you can get a good estimate of the number of sharks and from that you can get a good estimate of how many other things live in the area since sharks don’t eat rocks (no matter what the Discovery Channel says). If you’ve tried your hand at collecting mermaid’s purses, then why not report your findings at the Shark Trust’s Great Eggcase Hunt website?