Food chains link the creatures of coastal ecology

Don’t stick your hand in that shell! You don’t know who might be home. It could be a carnivorous snail or a “clawsome” crab. Take a look at our Texas state shell, the lightning whelk or left-handed whelk, which feeds on bivalves like oysters and clams. Perhaps the snail that makes the shell is still hiding inside, or perhaps the shell is home to a hermit crab. Unlike most crabs, hermit crabs use the shells of snails as homes to protect their soft bodies.

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Hermit crab taking residence in an empty lightning whelk shell.

Texas is home to some fascinating creatures, and our coast is no exception. In addition to the Gulf side beaches, there are salt marshes, jetties and the bay to investigate. Our coastal habitats are just waiting to be explored, and with the right gear, you can see organisms at every trophic level. (You knew I was going to talk about food chains, didn’t you?) 

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Lightning whelk snail retracted into its shell, operculum blocking the opening.

Most folks will notice some of the upper-level consumers: birds like pelicans and gulls. Who could miss the gull snatching your unattended hotdogs? Or the pelicans plummeting into the water face first to catch fish? Maybe you’ve noticed fishermen along the beach as they pull in small bonnethead sharks. Some animals may require good timing and tons of mosquito repellent to see, like our rare and critically endangered Kemp’s ridley sea turtle. If you pay attention, there are even rattlesnakes catching mice that are feeding on insects and plants in the dunes!Food Web

As you follow a food pyramid from the apex down to the base, top predators like humans and sharks feed on the organisms in the level below. There you might find the larger bony fish we feed on, like redfish or snapper, and below them you can find some of the crustaceans and mollusks they feed on in turn. Crustaceans, like our blue crabs, stone crabs, and the smaller ghost crabs, often scavenge in addition to feeding on mollusks, worms, or even plant matter. Many of our mollusks are filter feeders, like oysters, pulling algae and plankton from the water. Finally, at the base of the food pyramid, there are the producers. The phytoplankton and algae make their own food with energy from the sun.

A food chain pyramid is a great way to show different types of food chains on one example. I used a pyramid created by my friend Julia and drew examples of food chains from our coast on it. One side has the trophic levels on it and the other three sides have example food chains. What’s on the bottom of the pyramid? The Sun, of course!Pyramid

Coastal ecology isn’t just about sand, shells, and dodging gulls. It’s also about the interactions between plants, animals, and their environment. The plants anchor the dunes, the dunes protect and replenish the beach sand, the sand houses animals like mole crabs and mantis shrimp, and we get to enjoy it when we protect it.

If tracking home beach sand in your shoes, car, towels, and suits doesn’t excite you, our new Hamman Hall of Coastal Ecology may be just the air-conditioned trip to the coast you need on a scorching summer day in Texas. Members, come join us Memorial Day weekend to see wonders of the Texas coastline!

Fear the Snail: Inside the vicious world of the predatory gastropod

So snails suck, right? They’re boring and slow and they don’t do anything cool. Some of them make pretty shells that you find on the beach, but they’re pretty much slimy and gross and basically not interesting at all.

Said no one ever. At least not those who understand the world and daily life of snails. They’re tough, vicious, and sometimes terrifying in their adaptations to help them feed and protect themselves, especially in the case of marine snails, which can be as varied in shape, size, and color as the imagination.

“There are about 30,000 known species of snail,” said Gary Kidder, HMNS Discovery Guide and snail expert. “They’re a ‘Walt Disney’ class: if you can dream it, they can do it.”

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Slipper snail radula. Credit: Eric Heuple

Known in the science community as gastropods, meaning literally “stomach foot,” snails feed using a rasp-like tongue called a radula. Like most animals, the teeth vary from species to species based on what particular type of food the snail eats. In carnivorous snails, these teeth are like fish hooks that tear the flesh from their prey. Imagine having your skin licked off by a giant cat’s tongue! Terrible.

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The largest snail shell in the world, on display in the Strake Hall of Malacology.

Snails are not always small; they can grow to be massive. The Australian trumpet, or Syrinx aruanus, produces shells that can be as big around as your thigh. Measuring more than 30 inches in length, the record-holder for biggest snail shell in the world is on display in the Strake Hall of Malacology at the Houston Museum of Natural Science. It looks like you could fit a football inside this bad boy.

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Lightning whelk. Credit: DixieHwy

Predatory snails use some barbaric tactics to kill and eat their prey. There’s no saving a bivalve caught by a lightning whelkBusycon perversum (incidentally, the state shell of Texas). The lightning whelks pries open clams, wedging its soft foot between the halves of its shell, then it uses its radula to scrape out the clam a piece at a time. Kind of like a stranger kicking down your door and coming into your house to get you. Frightening.

That’s just the beginning. The moon snail, in the family Naticidae, bores into the shells of mollusks and crabs with its radula and an acid secretion. That’s right: acid. It melts a tiny hole through its prey and licks out its insides with its tongue. No thank you!

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Moon snail. Credit: Chris Wilson

To stun or kill their prey, many marine snails use some of the strongest venoms on Earth. The teeth in the radula of the geography cone, or Conus geographus, are modified to carry a venomous sting that disrupts insulin in its victims. Like a revolver loaded with up to twenty hypodermic needles (instead of six bullets), the cone snail harpoons its prey, sometimes with several stings in a matter of seconds.

“The venom gives you diabetes, basically,” Kidder said. “It makes you loopy. And if they’re able to hurt something our size, a fish, it’s usual prey, isn’t going to be an issue for it.”

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Conus geographus. Credit: Patrick Randall

The harpoon of the C. geographus can penetrate human skin and sometimes gloves and wetsuits depending on its size. A single sting from a Conus snail can cause muscle paralysis, difficulty breathing, and death. No antivenin exists; victims must be hospitalized until the venom wears off. Don’t pick these suckers up unless you’ve got comprehensive health insurance!

Scientists, however, see the cone snail’s venom as an opportunity for medicines, and are working to synthesize compounds from its unique chemical cocktail as treatments for a variety of diseases.

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Carrier snail. Credit: James St. John

Conus isn’t the only gastropod with potential benefit to humanity. The carrier shell, in the family Xenophoridae, Greek for “bearing foreigner,” uses a type of “concrete” to attach foreign objects to itself, reinforcing its own shell as it grows. The snail’s building media include other shells, pebbles, small pieces of coral, and in some instances human refuse like bottle caps. Scientists have even discovered new species from the shells attached to Xenophora.

“This is an aquatic saltwater snail that makes a cement that ‘dries’ underwater,” Kidder said. “If we can figure out how it does that, the economic possibilities are wild!”

So next time you see a land snail leaving a trail of slime, or a shell on the beach that once belonged to a marine gastropod, remember that in its own world, this slimy, slow-moving creature is a rock star.

Horse around with H. Alan Day and wild mustangs April 30

On April 30 at the Houston Museum of Natural Science, cattle rancher, cowboy, and author H. Alan Day will tell the story of establishing a sanctuary in South Dakota for unadoptable wild horses previously warehoused by the Bureau of Land Management. After Day successfully lobbied Congress, those acres became Mustang Meadows Ranch, the first government-sponsored wild horse sanctuary established in the U.S. His entertaining presentation will include the challenges of balancing the requirements of the government with the needs of the 1,500 wild horses and the land itself, and give an update on the sanctuary today. A book signing of The Horse Lover will follow the lecture. Books will be presigned by Sandra Day O’Conner, retired Supreme Court Justice and inductee to the Cowgirl Hall of Fame.

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Sandra Day. Credit: National Cowgirl Museum

The following is an excerpt by O’Connor from the forward of The Horse Lover, A Cowboy’s Quest to Save Wild Mustangs.

“When my brother, Alan, told me that he had agreed to keep fifteen hundred wild mustangs on his South Dakota ranch, I thought he had temporarily lost his common sense…

For more than 400 years, wild mustangs have existed in the region that is now the western United States. They fared well before the Taylor Grazing Act of 1934 reduced their habitat. But even in the last century there were many pockets of public land in the West where they could live free, breed, and multiply. But the pressures of the multiple-use policy of the Bureau of Land Management and the restricted uses of national forest and national park lands meant that many of the wild mustangs would be captured, sold, or destroyed. The wild horse and burro law dictated that the Bureau of Land Management was to capture many of them and care for them until they could be adopted. Sadly, many of them were not suitable for adoption. This opened the way for the project Alan undertook. the-horse-lover-cover-194x300

It is impossible to see a herd of wild horses running free without feeling a surge of excitement and enthusiasm for their vigor, power, and beauty. To watch them run with their manes and tails flying in the wind is to experience a sense of the ultimate freedom of motion. 

This book tells the story of the Mustang meadows project in a way that enables the reader to see and feel that excitement and to glimpse what was and what might have been with these splendid animals.”

Come early to see live mustangs at the museum in the sun dial plaza entrance. These horses from the Little Mustang Program, like those of H. Alan Day,  were also received from the Bureau of Land Management and are in need of adoption.h_alan_day

The Little Mustang Program in our area provides the opportunity for young horsemen to attain ownership of a wild horse (aka a mustang) and create their own positive and educational horse owning experience. This program is organized in accordance with the requirements set out by the Mustang Heritage Foundation’s Trainer Incentive Program and the BLM’s National Wild Horse Program. The horses are received from the BLM on a regular basis with a goal of adoption in 120 days. The adoption program is administered by V.E.T.S. Livestock Management Services Organization, Inc. 5340925377258.image

HMNS Distinguished Lecture

Quest to Save Wild Mustangs

H. Alan Day

Thursday, April 30, 6:30 p.m.

Click here for advance tickets.

HMNS greenhouse teaches how to plant a butterfly oasis in your back yard

They float on the wind, decorate your back yard in the spring and summer, and inspire warm emotions with their delicate wings. They seem carefree, at home in any meadow, but butterflies have more specific needs than we might imagine.

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Monarch butterflies don’t live just anywhere; they need habitat, too!

As urban sprawl continues to grow, reducing green space and native plant growth, natural butterfly habitats are shrinking. Butterflies require specific plants on which to feed and lay eggs. Caterpillars are finicky eaters.

Soni Holladay, Houston Museum of Natural Science Horticulturist and Greenhouse Manager, will lead a class Saturday, April 18, beginning at 9 a.m., to share information with the public about how best to plant a garden that will attract native butterfly species, creating a backyard butterfly nursery.

Holladay’s main concern is planting tropical milkweed to attract the famous migratory monarch butterfly. Though tropical milkweed is easier to grow, scientists have discovered it may play a part in declining monarch populations.

A parasitic species of protozoan called Ophryocystis elektroscirrha, or simply Oe, grows on the body of their monarch hosts. When infected monarchs land on milkweed to lay eggs, Oe spores slough off and are left behind. Caterpillars, which eat the milkweed, ingest the spores and become infected.

When the protozoans become too numerous, they can overwhelm and weaken individual butterflies, causing them to suffer. Several heavily infected monarch can take a toll on the local population. Oe can kill the insects in the larval or pupal stage, as well, before they can reach full adulthood.

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Tropical milkweed survives the Houston winters, making them a perennial plant and a possible danger to monarch butterfly populations.

Native milkweeds die off every year and grow back in the spring Oe-free as part of their cycle, but the evergreen tropical milkweed remains standing year-round, providing a vector for the protozoan to spread.

“We’re advising everyone who plants tropical milkweed to cut it back once a year or more,” Holladay said. Much like their native cousins, the tropical variety will return later, a healthy habitat for butterflies.

Holladay’s class will offer more details about this and other butterfly-raising issues. After the class, guests will tour HMNS greenhouses and our on-site butterfly-rearing operation. Tickets $23, all ages. Native milkweed plants and other seeds will be available to get you started.