Horseshoe crabs are known as “living fossils” because they have survived on Earth for more than 450 million years. Although they have evolved in small ways over the millennia, they haven’t changed nearly as much as the world around them. Over the years, horseshoe crabs have seen the rise and fall of the dinosaurs, lived through the rise of the mammals and survived three major extinctions, including a huge one 250 million years ago that wiped out about 96% of marine creatures and 70% of large land animals.
The Marine Science Institute's monthly column, Science and the SeaTM, is an informative and entertaining article that explains many interesting features of the marine environment and the creatures that live there. Science and the SeaTM articles appear monthly in one of Texas' most widely read fishing magazines, Texas Saltwater Fishing, the Port Aransas South Jetty newspaper, the newsletter of the Texas Chapter of the American Shore & Beach Preservation Association , and the Heartland Of America online newspaper. Our article archive is available also on our website.
This poison is called tetrodotoxin, a word coined after the puffer fish’s scientific name. It’s a potent neurotoxin that can kill even humans when ingested. Though this toxin was first identified in puffers, the fish don’t actually make it themselves — in a way, they borrow it.
When threatened, puffers puff themselves up by gulping down water and pumping it into their highly expandable stomachs, making their bodies difficult for predators to swallow. One spiny puffer species, called the balloonfish, swells to about 3 times its usual volume. Most of that increase is thanks to the stomach, whose many folds let it expand by 50 to 100 times! At the same time, hundreds of sharp spines all over its body stand erect.
What is the greatest size and age a living thing can achieve? Seagrass meadows may hold the answer.
Seagrasses are flowering plants that have adapted to live submerged in the ocean. Although there are only about 60 species, they cover a vast amount of the world’s temperate and tropical coastal areas.
Watch a stingray glide over the sandy sea floor and you can tell it’s in hunting mode — but the tricks the ray is using to search for prey may not be so obvious.
A stingray’s eyes are located on top of its wide, flat body, while its mouth is on the underside. This may not seem like the best design for a fish that has to scan the murky bottom for hidden clams and crustaceans. Luckily, rays are endowed with remarkable sensory abilities that make them ace hunters.
In Antarctica’s coastal waters, a group of perch-like fish called icefish dominates. The water column in these frigid seas is filled with tiny ice crystals, and fish are constantly exposed to ice through their gills and skin. They even ingest ice crystals when they eat and drink.
For years, scientists believed all sponges were filter feeders that trapped and fed on bacteria from water they pump through their bodies. But in 1995, researchers discovered that certain species of sponge enjoy meatier meals.
Since satellite monitoring began in 1979, sea ice in the Arctic has been on the decline, shrinking by about 10 to 12 percent per decade. In the summer of 2007, Arctic sea ice cover shrank to an unprecedented low. At this rate, researchers project that the Arctic may experience a summer completely devoid of ice by the end of the century.
Vast expanses of sea ice make the Arctic and Antarctic oceans perilous and inhospitable, but they’re also vital guardians of Earth’s climate.
Sea ice forms when ocean water is cooled to the freezing point by cold polar air. Freezing begins in fall, when the amount of light from the sun decreases, and ice continues to expand and thicken during the dark winter months. When summer returns, the sun’s energy warms the surface of the ice, causing portions of it to melt.