Sharks are often thought of in terms of superlatives, and perhaps no species has racked up as many “mosts” as the Great White Shark, Carcharodon carcharias. This is the star of “Jaws” after all, and probably the species most people who aren’t devoted to being familiar with fish visualize when they hear the word “shark.” Thanks to new research by Marra and friends (2019), we’re becoming familiar with the White Shark on the most basic level of all: the genetic level.
Not every species has had its entire genome decoded, and the White Shark is one of only a handful shark species to get this level of attention. The Whale Shark and the Elephant Shark (actually a species of chimera) have also had their genetic codes mapped, providing a couple of fairly closely-related species for comparison. By comparing the full genome of the White Shark with these other shark species and other vertebrates, the authors were able to identify specific mutations that have stood the tests of time and natural selection. Many of these genes are associated with the very traits that have made sharks such incredible survivors for going on 450 million years.
In November of 2018 Aquatica Submarines shipped a three person submarine, Stingray 500, across frosty North America on the back of a truck then over the rolling winter seas of the Gulf of Mexico to Belize aboard the R/V Brooks McCall. Our destination was a site located 7 miles into Lighthouse Reef – a perfect sinkhole in the ocean known as the Great Blue Hole. We traveled to this UNESCO World Heritage site to explore and document a geologic phenomenon in support of conservation science and to conduct outreach. Our mission was two fold, map the Great Blue Hole using high resolution sonar and take people worldwide on this journey with us on broadcast TV. Everything we collected, from CTD data and dissolved oxygen content, to video footageand experiential data, gives us the fodder we need to tell a story about an unusual place on our planet most people have never seen, until now.
Geology from not-a-geologist
Over the past 14,000 years the polar ice caps, formed during the last glacial maximum, have thawed and raised sea level in steps. These defrosting events are captured in a stone record of an oceanic sinkhole in Belize. The aptly named Great Blue Hole is a collapsed cave, filled with stalactite caverns, and built up from layers of fine limestone and rougher calcium carbonate walls. The stepped rise of sea level can be seen in the form of terraces carved deeply by erosion into the otherwise vertical rock walls. Straight vertical stretches of wall are free of erosion because sea level rose rapidly during a few brief decades between each step. As each melting event took place sea level rose dramatically, as much as 100 feet in 100 years, followed by centuries of stability. Preserved from the disturbance of time, and isolated in the darkness, the hole holds clues to a very natural part of our planet’s life cycle. It’s these terraces and stalactites we set out to map.
Life has unbelievably complex and diverse strategies to ensure survival. Organisms are able to go dormant during unfavorable conditions, and resuscitate once the environment becomes ideal again. This can play out over relatively short time periods such as when animals hibernate, or over longer periods where organisms can go into stasis, e.g. reviving bacteria from 250 million year old salt crystals.
Researchers in Russia recently thawed out permafrost sediment frozen for the past 42,000 years, and revealed once frozen and now living nematodes. Yes you heard that correctly, worms birthed and subsequently frozen during the Pleistocene (42,000 years earlier) were just resurrected in the 21st century. Frankenstein, eat your heart out.
Eophasma jurasicum, a fossilized nematode. (Photo credit: Ghedoghedo)
I’ve defaced this colonial-era image of Native American fishing methods from Roanoke Island, NC to show that sharks have been observed in North Carolina’s estuaries for quite some time. Original art: “The Manner of Their Fishing” by John White.
It’s a bit of a cliché to reference the movie Jaws when talking about sharks, but I’m going to do it anyway. There’s a pivotal scene where the giant White Shark is spotted moving into a salt pond, where it proceeds to terrorize the children of protagonist Chief Martin Brody. While no sharks are in the business of regularly eating humans, at least part of this scene is realistic: sharks do make use of inshore, estuarine environments like lagoons, bays, and the lower portions of rivers. Despite the fact that sharks are generally thought to stay out in the ocean, many species are not only comfortable entering estuaries, they actually depend on them. Some species make extensive use of estuaries as shelter from predators and/or a place to grab a bite themselves.
So it should come as no surprise that North Carolina’s Pamlico Sound, part of the Albemarle-Pamlico estuary (the second-largest in the continental U.S. after Chesapeake Bay) offers a lot of potential real estate for sharks. Unlike Chesapeake Bay, Pamlico Sound is a lagoon, which means it’s wide, shallow, mostly water, and connected to the ocean via fairly small inlets between barrier islands. It straddles the transition zone marked by Cape Hatteras between temperate and subtropical marine ecosystems, and the amount of seagrass growth there is second only to Florida in sheer area. This estuary is already well-known for its importance as habitat for such varied (as well as tasty and/or fun to catch) species as Blue Crab, Penaeid shrimps, Flounder, and Red Drum. However, the sharks of Pamlico Sound have mostly been known by scattered reports and sightings from fishermen. That is, until my co-authors and I were able to look through a nice data set to get an idea of which sharks are present in the sound and where in the estuary they might like to be. The results are now published in PLOS One, and here’s a quick summary of how we got them.
Hagfish are eel-like jawless fishes. They are primitive, lacking a vertebral column. They are deep-sea scavengers notorious for tying themselves into knots as they rip chunks of meat from carcasses. Your ancestors, at some point, probably looked a lot like a hagfish.
Hagfish at Mount Desert Island Biological Lab. Photo by author.
I thought they were eels?
Slime eel (as well as snot snake) is the common name for Pacific hagfish. Dr. Milton Love has the simplest guide to telling the difference between hagfish and eels: Look at the hand holding the fish. Is it completely covered in slime? Then it’s a hagfish.
So, it’s an Agnathan?
Hagfish are Cyclostomes. Hagfish systematics is kind of a mess right now, with competing hypotheses about where hagfish and their ancestors fit into the history of vertebrate evolution. Unless you’re a taxonomist, I wouldn’t worry to much about hagfish cladistics; it will likely change a time or two in your lifetime.
As 2016 winds to a close, and in the spirit of the holiday season behold the world’s smallest snowman, measuring in at 3 microns. To put that into perspective, the smallest grains of sands are approximately 60 microns.
Mini snowman, ~3 microns in height (Photo credit: Western Nanofabrication Facility)
This creation is the work of Canadian nanotechnologists from the Western Nanofabrication Facility. The snowman is made from three ~1 micron silica spheres stacked using electron beam lithography. The eyes and mouth were cut with a focused ion, beam while the arms and nose were sculpted with platinum.
Tiny snowman amongst other 1 micron silica spheres. (Photo credit: Western Nanofabrication Facility)
A cool feel good story to round off 2016 as we head into 2017. Happy New Year all!
A giant deep sea isopod on the sea floor. Photo via NOAA Photobank.
Conservation has long had the concept of Flagship Species—popular, charismatic species that serve as rallying points for conservation awareness and action. Formalized within the framework of conservation marketing, flagship species are focused around particular goals and audiences. Think of the WWF’s Giant Panda, Polar Bears and a thousand different arctic or climate change campaigns, or even the American Bald Eagle, whose decline galvanized the country into action. These animals are iconic. They connect people to species and ecosystems in crisis. They are Flagship Species.
The Giant Deep-sea Isopod is not a flagship species. The Giant Deep-sea Isopod addresses a much more fundamental issue: despite being the largest, most diverse ecosystem on the planet, most people have no direct connection, no frame of reference, for the deep sea. Read More
Pollination. I think most people understand why this is important (or maybe I should say, I hope). To put it simply, the process of pollination facilitates reproduction in plants by transferring pollen from one plant to another. In the terrestrial world, this can be mediated by physical forcing (e.g., wind) or by animals (e.g., insects) – and its why people are freaking out about the loss of bees due to pesticides (because they are a primary pollinator), but I digress. Until relatively recently, pollination by animals was not thought to occur in the ocean. Unlike on land, where most flowering plants rely on creatures to carry pollen, plant reproduction in an aquatic world was surmised to rely exclusively on currents and tides. However, a team of researchers led by marine biologist Brigitta van Tussenbroek revoked the long standing paradigm that pollen in the sea is transported only by water, discovering and documenting the process of zoobenthophilous pollination (a term they coined).
Gamarid amphipod feeding on pollen of a male flower of the seagrass Thalassia testudinum at night. (Photo credit: Tussenbroek et al. 2012)
Google maps is full of weird things. The planet is full of weird things. Weird things are awesome.
Rather than dig just a little bit deeper, they went on to wax poetic about giant squids, busted out some measurement tools to determine that it was 120m long, and promptly alerted the press. Also, another anomaly hunter says it’s a UFO.
If, however, they had pulled up a nautical chart, they would have realized that thisis Sail Rock, a well mapped outcropping that, from the sea, looks a bit like a ship under sail.
Sail Rock (http://www.scielo.cl/scielo.php?pid=S0718-71062013000100001&script=sci_arttext)
Update: Since I can’t find an easily-accessible nautical chart of the island online, here’s a high resolution scan showing the rock and its relation to Deception Island.
Sorry, folks, it ain’t a 120 meter long Kraken or an Underwater UFO. It’s a rock.
One-hundred-fifty meters hardly seems like anything at all.
Standing in the parking lot of OpenROV, I pace out 150 meters. The small sign, hanging against the wall of the battered warehouse, pointing visitors towards the entrance, is clear.
One-hundred fifty meters is less than half a lap around a standard running track. It’s the height of Old St. Paul’s Cathedral, the tallest building in the world, 700 years ago. The fastest man in the world could cover 150 meters in 14 seconds.
On land, 150 meters is barely noteworthy. Plunge into the sea and 150 meters is the wine dark deep. It is the edge of the photic zone, a world of eternal twilight. It is three times deeper than most SCUBA divers will ever venture. At 150 meters, the water pushes down with the weight of 16 atmospheres.
And, if you climb high into the Sierra Mountains and descend into the frigid alpine waters of Lake Tahoe, just off the coast of Glenbrook, Nevada, lying on a steep glacial slope at 150 meters depth is the wreck of the Steamship Tahoe.