The Toughest Snail on the Planet

Black smokers, a type of hydrothermal vent, create some of the harshest environmental conditions on the planet. These undersea chimneys propel superheated, sulfide-rich water from below the Earth’s crust into the deep ocean. Upon contact with the cold water of the ocean, dissolved iron sulfides precipitate out of solution and deposit onto the surrounding ocean floor. From the extreme heat (roughly 350 deg C), acidity, and suffocating chemical concentration of the water emerging from black smokers to the crushing pressure and complete darkness of the deep ocean, it’s shocking that organisms can even exist in this unforgiving abyss, let alone thrive. Yet as nature has proven time and time again, organisms adapt to exploit the conditions that we terrestrial dwellers consider most inhospitable.

Just like John Rambo, the organisms that can survive an environment as ruthless as a black smoker must be incredibly tough – even tougher than modern soldiers. For this reason MIT’s Haimin Yao has been studying the body defenses of the Scaly-foot Gastropod (Crysomalion squaminferum). The Scaly-foot Gastropod is a resourceful little snail that was discovered nine years ago at the base of black smokers near India, and it just may possess the most effective armor ever discovered.
Yao examined the shell at the nano-meter level to understand how it protects the soft body within from the extreme heat and acidity of black smoker water. It must also withstand the crushing power of predatory crabs. The shell of the Scaly-foot Gastropod is made of three layers, each composed of different materials to serve a different purpose. Together, they form a structure that's completely unlike any known armor, natural or man-made.

The outer layer is the thinnest and toughest, composed of iron sulfide particles extracted from the water surrounding the black smoker. This layer is designed to be sacrificed. When it is crushed by a crab claw (simulated in the lab by a diamond-tipped probe), the outer layer breaks but only into tiny cracks. By allowing these slight cracks, the outer layer dissipates the energy of the attack, and prevents the shell from shattering completely. The tough iron minerals of the shell can also wear down the crab's claw.

The middle layer is thick and soft. It is composed of organic matter rather than minerals. Its spongy consistency also absorbs the force of the crab’s claw, protecting the integrity of the inner layer. The outer and middle layers meet at a wavy junction rather than a flat one. This design keeps the two layers stuck together, preventing them from sliding apart.

Below the first two layers, the Scaly-foot Gastropod resembles the snails we’re familiar with. The inner layer of the shell is composed of calcium carbonate, the most common material for snail shells. If an ordinary snail were exposed to the acidic water of the black smoker, however, its calcium carbonate shell would rapidly dissolve. With the two outer layers, the Scaly-foot Gastropod can protect its inner shell, which provides structural support and prevents the shell from bending under the grip of a crab claw.

The three-layered armor makes this soft, vulnerable creature nearly invincible, even in the most extreme environment. Yao believes that this natural design could help to inspire the next generation of man-made defenses – from body armor to vehicles and sporting equipment. Perhaps we’ll see Scaly-foot Gastropod armor on Sylvester Stallone in the next installment of Rambo – Badass in a Mollusk Suit.

Learn more about the defenses of the Scaly-foot Gastropod in Yao’s article, published in the Proceedings of the National Academy of Sciences.

Photo: Our friend, the Scaly-foot Gastropod, courtesy of Anders Waren.

Species Profile: Bay Pipefish

Interesting fact from Baykeeper's upcoming Winter Newsletter: San Francisco's Seahorses are not limited to those plastered on the walls in the Powell Street BART Station.

What is a Pipefish?
The Bay Pipefish (Sygnathus leptohynchus) is a member of Syngnathidae – a family of fish that includes Seahorses and Sea Dragons. The Bay Pipefish shares many characteristics with its enigmatic cousins, including plates of bony armor, small tubular mouths, cryptic coloration, and secretive behavior. Like other Pipefish, however, the Bay Pipefish has a long, straight body.

What do they look like?
The Bay Pipefish is a long, thin fish that grows to about a foot in length. Its coloration varies between shades of green and brown. It may be possible that the Bay Pipefish changes its color to match its surroundings, but this is not known for sure. Just like Seahorses and Sea Dragons, the Bay Pipefish has a long tubular mouth formed by fused jaw-bones.


Where are Bay Pipefish found?
The Bay Pipefish inhabits eelgrass beds and shallow estuaries along the Pacific Coast from Baja California to Alaska. Hidden among blades of eelgrass, the long slender fish is almost completely concealed. The eelgrass beds also support an abundance of prey, allowing the Bay Pipefish to thrive. In the Bay Area, the Bay Pipefish can be spotted in eelgrass beds in San Francisco Bay, Suisun Bay, Drakes Estero, and Tomales Bay.

What do they eat?
The Bay Pipefish uses its tubular mouth to suck plankton prey out of the water like a vacuum cleaner, rather than biting it. When it is hunting, the Bay Pipefish remains completely still beneath its prey. Its eyes are capable of binocular vision, allowing it to determine the distance to its prey. When the position is just right, the Bay Pipefish will quickly snap its head up, placing its tiny mouth about an inch from the prey and delivering suction to capture its meal.

How do they reproduce?
Bay Pipefish reproduction begins in the early spring when eelgrass grows and plankton density increases in the water column. Like other male Syngnathids, the male Pipefish has a well-developed brood pouch on the underside of its tail. After the female deposits her eggs within the male's brood pouch, a layer of tissue grows to seal the eggs inside. The male Pipefish carries the embryos for several weeks, providing them with the nutrients, oxygen, and water they need to develop. When ready to hatch, hundreds of Pipefish young split the pouch and emerge into the water, resembling miniature versions of the adults.

What are the threats to Bay Pipefish in the Bay?
The greatest potential threat to the Bay Pipefish in the Bay Area would be the loss of habitat. Luckily for the Bay Pipefish and other eelgrass dependent species, the extent of eelgrass beds in the San Francisco Bay has actually been expanding in recent years. Although there is no commercial fishery for Pipefish species, they are collected for the Chinese medicine trade. At this time Pipefish are abundant, but if the demand for Pipefish by alternative health care markets increases, Pipefish might become as scarce as their Seahorse relatives.

Photo credit: Aquarium of the Bay