Among the stranger things that MBARI scientists see crawling around the deep seafloor are giant “sea spiders” or pycnogonids. They are very distant relatives of land spiders, scorpions, and horseshoe crabs. Shallow-water pycnogonids are typically a cm (1/3 inch) or less in size. However, several deep-sea species, such as this one, grow much larger.
Most pycnogonids feed by inserting their proboscises into soft-bodied invertebrates, such as jellies or sea anemones, and then sucking the juices out. The bodies of some pycnogonids are so small that part of their digestive tract extends into their legs. This pycnogonid has just been removed from the sample drawer of the remotely operated vehicle Tiburon, after having been collected on the seafloor, thousands of meters below.
A squat lobster and sea spider live on the fringe of a barrel sponge. Image captured August 5, 2010 by the Little Hercules ROV at 700 meters depth on a new seamount mapped by Baruna Jaya IV during the INDEX SATAL 2010 Expedition.
Image courtesy of NOAA Okeanos Explorer Program, INDEX-SATAL 2010
This half inch long sea spider is an amazing form of life. It has no lungs or gills, transmitting gasses directly through it’s slender exoskeleton. The digestive tract extends down it’s legs and is clearly visible here as snaky, colored tubes inside the transparent exoskeleton.
This specimen is on fire coral in 30 feet of water in Grand Cayman.
Sea Spiders are found in all oceans and at least one species can get up to 2 feet long in some deep sea areas.
Top: Female sea spider on hydroid Aglaophenia latirostris, 8 mm across. Moves very deliberately. Feeds on the hydroid. This individual has lost one leg, but it will not be replaced as these arthropods do not molt. (source)
Bttm: This male sea spider is brooding fertilized eggs he gathered from his mate. The resulting larvae will parasitize the hydroid Aglaophenia on which the adults feed. 8 mm across. These cryptic sea spiders move very slowly. (source)
A sea spider, in the class Pycnogonida, creeps along the top of a ridge at 1,960 m (6,430 ft) depth in the Northeast Providence Channel near Eleuthera Island in the Bahamas. The two arm-like structures hanging down from the body behind the proboscis are ovigers, used for carrying eggs.
(not spiders, but believed to be closely related to arachnids)
Many of Antarctica’s land animals may be teensy, but their sea creatures can get huge, thanks to the high amounts of oxygen in the water. Gillless creatures such as sea spiders breathe through holes in their bodies, which allows more oxygen to be absorbed into their bodies—thus allowing them to grow bigger over time.
For instance, in Europe, a sea spider “is the size of your little fingernail—and then you go to Antarctica and it’s the size of your dinner plate,” said Huw Griffiths, a marine bio-geographer at the British Antarctic Survey, Sea spiders “are more common and have more species in Antarctica than anywhere else in the world,” he added.
(via: National Geo) (photo: British Antarctic Survey)
THE STUNNING DEEP SEA DIVERSITY OF THE BEAR SEAMOUNT
by Dr. Michelle Staudinger,
Univ. of Missouri - Columbia and National Climate Change, and stationed at the Wildlife Science Center, VA, USA
On Wednesday August 29th, the NOAA Ship Pisces left Newport, Rhode Island and headed east-southeast towards the Bear Seamount (39°55’N 67°30’W) for a 10 day research cruise. The Bear Seamount is an extinct undersea volcano located south of Georges Bank, inside the US economic zone, and is one of the 30+ seamounts that comprise the New England Seamount chain. Most of what we know about the fauna around Bear Seamount has been gained since the year 2000 from a series of eight research surveys; prior to 2000 however, this seamount was considered one of the most understudied in the world.
As was true of past research expeditions, the primary goal of this survey is to document and collect fishes, cephalopods, and crustaceans living in mesopelagic and bathypelagic habitats using mid-water and bottom trawls deployed at 600 – 1500 meters, and 1,000 meters or greater, respectively.
What’s sets this survey apart from the rest of the series is that previous surveys were exploratory and this will be the first to collect quantitative data on community composition, and net catchability. Specimens will be archived in the collections at the National Museum of Natural History, Peabody Museum, the Museum of Comparative Zoology, and the Fish Collection at the Virginia Institute of Marine Science. There are also several graduate students and post-doctoral researchers onboard that have sacrificed their Labor Day weekends to collect data and samples for various research projects…
Most pycnogonids or sea spiders are just 1-10mm long, but in Antarctica, they can grow to the size of a human hand. In the extreme cold, where metabolisms are slow and there are relatively few predators, many invertebrates grow exceptionally large and live years longer than similar species in warmer waters.”
Many of the 1,000 or so pycnogonid species worldwide feed on encrusting animals such as corals, anemones, bryozoans, and sponges. Their bodies are miniscule, and their gut and reproductive organs extend almost to the tip of each limb.
A male Antarctic sea spider bearing its eggs was found in a region of the sea once covered by a giant ice shelf. The sea spider, or pycnogonid, may prove to be a species new to science… (read more: National Geo)
(photo: P.J. Lopez-Gonzalez/Alfred Wegener Institute for Polar and Marine Research)
A rare “treasure trove” of ancient sea spiders found in France fills a 400-million-year gap in the mysterious creatures’ spotty fossil record, scientists say. The well-preserved marine animals, called pycnogonids, were unearthed in 160-million-year-old fossil beds at La Voulte.
In a paper published online in the Proceedings of the Royal Society B, a team of French scientists describes 70 specimens—including the one seen above—from three distinct species found in the region’s Lagerstätte, a type of sedimentary rock formation.
“This Lagerstätte is very important, because during Jurassic times the water here was about 200 meters [656 feet] deep,” study co-author Sylvain Charbonnier told BBC News. The Jurassic period lasted from 199.6 to 145.5 million years ago…
Sealife of Antarctica: Sea Spider (class Pycnogonida)
More species of sea spider are found around Antarctica than any other place on the planet. And like many Antarctic species, the sea spiders here grow far larger than their cousins in warmer climes. Males of the species carry the developing young. When birthing time arrives, the fully formed baby sea spiders crawl out of their father’s leg. (via: Our Amazing Planet)