Sea Spider (Pycnogonid)

Sea Spider (Ammothea verenae)

These small sea spiders are Pycnogonids (Phylum Arthropoda) and live among the tube worms and limpets on hydrothermal vents of Axial Seamount. Photo credit: NSF-OOI/UW/WHOI; V11

Sea Spiders are not Arachnids but belong to Class Pycnogonida: spider-like marine Arthropods. They have four pairs of walking legs, which make up most of their bodies. Sea Spiders are so thin that they don’t need a respiration system, and instead exchange gas through their bodies. Due to their size, their muscles are only a single cell, which is surrounded by connective tissue. They use a tubular proboscis to scavenge food or feed on microbes. Sea Spiders reproduce by forming mating clusters where males collect eggs from females and then fertilize them. The father than cares for the eggs and young.

Sea Spiders of the species Ammothea verenae are found on and around hydrothermal vents at Axial Seamount. These organisms are a mere 1 cm in length, from proboscis tip to abdomen tip.

References:
http://www.wallawalla.edu/academics/departments/biology/rosario/inverts/Arthropoda/Chelicerata/Pycnogonida/Ammothea_verenae.html
http://animal.memozee.com/view.php?tid=3&did=26581
http://www.pmel.noaa.gov/eoi/nemo/explorer/bio_gallery/biogallery-Info.00061.html

Pyconogonids are abundant on many sulfide structures in the vent fields within the caldera of Axial Seamount. These 8-legged anthropods are commonly found in areas where venting has stopped, leaving variably oxidized edificies. Here, they are associated with snails an a small scale worm ~ 1 cm; in length. Credit: UW/NSF-OOI/CSSF; ROPOS Dive R1836; V15.
Pyconogonids are abundant on many sulfide structures in the vent fields within the caldera of Axial Seamount. These 8-legged anthropods are commonly found in areas where venting has stopped, leaving variably oxidized edificies. Here, they are associated with snails an a small scale worm ~ 1 cm; in length. Credit: UW/NSF-OOI/CSSF; ROPOS Dive R1836; V15.
These small sea spiders are Pycnogonids (Phylum Arthropoda) and live among the tube worms and limpets on hydrothermal vents of Axial Seamount. Photo credit: NSF-OOI/UW/WHOI; V11
These small sea spiders are Pycnogonids (Phylum Arthropoda) and live among the tube worms and limpets on hydrothermal vents of Axial Seamount. Photo credit: NSF-OOI/UW/WHOI; V11
The base of the small, 4 meter tall structure called Mushroom, is encased in a dense covering of tubeworms, palmworms, and limpets. Other life seen in this image includes  a sea anemone, and "spiders of the deep" called pycnogonids.
The base of the small, 4 meter tall structure called Mushroom, is encased in a dense covering of tubeworms, palmworms, and limpets. Other life seen in this image includes  a sea anemone, and "spiders of the deep" called pycnogonids.
Andrew with his prized sea spider. L. Combs, University of Washington, V22.
Andrew with his prized sea spider. L. Combs, University of Washington, V22.
A sea spider came up accidentally with vent worms and became a center of attraction. Credit: D. Mishra, University of Washington, V22.
A sea spider came up accidentally with vent worms and became a center of attraction. Credit: D. Mishra, University of Washington, V22.