Tag Archive: tube feet


TAXONOMY
Kingdom: Animalia
Phylum: Echinodermata
Class: Holothuroideaia
Order: Aspidochirotida
Family: Stichopodidae

Genus/species: Parastichopus parvimensis

GENERAL CHARACTERISTICS: Colored brown above, lighter below. Conical black-tipped papillae on the dorsal side provide the common name. The mouth and anus are on opposite ends of their cylindrical bodies. Tube feet aide in gathering food as well as ambulating.Length to 25 cm (10 inches). 

DISTRIBUTION/HABITAT: Monterey Bay, California to Baja California. Found on sandy or muddy-sandy soft bottoms between rocks or in eelgrass beds. Sub tidal to 27 m (89 feet) in depth.

DIET: Digests organic detritus and small organisms in soft sediments.

REPRODUCTION?DEVELOPMENT: Have separate sexes (look-alike), and eggs are fertilized externally. Broadcast spawning usually takes place in November, and each female can produce thousands of eggs. After fertilization, a larva is formed which metamorphoses into a Sea Cucumber after a few weeks.

MORTALITY/LONGEVITY: Eaten by sea stars including the sunflower star. Sea otters and humans are also predators. Lifespan estimated to be 5-10 years in the wild.

CONSERVATION: IUCN Red list; Not Evaluated

REMARKS: Holothuroids differ from echinoderms, because they have a water vascular system full of body fluid rather than sea water.  Like other echinoderms, cucumbers have a calcareous skeleton; but in their case it is only vestigial, composed of plates and spicules of lime buried in the skin and serving merely to stiffen the body wall. Respiratory trees are the lungs of a sea cucumber. These hollow branched organs lie inside the body cavity on either side of the posterior intestine. The base of the tree connects to a muscular cavity, or cloaca. Oxygen is transferred across the thin membrane into the fluids of the body cavity. When the oxygen is depleted, the main body wall contracts to squeeze water out of the trees. 
When threatened, it can expel all its internal organs through its anus (evisceration) and grow new ones in 2-4 weeks. It can also expel sticky filaments to ensnare or confuse predators. Warty sea cucumbers and their related species are sometimes called the “earthworms of the sea,” as they cultivate the seafloor in much the same manner as earthworms cultivate the soil. Oral tube feet around the mouth are covered with a sticky mucus that traps food particles from the seafloor’s sediment and mud. In areas where overfishing has reduced the population of sea cucumbers, the seafloor hardens, thus destroying a habitat for other bottom-dwelling creatures. Can walk on tube feet if stressed up to one yard every 15 min..Humans eat a variety of sea cucumber species, including Warty sea cucumbers. The demand is greatest in Asian countries, for consumption and folk medicine applications. It is considered to be widely overfished.

 

 

 

Parastichopus parvimensisIMG_8852 - Version 2

 

References

ADW Animal Diversity Web, U. of Michigan  http://animaldiversity.ummz.umich.edu/accounts/Parastichopus_parvimensis/

Encyclopedia of Life  eol.org/pages/597920/details

Monterey Bay Aquarium  www.montereybayaquarium.org/animal-guide/invertebrates/wa…

Ron’s flickr  https://www.flickr.com/photos/cas_docents/3702926813/in/set-72157608501343477

 Ron’s WordPress Shortlink  wp.me/p1DZ4b-s6

 

TAXONOMY
Kingdom: Animalia
Phylum: Echinodermata (“spiny-skinned” animals including sea stars, brittle stars, sea urchins, sand dollars, and sea cucumbers)
Class: Echinoidea  (sea urchins and sand dollars)
Order: Clypeasteroida
Suborder: Scutellina
Family: Dendrasteridae

Genus/species: Dendraster excentricus

GENERAL CHARACTERISTICS: Closely related to sea urchins, except for a more flattened, silver-dollar skeleton (test).
The tube feet, characteristic of echinoderms, are used for locomotion, respiration, sensing the environment, grasping and transporting food particles to the centrally located mouth on the underside of the test, and attachment to the substrate. The anus is near the edge of the test.
Very short spines which are covered with tiny hair-like cilia are closely packed together on the surface which feels like velvet.
Diameter to 8 cm (3.2 inches).

Eccentric Sand Dollar 3289660142_4458838cfd_b

DISTRIBUTION/HABITAT: Southeastern Alaska to Baja California. Found in subtidal to low intertidal zone on sandy or sandy-muddy substrates in cool water near the shore, but deep enough to avoid wave surge. Depth to 40 m (131 feet) but usually shallower.

Eccentric Sand Dollar 3427754072_18f944b159_b

DIET IN THE WILD:  They are oriented flat or more often vertical with entire bed oriented the same way to catch phytoplankton detritus, diatoms, and plankton such as crab larvae and amphipods. They are captured by mucous-covered spines and pincers (pedicillariae). Food particles are then carried to the mouth in the center of the lower body surface by cilia on spines where it is broken up by jaws of a small aristotle’s lantern. The tube feet are also used for grasping and transporting food.

REPRODUCTION: Broadcast spawner. Sperm and eggs are released from separate individuals. After fertilization, free-swimming bilateral larvae form, which eventually change to radially symmetrical individuals that settle to a sandy or muddy substrate similar to sea urchins.

Longevity: averages 10 years.

PREDATORS: Fish, sea stars, crabs, humans.

CONSERVATION: IUCN; Not evaluated.

REMARKS:  Cilia covered spines are used in wave-like motions for movement and burrowing. Tube feet away from the mouth are also used for locomotion. 
Young sand dollars ingest large sand grains that act like a diver’s weight belt to help them maintain position.
The age a sand dollar can be determined by counting the growth rings on the plates of the exoskeleton.

References

U. of Michigan (ADW) Animal Diversity Web  http://animaldiversity.ummz.umich.edu/accounts/Dendraster_excentricus/ 

Walla Walla University  http://www.wallawalla.edu/academics/departments/biology/rosario/inverts/Echinodermata/Class%20Echinoidea/Dendraster_excentricus.html 

Monterey Bay Aquarium  http://www.montereybayaquarium.org/animal-guide/invertebrates/sand-dollar

Ron’s flickr  https://www.flickr.com/photos/cas_docents/3289660142/in/set-72157608501343477

Ron’s WordPress shortlink  http://wp.me/p1DZ4b-1mA

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