sipuncula

Larva from the peanut worm, Nephasoma pellucidum

Worms from the phylum Sipuncula, commonly known as peanut worms, live in marine habitats and use small tentacles to gather organic debris from the water. First described in 1827 by a French zoologist, a related species was later identified by famed invertebrate zoologist E. Ray Lankester. Lankester dissected the new species between rounds of golf in Scotland. In celebration of his golfing holiday, he decided to name the species Golfingia vulgaris, which was later sorted into the Sipuncula phylum.

Image by Dr. Michael Boyle, Smithsonian Institution.

The Sipuncula  ("Peanut Worms")

… a group containing 144-320 species (estimates vary) of bilaterally symmetrical, unsegmented marine worms. Traditionally considered a phylum, molecular work suggests that they might be a subgroup of phylum Annelida. Sipunculids are all marine and are relatively common, and live in shallow waters, either in burrows or in discarded shells like hermit crabs do. Some bore into solid rocks to make a shelter for themselves. Although typically less than 10 cm long, some sipunculans may reach several times that length…

(read more: Wikipedia)

(image: A bucket of deliciously-looking purple worms, labeled 即劏北海沙虫 - “‘Sand worms’ from Beihai, to be killed on demand”) at a street vendor in Guangzhou. At 48 yuan / 500 g (around $7/lb), they look quite affordable… The second character in the sign (劏, in its simplified form), “to slaughter / to butcher”, is peculiarly Cantonese; photo by V. Menkov)

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Sipunculus nudus

…is a species of sipunculid (peanut) worm native to subtidal zones and seabeds worldwide. Like most peanut worms S. nudus lives most of its life in a self-made sand burrow where it sits and feeds on any organic material that passes by its burrow. Like certain sea cucumbers S.nudus only exposes its fragile tentacles to feed at night, and mostly works on its burrow during the day. S. nudus is considered a delicacy and is commonly sold throughout southeast Asia. 

Phylogeny

Animalia-Sipuncula-Sipunculidea-Sipunculiformes-Sipunculidae-Sipunculus-nudus

Image Source(s)

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Unidentified Peanut Worm (Sipuncula)
Pasir Ris, 7th June 2008

5 species of Peanut Worm have apparently been listed as occurring in Singapore, but whether these identifications are accurate is dependent on closer study by experts in the group, of which there are only a small handful in the world. It’s also unknown as to whether these species can be reliably identified and distinguished from one another in the field.

The Lowly Peanut Worm and Its Long Lost Relatives

by Jennifer Frazer

Breaking news: Peanut worms are annelids. Great! I hear you saying. What’s a peanut worm? (And possible sub-questions: What’s an annelid? And why should I care?) Good questions.

Annelids are the bristled, segmented worms. That is, bristles and segments are the synapomorphies for this group, or the shared, derived characteristics that distinguish them from other groups. A synapomorphy makes their grouping both scientifically valid and evolutionarily based*.

To simplify the classic story: Long ago there was a worm that evolved two special new traits its ancestors lacked:  bristles and segments. This ancestral worm produced offspring that evolved into all the leeches, hydrothermal tubeworms, polychaete bristle worms, and giant Australian earthworms of the world. As descendants of that first innovative worm, they all have segments. And they all have bristles, although sometimes segments or bristles are hard to see — as in earthworms. They also have parapodia, stumpy little extensions of their body on which the bristles are located. And everyone lived happily ever after, until fish hooks were invented. The End.

Well, almost.

Sometimes, the descendants of a creature that develops a distinctive trait may lose this trait for reasons of evolutionary expedience, or simply because there’s no reason not to. These creatures can fool us into thinking they are *not* a member of the group in question. This often happens with parasites that “de-evolve” because they no longer have to make it on their own; I wrote earlier this year about how microsporidia are actually highly evolved fungi called zygomycetes. We earlier thought they were rather bare-bones parasitic microbes, but their loss of many of the zygomycetes’ unique (derived) characteristics initially fooled us. Well, this has apparently also happened to a quirky little group of marine organisms called peanut worms, or “Sipunculids”…

(read more: The Artful Amoeba)     (photo: Pgrobe)

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Worms, part 2
1-2. Leech, Subclass Hirudinea. We tried to ID the species from a book, and we guessed Marsipobdella sacculata.
3-5. Peanut worm. Either its own phylum, or a class of Annelida, it’s a Sipunculan.
6-7. Ribbon worm, phylum Nemertea. Amphiporous sp.

Then we were done with worms, but we moved onto Arthropods which meant spiders and bugs :(

image

photo by Steve Trewhella

When you think of animals, think of this peanut worm, Golfingia vulgaris. This worm has short tentacles around the mouth, and burrows into the seabed in shallow waters. There is a record of one found 5540 m down in the Kuril-Kamchatka Trench, but most are less than 500 m deep. These worms use Hemorythrin as the oxygen carrying molecule in their blood, giving it a purple color.

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Peanut Worms - Sipuncula

These animals, which are commonly called “peanut worms” because some have the general shape of shelled peanuts, are not particularly well studied. Only about 320 species have been formally described, all marine and mostly from shallow waters. While some burrow into sand and mud, others live in crevices in rocks, or in empty shells. Still others bore into rock.

The body is completely unsegmented, and the intestine forms a twisted loop, with the anus on the side of the body. Typical of sipunculans is a forward (anterior) body section, the introvert, which can be retracted into the body by the retractor muscles. At the tip of the introvert (retracted in the specimen shown at the top of this page) is the mouth, which is surrounded by a ring of tentacles. The body cavity, or coelom, of sipunculans is large and filled with fluid, in which are found free-floating cells known as hemerythrocytes as well as free-floating clusters of cells known as ciliary urns. Sipunculans have no circulatory or respiratory systems; the coelomic fluid transports both nutrients and oxygen to all parts of the body. Nephridia filter the coelomic fluid…

(read more: UCMP - Berkeley)   

(images: T - DeWaine Tollefsrud, BL/BR - via UCMP)

Marine Worms:  Peanut Worms (phylum Sipuncula)

The peanut worm has a proboscis that resembles an elephant’s trunk, as well as a mouth that boasts an impressive array of tentacles. This bottom burrower feeds on organic materials found in mud and sand, and when done feasting it can turn the proboscis inside out to retract it inside its body. Peanut worms are often tiny but can reach 1.5 ft (0.5 m) in length.

Photograph by Darlyne A. Murawski, National Geographic

(via: National Geo)

vimeo

Larva pelagosphera (by Alvaro Migotto)