Saccoglossus
bromophenolosus King 1994
Common name(s): Acorn worm
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| Synonyms: |
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Class Enteropneusta
(acorn worms)
Family Harrimaniidae
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| Saccoglossus bromophemolosus
from Padilla Bay. The proboscis is to the right, the collar is in
the middle, and the trunk is to the left. The trunk is strongly
contracted and may be cut off. Total length of this individual"
16 mm |
| (Photo by: Dave Cowles, June 2009) |
Description:
Acorn worms
(Class Enteropneusta) are soft, round worms usually found in sand or
mud. Their bodies are divided into three regions:
An
anterior proboscis, a collar, and a posterior trunk, which is usually the longest. The
trunk
may be subdivided into several regions. They have a straight
gut
which starts at the anteroventral mouth which is found at the junction
between the proboscis and the collar, and ends at the posterior tip of
the trunk. Family Harrimaniidae has simple gonads, large,
yolky eggs, and perihaemal cavities but has no synapticles in the gill
bars, no hepatic caecum, and no tornaria larval stage. Saccoglossus species have an elongate proboscis and a posterior fold of the collar which slightly overlaps the trunk. Saccoglossus bromophenolosus
has a white to beige proboscis with a dorsal groove along its
length (photo). It has paired gill pores on both sides of the dorsal
ridge of the trunk starting just behind the collar. Its
collar is orange, brick red, or reddish green and its trunk is brownish
green, pinkish orange, yellowish brown, or yellowish white.
Adults have 90-123 pairs of gill bars. Length 60 to
142 mm.
Much of the information on this page is derived from Smith et al., 2003.
How to Distinguish from
Similar Species: Saccoglossus pusillus,
which is found from California to the N tip of Vancouver Island, is
found in more exposed areas and occurs in sand or under rocks.
It has a bright orange proboscis, collar, and trunk.
The dorsal groove in the proboscis is pronounced.
Total length is up to 60 mm. Adults have 26-53
pairs of gill bars.
Geographical Range:
Maine to Nova Scotia in the Atlantic, and Padilla Bay and Willapa Bay in Washington.
Depth Range: Most Enteropneusts are intertidal, though a few species range down to 100 m depth.
Habitat:
In the mud in muddy bays.
Biology/Natural History:
18s mtDNA sequences show that the Padilla Bay and Willapa Bay
populations are virtually genetically identical to one another,
implying that they were transplanted to Padilla Bay from Willapa Bay
relatively recently (they were reported in Willapa Bay in 1910 (after
oysters were introduced there from the east coast) and described there
by Woodwick, 1951). The WA specimens were identical to the Maine
specimens in their 18s mtDNA but differed from the Maine specimens by a
3 base pair difference in the 16s mtDNA sequence. The mouth is on
the ventral side at the junction of the proboscis and collar, usually
hidden in the groove which separates the proboscis/collar. The
gills are in the anterior part of the trunk, which has gill pores in
this section. The pores may be elevated, or may be sunken into a
longitudinal depression. The trunk also has a middorsal and a
midventral ridge. Sexes are separate but difficult to
distinguish. Eggs are large (up to 1 mm) and yolky in Family
Harrimaniidae, which also has direct development--no swimming
(tornaria) larva. S. pusillus near San Diego was found to stick
the eggs to the side of the burrow (or these may be a remnant left
behind after spawning).
An
isolated Enteropneust proboscis and collar lives and moves for some
time but does not apear to regenerate. Pieces of the trunk can
regenerate into an entire individual.
This species seems to avoid bright light, an observation also noted in Hyman, 1959.
Enteropneusts are so similar to one another that no Orders have been set up within the Class (Human, 1959)
Enteropneusts
burrow by using the proboscis. This is elongated and thrust
forward, then contracted longitudinally to form a bulge. This
bulge is moved posteriorly to the base of the proboscis, pulling the
animal forward. The collar and trunk move forward passively.
Cilia on the surface of the proboscis and collar also move sand
posteriorly.
References:
Dichotomous Keys:
Carlton, 2007
General References:
Scientific Articles:
Hyman, Libby H., 1959. The Invertebrates: Smaller
Coelomic Groups. pp. 72-155. McGraw-Hill Book Co., New
York. 783 pp.
King, G.M., C. Giray, and I. Kornfield, 1994. A new hemichordate, Saccoglossus bromphenolosus
(Hemichordata: Enteropneusta: Harrimaniidae) from North America.
Proceedings of the Biological Society of Washington 107: pp
383-390
Smith, Shannon E., Rob Douglas, Karen Burke da Silva, and Billie J.
Swalla, 2003. Morphological and molecular identification of
Saccoglossus species (Hemichordata: Harrimaniidae) in the Pacific
Northwest. Canadian Journal of Zoology 81: pp 133-141
Woodwick, K.H., 1951. The morphology of Saccoglossus sp. of Willapa Bay. Master's thesis, University of Washington, Seattle.
Web sites:
General Notes and
Observations: Locations, abundances, unusual behaviors:
In
this view the animal has writhed around into a position in which the
dorsal groove in the proboscis can be seen. Some of the gill bars
in the trunk can also be seen.
This
larger individual is about 100 mm long. Shown on the muddy sand
it was living in. Proboscis is to the left, then the collar, and
long trunk to the right.
The worms produce this fine fecal casting.
Authors and Editors of Page:
Dave Cowles (2009): Created original page
CSS coding for page developed by Jonathan Cowles (2007)