Eupentacta pseudoquinquesemita Deichmann, 1938  Common names:  White sea cucumber, False white sea cucumber
Synonyms:  None
Phylum Echinodermata  Class Holothuroidea   Order Dendrochirotida    Family Sclerodactylidae
	Eupentacta pseudoquinquesemita from Sares Head intertidal. Length 8 cm.
	Photo by: Dave Cowles, July 2020

How to Distinguish from Similar Species:  Looks almost identical to E. quinquesemita.  The subtle differences are that E. quinquesemita has wider and less abundant tube feet with a narrower space between the ambulacra.  Its body wall is also thicker, with more support from calcareous elements. E. quinquesemita has the large, oval ossicles and also smaller, basket-shaped ossicles in the skin which E. pseudoquenquesemita lacks.  E. quinquesemita is more abundant intertidally in British Columbia (and south?) while E. pseudoquinquesemita is more abundant intertidally in Alaska and is mostly subtidal in our area. 

"Quinquesemita" meand five foot paths, referring to the five distinct rows of tube feet.

Geographical Range:  Aleutian Islands to Puget Sound

Depth Range:  Intertidal to 200 m

Habitat: Under and between rocks and in crevices.  Often found in areas of strong current.

Biology/Natural History: This species often holds algae, shell, or rock fragments. Predators include the sea stars Solaster stimpsoni, Pycnopodia helianthoides, and Dermasterias imbricata, and juvenile Eupentacta are a staple food for Leptasterias hexactis.  In my experience adults rarely expose their tentacles during daylight hours or after capture.  Typically have bits of shell and other materials attached here and there to the tube feet.  Spawning occurs in the spring (March to May).  Development is indirect.  Eggs, embryos, and larvae are greenish in color.  The body wall is poisonous to at least some fish.  This species eviscerates (see below).  Thyonicola americana is a shell-less snail that parasitizes the gut.

General References:
  Harbo, 2011
  Lamb and Hanby, 2005
  Lambert, 1997
  O'Clair and O'Clair, 1998
  Ricketts et al., 1985
  Sept, 1999.

Scientific Articles:

Deichmann, E., 1937. The Templeton Crocker expedition. IX. Holothurians from the Gulf of California, the west coast of Lower California and Clarion Island. Zoologica (New York) 22 pp 161-176

Tikasingh, E.S., 1960. Endoparasitic gastropods of some Puget Sound holothurians. Journal of Parasitology (Supplement) 46 p 13

Takasingh, E.S., 1961. A new genus and two new species of endoparasitic gastropods from Puget Sound, Washington. Journal of Parasitology 47 pp 268-272

It is very difficult to distinguish between Eupentacta quinquesemita and E. pseudoquinquesemita by morphological features without dissolving the tissue away and examining the microscopic ossicles. All of them seem to be a faded cream color like this or nearly white so there doesn't seem to be that much difference in color. Kozloff's key feature is that the interambulacral areas of E. pseudoquinquesemita are wider than the tube feet are long, while in E. quinquesemita the tube feet are longer than the interambulacral areas. However, this individual  over the course of several minutes demonstrated that they can easily expand and contract, changing the interambulacral distance. Earlier much of the interambulacral region was wider than the tube feet are long, while in this photo part of the body has contracted so much that the interambulacral areas are hardly distinguishable. Lambert (1997) does note that E. pseudoquinquesemita is almost exclusively subtidal in the southern part of its range, which would include here. This individual, by the way, must have gotten disturbed when I collected it intertidally because it eviscerated (see below). Photo of the individual after evisceration by Dave Cowles, August 2020

The sister species E. quinquesemita is known to eviscerate, but little is recorded for this species. Shortly after collection the individual above began to eviscerate, starting at the anterior end. Within a few minutes it had eviscerated its oral tentacles, the anterior calcareous ring, and its entire gut (see below). Eerily, even after evisceration the oral tentacles continued to make feeding-like motions for about an hour, as seen in this video.

Photo of the viscera of the individual above. The buccal tentacles and calcareous ring are on the right and the gut is on the left.