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Eupentacta quinquesemita is stiff to the touch due to abundant calcareous ossicles in the skin and tube feet. The body grows to 5 to 10 cm in length. The non-retractile tube feet give it a spiny look. It has five rows of tube feet (four tube feet in width) with smooth skin between. The two ventral tentacles are smaller than the other eight. This character is useful for identifying this species when only the tentacles are visible. The expanded tentacles are creamy white with tinges of yellow or pink at the bases.
Skin ossicles: numerous large, porous, ovoid bodies dominate the ossicles but among them are small, delicate baskets. These latter are important in differentiating this species from Eupentacta pseudoquinquesemita.
Eupentacta quinquesemita is almost identical in external appearance to E. pseudoqinqesemita. The differences are subtle, and separation of these two species can only be determined with certainty by analysis of the skin ossicles. E. pseudoquinqesemita has softer, non-retractile tube feet, up to 10 across each row. In British Columbia and Washington this species is subtidal and often found in sediment. They often have small pieces of shell and other debris attached to their tube feet. If only the tentacles are visible, E. quinquesemita can also be confused with the white tentacles of Cucumaria pallida. However, C. pallida has 10 equal-sized tentacles, not 8 equal and 2 small. Pentamera trachyplaca and P. lissoplaca are also similar in general appearance but the ossicles are clearly distinct.
quinquesemita = five foot paths
Eupentacta quinquesemita is a suspension feeder. It spawns from late March to mid May. The female produces light green eggs, 370 to 416 μm diameter: the male releases sperm, and fertilization takes place in open water. The yolky egg develops into a non-feeding evenly ciliated larva. In culture, the larva grows to the armoured stage in 11 to 16.5 days.
The Sun Star (Solaster stimpsoni), the Sunflower Star (Pycnopodia helianthoides), the Six-armed Star (Leptasterias hexactis) and the Kelp Greenling (Hexagrammos decagrammus) prey on this species.
Eupentacta quinquesemita occasionally eviscerates through a rupture in the introvert just behind the feeding tentacles. Rough handling causes this reaction, but it also happens under natural conditions and on a seasonal basis. Evisceration typically occurs from September to November and regeneration of the ejected parts takes about two to four weeks. Researchers believe that this behaviour is a method of discarding a waste-laden digestive tract, and also getting rid of parasites that attach to it.
The internal parasite, Thyonicola americana, a shell-less wormlike snail, attaches elongated coils of eggs to the intestine of E. quinquesemita. The larvae are released into the intestine and probably escape through the anus. Any parasites that are ejected by evisceration perish. For more details see Byrne (1985a).
The body wall of this species contains a poison that, if ingested, can cause a fish to become sluggish and eventually die.
E. quinquesemita occurs along much of the coast in both protected and exposed regions. It is abundant in the intertidal and shallow subtidal of rocky shores. High densities of this species occur in strong currents. Juveniles (up to 1 cm) settle among hydroids and small algae in high current areas and on floating docks.
Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2021. E-Fauna BC:
Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab
for Advanced Spatial Analysis, Department of Geography, University of British
Columbia, Vancouver. [Accessed:
2022-08-08 10:24:23 PM]
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