Click on the image below to view an expanded illustration for this taxon. If more than one illustration is available for a species (e.g., two subspecies may be illustrated) then links to the separate images will be provided below.
Psolus chitonoides is an unusual species that resembles a chiton rather than a typical sea cucumber. It is dome-shaped, and covered with pale yellow to bright orange, shinglelike calcareous plates; about four rows between the mouth and anus. The sole is soft, flat and pale orange to white. The body is oval, and can grow up to 7 cm long and 5.8 cm wide. A plume of 10 equal-sized, bright red, white-tipped tentacles, protrudes through an opening in the dorsal plates at one end. Tube feet are confined to the sole. A series of two to four rows of robust tube feet run down each side of the sole; and another row of tiny tube feet in small depressions run down the outer edge of the sole. A staggered series of tube feet runs down the centre of the sole.
Skin ossicles: one type of circular perforated plate - some with knobs coalesced into a raised network - occur only in the ventral sole.
There are two species similar to Psolus chitonoides: Psolidium bidiscum and Psolus squamatus. P. bidiscum is smaller (1 to 3 cm), and is normally dredged from deeper water. It has tube feet piercing the dorsal scales; and the tentacles are pale pink or white, as opposed to the bright red, white-tipped tentacles of P. chitonoides. Psolus squamatus has white scales and is dredged from deeper waters.
chitonoides = like a chiton
Psolus chitonoides is a suspension feeder. The tentacles trap larger particles (greater than 2 mm) by bending inwards to form a cagelike enclosure. The mouth lips extend toward the particle as the nearest tentacle pushes it into the mouth.
Spawning occurs from mid March to late May, commonly in the early morning. A spawning male will swab its genital papilla with its tentacles, then lift the tentacles to disperse the sperm. Females release long ropes of brick red eggs (mean diameter 627 μm). Fertilized eggs develop into pelagic lecithotrophic vitellaria larvae. Late larvae and early juveniles are negatively phototactic and settle gregariously.
Toxic chemicals (saponins) discourage fish from nipping the tentacles. Even the Kelp Greenling (Hexagrammos decagrammus) - which commonly feeds on sea cucumbers - avoids P. chitonoides. The Sun Star (Solaster stimpsoni), the Leather Star (Pycnopodia helianthoides) and the Red Rock Crab (Cancer productus) prey on P. chitonoides.
Psolus chitonoides occurs in a range of habitats from exposed coast to sheltered inlets; although it seems to prefer clean, vertical rock that is free of sediment. Its soft, flat sole enables it to attach firmly to rock. Other organisms attach to the dorsal side, often only the tentacles indicating its location.
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:
2022-01-18 11:38:17 PM]
The information contained in an
E-Fauna BC atlas pages is derived from expert sources as cited (with permission) in each section.
This information is scientifically based. E-Fauna BC also acts as a
portal to other sites via deep links. As always, users should refer to
the original sources for complete information. E-Fauna BC is not
responsible for the accuracy or completeness of the original information.