Reproduction
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  Spawning & fertilisation
  Topics of spawning & fertilisation are considered in this section, while GONAD GROWTH, LARVAL LIFE & BROODING, and METAMORPHOSIS & SYMMETRY are considered in other sections.
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Research study 1
 

drawing of male and female sea cucumbers spawningIn many species, including Parastichopus californicus, spawning individuals raise up their front ends so that the gametes are released well free of the sea bottom. The gametes stream from a single pore within the photograph of a male sea cucumber Parastichopus californicus spawning out of one of its tuberclesring of tentacles, and fertilisation takes place in the open water.  The eggs are relatively large and yolky in sea cucumbers, and develop to a feeding larval stage known as an auricularia.  After a 3-5wk period floating in the plankton, the larvae metamorphose and settle to the sea bottom.  Cameron & Fankboner 1986 Can J Zool 64: 168.

NOTE  lit. “ear” L., perhaps owing to the sinuous appearance of its ciliated bands somewhat resembling a human ear



This spawning male Parastichopus californicus
appears to be releasing its sperm from one
of the tubercles on the upper surface 1X

 

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Research study 2
 

photograph of a male sea cucumber Parastichopus californicus spawning
Male and female Parastichopus californicus may intertwine their bodies and/or sway from side to side as they spawn, thus ensuring maximum fertilisation.  The eggs are light orange in colour and are slightly buoyant.  Both sexes are “dribble” spawners, and have an extended spawning season (April-August) in the San Juan Islands and British Columbia areas.  McEuen 1988 Mar Biol 98: 565.


A male Parastichopus californicus stretches out to spawn.
The sperm is visible as a milky string about three-quarters
ofthe way up the stretched part, on the upper surface 0.3X

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Research study 3
 

photograph of holothuroid Cucumaria miniata showing oral viewCucumaria miniata spawns March-May in San Juan Islands, Washington.  Eggs are greenish in colour and are released as compacted pellets (10-13mm length x 3-6mm dia) that float to the surface and break apart after about 20min.  Females spawn from a single gonopore, but males may spawn from up to 9 photograph of a sea cucumber Cucumaria miniata along with one of its egg pelletsgonopores.  Individuals of both sexes may stretch upwards into the water column when spawning.   Usually a male spawns first and creates a domino effect downstream in both males and females.  Note in the photo on the Right a female releasing a compacted egg pellet. Shimek 1987 Nat Hist (3): 60; McEuen 1988 Mar Biol 98: 565.

Cucumaria miniata in a laboratory aquarium
0.4X.
Photo courtesy Ron Long, SFU, Burnaby

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Research study 4
 

photograph of several sea cucumbers Cucumaria miniata with tentacles spread for feeding
Eggs collected soon after release or later at the sea surface following a mass spawning of Cucumaria miniata in the Bamfield area of British Columbia (18-19 March, 1991) are 87-97% fertilised.  In this incident most spawning takes place within 1.5h following slack low tide, although some individuals are still spawning up to and past the next high tide.  In this area mean densities are 46 individuals . m-2, and 95% of females are within 20cm distance of a conspecific individual – half of which are presumably males.  Each female may release up to 130,000 eggs.  Sewell & Levitan 1992 Bull Mar Sci 51: 161.

 

Several Cucumaria miniata in a rocky part of the
coastline around Bamfield, British Columbia 0.2X

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Select the single factor in the list below that does NOT correspond with what you know about conditions for optimal fertilisation success in Cucumaria miniata, then CLICK HERE for the answer:

aggregated distribution 
synchronous spawning 
low tide slack 
males downstream from females
slow current flow 

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Research study 5
 

photograph of sea cucumber Eupentacta quinquesemita feedingEupentacta quinquesemita spawns during May-June in San Juan Islands, Washington.  Eggs are light green or olive-green in colour, are slightly buoyant, and are released as a loose rope that soon breaks apart.  Females have one gonopore, but males have between 4-19.  McEuen 1988 Mar Biol 98: 565.

 




 

Sea cucumber Eupentacta quinq-
uesemita
in feeding posture 1.5X

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Research study 6
 

photograph of sea cucumber Psolus chitonoides
Psolus chitonoides spawns March-June in San Juan Islands, Washington.  Eggs are red or brick-red in colour and are released as a tightly packed, cylindrical egg strand (5mm dia) that fragments as it floats to the sea surface.  McEuen 1988 Mar Biol 98: 565.


Sea cucumber Psolus chitonoides. The
mouth is within the tentacles at the front;
the structure equidistant towards the back
is the anus covered with protective plates 0.6X

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