Reproduction
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drawing of sea cucumber spawningSexes are separate in temperate-dwelling sea cucumbers. Gonads are single and mop-like in form. Gametes are released from one or several gonopores that are mostly located on the membrane between mouth and tentacle ring.

 

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  Gonad growth
  Gonad growth is considered in this section, while SPAWNING & FERTILISATION, LARVAL LIFE & BROODING, and METAMORPHOSIS & SYMMETRY are considered in other sections.
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Research study 1
 

graph showing gonadal indices for sea cucumbers Parastichopus californicus in Indian Arm, British Columbia over a 2-year periosIn Indian Arm, British Columbia gonads of Parastichopus californicus develop through the summer and spawning is in late summer/early autumn. Sex ratios are not significantly different from a 1:1 ratio, and spawning is partially synchronous. Gonad indices are similar in the two sexes. Cameron & Fankboner 1986 Can J Zool 64: 168; for a detailed study on oogenesis in P. californicus see Smiley 1988 Biol Bull 175: 79.

NOTE  calculated as volume of gonad/fresh body mass (minus gonad and coelomic fluid) X 100. This is an unusual method of calculating a gonad index (for the more usual method, see Research Study 2 below) and makes it all but impossible to compare these results with those of other studies

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Research study 2
 

Around Sonoma County, California the black sea cucumber Cucumaria pseudocurata lives among sea mussels and on partially protected, vertical rock surfaces from the lower part of the mussel-bed to zero tide-mark. It is a brooding species.  Gonadal indices are highest in winter and lowest in summer. Spawning by males and females is synchronous, and occurs Jan-Mar.  Egg numbers per individual are dependent on size, and can reach over 300 in the largest females (>70mg live mass). Following their release, the eggs are held under the female‚Äôs body for about a month until they hatch.  Rutherford 1973 Mar Biol 22: 167.

NOTE  calculated as dry mass of gonad/dry body mass (including gonad) X 100. There are 2 lines on the graph representing the 2 sexes but, as the sexes do not differ significantly from one another, they are replaced here by a single combined blue line

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