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Small Size, Brooding, and Protandry in the Apodid Sea Cucumber Leptosynapta clarki.
The Biological Bulletin
|December 28, 2017
Summary
The sea cucumber Leptosynapta clarki is a simultaneous hermaphrodite, starting life as a male and transitioning to a female. This sequential hermaphroditism may reduce inbreeding in this brooding species.
Area of Science:
- Marine biology
- Reproductive biology
- Ecology
Background:
- The apodid sea cucumber Leptosynapta clarki displays small adult size, brooding (viviparity), and protandric hermaphroditism.
- Juvenile L. clarki are released as 1-2 mm individuals and mature as males within months.
Purpose of the Study:
- To investigate the reproductive biology and sex change dynamics of Leptosynapta clarki.
- To analyze the relationship between size and sex determination in L. clarki.
- To test the allometric hypothesis regarding small size and brooding in L. clarki.
Main Methods:
- Observation of juvenile and adult L. clarki.
- Analysis of size-sex relationships.
- Histological examination of gonads.
Main Results:
- L. clarki exhibit protandric hermaphroditism, with individuals maturing as males and later changing to females.
- A critical size for sex change was identified between 200-400 mg, with a 1:1 sex ratio at >500 mg.
- Transitional gonads suggest sex change initiation before the reproductive season.
- No evidence for allometric constraints on brood size was found, possibly due to low fertilization success and brooding in a distensible structure.
Conclusions:
- Sequential hermaphroditism in L. clarki may be an adaptation to reduce inbreeding in a species with limited dispersal.
- The reproductive strategy of L. clarki is influenced by size-dependent sex change and brooding behavior.
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