Recently, while diving with God’s Pocket, the sea suddenly clouded up. Anemones and sea cucumbers appeared to be releasing smoke and these green packets drifted by my mask.
Most often, divers prefer good visibility. However, in this case as I watched the sea turn white, I was euphoric that I happened to be in the water when orange sea cucumbers (Cucumaria miniata) and plumose anemones (Metridium farcimen) were broadcast spawning. Witnessing the magnitude of this great force that ensures these species will survive is as awe-inspiring as witnessing the annual spawn of herring or salmon.
While plumose anemones reproduce asexually as well (by pedal laceration), broadcast spawning allows for diversity through sexual reproduction.
During broadcast spawning, invertebrate males and females each release their sex cells into the water column – in astoundingly copious amounts.
You can imagine how many gametes must be released for there to be a chance of fertilization and for enough of the resulting larvae to survive and not to be eaten by the many filter feeders such as barnacles, anemones and sea cucumbers!
It is of course a good strategy to have males and females living in close proximity and that timing is everything! The spawn must be synchronized. To release sex cells when others of your kind are not doing so, would be a very failed reproductive strategy indeed. Probable cues for spawning are ocean temperature; the number of days/hours of sunlight (cumulative temperature); and/or the presence of a plankton bloom.
Apparently for both orange sea cucumbers and giant plumose anemones, the males are the first to release their gametes, triggering the females to spawn.
Research has also found that, in the case of orange sea cucumbers, females release around 130,000 eggs packaged in buoyant egg pellets. The egg pellets drift to the surface and dissociate into the individual eggs after about 20 minutes. Spawning in orange sea cucumbers most often happens within 1.5 hours after slack low tide which adds to the success by allowing for a greater concentration of sex cells, maximizing the chances of fertilization.
Through these images, I hope I have been able to relay the awe I felt at witnessing this biological marvel that has allowed these species to survive on Earth for thousands of times longer than we humans have walked upright.
Related The Marine Detective posts:
- Gumboot chitons spawning
- Super Mom – up to 300 young under her care [blog item on brooding anemones]
- A Snail’s Odyssey; Sea Cucumber Reproduction
- Lambert, Philip; Sea Cucumbers of British Columbia, Southeast Alaska and Puget Sound
- RaceRocks.com; Metridium farcimen