Did you notice the bright orange patches?
Any guesses about what it could be?
The next image will be closer and might give away part of the answer.
Now you can see that the bright orange patches are concentrated below upside down Ochre Sea Stars (Pisaster ochraceus).
Here's another example:
The bright orange patches are pools of many tiny eggs! Ochre Sea Stars are broadcast spawners — they release their gametes into the water during the spring. Females release eggs which tend to be orange, while males release sperm which are white. [Unless you happen to catch a sea star spawning, you can't tell its sex from its external appearance.] Fertilization occurs in the water and then the larvae will spend ~76-228 days in the plankton before undergoing metamorphosis and becoming juvenile sea stars.
Barbara captured some excellent footage of the sea stars shedding their gametes. Below is a short video clip showing a female first and then a male.
Note that spawning occurs more commonly when sea stars are fully submerged under water, but Barbara documented several sea stars spawning while out of (or partially out of) water. You don't get to see spawning sea stars very often, so I thought it would be worth including a video. [If you're viewing this in an e-mail and can't see the video player below, click on the title of this post to go to the web page.]
Many thanks to Barbara for sharing this observation as well as her images and videos. And thanks to Eric, also, for putting together the video clips.
6 comments:
So special!
I got out tidepooling for the first time in way too long in Santa Cruz, and was happy to see a number of healthy Pisaster ochraceous. How is the Bodega population?
Wow - thanks so much for sharing! Have been so curious about this but never seen it. Seems like sperm and eggs should come from some kind of orifice & the pisaster in the video shows eggs coming from 5 places. How does this work?
Every morning the "Natural History of Bodega Head" solaces me.
This posting is particularly striking. Sometime ago I observed on the beach several patches of an orangish, rubbery substance. It looked organic, but I could not identify it. I wonder now whether they could have been dried pools of starfish eggs. Will take a harder look next time around.
Thanks for sharing,
rodolfo
Hi, Hollis,
Good question. The basic idea is that in Ochre Sea Stars there ten gonads = two gonads per ray. And usually one gonopore per gonad (although in some sea stars there is a group of pores, and without doing more research, I'm not sure of the exact arrangement for Pisaster). So the reason you're seeing gametes shed from five different locations is because there are different gonopores associated with the different gonads in the different rays. Multiple rays = multiple gonads = multiple pores releasing gametes.
Jackie
Thanks once again, Jackie. So there are pores associated with the gonads. There must be some kind of trigger involved so release of eggs and sperm are synchronized and tides & phase of the moon don't seem remarkable on 4/28 other than not being extreme. Will try to look into this. Thanks again!
Hi, again,
Yes, there are various things that could trigger spawning. In this particular case, it's possible that a shift in weather and sea conditions and therefore seawater temperature might have been a factor. There was also an algal bloom at the time (primarily diatoms), which also could be a trigger. And, spawning individuals might induce other individuals to spawn. There are more factors involved in the timing of spawning, but these are a couple of things that could have been in play on April 28th.
Jackie
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