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FAQs about Sea Urchins, Sand Dollar Reproduction

Related Articles: Sea Urchins

Related FAQs: Urchins 1Urchins 2Urchins 3, Urchin Identification, Urchin Behavior, Urchin Compatibility, Urchin Selection, Urchin System, Urchin Feeding, Urchin Disease

Green banded goby and Diadema urchin, sexing Echinoids     12/13/12
Dear Bob
Can a green banded goby's association with a Diadema urchin cause it to cluster its spines together, in sort of ordered clumps?
<Mmm, yes>
Or is this a sign of ill-health in the urchin (which otherwise seems to be behaving normally)?
I have noticed of late that my urchin does this, but it was not until just now, and with the aid of a flashlight, that I discovered the tiny green banded goby had not perished as was feared a couple of months ago, but is alive and well, and considerably bigger.  A nice surprise!
Also, when the urchin sidles up the wall of the tank into flow and pumps a milky liquid into the water, is this sperm?
<Likely so; yes... could be eggs, but w/o having both to compare, they're hard to distinguish>
 Is he a he?  Can I get him a
she, of the same genus at least and do they cross-breed (just out of interest)?
<You can, but it's a guessing game... All Echinoderms are dioecious ("two houses"), i.e. separate sexes; but most all cannot be told apart sexually w/o taking them apart! Bob Fenner>

gravid sea urchins, determining   3/21/11
hello again! We are to collect the sea urchin Tripneustes gratilla for our thesis. How would you know if a sea urchin is gravid? Are there any physical indications? Is this applicable to any kind of sea urchin?
<Mmm, as you're likely aware, Echinoids are dioecious, separate sexes (male or female), and that they're by and large seasonal (less so in tropical species) in their stages of sexual "readiness"... the common method of assessment is to either sacrifice some individuals (can't be discerned as to male/female, nor gravidness externally) or process them chemically (to release eggs, sperm) to determine such. Bob Fenner>

Assistance please in identification  11/30/10
Hello from Australia and congrats on a great web site and an inspiring source of information.
<Howdy and thank you>
I require some assistance please in identifying a stringy yellow/ cream coating at the very base of my live rock. I have attached a photo.
<I see this>
It is only in this one small spot (hard to get to because of some overhanging rock) and does not appear noxious or particularly irritating to nearby corals. Nonetheless it would be good to identify as friend or foe!
<Almost assuredly this is a sponge/Poriferan. Friend>
I have also attached a photo of my baby sea urchin. I found him during tank cleaning about a month ago - at that time he/she was about half the size than in this photo. Mum (and I now assume Dad) are happy
eating Nori as well as commercial brands of red and brown sea weed that I tie to rocks and sink. They are very peaceful additions to the tank and have given me at least one offspring - quite possibly more.
Cute eh?
<Ah yes>
Are you able to provide any information on how/when they breed?
<Are separate sexes... as all Echinoderms... have a pelagic phase...>
I assume they are egg layers with the male fertilizing the eggs?
I have not witnessed anything close to urchin "action" in the tank!
<This individual was part of your "live rock" or other hard material introduced into the system... Not sexually derived here>
Thanks for your help and keep up the good work.
<Welcome! Bob Fenner>

Re: Assistance please in identification  12/1/10
Thanks for the reply. Can I please ask if you think it could be possible my sea urchin is the product of my two adults?
<Highly unlikely... read here: http://wetwebmedia.com/urchinreprofaqs.htm
The reason I ask is I have not introduced any new live rock or coral to my tank in over 6 months and this little guy has doubled in size in the last 1 month so I am guessing is not >6 months old.
<Mmm, could be... growing much slower previously>
Also it is exactly the same species as my two adults and with all the different types of urchins in pet stores over here it would seem coincidental to have a hitch hiker of the same breed. I did find a PhD student in Western Australia that was breeding them for his studies - although I was unsure of the type - so I assumed they bred readily in captivity?
<Can be induced to release gametes, IF brought into reproductive fitness, ripeness... but the pelagic larval stage is very hard to support in typical hobby settings. Requires specialized recirculation, a dearth of mechanical disruption (filtration)...>
Thankful for your reply and certainly not trying to argue the point
<No worries. Am glad to discuss any/all point/s. Perhaps this is an in situ reproductive event... BobF>
Kelly Neill

Mating sea urchins in an aquarium -- 01/03/10
Dear WWM,
<Hello KB.>
My sister has a saltwater aquarium. She has three sea urchins. They are different colors, and one has smaller spines.
<Sounds like different species.>
Might these urchins mate in her tank?
<Maybe, if at least two are of the same species. However, no offspring will grow up in the aquarium. The water is likely too different from natural seawater and lacks planktonic organisms the larvae would need as food. Mating urchins just release their eggs and sperm into the water, where they eventually may meet and develop into larvae and consequently urchins.>
How can she tell the difference between male and female?
<Only by dissecting them and knowing how their organs look like. See here and in the linked FAQs for more urchin info: http://www.wetwebmedia.com/urchins.htm especially http://www.wetwebmedia.com/urchinreprofaqs.htm>
Thanks, KB
<Cheers, Marco.>

Echinoderms: The Birds and the Bees - 7/1/08 blue tuxedo urchin baby i <Please capitalize in the future...> have a 29 gallon tank and I just got an urchin today (blue tuxedo urchin) and I noticed that it dropped a little white blob that looks like it has the same tentacles <Tube feet? Spines?> as the big one. I was wondering if it could have picked up a baby urchin because I got it right as it got in to my LFS- they didn't even take it out of the bag from there <homophone! 'their'> shipper yet so I was wondering if I have a baby urchin and what I can do to keep it alive if it is one? <Yes and no. "Baby" in the sense of small, perhaps- not in the sense of infantile progeny. Urchins have open reproductive traits; sperm and egg are released free of the parent. At fertilization the zygote quickly becomes a free swimming (pelagic) plankter. After several stages of growth, complete and partial metamorphosis, and settling out the urchin is secure in an adult form. It will forage for itself and fend against selective pressure given appropriate habitat. Benjamin>

Re: Echinoderms: The Birds and the Bees - 7/1/08 Thank you very much! I also noticed that last night as i turned off the light the infantile urchin crawled into the spines of the bigger urchin for what im assuming is protection. < camouflage...nothing filial here> This morning when I turned on the light I saw the urchins spines start to move the infantile urchin towards the glass wall which i think was its way of letting it forage for some of its food on its own. <More of a defense mechanism...this is not a mother and child; two unrelated organisms> At one point the current from my filter swept the smaller urchin off towards the filter so i quickly caught it on my finger and placed it gently on the wall. <Never handle an urchin without heavy gloves> Then about a minute later my Hippo Tang put it in its mouth and spit it back out and from there it fell into the crushed liverock at the bottom of my tank. do you think that it will be alright through that whole ordeal? <Yes> I haven't been able to find it because it blends well with the crushed liverock. <As it should> Thanks in advance for any advice i appreciate the help <I edited your first submission. I have done only what is necessary with this one to make it legible. Please show the courtesy of proper English grammar and syntax in your next submission, or we reserve full rights to ignore it. Benjamin>

Urchin Sex? - 05/14/08 Hi! <Hello!>> Researched through Google, found your site. <<Welcome>> Scrolled through for an answer prior to bugging you! (sorry!). <<No worries>> Our urchin is excreting a white string of material (think of like a frog laying a chain of eggs...). <<Ah yes…gametes likely>> The closest I found on Google was emission of sperm but no pictures to verify. Closest I found on your site was the article/question titled: Urchin blowing chunks. I've sent along a picture. <<Mmm, yes…does look like a sexual event (perhaps triggered by a change in water temperature and/or salinity)…and some chow for some of your tank denizens as well>> This went on for about an hour. When it finally stopped immediately did a 25% water change and checked levels throughout the night as well as kept vigil for any signs of change or distress. <<Depending on the size of the tank this may not have been necessary…but didn't hurt either>> Thanks for your help! <<Mmm…such as it was! [grin]>> This happened about 3 weeks ago, everything still thriving as though nothing happened. <<Indeed…nothing to be concerned about re this "event." Cheers, EricR>>

Culturing of sea urchin larvae  - 02/16/2006 Hi Bob, I accidentally found your webpage and hope that you might answer some of my questions. I really would like to do some research with sea urchin larvae. <Gosh... a stock process/experiment back in college...> At my institute they have some experience in reproduction of sea urchins (Psammechinus miliaris). And I also have support from a technician who has lots of experience in culturing marine organisms. I myself worked with fish - quite different stuff indeed. Nonetheless, I really would prefer to work with larvae instead of embryos. Indeed, I was told that larvae culture is quite laborious. Do you have any experience with invertebrate larval culture???? <A bit> How elaborate is that? What equipment do you need? <Mmm, some brood stock, mechanism to bring on gametogenesis, spawning... rearing tanks (sometimes specialized) and "good" water... new/natural or recirculated/filtered> And what about the feeding? <Very important... Often the single largest "stumbling block" in invertebrate culture. A computer search here saves much trouble> I won't be able to maintain an algae culture as feed for my cute larvae. But I heard that there are commercially available microalgae.  Indeed, I read a publication that larvae don't reach the same growth rate with a commercially available diet compared to a control diet with Dunaliella. And do you know anybody who could give me more tips??? <Sea Biscuit in the Seventh... Actually, there is much written/recorded re many species, groups... time to go to "the library"... and ask specifics later> Thank you very much! And best wishes from a future sea urchin culturist! :-) Sabine <Look on the Net for the names Rob Toonen, Frank Hoff, Ron Shimek... for "pet-fish" input... otherwise... ex libris. Bob Fenner>

Pincushion urchin releases gametes Good evening Bob. <James for Bob today>  An interesting anecdotal note: Last night I was performing a light water change of 3.5 gallons in a 55 gallon tank (about 30 minutes before lights out). I left the heater in the replacement water a little long so it was a few degrees higher than the tank water. I always put my replacement water into the sump, as it is the highest flow area of my system.  In any event, I did not realize that my pincushion was in the direct flow of my return just a few inches from the where the water dumps back into my tank. It was hit with successive waves of warm water. After I emptied the last of the replacement water, I noticed the urchin leap (not literally) from the rock it was on to the back of the tank and then race up the wall.  When it got to the top it released its gametes in long white stringy flows that dissipated like smoke in the current. The release was from the 5 gonophores in the cushion part of the urchin near its anus. The whole situation reminded me of an aquaculture job I had years ago when I was in college. At the time I worked on a clam aquaculture farm. In the spring the clams were forced to release gametes in a controlled tank setting by exposing them to a swift current alternating in cool and warm water. I wonder if the same can be induced in urchins and if that is what I experienced.  <It is not uncommon to see urchins release gametes with or without changes in current or temp. I have observed this several times.>  The urchin shows not ill signs from the experience and never even lost any of the shells it was carrying on its back. I'd give you my water parameters, but I didn't test last night and today's would be of little value. The urchin is well fed on GHA, which the urchin is systematically eradicating from my young tank.  <James (Salty Dog)> Paracentrotus lividus Info Needed (11/21/04) Hallo Bob, long time no hear from me as I was between jobs and I had stopped my on-line presence on MCH. <Steve Allen covering tonight.> Well the last month I was hired at last and now I am working for a fish farm in Greece. Well the fishy part now. I need badly your help!!! I would like to find any available information on the sea urchin of the species P. lividus, concerning projects of applied aquaculture of the species, the embryonic development and metamorphosis, as well as about the time of growth of the sexual matured animals. Topics of my interest are also the feeding techniques for the species and every relevant topic, from alimentary demands to the quality of gonads either for reproduction or for human consumption. I would like you to give me any www links or guidelines on bibliography you do have in mind on this particular matter, so I shall make an advanced search as we've managed to spawn them and we do have some first stages larvae and we'd like to go a bit further on that. Any help will be highly appreciated. Thank you very much in advance. Andreas I. Iliopoulos <All you need to do is go to www.google.com and input the term "Paracentrotus lividus." This will give you all sorts of references (I checked). Additionally, you may want to check at a university library if there is one in your area. Hope this helps.>

Urchin eggs? <Hi! MikeD here> my urchin which I was told to be a purple urchin is actually brown with purple tips on his spines well anyway he put out say.... 20 yellow tiny eggs it seems to be. it just sits in a hole in the rock which I assume is natural behavior?<While eggs are a possibility, I suspect you've just noticed your urchin having a bowel movement, and don't feel dumb about it, as it's an honest mistake, with most people never considering an animal that eats with its butt and that poops out of its head! Urchins are actually a source of the oceans sand as extra calcium and silica gleaned from the algae is excreted through a small hole on the very top>.he lost 2 spines because my damsel fanned him, but I don't know what the yellow balls are. Thanks for your time<Not a problem, as time is the one thing I have plenty of. You might want to keep an eye out for additional needle drop, as urchins such as yours require good water quality, and shedding being a prime indicator that parameters are dropping. Before the availability of modern dependable test kits, urchins were often used as "miner's canaries" to monitor water conditions> , Aaron Sea Urchins To whom can answer our questions: Hello my name is Christine and my partner and I are going to use sea urchins for our science fair project. We were wondering if anyone could assist us by answering a few questions we haven't been able to answer ourselves or by other means. Many of my questions have to do with finding an inexpensive way to keep the sea urchins and their eggs alive. 1.) What can we do instead of buying a "shaker" to keep the water moving in a small containment? <I don't know what a "shaker" is, but Urchins require fairly standard marine aquarium husbandry.> 2.) How and what can we feed sea urchin eggs? <I don't know, but I do know that urchins and their reproduction are routinely studied. You should be able to find literature at the library.> Is there a recipe we can make ourselves to feed the sea urchin eggs? <I would have to guess either phytoplankton or rotifers, but the references at the library should help you.> 3.) What can we do to keep the sea urchins alive, since we heard it is quiet difficult to even keep sea urchins for more than 3 days? <Very incorrect, given an appropriate environment urchins can be rather long lived.> If anyone can answer these questions we would be very much appreciate it. <Do take a look here http://www.wetwebmedia.com/urchins.htm and the linked FAQ files for a start. -Steven Pro>

- Urchin Spawning - <Greetings, JasonC here...> I recently purchased a fire urchin (I believe it is an Asthenosoma spp.) and last night all of a sudden it started expelling a white chalky substance out of the top. It looked like a tube of toothpaste oozing out of five tiny holes. The substance then was picked up by the current and distributed throughout the tank. Everyone seems fine including the urchin, anemone, and all of the fish but I am curious as to what occurred with the urchin. Can you shed any light on the subject. <Yup... likely an attempt to spawn by the urchin. Was either sperm or eggs.> Thanks, Ken Felix. <Cheers, J -- >

Spawning urchin event hi again Bob, something odd, when i pulled the last of the bio balls from my 130 FOWLR tank the other day, there was an immediate cloudiness in the tank, brushed it off as a bacteria bloom, it was gone in the morning along with the nitrates as i mentioned, I traded in my lion and Naso for a couple urchins and some emerald crabs today, I just tossed the floss in my now sump as i did always every few days when i had the bio balls and my tank is a white cloud again now, I am noticing that a new black urchin is spewing some sort of white stuff front the center of him, looks like long strings of white hair, then if spreads out like smoke and disappears, wondering if this is the cause or some bacterial thing going on, he is doing this constantly, should i not be tossing the floss as often now without the balls?, don't want to goof this up. thanks again.....Riot... <The urchin is releasing gametes... may be related to the change in water chemistry... you should check your mechanical filter media, clean it as often as you see it accumulating wastes. Bob Fenner>

Sea Urchin Question Mr. Fenner- My question relates to the use of Sea Urchin (Uni) as food in sushi bars and Japanese restaurants. <You know... as a kid in Japan I always wondered what Sea Urchin roe tasted like (too expensive for me then), and then when I moved to the source (Southern California) of a good deal of it, I couldn't understand what the big deal was/is... "Oh, you just haven't had it really fresh", I can hear my friends saying... Oh yeah? I've cracked Strongylocentrotus sanfriscanus tests open underwater, taken out my regulator mouthpiece and eaten it then/there... it is better fresh... but still tastes like "the bottom of a boat" to me (and don't ask me how I know what that tastes like, hee hee!> Can any toxins at all be absorbed into the human body from eating Sea Urchin/Uni the way it is served in Japanese restaurants? (Liver, stomach, pancreas, etc.) <Oh... I imagine there is some possibility... The biggest threat in my opinion is likely from "herring worm disease" (anisikiasis)... have a bit about this posted on our site, here: http://wetwebmedia.com/roundwor.htm Or, much more likely, liver disease from too much sake and good Japanese beer. Mmm, I'm getting thirsty. My point is, there's probably a greater risk from breathing car fumes getting to/going from the sushi bar than ingesting sea urchin eggs. Bob Fenner. Oh! And should mention, these are used in many fish foods.>

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