[Octopus]: Megamind - O Mercatoris(?) Hitchhiking Octopus

Nikky.Werr

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Hey everyone I am attaching this here from another forum where I requested an ID on this fellow and was directed to this amazing forum. This is how the story starts:

About two months ago I noticed my sump/refugium slowly becoming a shell grave, snails were being consumed as well as small crabs and hermit crabs. I thought I might have an aggressive gorilla crab or really anything "aggressive" but what I found two days ago. When I turned on the lights of the sump/refugium I saw this little fella darting into the darkness of the sheltering rocks. It's about 3cm in diameter so pretty small I think. I'd like to know what everyone thinks about keeping octopuses and their danger to other tank inhabitants. I've read very contradicting information regarding this subject. This little guy came along some live rock I picked up in Ocoa Bay, which is in the Dominican Republic, where I live. My plan is to return it to Ocoa Bay next time I go back but is there any possibility I could sort of "rear" it until it grows a little more. It looks so teeny and defenseless...
I know these picture aren't the best but you can see its coloration and somewhat tell skin pattern. He's pretty fast and hides once the lights go on, my lens is manual focus so yeah... I hope someone can ID this little fella. Any info about this little guy would be great, otherwise I'm just scrounging the web for info.
DSC_7961.jpg DSC_7963.jpg DSC_7964.jpg DSC_7967.jpg
I'd love to keep him and will do so until he becomes too big. I will have to research on octopus proofing the tank and I'm going to be aquascaping the DT so he has more places to hide. He's currently in the sump (where I found him) which is a 50 gallon and it's huge for his size (though I know the ocean is bigger so maybe it's actually small...). If anyone else knows anything about this little fella I sure would appreciate it.
I'm currently moving some things between my 50g and my 100g so that he or she can have a mostly his/her own tank. I don't see the octopus often just a few glimpses before I turn on the sump light But I can tell it's eating what i've put in for it which are crabs, snails, and a few small mollusks I caught in the same area where I got the live rock this little fella hitchhiked on. I have a friend who works at the local aquarium so when [Megamind is what I'm thinking of calling it] gets too big, he can live at the aquarium and I can check him out every now and then.
 

DWhatley

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Nikky, Megamind is adorable.

Looking at the accentuated eyes, mantle to arm length and coloration I am guessing a nocturnal dwarf that will not out grow a 30 gallon tank (but you do have to octoproof it). The eyes look a bit prominent for an O. mercatoris but we see them in south FL and they are likely to be common in the Dominican Republic. The only octopus that I KNOW is common to both (or I should say to Hatti and FL) is O. hummelincki (Megamind is definitely not hummelincki) but I suspect O. mercatoris as well as O. joubini are likely also common. O. joubini is also a red nocturnal dwarf that is often confused with O. mercatoris but I have never found a clear description of the visible differences (I believe O. joubini has longer arms, know it is a small egg species vs the merc large egg size and may be a bit more active). Some of the best in-tank images we have of O. mercatoris can be found in this older journal by gholland and @Neogonodactylus has the best detailed lab shots in the photo Gallery.

As far as controversy about keeping an octopus in an aquarium. Please feel free to mention where you have seen opposing thoughts and we will try to give answers based on the experiences we have had over the years.

Something I feel I should mention is that once an animal (which includes corals and even LR because of the animals within) is removed from the ocean and placed in an aquarium, it should not be returned to the ocean, even if it means the death of the animal. There are public aquariums that will do this but they run flow through systems (ie the water in the tank is piped in from the ocean) and nothing foreign to the water is ever placed in the tank. Returning an animal risks exposing others to harmful bacteria or invasive species.
 

DWhatley

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As an aside, one of the tank items I have found to be excellent for O. mercatoris is a collection of giant purple barnacle shells placed roughly at 1/3 of the tank height (from the bottom, 2/3 water on top). If you place these so that you can see in but the octopus still has a dark den, you will see more of it than if it uses crevices in the LR. There is no guarantee it will choose the barnacles, but all my females and most of my males found and chose this arrangement for their homes.
 

Nancy

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What a charming little octopus! I"'m glad you have a tank for him. D is right about barnacles - not only do they provide good places for your little octopus to hide, but they look nice in your tank!

Nancy
 

Nikky.Werr

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Wow thanks very much D. I'll take your advice on the barnacles. I had originally thought of taking Megamind back to Ocoa Bay after growing but I've received enough advisement against it. I hadn't thought about what I could introduce into the ocean from my system. If it comes to odds, which I don't think will happen, I can always take him/her to the aquarium where my friend works. I have to see about octopus proofing without inhibiting gas exchange.
Again, thanks D and Nancy, this is a lovely ceph community. I will update periodically or maybe start a journal for Megamind.
 

DWhatley

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I found the ReefCentral thread you referenced and was pleased to see someone there also mentioned the concerns about "returning" animals to the ocean after exposure to an aquarium. It is not one of those obvious concerns until you think about it.

I hope you had a chance to read and view the images for gholland's little hatchings that I linked in my first post (new members often miss the underline and coloration marking a link). I believe you will see the similarities with Megamind. However, keep in mind that even experts are fooled with these animals and only longer term observations (and sometimes only by necropsy) confirm what species you are observing. Fortuantely, care for shallow warm water animals is similar enough to give confidence to the keeper.

PLEASE do journal your adventure. I can easily move the thread to the journals forum if you would like to use it as the beginning.
 

Nikky.Werr

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I did check out the journal, they seem very similar. I realize misidentification is possible but it does seem pretty accurate.
Please do! I think I would add this anyways when I create a journal so if you can move it that would be greatly appreciated :D
 

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