[Octopus]: Iris - O. Briareus

My only concern with the live shrimp is that they may be attacking the babies. If you have not moved them, perhaps it would be better to leave them in the sump and use them for food a bit later as a dead or injured hand offering.

The blue eyes are a good marker for extreme youth when one is shipped and suggest the animal is under two months old. Afterwards, the fluorescence diminishes and they show as a thinner green edge around the eyes.

We have discussed that feasting on the dead may be almost necessary (especially in a tank environment). No evidence of such but just passing thoughts. The question I cannot not answer is whether they kill each other or if they are simply scavenging. I never saw dead animals in the tank so I expected the die offs were consumed. My interest is in whether they kill each other off (which is expected but not confirmed) and at what age this starts occurring (this seems young but can't be sure). I probably should have had at least 4 survivors, one that did not survive disappeared in the sump with an unprotected pump and the other was placed in the tank with Cassy and simply disappeared. At the time I placed the second in the tank with Cassy, I was afraid I was condemning him since Cassy was larger.
 
Latest observations:
Firstly, the little guys are much more active along the rocks, and tend to hang out on the glass less. Their swimming skills are improving (more controlled jetting and more graceful takeoff and landing).

For the past two nights I've just counted about 25 or so. I suspect that their numbers are definitely decreasing, but the lower count may also be affected by their exploration patterns (i.e. being harder to count).

Also, they seem to be pretty pugnacious -- going after each other constantly, and going after the ghost shrimp. I'm really not worried about the shrimp attacking the octobabies at all; it really seems to be the other way around. It's just a matter of time before one of the octos takes down one of the ghost shrimp.
 
I was thinking about food. Why not build a "box" out of needle point mesh, and throw a handful of chaeto in there. sew the box together with fishing line. that way the pods have a safe haven, but can still come and go as they please from the safety fuge. The chaeto can get light and the little ceph's can play with the mesh. Awsome documentation, really love this thread! Makes me want a critter that much more.
 
Mataconda: that sounds like a good idea! As long as the chaeto gets enough light. I guess if the chaeto grows a lot, you might have to open up the stitching to harvest it.
 
Update:
I counted about 35 last night, mostly on the glass, and they're definitely growing. I also found a couple of corpses, so they're definitely dying off as well. The ones that are large and healthy are also quite active, starting at around 9 or 10 p.m.

Hand feeding is still hit-or-miss. Not because I actually hit-or-miss when feeding, but because some of them accept frozen food and seem to eat it, and some just want to wrestle with me and then let the food float away.
 
A couple of shots from last night. These were shot with a flash in otherwise dim red light.

The first one I just thought looked nice and graceful. The second one shows one of the little guys taking a corpse back to a quiet corner...

D's question about whether they are taking each other out vs. scavenging is an interesting one. Does it really matter? I mean, they fight all the time, so presumably when a big strong guy gets in a fight with a little weak one, the little one might be killed. If that happens, bully will eat victim. So I'm not clear on why the question is so important from a feeding point of view.

From a behavioral point of view, I can see it -- basically: are these guys just "play fighting" like lion cubs, or are they really going after each other for the kill?

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My interest in the cannibalistic observation (great that you are observing it as this has been believed but not documented) is curiosity, behavior and nutrition oriented. If cannibalism provides nutrients/quantity that the food we get to them does not, then leaving the dead (however they die) in the tank is definitely a good idea. If they kill each other (vs scavenge) then it is important to separate the brood in the number of groups that produce the number of desired survivors. If a and b then the "survivor" tanks need enough arbitrary culls to feed them until our provided food is adequate. I think I should have had 5 survivors (I had two) and suspect two died because they were totally isolated (ie possibly, no siblings to consume) even though they ate nightly. The third I noted at the time that I was afraid I was condemning to death because I was placing it in the tank with another. Unfortunately, we don't get a lot of opportunity for observation so your excellent reporting and exquisite photos are helping to guide/experiement with the next opportunity.

... and darn I want you macro lens! :biggrin2:
 
Interesting thoughts D and Tmoct. I've heard that Great White pups fight in utero, and consume each other. So many octopuses hatch, and other animals prey on the hatchlings, so why not hatchlings preying on each other?
 
The nutrition angle is interesting, too. For me, land locked in MI, getting a supply of live mysis shrimp is hard. Knowing if they need the nutrition from the dead/killed sibs is helpful!
 
I know O. mercatoris can successfully be raised on Cyclop-eeze and shore shrimp since Trapper only had 6 hatchlings and the only one that died climbed out of the water and didn't find its way back but they don't have the reputation of being cannibalistic and we have several documented success of at least siblings living together. My larger brood of mercs, however, still only produced 5 adults so quantity of food may be more important than nutrition (but I know many of my first group of briareus fed at least daily). My second opportunity with briareus failed somewhere in the last week of incubation. The eggs started disappearing and the few remaining that hatched were not healthy so I am excited to watch this group to see what we might learn.

I have also wondered if the females might eat some of the eggs, particularly when the brood time is extended (like the GPO). @Neogonodactylus mentioned that there are some fish that lay special, infertile eggs (there is a name for it but I forgot :old:). He was sure that this kind of eggs was not produced by octopuses and had not observed consumption of normal eggs but had noted what appeared to be infertile or unsuccessful eggs disappearing.
 
If cannibalism provides nutrients/quantity that the food we get to them does not, then leaving the dead (however they die) in the tank is definitely a good idea.

From a practical point of view, I don't have any choice on this particular detail. My tank (and probably most octo tanks) have enough detritus-eaters to immediately devour any dead that are available. So if the surviving octos don't pick up the dead, someone else will (in my tank, bristleworms) very quickly.

Update from yesterday:
Yesterday afternoon I got my shipment of 1000 live mysids from Sachs, and dumped the whole bunch into the main aquarium. I've had fine netting covering the overflow since the octo-hatch, so the mysids didn't get immediately "overflowed" into the sump.

As you can imagine, the aquarium is literally crawling with mysids. Interestingly, almost none of the baby octos came out last night. Even the couple that I did see were very subdued and just sat there. Otherwise a very quiet night. My hope is that they all had a large mysid meal and decided to turn in for the night, or they just found all the mysids too annoying and decided to stay "inside". [The thought did cross my mind that I could have messed up the water quality or otherwise thrown the tank into imbalance, but I don't really see it having such a quick effect, and anyway the tank chemistry/ecology is very stable and resilient at this point, so I think it's probably fine.] Hopefully they'll re-emerge soon healthy, happy, and well-fed!
 
Actually, I have been surprised at how long (or it just seemed shorter with my first batch, I should go back and look) they have been coming to the wall at night. I believe they have now become truly benthic and will start being harder to spot. It may be that swimming food will now be ignored and only food found in the substrate consumed. Critters like amphipods and possibly pieces of chopped up shrimp may be the next phase.

My thoughts (ramblings) are more for designing future hatchling experiments than for changing anything in an existing environment. So far, with any species, they do better in the primary tank than any pristine environment and I keep wondering why.

Bristleworms may start to be a problem now. Anecdotal evidence may suggest they nip at the hatchlings but it is really not clear this is the case and most of us can't avoid them. The potential observations may be simple scavenging on dead but one sighting felt that arms may be removed and the worms are the first to notice when an octopus' skin begins to falter during senescence.
 
Actually, I have been surprised at how long they have been coming to the wall at night.

I'm not sure if I'm just being fooled by their "pose" when they just sit there on the glass, but it sure seems like the ones on the glass are smaller / paler / weaker looking than the ones crawling around and active. Not sure what to make of that. Again, it may just be an illusion.
 
When you do see them on the glass, try to look for missing/shortened arms. I spotted several at one point but, again, not sure if it was from sibling interaction or hungry worms.
 

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