New to the wonderful world of chephalopods

[platypus]

Hi!

I am a first year master student at Bar-ilan university in Israel doing my thesis on the behavior of a species of crab (Lybia sp.) and its symbiosis with sea anemones that it holds in each of its claws.
Basicaly little is known about this interesting symbiosis and i will be testing various aspects of it.
One of the things to be assesed is role of the anemones in protecting the crabs from predators.
Enter the most formidable crustacean predator- Octopus Vulgaris
A few weeks ago I started contemplating how I get my hands on a cephalopod. My first thought was a cuttlefish, they are in season now and fishermen pull them out all the time for bait. Octopus are less commonly fished in these parts (not eaten), and those caught are too big for my setup. I needed to get a juvenile one.
Long story short, On a trip out to sea (1 km from shore) whilst checking up on some one elses project (goose barnacle settelment) we pulled out a big peice of rusty metal, used as a weight, from 30m deep and...out came a small Octopus (to my great surprise and delight). In reterospect its not such a surprise. Ive dived at that location and its a totaly baren sand desert. So it makes sence that an octopus would chose our "weight" as a den.
In terms of size its less than an open hand and i have it kept for now in a 40 liter tank, with fresh sea water that i change very often, live sand and rocks, proper filtration (unforteonatly I dont have a protein skimmer at the moment but i hope that the frequent water changes compensate for this).
After having it for a week now it has setteled in to the tank, exhibits good color (not the very pale white scared color from the first day) and seems to be eating well (common crabs, ghost shrimp and a small fish) although I havent seen it hunt as of yet, just found lots of remains
I promise to post some pictures of my Octopus and crabs soon!
Other than to introduce my self i have a few questions-

1. how do I tell if its a male or female? I read that the male has a slightly different arm (one of them) but i cant find a good picture that shows a comparison. Is it possible to sex them at all ages?

2. Is a protein skimmer totaly mandatory or will frequent water changes (20-30% a week) and removal of dead prey be ok?

3. Is there a good, simple method to catch lots of crabs to feed it? like a simple trap setup ect.... (I dont have a local supplier of live, small, crabs and am getting tired of hunting them with a hand net on the rocks at the beach....).

4. how paranoid do i need to be about little crevices and holes in the lid of the tank? are they THAT prone to escape?

In terms of the experiments he/she will take part in, I probably wont be starting them for the next month or so, I want him/her to acclimatise properly and I still have some stuff to sort out in the crab setup. But the idea will be to expose the crabs to the Octopus and see how it affects their behavior (at first just "chemical" sensing, no actual face to face meetings.., perhaps in the future if i have lots of crabs ill test it "mano a mano").

Thanks ahead for any help you can provide! I must say that ive been totaly captivted by this magnificent animal since i got it. I cant get over how it changes its color/form in an instant (and then change back..)...and there is some thing about its eyes...they arnt "empty"...there is some thing behind them...

 

[dutchcourage]

What are you studying the pom pom crab or boxer crab?

 

[platypus]

Nomenclature

Lets get the terminology streight-
First, im talking about boxer crab and not boxer shrimp.
From my understanding pom pom crab usualy refers to the hawaiian species- Lybia Edmondsonii
(http://zipcodezoo.com/Animals/L/Lybia_edmondsoni.asp) and Boxer crab refers to the more common Lybia Tessellata (http://www.edge-of-reef.com/brachiuri/BRALybiatessellataen.htm).
At present I have some Lybia Leptochelis (http://www.dafni.com/crustacea/Lybia_leptochelis.jpg), yet another species in this family.
I hope to obtain some more of them and some Lybia Tessellata soon (the leptochelis i collect from the red sea, the tessellata i need to order from over seas).

 

[monty]

and your research sounds very interesting!

in general, 40 liters is way too small for a vulgaris; even for a bimac, which is considerably smaller, we recommed 55 gallons, which I think is around 200 liters... one of the main reasons for this is water quality, so if you're stuck with this tank in the short term, a skimping on the protein skimmer would probably compound any water quality issues. If you have to keep it in this tank, you're certainly doing the right things with water changes and removal of food detritus, but be aware that you may be on thin ice in terms of water parameter stability. I'm sure the tank experts can chime in with more details, but "the size of a hand" doesn't sound that small to me, and if it's a vulgaris it's likely to grow rapidly... how long are you planning to keep it for?

As for sexing it, many species are very hard to sex... in many species the males have one modified arm, but it's often hard to see and sometimes doesn't develop until sexual maturity. I'd have to look up vulgaris. Some octos, like the GPO, have secondary sexual characteristics-- in male GPOs, there are some oversized suckers that are easier to spot in mature animals. I don't know of any in vulgaris, but I don't have a reference handy to check for sure.

Good luck with your research and your octo!

- M

 

[pipsquek]

Vulgaris does exibit the larger suckers on the arms, but in all of my reasearch and time spent at the Monterey Bay Aquarium, I have never seen this feature on a GPO. I did get a view of the ligula, the tip of the arm) on one right against the glass, and looked for the enlarged suckers, but couldn't find any. By enlarged, it generally denotes a couple of suckers on some of the arms about a fourth of the total length from the beak that are 2-3 times the size of the surrounding suckers.

The hectocotilized arm of the male is the third right arm in many species. If you spend enough time observing your octo pal, look to see if it keeps the third right arm protected under the interbrachial membrane. Naturally, if they lose it in a fight or to a predator, they can not mate until it grows back, so they are prone to keep it balled up. This is not to say that they never use it, but it is substaintually less than the other arms. The ligula is the fat spoon shape bit at the end that is devoid of suckers.

Another thing to look for but very difficult to see is the groove in the interbrachial membrane between the third and fourth right arms. It runs from the center between the arms on the underside edge all the way to the tip of the third arm. The spermatofore is ejected out of the siphon into this groove to the tip that is inserted in the mantle of the female. It is difficult to see untill you know what you are looking for, and the beginning of the groove on the edge of the interbrachial membrane could easily be mistaken for a scar.

If you would like, I could email you a picture of my sculpture that has these features since there are vitually no good picture on the internet.

 

[platypus]

size

Thanx for all the input!
I intend on keeping him/her for as long as possible in terms of its size. Once it gets too big i'll return it to the exact location we found it. (and then hopefully ill find a new one)
I realize that a 40 liter aquarium is probably a bit small. I have a 120 liter or so tank but its got a crack, ill fix it soon and move him there.
What about the excaping issue? are they THAT prone to escape? At the moment i have a pretty heavy reflector on the the tank that holds the top down. no way he can move that. but, there is a little "space" between the lid and the tank were a small air pipe goes out.

 

[pipsquek]

Vulgaris really are prone to escaping. Just look up _Octopus and Squid_ by Cousteau. That being said, a free regular meal is pretty good incentive to stay put if your not to curious, hence full prisons.

And they can get through any hole that they can fit their beak through, so double check.

 

[Jean]

1. how do I tell if its a male or female? I read that the male has a slightly different arm (one of them) but i cant find a good picture that shows a comparison. Is it possible to sex them at all ages?

2. Is a protein skimmer totaly mandatory or will frequent water changes (20-30% a week) and removal of dead prey be ok?

3. Is there a good, simple method to catch lots of crabs to feed it? like a simple trap setup ect.... (I dont have a local supplier of live, small, crabs and am getting tired of hunting them with a hand net on the rocks at the beach....).

4. how paranoid do i need to be about little crevices and holes in the lid of the tank? are they THAT prone to escape?

1) You generally can't sex juveniles (even in those with a hectocotylus) and yours sounds like a juvy.

2) Freq water changes should be OK but be sure you remove ALL the debris, octopus are messy eaters! Buy some test kits to test the water chemistry.

3) A baited crab pot should get you plenty of crabs. Essentially this is a mesh basket with a funnel leading inward. Crabs get in but not out. You would need to check this regularly so the crabs are not stressed by being out in the open at low tide.

4) be paranoid ........be very paranoid! I would seal up EVERYTHING! remember duct tape is your friend! Basically if the beak can get through the rest will follow (and they can get their beaks through surprisingly small holes!) They can also lift quite heavy weights (estimated 7 - 9x their weight!) We have huge rocks on the top of our juves tank and big sliding doors that can be locked on the adults tank!

BTW Monty is right 40G is too small, It may do for a wee while but you'll need to go bigger (much!) fairly soon. Our juv is in 100L and our adult is in 1000L. you probably won't need to go that big, our species gets to 2-3 m arm spread! but certainly you'll need to get a bigger tank as it grows and boy do these grow!

cheers

Jean