Please, help me identify this species of Tremoctopus

[OB]

Dear all,

On http://marugoto.cool.ne.jp/tsushima/syokubutsu-zukan/journal/200308/august-collection2.htm I came across the picture as attached; my assumption would be this is T. violaceus, because of the eye spots, but as quite a bit of the webbing seems to be gone in this case.... If any of the experts could advise?

On a secondary note: the two holes on top of the head of Tremoctopus must surely serve a function; if anyone knows, I would be interested to find out, and as I don't own a copy of Nesis,..., sorry.

Cheers,

Olaf

 

[main_board]

Wow! I would love to know where the pictures on that site were taken. The vegetation is just fantastic! The pic of the tremy seems to stand out amongst the others, . T. violaceus seems about right, but I'm no expert. I'd be curious to know whats with the "holes" as well. Nesis doesn't really go into much detail regarding tremies and the picture doesn't exactly give a lot of discriminative detail. If only someone had The Marine Fauna of New Zealand: Octopoda (Mollusca: Cephalopoda) by a certain Kiwi teuthiologist. Hmmm...

Cheers!

 

[OB]

I guess http://tolweb.org/tree?group=Tremoctopus further reinforces my ocelli based assumption. Nice site.

Urrr, could the aforementioned holes be "water pores", associated with the hydrostatic organ as "recently reported by Bizikov (2004)"?

 

[Feelers]

The Marine Fauna of New Zealand: Octopoda (Mollusca: Cephalopoda)

Hah its funny you mention that book - I returned it to the library a week ago. Thats a nice picture.

 

[Steve O'Shea]

Whatever species of Tremoctopus it is, it is VERY MUCH a juvenile (compare it to the size of that leaf), so I would not ever directly compare it with any other image of a live animal that you have seen.

You have Tremoctopus violaceus violaceus
Tremoctopus violaceus gracilis
Tremoctopus gelatus
and Tremoctopus robsonianus to contend with.

Even though this specimen looks rather gelatinous, don't leap at that name T. gelatus. You really need the male in order to identify species in this group, in accordance with the existing classification anyway (unless you are fortunate to have a female with a detached hectocotylus in her mantle).

 

[OB]

Helpful and sufficiently realitycheckish, Steve

Do the ocelli disappear with age? Adult specimens seem to present "zebra" striping more than anything else; then again, the difference between a live thoroughly chamelonesque ceph and a washed up dead one...

Any thoughts on the pores? I'll get myself a copy of the 2004 Bizikov paper, also; should certainly help.

Cheers,

Olaf

 

[Steve O'Shea]

Hi Olaf. I've only ever seen one live animal of this species, a female that washed ashore several years ago and survived about a week in a public aquarium. It looked nothing like any of the images that I've seen elsewhere (some stunning ones referred to on this thread and one other [Eyecatching Discovery] in this forum). Photographs were taken, but your guess is as good as mine as to where these now are, at least 6 computer upgrades and two jobs since.

Another thing that you'll have to take into consideration is the pronounced sexual dimorphism in this group; the male comparatively minute. Some of the variation in colour that you refer to could be of sexual rather than ontogenetic nature, or even an inter-species difference. It sounds barbaric, but unless specimens are taken along with a photograph we'll never be able to establish what colour variant is sexual, ontogenetic or species related.

I've not worked on the pores myself, and have been raking my brain for the reference to their function (or presumed function) that I recall reading years earlier (it could have referred to the pores in Ocythoe); nevertheless, some literature does exist; when I happen upon it I'll post online (I've one of those mental rather than computerised indexing systems, and I think there have been a few short circuits and loss of information upstairs of late).
O

 

[bigGdelta]

Thanks once again doc for helping out us mere mortals. I wondered about the extra holes in the head myself when I saw the other thread.