Question:

This is something I observed some years ago in a Victoria, BC aquarium which I have not seen described:
In a tank were two Pacific Octopuses. They were pressed together ventral surface to ventral surface. What was striking was that each sucker connected exactly with the corresponding sucker of the other. They were obviously aroused, as they were each paper white. After about ten minutes they separated and normal colour returned.

Can you tell me what I witnessed?

Herb

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Discussions:

• Whether or not it is a fossil depends on the age of the specimen. That horse conch (Triplofusus giganteus) probably was dug up from a Pliocene or Pleistocene deposit in southern Florida. In the field, far from the ocean, surrounded by shells, sand and clay, it is clearly from a time (Ice Age or older) much older than now. Clean it up, and there is no obvious way to tell just how old it is. Incidentally, beach shells in many areas (famously Calvert Cliffs, Maryland) include fossils weathered out of the nearby sediments. Some other areas have Pleistocene (Ice Age) shells washed up onto the beach from underwater deposits. These can only be distinguished as fossils because the species no longer lives there.
  
  Coral is the skeleton of colonial polyps. When they die, and the coral is bleached by the sun, it may look like a fossil, but again it is the age that is critical. If the corals in Aruba were growing during a time when the water level was much higher, they probably are fossils. But if they are just sitting around, maybe they are Recent corals that were transported by people. ... Allen A.

• Most Cenozoic fossils (under 65 million years old) are original shell material. If they occur in rock being eroded by the sea, you may not be able to tell whether they are Recent or fossil unless you know the fauna(s). There is a locality about 100km north of here where early Miocene fossils are washing out of a beach outcrop and others are washing in from pliocene rocks on the shallow seabed... so the beach has Miocene, Pliocene and Recent shells washing-up... and the fossils look as good as the Recent ones.
  To be a fossil a shell must have been buried in a rock unit as the unit was being formed... the rock can be sedimentary (sandstone, limestone, musdtone etc), volcanosedimentary (airfall ash deposits ie tuffs) or volcanic (lava flows). Tuffs can have really good mollusc faunas! The rock need not be hard... indeed, it can be loose (unconsolidated). I guess, though there is no set rule, the shells should be fairly old... say over 500,000 years. However crabs in burrows which are hardening to concretions in harbor sediments near here right now would have to be considered fossils, even though they are only a few years old. And a shell which died 1 million years ago and has been lying loose on the seafloor ever since is not a fossil (these occur off the SE New Zealand shore too). I might meet some of these when I go out on the Otago University's Marine Sciences Dept boat tomorrow.
  Coral skeletons are biogenic rocks... and old uplifted reefs can be considered to be fossil. These occur in the Caribbean and SE Asia. ...Andrew G.

• Many Cenozoic molluscan fossils (ie those under 65 million years old) are original shell material. If they occur in rock being eroded by the sea, you may not be able to tell whether they are Recent or fossil unless you know the fauna(s). There is a locality about 100km north of here where early Miocene fossils are washing out of a beach outcrop and others are washing in from Pliocene rocks on the shallow seabed... so the beach has Miocene, Pliocene and Recent shells washing-up... and the fossils look as good as the Recent ones.

  To be a fossil a shell must have been buried in a rock unit as the unit was being formed... the rock can be sedimentary (sandstone, limestone, musdtone etc), volcanosedimentary (airfall ash deposits ie
  tuffs) or volcanic (lava flows). Tuffs can have really good mollusc faunas! The rock need not be hard... indeed, it can be loose (unconsolidated). I guess, though there is no set rule, the shells should be fairly old... say over 500,000 years. However crabs in burrows which are hardening to concretions in harbor sediments near here right now would have to be considered fossils, even though they are only a few years old. And a shell which died 1 million years ago and has been lying loose on the seafloor ever since is not a fossil (these occur off the SE New Zealand shore too).

  Coral skeletons are biogenic rocks... and old uplifted reefs can definitely be considered to be fossil. These occur in the Caribbean and SE Asia.