I’D LIKE TO BE AN OCTOPUS
by Arthur W. Siebens, Ph.D., Copyright 2001
to the tune of “Octopus’s Garden,” by Richard Starkey, as performed by the Beatles

I’d like to be, under the sea, an octopus reclining in the shade
But I’m a man, stuck on the land, wondering how the two of us got made
Is he really, so different from me? What is our phylogeny?
I wonder why, he’s classified, as an octopus, not a jellyfish that strayed
Taxonomists rate, four crucial traits, in animals when they see ‘em
1) True tissues there? 2) How many layers? 3) Body cavities? 4) The origin of the coelem1?
Digestion’s an issue, if you lack true tissues. In Porifera, (sponges) it’s intracellular digestion they use
If you’re diploblastic, you may look like plastic—there’s radiata, (radial symmetry, e.g., jellyfish) you barely
see the mesoglea (the “jelly” between the epidermis [from ectoderm] and gastrodermis [from endoderm]).
Three body layers 2 (triploblastic)? Moved up the stairs! You’re made from ecto-, meso-, endoderm
The acoelomate format, is very flat, some are “long-term” (parasites), like that 20 meter tapeworm!
That one-way digestive tract, that acoelomates lack
Helps pseudocoelomates (e.g., nematodes) move food from the front (anterior) to the back (posterior)
In the roundworm design, mesoderm doesn’t line, the whole coelem, yet that worm is made firm (a
hydrostatic skeleton makes movement more efficient).
Now, if you discover, that mesoderm covers, the whole coelem, you’ve got a coelomate
And if in gastrulation, endoderm migration, makes the mouth form where the blastopore was at
You’ve got a protostome (meaning first the mouth) you see, and an octopus might develop, not me!
Annelids (e.g., earthworms) and cephalopods (a class of phylum mollusca; e.g., OCTOPUSES!, squids), other
mollusks (e.g., bivalvia [clams] and gastropods [snails]) and arthropods (e.g., classes insecta, arachnida, crustacea) are
protostomes but I’m not like that.
My mouth came second, when Mother Nature beckoned, for my archenteron to make my anus first
Though a deuterostome (meaning second the mouth), I’ve got a good home
High above the waves, I could have a worse curse
I’ve also got good company—there’s lots of vertebrates (e.g., fish, marine mammals), and echinoderms (e.g.,
sea stars) that live in the sea!
Still, I’d like to be, under the sea, like an octopus, reclining in the shade.
An octopus, reclining in the shade. 1A body cavity completely lined with mesoderm in which the digestive tract and other organs are suspended.
2The larvae of triploblastic organisms are bilaterally symmetric, even when the adult form is radially symmetric (e.g.,
echinoderms such as sea stars)