In any case, Cyclops, although monocular, is bilaterally symmetrical.
Well…I’ve been looking at the dtructure of the sipunculids in my copy of Principles of Comapartive Anatomy of Invertibrates by Baklemishev…and the bilateral symmetry of the organisms’ body plan eludes me. I suppose one could argue that non-platyhelminthic worms, including annilids are bilaterally symmetric, but that would be debatable. The same applies to more advanced forms with eyes, such as cephalopods.
Uh… I get the feeling I’m terribly wrong, because if I was right this would’ve been everybody’s first answer… but don’t squid have only one eye? Including giant squid?
Or did I read the same Superman comic?
ALl those organisms are indisputably bilaterally symmetrical.
Bilateral symmetry only really applies to the embyonic/larval stages of an organism, not to the adult form. It reflects the difference between the more advanced forms and the more primitive largely aceolomate radially symmetrical groups.
Many organisms lack bilateral symmetry as adults but are undoubtedly symmetrical as juveniles and have evolved from bilaterally symetrical ancetsors (ie secondary asymmetry). Humans are one example of this. A human divided down the midline would lack two heart chambers and the associated blood vessels, large portions of the liver in one half and more importantly an entire organ: the appendix. Other chordates such as the sedentary tunicates take this to an even more advanced extreme level. You couldn’t even find a line of symmetry for most sea-squirts. Similarly most gastropod molluscs lack a distinct line of symmetry because the mantle and contained body cavity is off-centre. At the absolute extreme range the females of some parasitic barnacles are nothing more than amorphous clusters of cells in the adult form. None of this means that arthropods, mollusca or chordates aren’t bilaterally symmetrical even though in common speech it may be incorrect to refer to certain individuals as being so.
On the other hand we have organisms like starfish, annelids and sipunculans which give the impression of radial symmetry, but are in fact bilaterally symmetrical (ie secondary radial symmetry). There is only one plane of symmetry on which you can split an adult sipunculan or annelid and get the nerve chord and gut anywhere near equally divided. Hence they are indisputably bilaterally symmetrical even without having to study the symmetrical trochophore larvae.
Oh, and Anal Scurvy squid most definitely have two eyes.
Neat! Do you have a picture of an Anal Scurvy Squid?
Would you really want to see it if he did?
The purple monocornus homophagius discovered by Mr. Sheb Wooley possessed a single eye.
No, no, no, yabob, the creature discovered by the esteemed Dr. Wooley was not itself purple… It was a monocornus homoviolephagius. You are correct, however, in that it only had one eye.
I think Billy Crystal has only one eye. That’s the way it looks in his publicity photos right now.