For those of you who have a penis, imagine for a moment that it is ten times the length of your body. Your first reaction might be “That would be awesome!” But after you’ve had time to calm down and give the idea a little more thought you would realize you’d have no place to put your ridiculously long penis and no person to… uh… put it in (sorry). You’d have to drag it everywhere and nobody could sit next to you in the front seat of your car because your 60 foot penis would take up the whole passenger side. For those of you who don’t have a penis you are probably thinking this topic would do better under the heading “That’s Gross and Scary”. And you’d be right, UNLESS you are a barnacle in which case you’re not reading this so nevermind.
So now imagine you ARE a barnacle. You’re sessile, that is, permanently fixed to a surface, forced to forever look at the same barnacle neighbors who look just like you which is totally boring. Okay, you’re not really LOOKING at your neighbors ‘cause your head is cemented to a rock (or piling, or whale, or whatever), upside down inside your home of hard, calcareous plates, with your feathery little legs up in the air (er…water) filtering DSMs (Delicious Suspended Morsels). All of a sudden you need to mate- you HAVE to. You can’t go look for a mate- you’re stuck- you have to settle for the barnacle right next to you. Or DO you???
No you do not because (and this is the COOL part) you have a REALLY long penis, in fact the greatest schlong (scientific term) to body ratio of any animal! You can reach that barnacle way over there! Ooooh! And that one too! You can reach almost everyone in your neighborhood and that’s what you want to do- genetic diversity is good, it’s great, it’s the best way to go!!!
“Wait just a darn minute…” you say, “What if everyone around him is a boy barnacle and his poking them is completely futile?” Excellent question! “He” is not a “he” but a “he/she”. Simultaneous Hermaphroditism (most barnacle species)- the answer to sexual reproduction for the mobile-y challenged. Mother Nature is so smart!
Note: There is much conflicting info about the actual penis to body length ratio- depending on where you look (and not all sources are reliable) the estimates range from 8x to 40x body length. The latter seems unlikely. I have scoured two invert texts, a zoology text, a crustacean biology text and various field guides, none of which are specific on this topic- I’ll keep digging.