and then I thought... jep... it reminds of this 
An even better candidate for those would be the spiny enemies in the kelp forest.
Or the creatures that jump from wall to wall... did nobody think of this 
when he/she saw them for the first time ?
There is also a similar looking boss in Blaster Master (also featured on the cover of the game). Metroid does predate Blaster Master by about 2 years though.
so - did anyone find other allusions ?
(btw - I think nobody mentioned it before, but did you know that when you hold down the left mouse button in the main menu, the little fishis start to swim faster and circle wider around the cursor ? no ? now you do)
No, and no. But now I'm sure that I will be looking.
On a side note, most videogame enemies are based around real life creatures, so it's not to surprising... Definitely shows where some of the inspiration may have came from though (aside from actual sea life of course.)