so, as you may know, i hate homework. i was getting all stressed out about my bio paper. normally, i feel like i can totally whip these things off, no sweat. i was getting all pumped about writing about the feeding habits of starfish. they can extend their stomach outside their bodies and actually into a waiting mussel that their tube feet have pried open. they then secrete their digestive juices directly into the bivalve's shell and it dissolves the tissue into a bunch of goo that it sucks up before retracting its stomach back inside its body.
i mean, HOLY SHIT. look at this white, ghosty stomach outside the body!
i was feeling pretty good about it and went to ask my professor a question after class about how he wanted the paper structured. when i explained my exciting topic, he looked a little less than enthused. apparently, he was a stickler for these "requirements" he had handed out, like needing to compare morphological and molecular data sets in order to make some conclusions was like important for his assessment or something. apparently, a paper about how cool i think this animal's really sci-fi feeding habits are wasn't gonna cut it.
so, i actually read the assignment which had something to do with deuterostomes and division of phylla. what? i guess if maybe i had bothered to make those flash cards before the last day of class, maybe i would've known what one of the key taxons of the course actually was.
deuterostomes, which means"second mouth," it just so happens, are a class of bilaterians that includes us chordates, these KRAZY worms called xenoturbella and echinoderms like starfish and sea urchins. they are characterized by their blastopore's development during gastrulation. blastopores are the things in embryos that turn into an orifice.
what sets deuterostomes apart is that this blastopore turns into an anus and we get a mouth later. protostomes get a mouth first and then maybe develop an anus later on.
oh wait, what?! the first structure we develop as lil baby embryos is totally butthole. and i get to write a whole paper on the evolutionary and phyllogenetic importance of butthole chronology. yes!