text: Yo, listen up, I got a story to tell
  'Bout a marine bivalve, Mytilus edulis, dwell
  The Lap locus got a product, let me break it down
  A neutral aminopeptidase, membrane-associated, sound
  
  It's kickin' in the intestines, on the microvilli
  Digestive cell lysosomes, that's where it be
  In different salinity areas, populations clash
  Genetically differentiated, Lap locus makes a splash
  
  From the Atlantic Ocean to Long Island Sound
  There's a cline, allele frequency goin' around
  Steep as it gets, from 0.55 to 0.15
  Connectin' those populations, it's a gene flow scene
  
  But hold on tight, 'cause there's more to this game
  An annual cycle, gene flow and mortality to tame
  After death, gene frequencies, they align
  With salinity and enzyme activity, it's a sign
  
  The cline's unstable for immigrants, spatial and in time
  But for residents after death, it falls in line
  Mortality ain't random, nah, it's got a plan
  Lap locus playin' a role, it's in high demand
  
  The aminopeptidase enzyme, it's got some tricks
  Selected genotypes, they lose weight quick
  Utilizin' nutrient reserves, at a different pace
  Certain genotypes, they lead the weight-loss race
  
  Aminopeptidase genotypes, adaptin' all the way
  To different temps and salinities, that's what they say
  Biochemical, physiological, population traits in sync
  This mechanism's the link, no need to think.