morbidology:

Did you know that octopi reproduce only once? They put all of their energy into generating and caring for the many eggs. The octopus will find a den to lay her eggs. Following their hatching, she will not eat and will spend all of her time caring for the eggs by cleaning and aerating them. After they hatch, the mother shall die and the exact scientific reason for this is unknown. They evidently use up all of their energy while caring for the eggs and it’s believed that losing their eggs come as a psychological shock, It is generally agreed that octopuses are intelligent creatures and many scientists feel as though they see no purpose in life following their eggs hatching, that combined with the exhaustion results in them giving up and dying. The male also dies shortly after mating.