The longest guarded incubation known for fish eggs is 4–5 months, by the Magellan Plunder Fish in Antarctic waters. For birds, the longest uninterrupted egg brooding is 2 months, by the Emperor Penguin. Among live-bearing species, elephants gestate for 20 to 21 months, frilled sharks carry their embryos internally for about 42 months, and the internal gestation period of alpine salamanders can reach 48 months before birth.
One of the craziest things about this: Octopus mothers aren't thought to eat when they are raising their young. So how did it survive? The scientists don't know, but the cold temperatures and slow metabolic rate of deep-sea animals may have helped. But it seemed to take a toll on the octopus, a member of the species Graneledone boreopacifica; over the course of brooding, the scientists observed her turn from a pallid purple to a much paler white, and they noticed the "diminishing size and tumescence [or swollenness] of the mantle, loss of skin texture, cloudy eyes, slack skin, and a loss of pigmentation."
One advantage to investing so much maternal care is that when these species' eggs hatch, they emerge like miniature adults and can therefore skip the juvenile stage that other octopuses have to pass through. Scientists think this gives them a better chance of surviving in the dark, mysterious world of the deep sea.