As a rule, cephalopods (squid, octopus, cuttlefish) lead short, active lives. Most known species live for just about one year, they have a single batch of offspring, and then they die. Their growth rates rival any other invertebrates and their metabolic rates are among the highest in the Animal Kingdom. “Live fast, die young” is the epithet that many scientists apply to the lifestyle of these mollusks – at least those who live in shallow water.

Recent studies of deep-sea squid and octopus suggest that the paradigm may not apply to all. A new paper by our team clearly demonstrates that deep-sea squid live longer and slower than their nearshore relatives. The study used MBARI’s ROVs to collect living squid in pristine condition and gently bring them up from deep water. Once installed in the lab, the squid were bathed in tetracycline, a biological dye that stains certain tissues a bright green under UV light.

Squids have small “stones” in their organs of balance that readily take up tetracycline. These statoliths grow at a steady rate throughout the life of the squid in a pattern of concentric rings, sort of like the rings in a tree. By turning the statoliths of a living squid green, then returning the animal to clear water, it is possible to count the number of unmarked rings that accumulate and correlate them with the time since staining. In the case of the deep-sea squids, one new ring was added each day.

With this knowledge as a reference, the rings of a broad size range of squids were counted in order to draw growth curves. The results clearly show that deep-sea squid live at least two to three times longer than their shallow water counterparts. When this information is coupled with metabolic rate measurements made with our MRS we get a whole new picture of life expectancy for this large group of cephalopods.

With increasing exploration and exploitation of the deep-sea environment, basic life history data for abundant and trophically important deep-sea taxa is required to predict the consequences of anthropogenic influences and climate forcing. Understanding the pace of life of deep-sea fauna will enable us to better understand recovery rates and resilience.

This new data set expands the knowledge base from which conclusions about squid longevity can be drawn. Coupled with MBARI’s previous discoveries, an entirely new notion of the pace of life for deep-sea cephalopods is emerging. Prior to 2005, parental care was unknown in squids. MBARI’s subsequent discoveries that species from two distinct families of deep-sea squid brood their eggs has upended that notion and has led to revised estimates of their longevity. In addition, our discovery that a deep-sea octopus has a 4.5-year brooding period (the longest by a factor of 3 for any animal species on Earth) reinforces the new paradigm of significantly greater longevity for deep-sea cephalopods.