Abstract
Octopuses typically have a single reproductive period and then they die (semelparity). Once a clutch of fertilized eggs has been produced, the female protects and tends them until they hatch. In most shallow-water species this period of parental care can last from 1 to 3 months, but very little is known about the brooding of deep-living species. In the cold, dark waters of the deep ocean, metabolic processes are often slower than their counterparts at shallower depths. Extrapolations from data on shallow-water octopus species suggest that lower temperatures would prolong embryonic development periods. Likewise, laboratory studies have linked lower temperatures to longer brooding periods in cephalopods, but direct evidence has not been available. We found an opportunity to directly measure the brooding period of the deep-sea octopus Graneledone boreopacifica, in its natural habitat. At 53 months, it is by far the longest egg-brooding period ever reported for any animal species. These surprising results emphasize the selective value of prolonged embryonic development in order to produce competitive hatchlings. They also extend the known boundaries of physiological adaptations for life in the deep sea.
Highlights
In April of 2007 we used a remotely operated vehicle (ROV) to inspect an isolated rocky outcrop, 1397 m deep, at the sedimentcovered base of a sloping wall in the Monterey Submarine Canyon, off central California
The eggs of G. boreopacifica are elongate vesicles which taper to short stalks that the mother cements to hard substrate [3]
We measured the size of exposed eggs several times over the course of the brooding period (Figure 3)
Summary
In April of 2007 we used a remotely operated vehicle (ROV) to inspect an isolated rocky outcrop, 1397 m deep, at the sedimentcovered base of a sloping wall in the Monterey Submarine Canyon, off central California. We had visited the site several times before and knew it to be a location where females of Graneledone boreopacifica Nesis 1982, attach and brood their eggs. When we returned to the site 38 days later, in May, 2007, we found the same individual octopus, identified by characteristic scars, up on the rock and guarding a clutch of attached eggs (Figure 1).
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