Presenter: Jim Barry (MBARI)

Description:
Thousands of abyssal octopuses (Muusoctopus robustus) are known to nest in warm geothermal springs at the “Octopus Garden” located in the foothills of Davidson Seamount near 3200 m depth, first discovered during a NOAA Ocean Exploration cruise in 2018. We hypothesize that nesting in the warm waters at these springs benefits M. robustus through accelerated metabolism and embryonic development. Reproduction in octopuses is linked tightly to environmental temperature with rapid embryonic development in warm seas and exponentially slower rates in cooler waters. Deep-sea octopuses typically have long brood periods, requiring as much as ~1590 days in bathyal Granadelone boreopacifica living in ~3.5 ^oC waters, the longest known brood period for any organism. M. robustus inhabits waters near 1.6 ^oC, where predicted brood period exceeds 10 years, a seemingly incredible feat. Using repeated visits with submersibles from 2019 to 2021, we estimated egg development rates and nest residence times for female M. robustus, and logged temperature and oxygen measurements in nests. Brood periods for 26 females averaged 576 days and nest residence times were from 559 – 644 days. Temperatures near nests varied from 1.6 to 10.5 ^oC and mean temperature adjacent to egg clusters was 5.1 ^oC. Based on the development-temperature relationship observed among other octopus species, the expected incubation period at 5.1 ^oC is 623 days. Although the risk of thermal stress may be high, rapid development possible in hydrothermal springs appears to have led to selection for this breeding behavior in M. robustus. Hydrothermal vents have received great attention due to their role as oases of deep-sea life, mainly due to the reduced compounds available to support chemosynthesis. However, the potential influence of warming in geothermal deep-sea habitats on life processes such as growth, reproduction, feeding, or predator-prey interactions, has received little attention.