Extended Pelagic Life in a Bathybenthic Octopus

Abstract

Planktonic stages of benthic octopuses can reach relatively large sizes in some species, usually in oceanic, epipelagic waters while living as part of the macroplankton. These young octopuses appear to delay settlement on the seabed for an undetermined period of time that is probably longer than for those octopus paralarvae living in coastal, neritic waters. The reason for this delay is unknown and existing information about their biology is very scarce. Here we report on the presence of juvenile and subadult forms of the bathybenthic octopus Pteroctopus tetracirrhus in oceanic waters of the South and North Atlantic and its association with the pyrosomid species Pyrosoma atlanticum, apparently used by the octopus as a refuge or shelter. The relatively large size of the P. tetracirrhus living in oceanic waters as the individuals reported here, together with the morphological characteristics of this bathybenthic species including its gelatinous body, minute suckers embedded in swollen skin and the deep interbrachial web, indicates that P. tetracirrhus may be considered a model of a transitional octopus species that is colonizing the pelagic environment by avoiding descending to the bathyal benthos. This process seems to occur in the same way as in the supposed origin of the ctenoglossan holopelagic octopods of the families Amphitretidae, Bolitaenidae, and Vitreledonellidae, which have arisen via neoteny from the planktonic paralarval stages of benthic octopuses.

Morphological and Molecular Assessments of Bobtail Squids (Cephalopoda: Sepiolidae) Reveal a Hidden History of Biodiversity

“…Methods such as the Automatic Barcode Gap Discovery (ABGD, Puillandre et al, 2012), the statistical parsimony networks (e.g., Pons et al, 2006), the Bayesian Poisson Tree Processes model (bPTP, Zhang et al, 2013) and the Generalized Mixed Yule Coalescent approach (Fujisawa and Barraclough, 2013) assist in taking taxonomic decisions for challenging species, like cryptic species complexes (e.g., Fernández-Álvarez et al, 2020) or other morphologically challenging organisms. Molecular species identification methods, such DNA barcoding (Hebert et al, 2003), provide tools for identification of challenging organisms, such as undescribed ontogenetic stages of known species (e.g., Fernández-Álvarez et al, 2017, Olmos-Pérez et al, 2018aVillanueva et al, 2020).…”

Cephalopod ontogeny and life cycle patterns

“…Although a longer planktonic period is often associated with increased mortality and advection (Morgan, 1995), it can also be advantageous for maximizing dispersal when benthic habitats are constantly changing or when habitat choice for settlement has important implications for survival. Some benthic octopods, such as Octopus rubescens (Hochberg et al, 1992), Pteroctopus tetracirrhus (Villanueva et al, 2020), and Macrotritopus spp. (Judkins and Vecchione, 2020) can attain large sizes in the water column in coastal and oceanic waters (Villanueva and Norman, 2008).…”

The evolution of predator avoidance in cephalopods: A case of brain over brawn?

“…Meanwhile, as noted above, Caribbean reef squid conceal themselves among coral and seaweed to hide from potential predators. Young fourhorn octopus (Pteroctopus tetracirrhus) still in their pelagic phase are thought to gain some level of protection from hiding inside the cylindrical tunicate Pyrosoma atlanticum (Villanueva et al, 2020). Additionally, several species of octopus use objects that they find on the seabed as tools to hide from predators.…”