ROV Observations on Reproduction by Deep-Sea Cephalopods in the Central Pacific Ocean

Michael Vecchione

doi:10.3389/fmars.2019.00403

Abstract

Telepresence-enabled operations by remotely operated vehicles (ROVs) allow many researchers a unique perspective on morphology, behavior, and small-scale distributions of deep-sea animals. I present some examples of cephalopod natural history from recent ROV dives in the central Pacific Ocean. These examples include clues to reproductive behavior of deep-sea squids and cirrate “dumbo” octopods. During 7-12 March 2017, the ROV Deep Discoverer (D2) operating from NOAA Ship Okeanos Explorer recorded high-definition video of several squid in the genus Chiroteuthis. These included a mature male, a mature female, and a moribund squid identifiable as C. picteti. The female had obviously mated, with spermatangia implanted in many locations, and was holding in its arms another squid that appeared to be another Chiroteuthis. Considered together, these observations may indicate a deep-sea spawning aggregation and, possibly, sexual cannibalism. Another series of observations by D2 revealed eggs of cirrate octopods attached to octocorals. The remarkable thing about these observations was that in two of them (18 March and 4 May) the egg chorion had swollen and burst the external egg capsule. This may explain how the hatching embryo is able to escape from the tough protective coating secreted by the oviducal gland of cirrates but not secreted by the better-known incirrate octopods.

Highlights

The Campaign to Address Pacific Monument Science, Technology, and Ocean Needs (CAPSTONE) was a multi-year study of deep-water United States marine protected areas (Kennedy et al, in press)
Three observations (Table 1 and Figure 1) by the remotely operated vehicles (ROVs) Deep Discoverer (D2) revealed eggs of cirrate octopods attached to cnidarian colonies
The remarkable thing about these observations was that in two of them (Figure 1, Top and Middle) the egg chorion had swollen and burst the external egg capsule. These two observations were very similar in overall morphology and both eggs were attached to “bubblegum” octocorals

Summary

INTRODUCTION

Observations from the Remotely Operated Vehicle (ROV) Deep Discoverer in 2017 included several that were instructive about reproduction by deep-sea cephalopods. I present observations contributing to two separate topics relative to reproduction by deep-sea cephalopods: (1) Cirrate octopod eggs and how they likely hatch, and (2) Mating, possibly in a population aggregation, and possible sexual cannibalism in a chiroteuthid squid species. Unlike more familiar incirrate octopods, cirrates coat their eggs in a thick layer secreted by the oviducal gland (Vecchione et al, 1998). In contrast with incirrates, recent observations of a fully developed cirrate embryo (Shea et al, 2018) found no evidence of a hatching gland. Observations on mating by deep-sea squids are few, but have indicated diverse patterns (Hoving et al, 2014).

MATERIALS AND METHODS

RESULTS

18 March 2017 05 May 2017 10 May 2017