A new study reviews what we know and what we don’t about some fascinating creatures of the deep.
Mention the word ‘mollusc’ and snails and slugs come to mind, but squids, cuttlefishes and octopuses (the cephalopods) belong to this group as well. New technologies applied in recent years to the study of deep-sea cephalopods are providing insights into the secrets of these enigmatic animals.
Early reports were often derived from findings of floating or stranded carcasses. These reports progessively increased as a growing number of specimens were found in the stomach contents of large deep-sea-feeding predators such as whales, or were captured by commerical and scientific nets. However, because these specimens were brought lifeless to the surface or were partly digested remains, little could be inferred about the lives of these cephalopods.
Modern underwater samplers and optical and acoustic technologies are now allowing us to see these animals alive in their natural habitats and even capture them live or essentially intact. These tools, combined with the development of a range of molecular and biochemical techniques have expanded the scale of scientific approaches to address unanswered questions and have raised new and intriguing ones.
The use of submersibles, either manned or remotely operated vehicles (ROVs) have been pivotal in increasing our knowledge of deep-sea cephalopods. They can search areas not accessible to net sampling and both can be configured to collect specimens using suction devices known as detritus (or ‘D’) samplers. Live specimens can then be brought intact to the surface where experiments, physiological measurements and behavioural observations can take place, in addition to tissue sampling for molecular studies.
An extension of the development in ROV operations has been the ‘telepresence’ strategy in which video, data and two-way communications are linked via satellite between the ship and a shore-based station from which they can be disseminated to scientists and the public at remote command centres and any computer connected to the Internet. The current ease of communication has facilitated global initiatives and collaborative projects that are steadily increasing our knowledge of deep-sea fauna.
Our new insights resulting from these tools gave rise to a workshop on deep-sea cephalopods as part of the Cephalopod International Advisory Council Symposium held in 2012 in Floranópolis, Santa Catarina, Brazil. I was priviledged to attend this conference and participated in the workshop, the results of which have just been published.
Cephalopods play an important role in deep-sea ecosystems as both predator and prey species. Many major gaps remain in our knowledge of these animals, including their basic biology, ecology, trophic roles (i.e. how they function in relation to other marine creatures) and taxonomy.
Museum specimens have great value for testing hypotheses based on in-situ observations and vice versa. Observations on live animals are complementing museum collections and the value of each is greatly increased by the other.
Dr Mandy Reid
Collection Manager, Malacology