Into the deep end – snail systematics on the ocean floor

Author(s)

Dr Anders Hallan, Dr Francesco Criscione
Category

AMRI
Published

24 August 2017
Read time

2 minutes

AMRI researchers have started on a three-year project to unravel the mysteries of the turrid gastropods of the Australian deep sea.

Deep in the abyss, where no sunlight is granted access and the water pressure would likely crush yours truly into a Rubik’s cube, a diversity of animals exists that we know very little about. To us, this is a hostile world often seen as alien, a view bolstered whenever new, bizarre and remarkable creatures occasionally surface.

Thanks to deep-sea exploration such as recent surveys conducted aboard the CSIRO Investigator vessel, we now have access to a suite of unnamed species of the gastropod group Turridae. Natural born spear-fishers, these predatory snails ‘harpoon’ unsuspecting polychaete worms with their modified, often venomous radulae (teeth). Turrids, so named because of their commonly elongate, turreted shells, are closely related to the cone snails. Some cone species have powerful venoms potentially fatal to humans, and their biochemical compounds have important pharmaceutical applications. Recent research shows that turrids may also be of medical importance, and calls have been made for a better understanding of their systematics to more effectively direct future research on their toxins.

Turrids, when defined as the conglomerate now consisting of 13 closely related families, are the most diverse of any mollusc group. Globally, there are more than 4000 named species, but we believe that the number of undescribed species is likely to be even higher. Over the next three years, in collaboration with researchers at the Natural History Museum in Paris (Muséum national d'Histoire naturelle, or MNHN), we aim to study the systematics and evolution of these highly specialised predators with a focus on the deep-sea fauna of temperate Australia.

The classification of turrids is fraught with complications. For instance, identifying reliable characteristics to understand their evolutionary relationships, such as the morphology of their shell and radula, can be notoriously difficult. So-called ‘turrid pairs’ are often encountered, where two distinct species may have virtually identical adult shells but differing protoconchs (larval stage of the shell, at the apex), and vice versa. To complicate matters further, different malacologists have often emphasised different characters, making any consensus regarding their classification difficult to achieve. However, some of this controversy has arguably been resolved by our colleagues at the MHNH, whose studies, combining morphology with genetic analyses, have allowed for significant advances in our understanding of these extremely diverse gastropods.

Our collaboration with Paris will not only give us the benefit of their expertise, but also allow us to build on their important classification framework to better understand the Australian fauna. It is with this collaborative structure in place, and acknowledging a research grant awarded by the Australian Biological Resources Study (ABRS), that we will embark on the intimidating task of describing an estimated 60 new species, occupying depths between 800 and 5000 metres from throughout southern Australia (no Australian turrid below 800 m has been named to date). In return, we hope to provide material that is beneficial to their research, particularly filling crucial geographic gaps in their next-generation sequencing (NGS) genetic analyses vital to understanding how the group has evolved.

The ocean depths constitute some of the last true wildernesses on Earth, and our knowledge of the deep-sea fauna is only in its infancy. This study hopes to shine a little light on this biodiversity, one we only get to know through fragments such as the material collected by the Investigator.

Dr Anders Hallan, ABRS Postdoctoral Researcher, AMRI
Dr Francesco Criscione, ABRS Postdoctoral Researcher, AMRI

Additional information:

Dr Anders Hallan and Dr Francesco Criscione at AMRI have recently started an ABRS-funded research project entitled ‘Into the abyss: systematics and evolution of temperate Australian deep-sea 'turrid' gastropods’.