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Sea elephants and where to find them

Posted on 25-01-2018 by Toine Baken

Our very own Debbie Wall-Palmer about two new articles on atlantid heteropods (zooplankton)!

Today, the 25th of January, a new study on atlantid heteropods (zooplankton) is published as a Feature Article in Marine Ecology Progress Series. A second article, in Progress in Oceanography, will be published in a month and is already available online pre-proof. We asked our own Debbie Wall-Palmer, the lead author and one of the Naturalis researchers working on them, some questions!

 

Let’s start with your conclusions: what did you find?
“We discovered interesting things about atlantid’s daily vertical migration patterns. Small atlantid zooplankton species remain in shallow waters of <140 m at all times, whereas larger atlantids migrate to deep waters during the day, returning to shallow waters at night. Also, atlantid shells are produced in the upper 150 m of the water column in a region where food is abundant. We have also discovered 30% more clades (hypothetical species) than the ones described so far and for all these groups we have gained a better understanding of their geographic distributions as well as producing some good genetic reference data.”

So, what are atlantid heteropods?
“Atlantids are small (<14 mm), predatory swimming snails with flattened disk shaped shells of calcium carbonate (aragonite). They have a modified foot, which they use as a swimming fin in their side-to-side swimming motion. Atlantids also have a ‘trunk’ with the mouth at the end, and large eyes that they use to continuously scan the water for predators and prey.”

Atlanta 1

"We caught this  Atlanta peronii during our latest cruise in the Atlantic Ocean, AMT27. It seemed to be looking at us just as much as we were looking at it." 

What was your research goal?
“The goal was to answer some fundamental questions about atlantid heteropods, such as ‘where do they live?’ and ‘how many species are there?’. So far, not much was known about them. Also, we wanted to provide a genetic (mtCO1) dataset that makes it easier to identify atlantids, which will encourage researchers to identify them in future plankton studies.”

Why is this research important?
“Because atlantids form their shells in the upper parts of the water column, they are heavily affected by ocean acidification caused by elevated concentrations of carbon dioxide in the atmosphere, which makes shell formation more difficult. If we gather information about their distribution now, we can detect any future changes. Also, they may be useful indicator organisms of ocean acidification! For this field of study specifically, the research is fundamental to future studies as we now know more about atlantid distributions and have more data that helps identification. This makes it easier to target certain species in a region to study ocean changes.”

SEM image atlantid

SEM image of Atlanta brunnea showing the beautiful shell sculpture. "Our DNA barcoding revealed that A. brunnea is actually two species."

How did the research go about?
“The research has been carried out over around four years (2014-2018), collecting specimens from the field ourselves or sharing them with other researchers. I myself spent nine weeks at sea in the Indian and Pacific ocean to collect material. We also examined collections at multiple institutions, including a very nice atlantid collection at Naturalis. I spend four months delving into old jars and bottles of zooplankton, some collected over 100 years ago! I was also in the lab for a long time, preparing specimens for genetic and geochemical analysis. The majority of the work was done at the University of Plymouth (UK) and at Naturalis, where the research is currently continuing.”

What was your favourite part of the research?
“Definitely collecting specimens and watching them under the microscope. Atlantids are very strange looking snails with (relatively) large eyes, a swimming fin and a long trunk. This gives them the common name ‘sea elephant’. They are always very curious of their surroundings and have a lot of interesting behaviours. My favourite is the way they use their flexible trunk to preen (and clean?) their shells like tiny cats.”

Any favourite atlantid?
“Yes! It has to be Oxygyrus inflatus (although our research shows it may be four species...). Oxygyrus has an amazing shell, covered all over with zig-zag ridges. In the adult stage this species is unique amongst the atlantids because the shell is overgrown by a layer of conchiolin, a flexible cartilage-like material. On our recent cruise Atlantic Meridional Transect 27, we found the best specimen we have ever seen. We named him ‘Simon’."

Simon 1

'Simon', an Oxygyrus inflatus. The researchers' favourite!