DNA study in the Pacific reveals 2000% increase in our knowledge of mollusc biodiversity

Lead author Dr Helena Wiklund examining specimens on the RV Melville in October 2013
Lead author Dr Helena Wiklund examining specimens on the RV Melville in October 2013

Scientists working in the new frontier for deep-sea mining have revealed a remarkable 2000% increase in our knowledge of the biodiversity of seafloor molluscs.

The 21 mollusc species newly described thanks to the latest DNA-taxonomy methodology
The 21 mollusc species newly described thanks to the latest DNA-taxonomy methodology

Tweny-one species, where only one was previously known, are reported as a result of the research which applied the latest DNA-taxonomy methodology to mollusc specimens collected from the central Pacific Clarion Clipperton Zone (CCZ) in 2013. They are all described in the open access journal ZooKeys.

Among the discoveries is a monoplacophoran mollusc species regarded as a ‘living fossil’, since it is one the ancestors of all molluscs. This is the first DNA to be collected from this species and the first record of it from the CCZ mining exploration zone – a vast 5-million-km² region of the central Pacific that is regulated for seabed mining by the International Seabed Authority.

“Despite over 100 survey expeditions to the region over 40 years of mineral prospecting, there has been almost no taxonomy done on the molluscs from this area,” says lead author Dr Helena Wiklund of the The Natural History Museum in London (NHM).

Dr Wiklund undertook a comprehensive DNA-based study of the molluscs to confirm species identities and make data available for future taxonomic study. This was coupled with the expertise of the NHM’s Dr John Taylor, who led the morphological work.

The molluscs were found in samples taken on and in the mud surrounding the potato-sized polymetallic nodules that are present in high abundance across the CCZ. These nodules are the target for potential deep-sea mining being rich in cobalt, copper, nickel, manganese and other valuable minerals.

The data are vital for the future environmental regulation of deep-sea mining, but have also revealed surprising patterns.

“I was amazed to discover that specimens collected during the 19th century by HMS Challenger were probably the same as ours over a range of 7000 km, but that data lodged on genetic databases from closer but shallower depths is likely to be from a different species,” comments Dr Thomas Dahlgren, population geneticist at Uni Research, Norway and University of Gothenburg, Sweden, who studied in detail a species called Nucula profundorum.

“Our efforts are now focussing on studying the DNA from many more samples of this species to examine connectivity and potential resilience to deep-sea mining,” he added.

Dr Thomas Dahlgren sieving sediments to find new clam and snail
Dr Thomas Dahlgren sieving sediments to find new clam and snail species

“It is a simple truth that we cannot move forward on regulatory approval for deep-sea mining without fundamental baseline data on what animals actually live in these regions,” says Principal Investigator of the NHM Deep-sea Systematics and Ecology Research Group, Dr Adrian Glover.

“Our work has highlighted obvious gaps in our knowledge, but also shown that with even relatively modest effort, we can greatly increase our understanding of baseline biodiversity using DNA-taxonomy.”

Creating a library of archived DNA-sequenced samples from known species allows for the future possibility of using the latest environmental DNA (eDNA) methods to ‘search’ for these species using just tiny samples of mud or seawater.

“Its akin to forensic science’, says Dr Glover. “You can’t use eDNA to find the criminals or species unless you have a library of information to compare them too”.

All data and specimens from the study have been lodged at the NHM and online repositories to make them accessible for future study. Of particular importance are the frozen tissue collections, which are housed in the state-of-the-art Molecular Collections Facility at the NHM and available for loan or further DNA work.

 

Original source:

Wiklund H, Taylor JD, Dahlgren TG, Todt C, Ikebe C, Rabone M, Glover AG (2017) Abyssal fauna of the UK-1 polymetallic nodule exploration area, Clarion-Clipperton Zone, central Pacific Ocean: Mollusca. ZooKeys 707: 1–46. https://doi.org/10.3897/zookeys.707.13042

The Godzilla goby is the latest new species discovered by the Smithsonian DROP project

As part of the Deep Reef Observation Project (DROP), initiated by the Smithsonian Institution, a new goby fish species was discovered in the southern Caribbean. Living at depths greater than conventional SCUBA divers can access, yet too shallow to be of interest for deep-diving submersibles, the fish will now be known under the common name of the Godzilla goby.

Its discoverers Drs Luke Tornabene, Ross Robertson and Carole C. Baldwin, all affiliated with the Smithsonian Institution, have described the species in the open access journal ZooKeys.

Formally called Varicus lacerta, the species name translates to ‘lizard’ in Latin and refers to the reptilian appearance of the fish. Its prime colors are bright yellow and orange, while the eyes are green.

The new goby also has a disproportionately large head and multiple rows of recurved canine teeth in each jaw. This is also why the research team has chosen the common name of the Godzilla goby.

Apart from its lovely coloration, the new fish stands out with its branched, feather-like pelvic-fin rays and the absence of scales.

The scientists caught the Godzilla goby thanks to the manned submersible Curasub, which had already helped in discovering several species over the course of the project. Last year, Drs Ross Robertson and Carole Baldwin had another new goby published in ZooKeys. That time, they even named it after the submersible. Earlier this year, the DROP team also described nine additional new species, many of which were collected by the Curasub.

The manned submersible Curasub reaches depths up to 300 m in search of tropical marine fishes and invertebrates. As a result, it provides new information on the fauna that inhabits poorly studied deep-reef ecosystems.

The sub relies on two hydraulic arms, one equipped with a suction hose, and the other designed to immobilize the fish with an anaesthetizing chemical. That way, not only do the researchers gather live specimens, which once collected, are deposited into a vented acrylic cylinder attached to the outside of the sub, but also individuals suitable for critical DNA analyses.

Img 2 Baldwin Robertson

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Original source:

Tornabene L, Robertson DR, Baldwin CC (2016) Varicus lacerta, a new species of goby (Teleostei, Gobiidae, Gobiosomatini, Nes subgroup) from a mesophotic reef in the southern Caribbean. ZooKeys 596: 143-156. doi: 10.3897/zookeys.596.8217