Newly discovered tiny clam spends life crawling between sea urchin spines

The discovery of the creature, which is less than an eighth of an inch long, sheds new light on a little-known group of marine mollusks called galeommatoidean bivalves, say scientists.

Marine biologist Dr. Paul Valentich-Scott, of the Santa Barbara Museum of Natural History in the US, led the research along with colleagues from the University of Cape Town, Stellenbosch University and the Sea Change Trust in South Africa, plus the University of Colorado Boulder in the US.

Dr. Valentich-Scott said their findings, published in the journal ZooKeys, offer a "curious glimpse" into the habitats, symbiotic relationships, and taxonomy of the "interesting" creatures.

The study focused on four species of galeommatoidean bivalves collected from the Western Cape region of South Africa.

Among them was one new species, Brachiomya ducentiunus.

Dr. Valentich-Scott said the tiny clam, which is just two millimeters in length, spends its life crawling between the spines of sea urchins.

The new species has so far only been found in False Bay, South Africa, where it was discovered attached to the burrowing sea urchin Spatagobrissus mirabilis in coarse gravel at a depth of around three meters (10 feet).

It has not been observed free-living, without the host urchin, says the research team.

Brachiomya ducentiunus was discovered while preparing and working on the 1001 Seaforest Species project, a research program aimed at increasing awareness of regional kelp bed ecosystems colloquially referred to as ‘the Great African Seaforest’.

Study lead author Dr. Valentich-Scott said: "This study marks a significant advancement in our understanding of the biodiversity and ecological interactions of galeommatoidean bivalves.

"By uncovering the hidden lives of these small but ecologically important organisms, we hope to contribute to the broader knowledge of marine biodiversity and the conservation of these unique habitats."

Co-author Professor Charles Griffiths, of the University of Cape Town, said: “A large proportion of smaller marine invertebrates remain undescribed in western South Africa and almost any project that samples specialized habitats turns up many new records and species.”

Co-author Jannes Landschoff, a marine biologist at the Sea Change Trust, said: “Creating foundational biodiversity knowledge is a most important step to the humbling realization of how fascinating and uniquely diverse a place is."

He added: "I see this every day through our work in the rich coastal waters of Cape Town, where an extensive underwater kelp forest - the ‘Great African Seaforest’ - grows.”