Xenophyophores are multinucleate unicellular organisms found on the ocean floor throughout the world’s oceans, at depths of 500 to 10,600 metres. They are a kind of foraminiferan that extract minerals from their surroundings and use them to form an exoskeleton. They select certain minerals and elements from their environment that are included in its tests and cytoplasm, or concentrated in excretions. The selected minerals vary with species, but often include barite, lead and uranium.
Xenophyophores are an important part of the deep sea-floor, as they have been found in all four major ocean basins. However, so far little is known about their biology and ecological role in deep-sea ecosystems. Xenophyophores are difficult to study due to their extreme fragility.
Scientists collected a spatangoid urchin, about 5 cm diameter, which was wearing a cloak consisting of over 1,000 protists and other creatures, including 245 living xenophyophores, each 3–6 mm. The fragility of the xenophyophores suggests that the urchin either very carefully collected them, or that they settled and grew there. Among several possible explanations for the urchin’s behaviour, perhaps the most likely are chemical camouflage and weighing itself down to avoid being moved in currents.