Loricifera inhabiting spherical agglutinated structures in the abyssal eastern equatorial Pacific nodule fields

Abstract

Loriciferans are known to survive in extreme environments, most notably in the case of a recently described Spinoloricus species from a hypersaline anoxic Mediterranean basin. Our new discovery of members of the genus Rugiloricus inside spherical agglutinated structures from sediment samples collected in the manganese nodules fields of the eastern Clarion-Clipperton Zone (CCZ, abyssal equatorial Pacific) demonstrates that these tiny animals are able to spring fresh surprises. Nearly all developmental stages of an undescribed Rugiloricus species were found inside the spheres, from the first instar larva and large free larva to the two stages of the postlarva inside the larval exuvium. Only the adults were missing. The spheres themselves were almost certainly not created by the loriciferans. Their origin is unclear, although similar agglutinated structures from the same study area contain cells that resemble monothalamous foraminifera, suggesting that they are possibly made by foraminifera. One of our CCZ samples also yielded a single free specimen of the loriciferan genus Pliciloricus that was not hidden inside an agglutinated structure. This specimen is particularly interesting because, like nested Russian dolls, it has all stages inside the larval exuvium: first the larval exuvium itself with the two toes, then a very thin postlarval exuvium and finally the adult male with two testes filled with mature spermatozoa.