New Echinoderm-Crab Epibiotic Associations from the Coastal Barents Sea

SIMPLE SUMMARY: New biodiversity records are important for expanding our knowledge about the symbiotic associations of the commercially important red king crab. This species was introduced into the Barents Sea, and now its population supports a viable fishery in the area. There are only a few reports regarding epibiotic relationships between echinoderms and marine crabs in general and the red king crab in particular. In our paper, we provide new data on the occurrence of the common starfish, Atlantic sea cucumber, green sea urchin, and brittle star on the invasive red king crab in the Barents Sea. The associations between echinoderms and red king crabs could have important ecological implications and provides an interesting example of how a prey species can avoid death by infesting its predator. ABSTRACT: During diving surveys for a Russian research project that monitored introduced species, red king crabs (Paralithodes camtschaticus) were collected at a coastal site of the Barents Sea to study the structure and dynamics of this species. Sampling of the organisms colonizing the crabs was part of this research project. For the first time, the presence of relatively large specimens of the common starfish Asterias rubens as epibionts of P. camtschaticus was observed in July 2010, 2018, and 2019. In 2010 and 2019, we also found three other echinoderm species (the Atlantic sea cucumber Cucumaria frondosa, the green sea urchin Strongylocentrotus droebachiensis, and the brittle star Ophiura sarsii). These findings add to the current list of associated species on king crabs not only in the Barents Sea but also in native areas of this host. Red king crabs have been documented as predators for these echinoderm species, and our records show additional possible interactions between king crabs and echinoderms in this region. More likely, the epibiotic lifestyle allows these echinoderms to avoid predation from red king crabs. There are no potential disadvantages derived by red king crabs through their relationships with the echinoderm epibionts due to low occurrences of these associations. We suggest no negative effects for the local red king crab population and populations of other commercial species in the Barents Sea.