Sea urchin diseases: Effects from individuals to ecosystems

Diseases affect all facets of life, at the cell, tissue, organ, individual, population, and ecosystem level, and those associated with marine organisms are no exception. In particular, echinoids are one group which have had well-documented disease outbreaks in the marine biome. For example, over 40 species of sea stars from the west coast of North America have recently been found to suffer from an outbreak of a disease known as sea star wasting syndrome or Asteroid idiopathic wasting syndrome (Eisenlord et al., 2016). Although similar “die-offs” have occurred in the 1970s, 1980s, and 1990s, this recent outbreak has run at unprecedented magnitude, with upward of 60% disease prevalence at some sites and records across a wide geographic area (e.g., 84% of sites surveyed within one study)—see www.eeb.ucsc.edu. This is now being heralded as the greatest recorded mass mortality of a marine animal, exceeding the previous record, which was Diadema antillarum and their die-off in the Caribbean during the 1980s (Lessios et al., 1984a, Mumby et al., 2006). However, quite surprisingly, the causal agent for both diseases remains unknown (Lessios et al., 1984b, Miner et al., 2018). Various hypotheses have been suggested, from bacteria to viruses, however, evidence is lacking to point convincingly to one agent over another (Clemente et al., 2014).