Hermissenda crassicornisOpalescent nudibranch
Once thought to occur across the entire North Pacific, however is now known to be a part of a species complex along with H. emurai (Japan and Russian Far East) and H. opalescens (Sea of Cortez to Northern California). Ranges from Alaska to Northern California, with some overlap in distribution with H. opalescens around the San Francisco Bay Area. Distinguished from H. opalescens by a longitudinal white band running anteriorly from the base to tip of each ceras. The body is translucent white in colour, with an orange longitudinal stripe between rhinophores.
Max Size: 8 cm
Sea Temperature Range: 5.1-26.6°C
Habitat Generalization Index: N/A
Also referred to as the SGI (Species Generalisation Index), this describes the habitat niche breadth of the species. Species with values less than 15 are found in a relatively narrow range of reef habitat types (specialists), while those over 25 may be found on most hard substrates within their range (generalists). Learn more here.
Conservation and Rarity
IUCN Status: Not Evaluated
Occurrence: Widespread (61.4% of sites)
Occurrence describes how often the species is found on surveys within its distribution. It is calculated as the % of reef sites surveyed by RLS divers across all the ecoregions in which the species has been observed
Abundance: Several (7 per transect)
Abundance is calculated as the average number of individuals recorded per RLS transect, where present.
Edit by: Jo Schmid