Craig Hoover
Guest
While diving Reef Point in Laguna this past week, I found a small congregation of Cuthona divaes. They were on a rocky reef in 45 feet of water. I put together this post to help divers find this beautiful creature. Data is from personal observations on weekly surveys over the past 18 months. Supplemental information is from Nudibranchs of the Eastern Pacific, Behrens, 2005 and Nudibranch Behavior, Behrens, 2007.
Cuthona divea is a sea slug. Its common name is Correas aeolid. It is a member of the phylum Mollusca, class Gastropoda, subclass Opisthobranchia, order nudibranchia, suborder Aeolidina, family Tergipedidae, genus Cuthona and species divae.
It may be found on rocky reefs at depths that support its food source, Hydractinia milleri, commonly known as the hedgehog hydroid. Hydractinia seems to favor reefs that are at least several feet tall and are deeper than 20 feet. Shallower than these depths, algae outcompetes invertebrates for space on stable surfaces. Caves and undercut ledges may be an exception due to the lack of light reaching these surfaces.
Cuthona ranges from Vancouver, Canada to Point Loma in San Diego. I observed this slug at sites from Malibu to Laguna; representing the southern range of this species. Observations in this study are in the Southern California Bight and may not parallel trends north of Point Conception.
Cuthona is present in small numbers between the months of March and September. This slug has been observed on 18 separate occasions over the past 18 months and 46 of 47 sightings were between March and September. More time is necessary to compare the population dynamics of fall and winter 2010 with fall and winter 2011. Cuthona was not observed in abundance during this study. A site with a stable population of more than a few individuals has not yet been located.
Cuthona has been observed with its eggs between March and September. Temperatures recorded in this time interval were between 51 and 57 degrees Fahrenheit. These temperatures represent average highs and lows for the year at depths between 30 and 50 feet where observation took place. This data suggests that egg laying in this species is not determined by temperature within this narrow range. More data is necessary to confirm this.
Cuthona divea is a sea slug. Its common name is Correas aeolid. It is a member of the phylum Mollusca, class Gastropoda, subclass Opisthobranchia, order nudibranchia, suborder Aeolidina, family Tergipedidae, genus Cuthona and species divae.
It may be found on rocky reefs at depths that support its food source, Hydractinia milleri, commonly known as the hedgehog hydroid. Hydractinia seems to favor reefs that are at least several feet tall and are deeper than 20 feet. Shallower than these depths, algae outcompetes invertebrates for space on stable surfaces. Caves and undercut ledges may be an exception due to the lack of light reaching these surfaces.
Cuthona ranges from Vancouver, Canada to Point Loma in San Diego. I observed this slug at sites from Malibu to Laguna; representing the southern range of this species. Observations in this study are in the Southern California Bight and may not parallel trends north of Point Conception.
Cuthona is present in small numbers between the months of March and September. This slug has been observed on 18 separate occasions over the past 18 months and 46 of 47 sightings were between March and September. More time is necessary to compare the population dynamics of fall and winter 2010 with fall and winter 2011. Cuthona was not observed in abundance during this study. A site with a stable population of more than a few individuals has not yet been located.
Cuthona has been observed with its eggs between March and September. Temperatures recorded in this time interval were between 51 and 57 degrees Fahrenheit. These temperatures represent average highs and lows for the year at depths between 30 and 50 feet where observation took place. This data suggests that egg laying in this species is not determined by temperature within this narrow range. More data is necessary to confirm this.
