Blog 10 – Copepods

I never imagined that I could find so many similarities between the ocean and the desert. They both bring me a great amount of happiness and serenity. They are open and seem so endless. They are both immensely beautiful. And… they have copepods!

Copepods are incredible crustaceans adaptable to many living conditions. They are small, yet visible with the naked eye. They move fast and most are transparent. Their first pair of antennae are long and curved like a smooth elongated “S.” Sensitive receptors are at the end of these antennae which enable the copepods to detect changes in flow and in chemical changes. Their bodies have a cylindrical shape and most have a rapidly beating heart!

Copepods are found all around the world wherever water is present. There are copepods living in the Salton Sea near the Imperial Valley desert. Just recently, a new species was discovered living in a single pond in the Chihuahuan Desert in Northern Mexico!


Copepod found in one of our net tows.

With more than 13,000 species, mostly living in marine waters, copepods are the most abundant animals living in the ocean away from the seafloor.


Maxillipeds help copepods in feedings. These look like beautiful feathers. Photographed by Dr. Rasmus Swalethorp.

In our cruise we have experts studying copepod population growth of three species found in the California Current. These species are collected by Cat Nickels, a Ph.D. student working in Dr. Mark Ohman’s laboratory.


From left to right, the three species collected by Cat Nickels: Calanus pacificus herbivore, Eucalanus californicus ambush predator, and Metridia pacifica omnivore.

Every morning during our cycles of research while we follow a patch of ocean water, Cat collected 30 females from each of the three species. Next, she would incubate them at the right temperature, fed them freshly collected ocean water containing tiny phytoplankton food, and checked for egg production every 12 hours. If she found eggs, she would separate the female from her eggs to prevent her from eating them. Then Cat would continue making observations and count the number of eggs that hatched.


Cat Nickels, Ph.D. student counting hatched copepod eggs.

Her experiments compare how reproduction varies with phytoplankton intake for the three copepod species. Studying copepod reproduction is important because it can provide clues to the success of different species as conditions change in the future ocean.


Dr. Mark Ohman, Scripps Institution of Oceanography, is also the Director of California Current Ecosystem LTER site