Update from Director Mike Schaadt (11/6/12): The female argonaut at CMA died sometime in the night Fri. 11/2. While at CMA the animal was kept in a tank closely matched to natural water temperature for this subtropical/tropical open ocean resident. CMA staff heard from other scientists that empty argonaut shells were found along San Clemente beach. It is likely that this animal would have also perished in the ocean as the warm water current that delivered it here stopped, returning our water to more typical cold temperate temperatures. While at CMA, CMA staff scientists made observations on the argonaut’s behavior (eating, swimming times, resting times, etc.) and reproductive activities. For instance, the argonaut ate pieces of shrimp, smelt and squid up until the day before it died. We believe that no researcher has ever had a chance to count the number of hatchlings that a female argonaut releases and CMA staff scientists coordinated the efforts of many other CMA staff (including education, administrative and custodial) and young students aspiring to be scientists in counting 22,272 hatchlings (paralarvae). In addition, CMA staff scientists were able to record on video the hatchlings feeding and we believe this to be a first. The hatchlings were kept alive about a week but despite trying many different food sources all perished by the second week. This is the longest anyone has reported keeping argonaut hatchlings alive in an aquarium tank. It is good to remember that the reproductive strategy of having many young, like argonauts, is that the chances of survival for any one hatchling is miniscule. In fact, on average in the ocean only two hatchlings survive to grow to be reproductive adults from over 22,000 hatchlings in a reproductive event. We know this mainly due to the fact that the argonaut population appears to be stable meaning that each female only replaces herself and her mate in her lifetime. By providing a safe place for this tropical visitor to live, CMA was able to share with our guests and students this animal’s interesting life history. We were also able to add to the knowledge of this octopus’ biology that may lead to more success on providing a home for these animals if they are deposited in our area in the future.
Update from Director Mike Schaadt (10/29/12): The female argonaut that was given to CMA over two weeks ago is still alive and eating. Just today she showed hunting behavior as she caught and ate pieces of shrimp and squid. Between Sunday 10-21 and Friday 10-26, many individual CMA staff spent time counting out 22,272 argonaut paralarvae (hatchling argonauts)! The female has not released any more hatchilngs. CMA staff scientists have witnessed feeding by the hatchlings under a microscope. We are trying different live planktonic food sources so we can find what they eat best. According to the literature, the longest argonaut hatchlings have been kept alive is seven days. The water temperature in Southern California continues to return to normal cool temperatures, too cool for the female or hatchlings to survive. We keep them in a system with warm (23C or 74F) clean seawater at CMA. As a reminder, in the wild for a normal population of animals that is not increasing or decreasing each adult female argonaut only replaces herself and her mate in her lifetime. If each female can spawn about 22,000 hatchlings, that means that under the best of conditions in the wild, only two will survive to be reproductive adults. As we continue our efforts to grow the hatchlings, we are aware of the importance of continuing to make good observations and meticulous documentation so we can learn more about this open ocean resident.
Update from Director Mike Schaadt (10/24/12): The female argonaut at CMA is still eating and her eggs are still hatching. As of Wednesday, October 24, CMA staff scientists have counted over 16,000 hatchlings. In talking with other scientists that study this animal, we have found that there have been very few instances where this octopus has released hatchlings in a lab setting. The data being carefully collected by scientists and scientists-in-training in CMA's Aquatic Nursery is valuable in further understanding this open ocean resident. An additional example of the information being gathered is that today, CMA staff scientists observed hatchling argonauts under the microscope actually grab and eat ostracods that were collected in a plankton tow.
Original article: On Saturday, October 13, 2012, a female argonaut (aka paper nautilus) was caught by fishermen when they were fishing for squid a couple of miles from Los Angeles Harbor. These animals are usually only found in tropical and subtropical seas; finding one in Southern California indicates warm water currents from the south are most likely prevalent.
“The argonaut is residing in a warm water aquarium tank in the Aquatic Nursery and we are learning as much as we can about this unusual warm water visitor. At CMA, we give people the opportunity to learn about our local ocean and marine life to inspire a passion for the ocean and its inhabitants in others,” said CMA Director Mike Schaadt. “Sharing information, photos and video of the argonaut gives people a chance to find out about an animal that normally can’t survive off our coast, but is is deposited by warm water currents occasionally. This is all part of our mission to promote knowledge, appreciation and conservation of the marine life of Southern California."
Argonauts are a type of octopus. They eat plankton such as krill, shrimp and pelagic snails. Female and male argonauts reach dramatically different sizes; females grow to be about 18 inches and males only one inch! The female argonaut creates a thin, laterally compressed calcareous shell, which is secreted and formed by the first arm from a wide sail-like lobe. This shell has one chamber that is used as a brood pouch for eggs.
Male argonauts have a highly modified third arm used to carry sperm to the female. This modified arm is called a hectocotylus, which breaks away from the male during mating and actually crawls into the female to remain until the female is ready to fertilize her eggs. On Sunday, October 21, staff members at CMA discovered that the argonaut had been carrying fertilized eggs in her shell because sometime early Sunday morning eggs hatched.
“This is the first time eggs of this species of octopus have hatched at CMA and one of the few times anywhere else in the world. Under the direction of CMA staff in the Aquatic Nursery, young scientists-in-training counted more than 5,000 extremely small hatchling argonauts (about 1mm in length) as they were placed into an adjoining tank,” said Schaadt. “Very little is known about this tropical/subtropical animal including the number of hatchlings a female can release at one time. Today (10/22), an additional 1,500 hatchling argonauts were counted.”
CMA staff members are documenting hatchling development and also recorded video of the color-changing cells called chromatophores with a microscope. (Chromatophores embedded in the skin of argonauts and most octopuses and squids help them blend into their surroundings.) “We will continue to document our observations of the female argonaut's behavior,” said Schaadt. “She is actively swimming up to and taking food offered by staff.”
To see more videos and photos of the argonaut, please visit Cabrillo Marine Aquarium’s Facebook and YouTube pages.