The Octopus Project: Raising Octopus bimaculoides Hatchlings In Captivity

Raising O. bimaculoides is a challenge, but it proves to be a rewarding experience.

Two-spot octopus about to eat a guppy fry. Photo by Andrew Tran and Alex Duman
Two-spot octopus about to eat a guppy fry. Photo by Andrew Tran and Alex Duman

Just keeping healthy and happy octopuses requires the aquarist both to provide enriched environments and limit possible escape routes. An even more taxing endeavor centers on hatching, raising, and maintaining octopus larvae. While raising these picky eaters is an immense challenge, it is an extremely rewarding and exciting adventure that few aquarists are fortunate enough to experience.

 

There may be more than 300 species of octopuses in the world’s oceans. These eight legged legends – inspirations for many Greek tales – vary greatly in size, but those we normally encounter in aquaria hold true to the voracious appetites portrayed in these ancient tales. Unlike in the fables, their main diet consists of crustaceans, an assortment of other invertebrates, and fish that they can extract from impressively small crevices. The success of these animals in hunting, escape, and maneuverability is a product of their hydrostatic skeleton that allows them to adjust their shape to slip through cracks and project hundreds of skin papillae upward to give the appearance of texture further enhancing their camouflage capabilities. In addition to changing shape, most octopuses are masters of color change, using highly coordinated chromatophores to rapidly change colors for camouflage and social signaling to fellow octopuses. Alas, this perceptive and bright cephalopod suffers the limitation of a generally short life span in both captivity as well as in the wild.

One particular species, Octopus bimaculoides commonly known as the California two-spot octopus, are relatively hardy and have peaceful temperaments making them one of the best pet octopuses for an advanced aquarist looking to take on a challenge. This species receives its name from two beautiful deep blue false eyespots located on either side of the head.

Several months ago, the Rhanor Gillette Laboratory at the University of Illinois in Urbana-Champaign ordered an adult male O. bimaculoides for the purpose of researching memory in the peripheral nervous system. However, it was immediately apparent on arrival that the specimen was a female. Not only that, but within a month she laid eggs in an empty abalone shell, ceased eating, and mostly stayed under the shell to protect and care for the eggs. Now, the initial research project was unrealistic. When we discovered that the eggs were developing, our new objective became to successfully raise the offspring of an octopus native to coastal California in the middle of land-locked Illinois. We were successful, using artificial seawater and learning to feed the larvae with live prey not normally found in their environment. Now, we aim to share our findings with other enthusiasts so they too can share in this experience.

Aquarium Set Up

A spacious 40-gallon breeder (151 L) aquarium was used to house the adult O. bimaculoides and her developing young. The temperature was maintained at 64.4°F (18°C). An undergravel filtration system, sponge filter and protein skimmer were used to maintain the water quality. Crushed shells served as the substrate, with large clam shells, abalone shells, and live rock for decor and size-appropriate hiding spaces. A 25-percent water change was conducted weekly using pre-prepared Instant Ocean Sea Salt Mix and deionized water.

A second 15 gallon (57 L) bare-bottom aquarium was set up and maintained at 59°F (15°C). Two air stones and a sponge filter were used to promote water circulation and maintain water quality. The aquarium housed two clutches of eggs that were removed from the mother octopus and allowed to develop on their own. Each clutch was contained within a slender 150 ml Erlenmeyer flask with a single airstone suspended directly above the eggs to increase water currents around eggs and promote exchange of nutrients and removal of waste byproducts. A 33 percent water change was conducted biweekly to keep the aquarium clean.

Eggs Capsules

A month after arrival, the female O. bimaculoides laid approximately 200 fertilized egg capsules under a large abalone shell. Her demeanor changed drastically, most notably she refused to eat and confined herself under the abalone shell with her developing eggs. This type of behavior is similar to many other species of octopus. Egg laying serves as an indication of the end of the life cycle for these creatures, which occurred to our O. bimaculoides mother about four months after she laid her eggs.

One month after the eggs were laid, eyespots were visible. As the months passed, more characteristics were observed. At two months post-laying, the embryos developed pigmentation in their chromatophores. At first the pigmentation was minimal, but within a month, the octopus larvae displayed advance control of their chromatophores, changing from white to vibrant yellows and dark browns in a matter of seconds. At the end of the third month, the embryonic octopuses seemed to grow restless, moving and shaking within their egg capsules, suggesting that hatching was imminent.

One clutch of around 20 fertile eggs was removed from the mother 49 days post-laying and placed in a 15 gallon (57 L) aquarium 5.4°F (3°C) cooler than the main aquarium. A second and third clutch containing 15 to 40 eggs each were removed 72 days post-laying. The lower temperature in the 15-gallon aquarium markedly delayed the development of individuals from all three of the clutches relative to those in the main aquarium. The initial clutch removed had considerably fewer individuals hatch, and individuals from clutches removed to the cooler environment after 72 days showed greater hatching rates relative to the first clutch, suggesting eggs less than 72 days are significantly less tolerant to temperature fluctuations and stressors than their more developed siblings.

Hatchlings

Of the roughly 200 hatchlings, 18 of the larvae were housed in separate homemade containers ranging from 100 mL to 5 L to reduce cannibalistic encounters. Each container was constructed from household plastic Tupperware that was thoroughly washed. Large holes were cut out of the tops and replaced with fine mesh to prevent octopus escape, while providing adequate circulation to the developing juveniles. Additionally each container had several small shells about 2 cm in size for the developing juveniles to hide in and feel secure. Containers were cleaned daily using Pasteur pipettes with rubber bulbs to remove any and all solid waste.

two spot octopus
Two-spot octopus hatchlings.

Hatchlings are known to feed on live amphipods and mysid shrimp. As we were on a budget and in the middle of the Midwest, we had to get creative! We knew that when it came to feeding, live food was crucial to stimulate the innate predatory response. Young octopuses in the wild usually only pursue live food, and it was essential that we mimic this to increase their likelihood of survival. We tried a variety of live food, from bloodworms to guppy fry, and found success in feeding and raising the hatchlings including acclimating them to frozen shrimp.

None of the larvae accepted a first meal consisting of bloodworms until six days after the first larvae began hatching. Bloodworms offer an abundant and cheap source of live food that will wiggle vigorously and attract the curious and hungry juveniles into pursuing them. It is also visually easy to see if the young octopuses are eating at this age, as the red pigments of the bloodworm show through in the octopuses’ stomachs. Guppy fry were also offered 12 days after the initial wave of hatching which the larvae eagerly accepted. This common aquarium fish is an excellent food source as it tolerates high salinity and relatively low temperatures long enough to attract attention of the octopuses. A batch of newly hatched crayfish from another lab project also proved very attractive to the ravenous and rapidly growing larvae. Again crayfish are also tolerant of water salinity and can survive for several minutes in a marine environment before becoming dinner.

Eventually after 33 days after hatching some individuals began accepting frozen shrimp morsels cut into pieces of about 1 to 2 mm. This was accomplished by only introducing frozen food to the young hatchlings. At first there was resistance, but as the young octopuses went a couple days without food, they readily accepted the thawed out treats.

Looking Forward

Raising O. bimaculoides is a challenge, but it proves to be a rewarding experience. What sets these animals apart from raising many other marine animals is the process and patience that it requires. We have shown that development can be delayed successfully and dramatically by decreasing the temperature slightly by 5.4°F (3°C) which is accomplished more optimally at least two months after initial egg-laying to increase larval survival and hatching rate.  Additionally the young larvae readily accept a wide variety of live food and will gradually accept frozen foods with age. The young were raised and eventually reached the size of a quarter. Unfortunately summer was upon us and we had to leave the university for summer internships. It was decided that the best avenue for these octopuses was to ship them off to another laboratory where they could continue to be studied.

We truly enjoyed having these octopuses and highly recommend it. These animals will keep any aquarium enthusiast on their feet. If ever given the chance to raise octopus hatchlings, we highly recommend taking on the challenge. The work is worth every second. Raising baby octopuses is an experience that not many get the opportunity to have. For more information, check us out at theoctopusprojectuiuc.weebly.com

Article Categories:
Fish · Lifestyle

Leave a Comment

Your email address will not be published. Required fields are marked *