Caribbean Reef Octopus

Caribbean Reef Octopus

Kingdom: Animalia

Phylum: Mollusca

Class: Cephalopoda

Order: Octopoda

Family: Octopodidae

Genus: Octopus

Species: O. briareus

Description

Octopus briareus, also known as the Caribbean reef octopus, is a very common octopus located in the Western Atlantic. It is thought to be one of the most intelligent species of octopus (Caribbean Reef Octopus 2014). It can be found in various locations throughout the Caribbean Islands as well as northern parts of South America. They live in shallow to moderate depths of around 5-30m can be found around a variety of different substrates, such as coral reefs and sea grass. They are generally active animals and move around from den to den unless they are mating (Caribbean Reef Octopuses, n.d.). These octopuses have distinct green and blue colors on their bodies. They can sometimes also have brown markings, which people will see and often confuse them with the Common octopus (Caribbean Reef Octopus 2014). The Caribbean reef octopus can grow up to 12 cm in length and weigh 1.5 kg (Robinson 2000). They have 8 arms that can be as long as 60 cm (Robinson 2000).

Behavior/Feeding Characteristics

Crustaceans make up most of the diet of these octopuses, but they will sometimes feed on fish and other invertebrates. These octopuses usually live and hunt alone, and hunt at night because they are nocturnal animals. This octopus also may use a unique prey capturing method, in which the octopus will form a dome over its prey using its tentacles (Caribbean Reef Octopuses, n.d.). Like other species of octopus, the Caribbean Reef Octopus has specialized cells in its skin called chromatophores that it can use to change its skin color and camouflage itself to the surrounding environment. It can use camouflage to wait for prey items as well as hide from other predators. If ever attacked by a predator, the octopus will release an ink cloud that it uses to escape (Robinson 2000).

Reproduction

The Caribbean Reef Octopus, like many other cephalopods and octopuses, reproduces sexually. Males and females are difficult to tell apart, as the gonads are hidden in both sexes (Robinson 2000). Males are identified by a type of specialized arm called a hectocotylus. The hectocotylus is the male’s reproductive organ that it uses to transfer sperm to the females during mating (Caribbean Reef Octopuses, n.d.). Although these octopuses are mainly solitary, you may see males interacting and competing for a female when they want to mate. During mating, the male latches himself to the female, transfers sperm into the female’s mantle cavity, and then her oviduct. After mating, females will then isolate themselves to lay their eggs. Females have been studied and seen laying up to 500 eggs at once. The eggs will hatch after around 50-80 days and the females will wait with their eggs until they are hatched (Robinson 2000). The lifespan of the Caribbean Reef octopus is quite short, so the octopus offspring mature very quickly and are ready to mate in less than half a year.

Interactions with Caribbean Spiny Lobster

As previously discussed, the main source of food for the Caribbean reef octopus is crustaceans, and a very common species of crustacean that lives in the same region is the Caribbean spiny lobster (Panulirus argus). In a paper published by Mark Butler and Jennifer Leer, it discusses how these two organisms take part in something called intraguild predation. This is defined as predation that “occurs when species simultaneously compete for resources and interact as predator and prey” (Butler & Leer 2009). They conducted a study across various sites throughout the Florida Keys. Artificial shelters that had been placed years in advance were used because of the difficulty of measuring octopus abundance in real dens (Butler & Leer 2009). During their research, they found that the Caribbean reef octopus and the Caribbean spiny lobster compete for dens and other forms of shelter when there is a low amount (Butler & Leer 2009). As you might expect, the Caribbean reef octopus would come out on top of this competition. Having shelter is a key factor for the survival of both these organisms, as they depend on them for protection from predators. They concluded that a negative correlation existed between the two species because of two main reasons: predation and lobsters avoiding areas heavily occupied by octopuses (Butler & Leer 2009). There were several other key points they discovered throughout their research as well. As you might also expect, areas with higher concentrations of octopus had higher predation on lobsters. They also found that the lobsters only real mechanism of reducing predation was having other lobsters around as well as other types of prey. Increased size of the lobsters had no effect on reduced predation by the octopuses (Butler & Leer 2009).

In another paper, like the one above, Dianne Berger and Mark Butler focus more on the concept of how juvenile lobsters select their dens based upon the presence of octopuses. They wanted to know if lobsters used chemical detection to avoid octopuses as well as how lobsters were distributed based on the location of nearby octopuses (Berger & Butler 2001). To set up their experiment, they made artificial shelters and placed them in groups. They had the dens placed apart from each other at various distances of 0.1m, 0.5m, 2m, and 10m. From their results, they found that the Caribbean spiny lobster has chemical sensors that it uses to detect the presence of nearby octopuses, as more lobsters chose dens that did not have the chemical indicator given off by octopuses. (Berger & Butler 2001). In terms of distribution, they determined that octopuses and lobsters were very rarely, if at all, found together inside the same den, or dens within 2m or less of each other (Berger & Butler 2001). Only in dens that were 10m apart was there a good chance to see these species living nearby.

All in all, it was determined that the reason competition between these two species exists at all is because of the limited supply of shelters as well as competition for molluscs, a prey item shared between both octopuses and lobsters (Berger & Butler 2001). In their discussion section, Berger and Butler discuss an interesting concept called “switching predators”. If octopuses and lobsters are both feeding on molluscs, the mollusc population is going to go down significantly. Then the octopuses will be forced to “switch” to a different food source, likely being crustaceans like the juvenile lobsters, which will in turn increase the predation of lobsters by octopuses (Berger & Butler 2001). So, in a rather unfortunate predicament, lobsters are increasing their chances of being preyed upon simply by eating their normal food on a daily basis.

Works Cited

"Caribbean Reef Octopuses, Octopus briareus ~ MarineBio.org." MarineBio Conservation Society. Web. Accessed Monday, November 22, 2017. <http://marinebio.org/species.asp?id=552>.

Robinson, A. 2000. "Octopus briareus" (On-line), Animal Diversity Web. Accessed November 22, 2017 at http://animaldiversity.org/accounts/Octopus_briareus/

Berger Dianne K. Butler IV Mark J. (2001) Octopuses influence den selection by juvenile Caribbean spiny lobster. Marine and Freshwater Research 52, 1049-1053.

Butler, M., & Lear, J. (2009). Habitat-based intraguild predation by Caribbean reef octopus Octopus briareus on juvenile Caribbean spiny lobster Panulirus argus. Marine Ecology Progress Series,386, 115-122. Retrieved from http://www.jstor.org/stable/24873452

Caribbean Reef Octopus. c2014. Octopus World: Bio Expedition; [accessed 27 Oct 2017]. http://www.octopusworlds.com/caribbean-reef-octopus/

Image 1 – Caribbean reef octopus - http://cdn.octopusworlds.com/wp-content/uploads/Caribbean-Reef-Octopus_624.jpg

Image 2 – Caribbean reef octopus 2 - http://marinebio.org/upload/_cephs/octopus-briareus/9.jpg

Image 3 – Caribbean reef octopus 3 - http://marinebio.org/upload/_cephs/octopus-briareus/3.jpg

Image 4 – Caribbean spiny lobster - https://www.keywestaquarium.com/wp-content/uploads/2016/07/caribbean-spiny-lobster.jpg