Marine Invertebrates of Bermuda Grass Octopus (Octopus macropus) Rebecca Borns and James B. Wood (Ed) Abstract Taxonomy  Habitat  Ecology  Recent Research  Commercial Importance  Bermuda Laws  Personal Interest  References  Links

Abstract


The Octopus macropus, also known as the White-spotted octopus, Grass scuttle, or Grass Octopus, was originally described by Risso in 1826 off of Nice. Its typical habitat is near-shore, however sometimes it can be found deeper in the Mediterranean Sea. In addition, several species similar to O. macropus live in shallow tropical and temperate waters throughout the world. The O. macropus is actually described in 2003 as the “Octopus macropus species complex,” since there are at least 12 species of octopus with the red and white-spotted morphology and similar activity patterns. This octopus has a planktonic post-hatching phase and then spends its adult life on the ocean bottom. This octopus has long arms, with the first arm pair being the longest and stoutest, and has shallow webbing among the arms. It also has a higher sucker count than most octopuses. Its activity is predominantly to exclusively nocturnal. While in the daylight of an aquarium its camouflage seems poor, it is extremely successful at night in its natural environment.


Taxonomy


Phylum:Mollusca
  Class:Cephalopoda
    Order:Octopoda
      Family:Octopodidae



Habitat


The Octopus macropus tends to live in shallow waters 1-17 meters deep along rocky, sandy, or grassy bottoms (Sterrer, 1986). It is found in the Atlantic Ocean, Pacific Ocean, Indian Ocean, Mediterranean Sea, and Caribbean Sea (Norman, 2003).


Ecology


Feeding
Octopuses are very opportunistic and versatile predators that eat a wide range of prey (Iribarne, 1991; Fiorito and Gherardi, 1999). They manipulate objects and surfaces with their arms, and sometimes even use their funnel to flush the seafloor for prey (Iribarne, 1991). The predatory lifestyle is possible due to the octopus’s highly effective sense organs and an elaborate nervous system (Byrne et al., 2002). The highly developed cephalopod eye, along with a combination of senses are often relied upon for detection of prey at longer distances (Iribarne, 1991; Fiorito and Gherardi, 1999). Octopuses rely on chemosensory cues from prey along with prey movement and general shape, as they are color blind (Iribarne, 1991; Byrne et al., 2002). Octopuses appear to prefer crustaceans, especially crabs, when available (Iribarne, 1991). Their wide range in diet is made possible because they are able to drill through shells, making hard-shelled invertebrates a regular part of their diet (Iribarne, 1991). In order to drill, octopuses use salivary glands to produce chemicals and enzymes that weaken shells (Fiorito and Gherardi, 1999). The radula can then crack open the weakened shell and the salivary papilla along the terminal teeth inject a paralyzing toxic agent that causes the prey to relax all of their muscles (Norman, 2003). This immobilizes and partially digests the prey, making ingestion easier for the octopus (Fiorito and Gherardi, 1999; Norman, 2003). However, octopuses often first attempt to pull open crustaceans (Steer and Semmens, 2003). Although pulling is 1.29 times more costly than drilling, it often is much faster (Steer and Semmens, 2003). Therefore, the octopus minimizes its prey handling time, allowing it to move on to its next prey (Steer and Semmens, 2003). According to Fiorito and Gherardi (1999), the versatility and adaptations of octopus feeding behavior has played a large role in the continued evolutionary success of octopuses.

Activity
There have been few field observations of the Octopus macropus because of its nocturnal activity patterns (Boletzky et al., 2001). Its activity is predominantly to exclusively nocturnal (Boletzky et al., 2002). Some are crepuscular (Meisel et al., 2006). This is probably a result of the availability of food and the activity patterns of predators and prey (Meisel et al., 2006). Meisel et al. (2006) attempted to see if O. macropus would display the same activity patterns if the living conditions were changed in a controlled manner with natural daylight and artificial daylight. O. macropus remained entirely nocturnal (Meisel et al., 2006). Yet Octopus vulgaris, a more aggressive species in the experiment whose habitat overlaps that of O. macropus, was active during day and night light conditions, gradually becoming more active during the daytime over a period of three days (Meisel et al., 2006). This was attributed to lack of predator threat and the influence of human feedings and activity (Meisel et al., 2006).

Spawning and Embryonic Development
Boletzky et al. (2001) provided the first record of spawning and embryonic development of the Octopus macropus. In this study, a female was mated in a tank with one male in one month and with a second male the next month. Approximately three months after mating, Boletzky et al. (2001) discovered over 1,000 eggs along the wall of the holding tank. The ova were 4.0*1.2 mm long (Boletzky et al., 2001). The first hatchling was found approximately two months later, indicating a two-month embryonic development period (Boletzky et al., 2001). The hatchlings continued to appear for the next two weeks, suggesting a spawning period of two weeks (Boletzky et al., 2001). They were a tiny 5.5 mm long with a head width of 1.9-1.5 mm (Boletzky et al., 2001). The hatchlings already looked like juvenile octopuses with their short-arms and active swimming activity (Boletzky et al., 2001). Several of the identifying features of the adult O. macropus were already present, such as the chromatophore (pigment) patterns (Boletzky et al., 2001). The young octopuses were able to survive three to four days without food (Boletzky et al., 2001). These octopuses “live fast and die young” with a lifespan of 1-2 years, ending in a single breeding season in which the female starves herself while expending all her energy producing young (Meisel et al., 2006; Boyle and Daly, 2000).


Recent Research


While over 150 octopuses sharing the basic structural plan of eight arms lacking cirri, biserial sucker rows, an ink sac, absence of fins, a saccular mantle with a wide opening, and males displaying a modified tip on the third arm, there is still considerable debate over the phylogeny and taxonomy of this genus (Guzik et al., 2005). Octopuses display high variation in skin pigmentation and patterns along with behavior (Guzik et al., 2005). However their similar structural morphology makes it difficult to identify evolutionary relationships (Guzik et al., 2005). Therefore, Guzik et al. (2005) has been doing genetic tests on over 26 species of octopuses, including Octopus macropus, in attempts to examine recent and ancient divergences among octopuses. These tests included those of mitochondrial DNA genes, Cytochrome oxidase subunit III, Cytochrome b apoenzyme, and the nuclear DNA gene Elongation Factor-1a (Guzik et al., 2005). One of their results was that the O. macropus species group and the Octopus australis species group appeared to be very closely related (Guzik et al., 2005).


Commercial Importance


Although there is no documented commercial importance of the Octopus macropus, the octopus’s preference for crustaceans has made it a nuisance in many commercial fisheries for spiny lobster (Brock et al., 2006). Octopus maorum of the O. macropus species complex is responsible for killing 1% of the annual spiny lobster catch in Western Australia fisheries, 4% in Southern Australia, and 10% in New Zealand (Brock et al., 2006). Therefore, researchers recently worked to develop two-chambered traps that would prevent the crafty octopuses from stealing spiny lobsters from the fishermen’s traps (Brock et al., 2006). This was a difficult task since octopuses are able to pass through openings that are small relative to both their body size and to the spiny lobster’s body size (Brock et al., 2006).


Bermuda Laws


There are no laws that directly affect the Octopus macropus. However, Marine Protected Areas would include octopuses. These are any areas of the marine environment that have been reserved by federal, state, territorial, tribal, or local laws or regulations to provide lasting protection to part or all of the natural or cultural resources therein (de Putron, 2007).


Personal Interest


I have always been interested in animal behavior. I was the little girl who had to be dragged away from zoos, aquariums, or pet shops, as I could stare for hours at one individual animal, analyzing its every little movement. I became interested in octopuses the first week of Marine Invertebrate Zoology when we watched a video on cephalopods called "Tentacles." I was intrigued by the video footage and information presented. I had never heard that an octopus has a short lifespan of four years or that only 2 of 57,000 eggs laid by an octopus survive to adulthood, as the video pronounced. I was also sure that they must be interesting invertebrates after an image of Dr. James Wood’s office, which was covered in octopus memorabilia, was displayed on the video. I was excited to learn more about the Octopus macropus.


References

Boletzky, S.V, Fuentes, M., and Offner, N. 2001. First record of spawning and embryonic development in Octopus macropus (Mollusca, Cephalopoda). Journal of the Marine Biological Association of the United Kingdom. 81(4): 703-704.

Boletzky, S.V., Fuentes, M., and Offner, N. 2002. Developmental features of Octopus macropus Risso 1826 (Mollusca, Cephalopoda). Vie et Milieu-Life and Environment. 52(4): 209-15.

Boyle, P.R. and Daly, H.I. 2000. Fecundity and spawning in a deep-water cirromorph octopus. Marine Biology. 137: 317-324.

Brock, D.J., Saunders, T.M., Ward, T.M. Linnane, A.J. 2006. Effectiveness of a two-chambered trap in reducing within-trap predation by octopus on southern spiny rock lobster. Fisheries Research. 77: 348-55.

Byrne, R.A., Kuba, M., and Griebel, U. 2002. Lateral asymmetry of eye use in Octopus vulgaris. Animal Behaviour. 64: 461-68.

de Putron, S. 2007. Marine Ecology Lecture.

Fiorito, G. and Gherardi, F. 1999. Prey-handling behaviour of Octopus vulgaris (Mollusca, Cephalopoda) on bivalve preys. Behavioural Processes. 46: 75-88.

Guzik, M.T., Norman, M.D., and Crozier, R.H. 2005. Molecular phylogeny of the benthic shallow-water octopuses (Cephalopoda: Octopodinae). Molecular Phylogenetics and Evolution. 37: 235-48.

Iribarne, O.O., Fernandez, M.E., and Zucchini, H. 1991. Prey selection by the small Patagonian octopus Octopus tehuelchus d’Orbigny. Journal of Experimental Marine Biology and Ecology. 148: 271-81.

Norman, M. Cephalopods A World Guide: Octopuses, Argonauts, Cuttlefish, Squid, and Nautilus. Hackenheim, ConchBooks, 2003.

Meisel, D.V., Byrne, R.A., and Kuba, M. 2006. Contrasting activity patterns of two related octopus species, Octopus macropus and Octopus vulgaris. Journal of Comparative Psychology. 120(3): 191-97.

Steer, M.A. and Semmens, J.M. Pulling or drilling, does size or species matter? An experimental study of prey handling in Octopus dierythraeus (Norman, 1992). Journal of Experimental Marine Biology and Ecology. 290: 165-78.

Sterrer, W. 1986. Marine Fauna and Flora of Bermuda. United States of America: John Wiley and Sons, Inc.


Links


The Cephalopod Page
Octopus macropus video
Octopus macropus on CephBase