The Atlantic longarm octopus is well-named — its arms can be up to seven times longer than the rest of its body!
Those arms come in handy for digging dens in the sand. Longarms are much neater around their dens than other octopuses; they don’t scatter food remains that could attract predators. They’ve also been seen kicking other creatures out of their dens — including other longarms!
If this octopus needs a quick escape, it uses its arms to bury itself in the sandy seafloor.
The Macrotritopus Problem:
The adult form of species defilippi was first described as Octopus defilippi (1851). Macrotritopus was originally described from a single juvenile specimen (M. equivocus) with elongate third arms. Several young planktonic octopus species were included within this genus because their third arms were longest and this paralarval group was known as “Macrotritopus larva”.
Adult forms of this genus were unknown until captive rearing in 1985 of Octopus defilippi eggs hatched into this distinctive larval type, connecting the juvenile and adult forms. The mystery was solved, and the genus name was changed to Macrotritopus defilippi.
But it doesn’t stop there. This genus is still in need of revision. M. defilippi is currently the only described species in the genus; however, there are two poorly described unresolved species known only from planktonic hatchlings (M. equivocus and M. scorpio) and potentially three undescribed Indo-Pacific species, including “Octopus sp. 17” from Australia.
Just recently (2019) a new species of Macrotritopus was described for the southern Caribbean as Macrotritopus beatrixi. Distinguishing features between the two species include digestive tract, radula, ink sac, beak, hectocotylized arm suckers, web, and eyes. Further research of Macrotritopus including molecular analysis is needed to confirm this new species and species identified as M. defilippi in different geographical regions.
It is considered to be a small to medium-sized octopus. This species has a long, narrow mantle and very long arms. Mantle length for adults has been reported between 55-90 mm (3.5 inches) and arms 4 to 7 times the mantle length! Total length for M. defilippi was reported from 4 collected specimens (2 males, 2 females) between 214-224 mm (~ 9 in).
This species is thought to live for about 12 months.
Found in the Mediterranean Sea, eastern & western Atlantic Ocean, Caribbean Sea, and Indian Ocean.
M. defilippi is a shallow-water octopus. It lives in soft bottom habitats from 0- 60 m (197 ft), but has been reported down to 200 m (656 ft). Its den and surrounding habitat is mostly composed of sand or mud. Using its long arms, it can create its own burrow for its den and has been observed “kicking out” other longarm octopus and sand-dwelling fishes (such as blennies and gobies) for their home.
M. defilippi is a sand-dwelling species similar to the octopuses in the “Long-Armed Sand Octopus” clade, which includes the Indo-Pacific mimic octopuses (Thaumoctopus mimicus, Wunderpus photogenicus, White V’ octopus, and Hawaiian Long-Armed Sand octopus), that require sand habitat. M. defilippi has not been invited into this “Long-Arm” club because no tissue samples exist for genetic analysis.
This species eats mainly crustaceans (especially crabs that live in the sand), but has also been reported to eat worms in the Mediterranean. In the western Atlantic, this species diet was composed of 94% crustaceans (mainly crabs but also small mantis shrimp) and 6% bivalve. This species was also observed to eat on-the-go and not discard prey remains around its sandy den that could potentially attract predators.
The base color of this species is cream-brown with a loose net-like pattern of darker brown narrow lines on dorsal mantle and regular narrow dark brown bands along arms. Its skin generally has a low wrinkled appearance with scattered, moderate size papillae. Small papillae over eyes, but papillae can get very long to look like algae! Distinguishing skin features include white arm bars with round spots along the entire arms, single heart shaped white spot at tip of mantle (extreme anterior mantle) and pink iridescence under eyes.
This species has a several tricks up its sleeves [arms] for avoiding predators. To name a few, it can quickly bury into the sand or blend in by flattening its body (flat camouflage). It uses flounder swimming to travel across the open sandy plains and mimics the swimming behavior (posture, style, speed, duration) of the flounder (Bothus lunatus) that also inhabits the area. The flounder swimming speed of this species was clocked at 9 cm/s. That’s about 1 foot every 3-4 seconds! This species is also known to use arm postures to look like seaweed (masquerade) in its surrounding environment.
To get a better look at its surroundings, this species will use a tripod stance (standing tall on arms) before and during foraging events. This behavior can help avoid predators and select new feeding spots. This species forages during the daytime and scientists in Florida have followed this octopus during foraging events that lasted 2-3 hrs!
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Bennice CO, Brooks WR, Hanlon RT. Behavioral dynamics facilitate resource partitioning and enable tight coexistence of two octopus species in a shallow South Florida lagoon (in prep for JEMBE)