Two-spotted Octopus, Octopus bimaculatus
Two-spotted Octopus, Octopus bimaculatus. Octopus collected within Magdalena Bay, Baja California Sur, October 2018. Length: 25 cm (9.8 inches). Catch and identification courtesy of Bob Hillis, Ivins, Utah.
Two-spotted Octopus, Octopus bimaculatus.Underwater photograph taken within Zihuantanejo Bay, Guerrero, March 2022. Photograph courtesy of Ron Woheau, Zihuantanejo.
Phylogeny: The Two-spotted Octopus, Octopus bimaculatus (Verrill, 1883), is member of the Octopodidae Family of Octopuses. The Octopus genus is one of twenty-three genera in the Octopodidae Family, and there are seventy-three species in the Octopus genus. They belong to class Cephalopoda, which includes cuttlefish, nautiloids, and squid. They are also known as Verril’s Two Spot Octopus and in Mexico as Pulpo Manchado. The genus name Octopus comes from the Greek words meaning “eight foot”, referring to the eight arms. The species name bimaculatus comes from New Latin and means “twice-spotted”.
Morphology: The Two-spoted Octopus is a mid-sized octopus that reaches a maximum length of 61 cm (2 feet 0 inches). Their arms are four or five times the length of the mantle. They are highly variable in color. They are normally mottled in appearance and may be light brown, reddish-brown, gray or yellow-green. They have two dark ocelli (fake eye spots) on their mantle that are found beneath their real eyes and between the second and third arms. The ocelli turn bright blue with broken chain-links when the octopus becomes alarmed or agitated. Their skin is warty in texture, more so than other Mexican octopuses. The Two-spotted Octopus is very similar to, and most likely to be confused with, the California Two-spot Octopus, Octopus bimaculoides (found only north of Ensenada, Baja California; eye-spots with unbroken chain links) and Hubbs’ Octopus, Octopus hubbsorium (lack the two prominent ocelli spots).
Habitat and Distribution: The Two-spotted Octopus is found on and within rocky substrate in the intertidal zone and to depths up to 55 m (180 feet). The Two-spotted Octopus is a tropical to subtropical Eastern Pacific species, and is a resident of all Mexican waters of the Pacific Ocean.
Diet: Two-spotted Octopus are opportunistic night-time predators that feed primarily on bivalves, crustaceans and gastropods.
Predators: Two-spotted Octopus are preyed upon moray eels, harbor seals, sea lions, and sharks.
Reproduction: Two-spotted Octopus are gonochoric ( male or female for life). Reproduction is sexual with internal fertilization. In the male of this species one arm is modified to carry sperm in an open groove on the ventral edge. This arm is known as a hectocotylus, and in this family, is not detachable. The male inserts this arm under the mantle of the female during reproduction, delivering packets of sperm (spermatophores). After fertilization, the female will create a den and seal herself in to lay her eggs. A single female can lay thousands of eggs. She will care for her eggs by blowing cool water over them from her siphon to keep them oxygenated. During the process of caring for her eggs, the female often expires due to starvation and exhaustion. After the eggs hatch, which may take 150 to 210 days, the mother will leave the den if she survives and the larval octopus will drift with the tide before settling on the ground to begin developing. On average, these octopuses produce 70,000 offspring. They mate only once in their twelve to eighteen month life span.
Ecosystem Interactions: Two-spotted Octopus host ectoparasitic flagellates and ciliate protozoans, which live on the octopus’ gills.
Human Interactions: Two-spotted Octopus are one of the more abundant species of larger octopuses found in Mexican waters and are fished commercially. Overfishing can cause localized population collapses. From a conservation perspective the Two-spotted Octopus is currently considered to be of Least Concern with stable, widely distributed, populations.