Day Octopus

Octopus cyanea Gray, 1849

Octopus cyanea Gray, 1849:15.

Octopus marmoratus Hoyle, 1885:227.

Octopus horsti Joubin, 1898:23.

Polypus herdmani Hoyle, 1904:187,pl. 1.

Polypus glaber “Rüppell, MS” [see Wülker, 1920:51].

Octopus cyanea var. gracilis Robson, 1929:98.

Callistoctopus magnocellatus Taki, 1964:298, figs. 42–46, pl. 4: figs. 1, 2 [after Norman, 1991].

DIAGNOSIS.—Animals large (to 900 mm TL; to 160 mm ML). Mantle broadly ovoid (MWI 54–67–81); head narrow (HWI 42–55–67), demarked from mantle by moderate constriction; eyes large, projecting above surface of head. Funnel large, broad, bluntly tapered (FLI 30–38–48); funnel organ W-shaped, limbs broad, outer limbs length of median limbs. Arms long (ALI 196–582), stout at base, tapering to narrow tips. Arm lengths subequal, arm order IV = III = II > I. Suckers raised above arm surface, moderately large (SI females 7–9–11, males 7–10–12), 10th to 13th suckers usually largest, enlarged on arms II and III of mature males. Right arm III of males hectocotylized, shorter than opposite arm (HAMI 296–351–436; OAI 71–82–88); ligula narrow, very small (LLI 0.4–1.2–1.7); ligula groove shallow, with about 10 fine, transverse ribs; calamus short, blunt (CLI 35–38–41); hectocotylized arm with 160–229 suckers. Web shallow (WDI 14–19–29), web formula C > B = D = E > A or B = C = D = E > A. Radula with A4-5 symmetrical seriation of rachidian. Ink sac present. Gill lamellae 9–11 on outer demibranch. Mature female with small eggs (capsule ~2.7 mm long, 0.5 mm wide); method of attachment to substrate unknown. Penis (PLI 4–14–27) with single-coiled diverticulum; spermatophores short (SpLI 32–40–50), slender (SpWI 1.3–1.5–1.6), with large, coiled sperm reservoir (SpRI 30–33–38).

Integumental sculpture consists of fine reticulations forming patch and groove system on dorsum. Ventral surface smoother. Unbranched papillae present on dorsum. Four large, unbranched papillae in diamond pattern present on dorsal mantle. Pattern of large papillae on brachial crown includes unbranched papilla between and slightly below eyes and pair of papillae midway between eyes and edge of dorsal web. Other smaller, unbranched papillae scattered over dorsum. Single large, unbranched papilla obvious in supraocular region, surrounded by 3 to 4 smaller papillae. Lateral integumentary ridge or fold around mantle circumference absent. In life, color of resting animals cream to white with 2 red, longitudinal bands on dorsum from mantle through eyes to brachial crown; when stimulated, animals turn dark brown, or grey white with marked black ocelli, or produce mottled and sculptured cryptic patterns. Large ocellus on each side of head between eyes and web margin, consisting of black central spot (approximately 0.15 times ML) surrounded by pale ring and narrow, black ring. Ventral faces of arms marked by alternating thin, dark brown and cream-colored bands; 3–7 rows of cream-colored spots run along dorsal surfaces of all arms from web margins distally to arm tips. General color of animals preserved in ethyl alcohol cream to drab, slate grey with ocelli and other markings visible, or dark brown to purple with diagnostic markings obscured.

ORIGINAL DESCRIPTION.—Gray, 1849:15.

TYPE LOCALITY.—Australia (as “coast of New Holland”) (no other details).

TYPE.—Lectotype: BMNH 1928.2.4.1, 1 male, 106 mm ML (designated by Norman, 1991). Specimen in good condition, preserved in ethyl alcohol. Another type specimen in the BMNH collection listed in the original description (unknown sex and size, from unknown locality, and unregistered) remains untraced.

DISTRIBUTION AND BIOLOGY.—Northern Australia from North West Cape, Western Australia, to the southern end of the Great Barrier Reef, Queensland, and also with a widespread, Indo-West Pacific distribution. Found living on shallow coral reefs and islands, at depths of 0–18 m (Norman, 1991).

Aspects of the biology of O. cyanea, including behavioral data, were described by Norman (1991, 1992b). Further information on behavior based on color and body patterns was included in Roper and Hochberg (1988). A review of the life history of O. cyanea was given by Van Heukelem (1983).

Octopus herdmani (Hoyle, 1904)

DIAGNOSIS.—Animals medium-sized to large (to 95 mm ML; to 550 mm TL). Mantle width moderate (MWI 61). Arms moderate in length (ALI 65), stout, arm formula II = IV>III>I. Suckers densely spaced, first 4 dorsal suckers uniserial. Surface of mantle with numerous papillae, some elongate anteroposteriorly; 4 papillae form rhombus centered on midline; 2 or 3 minute warts above and behind each eye. Arms I and III with several elongated papillae. Color in preservation dull brownish grey dorsally. Large ocellus present at base of arms III consisting of pale center surrounded in turn by broad dark ring, narrow pale ring, and narrow dark ring.

ORIGINAL DESCRIPTION.—Hoyle, 1904:187, pl. 1, as Polypus herdmani.

TYPE LOCALITIES.—Northern Indian Ocean, Ceylon (= Sri Lanka): Galle; Palk Bay; north of Periya Paar; Pearl Banks, Gulf of Manaar; south end of Cheval Paar.

TYPES.—Syntypes: BMNH 1947.5.5.5, 1, sex undetermined, 10 mm ML, Hoyle no. 216, previously dried, blackened, in alcohol, poor condition; BMNH 1947.5.5.6–8, 3, sex undetermined, 6 mm ML, 6 mm ML, 10 mm ML, Hoyle nos. 224–226, previously dried, darkened, in alcohol, poor condition; disposition of 5 additional syntypes unknown, not traced.

Octopus marmoratus Hoyle, 1885

DIAGNOSIS.—See “Discussion.”

ORIGINAL DESCRIPTION.—Hoyle, 1885:227.

TYPE LOCALITY.—Hawaiian Islands, Oahu, Honolulu.

TYPES.—Syntypes: BMNH 1889.4.24.25–26, 1 male, 1 female.

Octopus cyanea gracilis Robson, 1929

DIAGNOSIS.—See “Discussion.”

ORIGINAL DESCRIPTION.—Robson, 1929:98.

TYPE LOCALITY.—Northern Indian Ocean, western Bay of Bengal, India, Madras.

TYPE.—Holotype: BMNH 1907.9.28.1, female.

Octopus horsti Joubin, 1898

DIAGNOSIS.—Animal large. Ocellus present at base of arms III. Irregular series of dark maculations along side of arms between suckers.

ORIGINAL DESCRIPTION.—Joubin, 1898:23.

TYPE LOCALITY.—Red Sea, Djeddah.

TYPE.—Holotype: RML, sex undetermined, ML unknown, condition unknown.

Octopus cyanea, also known as the big blue octopus or day octopus, is an octopus in the family Octopodidae. It occurs in both the Pacific and Indian Oceans, from Hawaii to the eastern coast of Africa. O. cyanea grows to 16 cm in mantle length with arms to at least 80 cm. This octopus was described initially by the British zoologist John Edward Gray in 1849; the type specimen was collected off Australia and is at the Natural History Museum in London.

coastal