Caribbean Reef Octopus

Octopus briareus Robson, 1929

DIAGNOSIS.—Animals medium-sized to large, to 120 mm ML, wt to 1000 g. Mantle round, widest near middle (MWI 62–92) with slight constriction in neck area; head moderate to wide (HWI 62–83); eyes prominent. Funnel organ W-shaped, with inner and outer limbs subequal in length. Arms long (ALI 80–95), arms II and III larger, thicker, somewhat swollen in midregion (AWI 21–37), arm order II = III > IV > I. Suckers large (SIn 13–22), larger on arms II and III; especially enlarged suckers absent in males and females. Right arm III of males hectocotylized; ligula small but well developed (LLI 3–4), broad, rounded distally, with lateral fringing membranes and with central ridge and about 12–16 transverse laminae; calamus moderate in size (CLI 28–32). Web shallow to moderate in depth (WDI 12–20), web formula A = B = C = D>E. Ink sac present; gill lamellae 6–8. Mature eggs large, capsule 10–14 mm long X 4–5 mm wide, stalk 5–10 mm long, egg masses with 200–500 (rarely to 1000) eggs arranged in clusters of 7–34 (mean = 25). Hatchlings benthonic, mean ML 5.5 mm. Penis small (PLI 31–34), with well-developed diverticulum; entire penial apparatus boomerang-shaped. Spermatophores long (SpLI 126). Radula with A3 seriation of the rachidian. Color in life iridescent blue-green with chromatophores retracted, frontal white spots absent.

ORIGINAL DESCRIPTION.—Robson, 1929b:612, fig. 1.

TYPE LOCALITY.—Western tropical Atlantic Ocean, Netherlands West Indies, off Curaçao.

TYPES.—Syntypes: ZMA, 1 male, 40 mm ML; BMNH 1946.10.8.3, 1 male, 31 mm ML.

DISTRIBUTION.—United States, South Florida, southeastern Gulf of Mexico; Bahamas; Caribbean Sea to northern South America (to ∼40°W); in association with coral reefs.