Paroctopus mercatoris (Adam 1937)

Octopus mercatoris Adam, 1937

DIAGNOSIS.—Animals small (to 20 mm ML). Mantle moderate in width (MWI 64–73); neck constricted; head subequal in width to mantle (HWI 71–76); eyes relatively large. Funnel organ W-shaped, inner and outer limbs subequal in size. Arms moderate in length (ALI 78), arm order III > II > IV > I but nearly equal. Suckers elevated, moderate in size, larger in female (SIn 12) than in male (SIn 9.5), ASC 143; in male, 1 or 2 suckers in sucker rows 3 to 4 on arms I–III especially enlarged (SIe 13.5). Right arm III of male hectocotylized (HALI 175), noticeably shorter than fellow (FAI 71); ligula small (LLI 4); calamus small (CLI 20); HASC 80. Web shallow (WDI 16), web sectors nearly subequal in depth. Ink sac present, gill lamellae 6 to 7. Mature ovarian eggs small, capsule ∼3 mm long. Penis short, stubby, with simple, subspherical diverticulum (PLI 11). Radula with B4 seriation of rachidian. Skin of mantle, head, web, and arms smooth; small supraocular papillae present. Color in preservation (ethanol) tan.

ORIGINAL DESCRIPTION.—Adam, 1937b:76, figs. 32–35.

TYPE LOCALITY.—Subtropical western North Atlantic Ocean; Gulf of Mexico, United States, Florida, Dry Tortugas, 120–132 ft (36.6–40.26 m) (male syntype), Tampa Bay, 42–60 ft (12.81–18.3 m) (female syntype).

TYPES.—Syntypes: ISBN 10.911, 1 male (with spermatophores), 20 mm ML, 1 female, 20 mm ML.

DISTRIBUTION.—Known with certainty only from the type localities (see “Discussion”).

Octopus mercatoris, the Caribbean dwarf octopus, is a small octopus species native to the Caribbean Sea region of the Atlantic Ocean.

Though they are common, Octopus mercatoris are rarely seen.

The Caribbean dwarf octopus is mainly nocturnal, hunting by night and staying in a cave during the day. While most octopuses are cannibalistic, O. mercatoris is less cannibalistic than other species, and is sometimes found in small groups under rocks. They eat crabs, shrimps, and small fish.

This species has an average lifespan of 8–10 months. Because their eggs are large, they are sometimes kept and bred as pets.