Amphioctopus ovulum (Sasaki 1917)

Octopus ovulum (Sasaki, 1917)

DIAGNOSIS.—Animal small to medium-sized (24–45 mm ML). Mantle ovoid, broadest medially (MWI 50–74); neck slightly constricted; head relatively broad (HWI 36–53); eyes moderately prominent. Funnel organ W-shaped, medial and lateral limbs narrow, subequal in length. Arms short to moderate (ALI 60.7–75.6), slender, tapering to attenuate tips, arms subequal in length but most often with arm formula IV > III > II > I. Suckers moderately elevated, proximal 5 to 6 suckers on each arm uniserial, suckers biserial distally. Right arm III of males hectocotylized (HALI 150.0–183.8), shorter than fellow (FAI 69.3–80.8); ligula small (LLI 5.8–6.3); calamus minute, conical; HASC 118–140. Web depth moderate (WDI 21.6–26.8), web formula typically C = D > B = E > A, sector A very shallow. Gill lamellae 7 to 8. Mature ovarian eggs small, capsule to 3 mm long. Penis slender, with swollen, recurved diverticulum, collectively shaped like numeral “6.” Spermatophores long (SPL 49–61 mm), slender; sperm mass with 230–270 coils. Radula with penticuspid rachidian of unknown seriation. Dorsal surfaces of mantle, head, and arms densely covered with uniform papillae, in places forming longitudinal ridges. Two large supraocular papillae on each side of head, anterior one smaller. Ocellus present below each eye, 4 mm in diameter, consisting of blue to violet irridescent ring surrounding darkened spot. General color in preservation drab with several broad, dark longitudinal stripes on mantle, pale ventrally.

ORIGINAL DESCRIPTION.—Sasaki, 1917:364, as Polypus ovulum.

TYPE LOCALITY.—Western North Pacific Ocean, Japan, Tokyo (fish market); Nagasaki.

TYPES.—Syntypes: ?TNSM, 11 males, 5 females, presumed no longer extant (I. Gleadall, pers. comm.).

DISTRIBUTION.—Japan, Nagasaki and Tokyo.