Amphioctopus polyzenia (Gray 1849)

Octopus polyzenia Gray, 1849

DIAGNOSIS.—Animals small (to 130 mm TL; to 38 mm ML). Mantle ovoid (MWI females 58–69–78, males 50–69–85); head wide but narrower than mantle (HWI 41–50–63), demarked from mantle by moderate constriction; eyes large, projecting above surface of head. Funnel large, stout, bluntly tapered (FLI 34–40–51); funnel organ W-shaped, limbs thick, outer limbs slightly shorter than median limbs. Arms long (ALI females 236–309, males 201–252), robust, tapering to fine tips. Arm lengths unequal, arm order usually IV = III > II > I or IV > 111 > II > 1. Suckers raised above arm surface, of moderate size (SI females 8–9–13, males 10–12–14), 14th to 16th suckers usually largest, enlarged on all arms of mature males. Right arm III of males hectocotylized, shorter than opposite arm (HAMI 152–177–195; OAI 77); ligula conical, small (LLI 5–6–7); ligula groove shallow, with raised, longitudinal midrib; calamus long, pointed (CLI 41–51–69); hectocotylized arm with 45–52 suckers. Web moderately deep (WDI 26–31–39), web formula D > C = E > B > A or D = E > C > B > A. Radula with A4 symmetrical seriation of rachidian. Ink sac present. Gill lamellae 6 to 7 per outer demibranch. Mature female with large eggs (capsule ~8 mm long, 3 mm wide) joined by fine central stalk, attached to substrate in festoons. Penis moderately long (PLI 14–17), with single-coiled diverticulum; spermatophores relatively short (SpLI 34), moderately wide (SpWI 6), with large, coiled sperm reservoir (SpRI 56).

Integumental sculpture consists of pattern of fine, rounded epidermal tubercles. Tubercles present on dorsal and ventral surfaces of mantle, brachial crown, and arms, extending onto arm faces and oral surface of dorsal and dorsolateral webs; tubercles absent from ventral arm crown. Longitudinal, raised skin ridges present on dorsal mantle, with largest forming diamond arrangement; additional shorter ridges present on dorsal and lateral mantle. Arborescent papillae obvious in ocular region, with 1 large and 2 small supraocular papillae. Lateral integumentary ridge or fold around mantle circumference absent. Color of live animals unknown. Color of animals preserved in ethyl alcohol generally cream to pink brown with dark mottling and light patches on dorsum. Dorsal mantle pattern of light-colored, oval patches containing raised skin ridges, central 4 arranged in diamond shape forming faint crucifix pattern. Dark brown, rectangular block between and slightly behind eyes in some specimens. Frontal white spot, consisting of 2 light spots, on dorsal arm crown below midpoint of eyes; anterior cream-colored spot containing primary papillae; posterior spot pink to peach. Dark brown to black ocellus on either side of arm crown between bases of arms II and III (~ 0.1 times ML), containing small, iridescent blue ring. Dark ocellus can fade in preserved specimens leaving only iridescent ring visible. Dark transverse bars on all arms, widely spaced with 3 to 4 suckers between each bar.

ORIGINAL DESCRIPTION.—Gray, 1849:13.

TYPE LOCALITY.—Australia, Northern Territory, Port Essington (11°16′S, 132°09′E), no depth data.

TYPE.—Holotype: BMNH 1845.5.14.78, male, 12 mm ML. Specimen “not in very good condition” (Robson, 1929:73).

DISTRIBUTION AND BIOLOGY.—Endemic to tropical waters of northern Australia, from Dampier Archipelago, Western Australia, to central Queensland. A species living in shallow coastal waters, on open substrates of sand or mud, at depths of 1–20 m (Norman, 1993a). Biology unknown.