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This transparent, gelatinous and nearly colourless octopod is small (90 mm ML, Nesis, 1982/7) and has the body foreshortened in the anterior-posterior axis. The arms bear one row of suckers proximally but two rows near the arm tips; the web is deep. The mantle is fused to the posterior end of the funnel leaving three openings into the mantle cavity. One is the funnel orifice and the other two are the remnants of the mantle aperature located lateral to the funnel. The eyes are in a dorsal position, tubular in shape and with their bases in contact; however, the optical axes diverge by 70° (see photograph below). This is the only octopod known to have tubular eyes. The stomach is reported to be anterior to the digestive gland but actually lies on the dorsal surface of the gland. The third right arm is hectocotylized. Young Amphitretus probably occupy upper mesopelagic depths during the day, judging by their morphology and a few captures. Little is known of the life history and biology of this unusual octopod.
Figure. Dorsal and side views of A. pelagicus photographed in a small ship-board aquarium off Hawaii. The octopod is crawling on the side of the tank (from Young et al., 1999).
An incirrate ...
- with tubular eyes.
- with funnel fused ventrally to mantle.