File:American malacological bulletin (1988) (18156571735).jpg

Title: American malacological bulletin
Identifier: americanmal6719881990amer (find matches)
Year: 1983 (1980s)
Authors: American Malacological Union
Subjects: Mollusks; Mollusks
Publisher: (Hattiesburg, Miss. ?) : (American Malacological Union)
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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HANLON AND WOLTERDING: OCTOPUS BRIAREUS 37 same tank with an octopus (Fig. 48). The former instance was observed 51 times; however, in two instances the opposite reaction occurred - the dark side was away from the stimulus. In one instance when a large crab was put in the tank, the octopus showed the chromatic components of Deimatic toward the crab, while showing Uniform Darkening on the other side. Six behavioral maneuvers are noteworthy. The Parachute Attack (Figs. 49, 50) is associated with foraging and feeding. Sinel (1906) first described this motor action pattern in which the octopus "rises above its victim, and with ten- tacles so out-stretched that the web that joins them part of their length forms a parachute, it descends like a cloud on its victim." The general body pattern is Dark hood and white arms with smooth skin. These chromatic and textural com- ponents of the pattern appear just when the octopus has posi- tioned itself above the prey and is beginning to descend upon it. Upon descent, the arms and interbrachial web are spread rapidly in parachute fashion, and the octopus settles on the prey and entangles it; the octopuses then immediately went to Uniform Darkening. Several variations were observed (Fig. 23; Hanlon, unpub. field data). In the Pincer Feeding Approach (Fig. 45) the octopus is in a brown Uniform Light Phase, often papillate (Comp. 21). This maneuver is used to seize prey. The second pair of arms curve forward during the approach, and the fourth pair ex- tend forward from underneath. The mantle is distended (Comp. 31) while the octopus holds its breath and moves toward the prey. The prey is grabbed in one motion as the pincer (arms 2) is closed and the fourth pair of arms shoots forward. Side Arm Attack is used when prey are close. The arms on the side toward the prey coil back, with the suckers out- ward. Three or four arms extend rapidly above the prey then grasp it and pull it into the web. The body pattern is usually Uniform Darkening with Coarse skin. During countershaded swimming in a backward direc- tion (Fig. 42) the dorsal body surface is in brown Uniform Light Phase while the ventral surface is pale. The skin texture is coarse (Comp. 20) and iridescence is usually present from the reflecting cells. This pattern provides the necessary com- ponents for effective countershading of a swimming organism (Cott, 1940). Mating behavior and copulation (Figs. 51-55) were observed and three postures were noted: (a) the male most commonly sat atop the female with his arms and interbrachial web covering the female's mantle and head, and (b) occa- sionally the female rotated around from her posture described in (a) until the oral surfaces of her suckers were against the oral surfaces of the male's suckers, (c) the male and female sat about 10 cm apart while the male extended his hec- tocotylized arm toward the female. During copulation the male's hectocotylus was inserted into the female's mantle cavi- ty. Coloration and skin texture were variable. Brown Uniform Light Phase and Chronic General Mottle were the commonest patterns. During two matings the males turned pale white and showed Dark hood (Comp. 15) for short periods. Iridescence on the skin was common in all patterns. Three Cleaning Maneuvers were observed. Commonly an octopus would shed the sucker discs by twirling its arms against the body and blowing them away with jets of water. A second maneuver was performed by females after mating; they would rapidly move the arms inside and on the outside of the mantle. Finally, females cleaned eggs in their lair by continually grooming the egg capsules with their arm tips. ONTOGENY OF PATTERNING Figure 56 gives the times of appearance of the com- ponents, patterns and maneuvers of Octopus briareus cultured in the laboratory. At hatching, there are no iridophores or leucophores evident in the skin (they begin to appear at two
Text Appearing After Image:
Fig. 39. Diagrammatic representation of: A - Head bar, B - Transverse mantle bar, C - Prominent mantle papillae. Two prominent eye papillae are also indicated. Fig. 40. Protective posture. Fig. 41. Deimatic pat- tern. Fig. 42. Backwards swimming. Fig. 43. Backward medusoid swimming. Fig. 44. Forward swimming. Fig. 45. Pincer Feeding Ap- proach to a small crab. Fig. 46. The acute pattern Passing Cloud being shown unilaterally on the right. Stippled areas indicate suc- cessive waves of chromatophore expansion.

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