File:American malacological bulletin (1988) (18130095286).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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Fig. 47. Chronic General Mottle in a laboratory reared adult reared in isolation. Note Flattened Head (29). Fig. 48. The Passing Cloud pattern being shown unilaterally (on the animal's right side) in an animal approximately 200 days old. Fig. 49. The Parachute Attack in a young oc- topus (about 60 days old). Fig. 50. The Parachute Attack maneuver onto a crab in an animal 144 days old; note Dark hood (Comp. 15). weeks) and the chromatophores are relatively sparse. Therefore, patterning is limited for the first two months or so. During this early period the Extrategumental chromatophores are important, as are the Reflective eyeballs and Branchial hearts. Newly hatched Octopus briareus appear to be restricted to four general body patterns. The first is the chronic pattern Uniform Light Phase in which the skin is translucent white, the eyes are prominent and silvery-blue, the visceral organs appear pinkish through the mantle, and the dark Branchial hearts show through the mantle and produce the effect of two false eyespots at the posterior end of the mantle. After ap- proximately four weeks the mantle becomes thicker and more opaque, and Uniform Light Phase becomes more adult-like in appearance because the internal organs are not obvious. This pattern is common when young animals rest on a light or white object and when they are swimming. The second chronic pattern is characterized by the full expansion of the Extrategumental chromatophores on the arms and viscera (Figs. 4, 25) while most or all of the other chromatophores on the body are retracted. This pattern was most often seen when the animal was sitting on a dark ob- ject or when the octopus was moderately excited upon sighting a moving object nearby. The third common pattern was Uniform Darkening in which all chromatophores were expanded maximally. The overall color was dark brown and the pattern rarely lasted beyond two minutes. This pattern was observed when the oc- topus was very excited, as when attacking a crab or when startled by a nearby object. The fourth pattern observed in animals younger than three weeks was unilateral Uniform Darkening. The dark pat- terning was always seen on the side of the octopus facing another octopus or a larger crab that had been put in as a prey organism. Some gradual changes take place between days 20 and 50. The number and density of chromatophores begins to increase and papillae develop at about day 30. The first to appear are single large papillae above each eye. By day 30 some iridophore cells first appear on the mantle as small (0.5 -1.0 mm) isolated patches of reflective silvery-blue (Figs. 27-29). They then soon appear over the heads and arms, and groups of them begin to form the chromatic components Head bar, Transverse mantle bar and White transverse arm bands. An example of a small animal just at this transition can be seen in figure 29. A modified form of Passing Cloud has been

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