File:American malacological bulletin (1988) (18153028502).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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30 AMER. MALAC. BULL. 7(1) (1989)
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studies, although two animals lived particularly long: one male lived 500 days in open-system culture and another male lived 492 days in closed-system culture. Both animals attained only a moderate size, and both had almost certainly mated in the time period of 190 to 200 days. In the vast majority of natural deaths males and females underwent a two to four week period of deterioration, during which feeding was sporadic and the skin, arms and internal organs degenerated (Fig. 17). In most males, this deterioration occurred at varying periods after mating and growth to a large size. In females it occurred after egg laying and brooding. The most obvious manifesta- tion of senescence was that the skin tone degenerated and the skin became gray and the papillae were inoperable. The mechanisms of death are unknown but are probably linked to the hormone system that regulates sexual maturation (Van Heukelem, 1979; O'Dor and Wells, 1987). Rearing studies from different brood stocks in different years show consistently that the life span ranges from ten to 17 months; field data indicate the same (Hanlon, 1983). Efforts to increase longevity by feeding brooding females or rearing octopuses at constantly warm temperatures with high food availability result in the same mortality as brooding females without food or octopuses reared in open systems with normal temperature fluctuations. BEHAVIOR The importance of behavior in describing and understanding all activities of octopuses cannot be over stressed. Octopuses are generally solitary until they mate. Their soft bodies require that they avoid predator detection during their daily foraging for food. They accomplish this by camouflage, by operating mainly in the dark, by taking ad- vantage of bottom relief for protection and, at last resort, by threatening predators with specific body patterns or by eject- ing ink and escaping. Octopus behavior is complex. The central nervous system (CNS) is large and organized into many discrete lobes (Young, 1971). Their vision is superb (Messenger, 1981) and they have demonstrated abilities of learning and memory (Wells, 1978). In Octopus briareus these attributes are used to compete in the high-density habitats associated with Carib- bean coral reefs (Hanlon, unpub. data). Predators on oc- topuses are fishes and mammals (e.g. Randall, 1967; Packard, 1972). We attempt in this section to describe and explain the main facets of behavior of Octopus briareus. The data are based mainly upon laboratory observations (over 1400 hours) but have been corroborated with field observations throughout the Caribbean Sea (Hanlon, unpub. data). Laboratory obser- vations were made mostly (> 60%) during the day, with numerous observations made at night with the lights on, and a few at night with a 30-watt red light. Distinctive body pat- terns and behaviors of O. briareus that are useful in species identification have been compared by Hanlon (1988). MORPHOLOGY OF BODY PATTERNS Anyone who has observed a live octopus takes im- mediate notice of the changing color and texture of the skin as well as the soft, supple body that can assume a variety of shapes. The appearance of an octopus at any given mo- ment is known as a body pattern, and its expression is mediated by the remarkably well-developed eyes, CNS and skin. The octopus is almost certainly color blind (Messenger, 1981), but it can blend with its background by adjusting the expansion of its numerous, neurally controlled chromatophore organs in the dermis of the skin. The chromatophore system is regulated primarily by visual input to the eye. Together, the eyes and skin constitute a system for camouflage that matches luminance (Messenger, 1979). Below the chromatophores in the dermis is a system of broad-band reflecting cells (i.e. iridophores, reflector cells and

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