The rest of the body grows faster than the eyes, which therefore shrink in proportion to the body, as in human children. Although still used for sighting prey, predators, and conspecifics, the eyes will no longer have to be able to see underneath the body when the adult octopus is sitting on the substrate, or sea bottom.
The arms grow longer. Common octopus hatchlings have arms 37 percent as long as the mantle, but at settlement, the arms are 91 percent of the mantle length and are still short of the up to 400 percent of mantle length at adulthood. Benthic adult octopuses use their much longer arms in different ways from the paralarvae. The arms are used for probing under rocks, throwing arms in parachutelike webovers in prey capture, for defense, and in mating.
In a quick transformation just before settling, the maturing paralarvae grow more chromatophores and suckers on their arms, compared to hatchlings having only a couple of working chromatophores and a couple of suckers per arm. Adult octopuses live in a much more complex and varied environment than the paralarvae do, and they have to develop skin patterns and papillae for camouflaging, and suckers for manipulating the environment and catching prey. Sigurd von Boletzky (1987b) suggested a further transition of the hatchlings, their brain size. The brachial lobe, the brain area that controls the arms, enlarges, and there may be changes in the memory area of the brain, the vertical lobe, which helps the adult octopus to adapt to changing environments, to capture various prey animals, and to escape from different predators.
Another change from the planktonic to the benthic mode of life takes place in the octopusâs cardiopulmonary system. Since planktonic paralarvae swim constantly, using their water jets as a squid does, they must get oxygen out of the water at the same time as they are swimming. Therefore, the water jet is used for locomotion as well as for respiration. Benthic octopus adults are rather poor swimmers: human scuba divers can frequently keep up with or even pass them. Martin Wells and his students (1978) showed one reason for their poor swimming: an adult octopus goes into temporary cardiac arrest and oxygen debt while swimmingâthe three hearts literally stop beating. After a major swim, the octopus needs to rest a while and âcatch its breath.â In addition, the pigment in the blood of theoctopus is the oxygen-binding hemocyanin, which is less efficient than our hemoglobin. But to date, no one has measured and reported the cardiorespiratory efficiency of paralarval octopuses.
We scientists know little about the important transition from a pelagic to benthic life for octopuses. Itâs a big ocean out there, the paralarvae are still tiny, and only when someone finds them by accident at the right time do we gain any insight into the process. Maybe as they get bigger and heavier, they sink. Maybe as the brain develops, different areas mature and dictate bottom-seeking behavior rather than planktonic behavior.
The paralarvae that are ready to settle and take up a benthic life have to be changed both physically and mentally from their life in the plankton. Species of octopus paralarvae have been studied in groups. Red octopus paralarvae have been observed from an ROV (remotely operated underwater vehicle) at a depth of 500 ft. (150 m), hovering in mid water off Los Angeles in the Catalina Channel. Since the observed paralarvae were far below the plankton layer, they had probably achieved the right size for settlement and were on their way to the bottom, gradually drifting down en masse. Many adults were seen on the bottom at this location, and thousands of these paralarvae were seen together in a loose group. Based on the results of rearing experiments in the laboratory, the paralarval size may be the most important factor in determining whether an octopus is ready to settle or not. It is possible that these red octopuses were the
The arms grow longer. Common octopus hatchlings have arms 37 percent as long as the mantle, but at settlement, the arms are 91 percent of the mantle length and are still short of the up to 400 percent of mantle length at adulthood. Benthic adult octopuses use their much longer arms in different ways from the paralarvae. The arms are used for probing under rocks, throwing arms in parachutelike webovers in prey capture, for defense, and in mating.
In a quick transformation just before settling, the maturing paralarvae grow more chromatophores and suckers on their arms, compared to hatchlings having only a couple of working chromatophores and a couple of suckers per arm. Adult octopuses live in a much more complex and varied environment than the paralarvae do, and they have to develop skin patterns and papillae for camouflaging, and suckers for manipulating the environment and catching prey. Sigurd von Boletzky (1987b) suggested a further transition of the hatchlings, their brain size. The brachial lobe, the brain area that controls the arms, enlarges, and there may be changes in the memory area of the brain, the vertical lobe, which helps the adult octopus to adapt to changing environments, to capture various prey animals, and to escape from different predators.
Another change from the planktonic to the benthic mode of life takes place in the octopusâs cardiopulmonary system. Since planktonic paralarvae swim constantly, using their water jets as a squid does, they must get oxygen out of the water at the same time as they are swimming. Therefore, the water jet is used for locomotion as well as for respiration. Benthic octopus adults are rather poor swimmers: human scuba divers can frequently keep up with or even pass them. Martin Wells and his students (1978) showed one reason for their poor swimming: an adult octopus goes into temporary cardiac arrest and oxygen debt while swimmingâthe three hearts literally stop beating. After a major swim, the octopus needs to rest a while and âcatch its breath.â In addition, the pigment in the blood of theoctopus is the oxygen-binding hemocyanin, which is less efficient than our hemoglobin. But to date, no one has measured and reported the cardiorespiratory efficiency of paralarval octopuses.
We scientists know little about the important transition from a pelagic to benthic life for octopuses. Itâs a big ocean out there, the paralarvae are still tiny, and only when someone finds them by accident at the right time do we gain any insight into the process. Maybe as they get bigger and heavier, they sink. Maybe as the brain develops, different areas mature and dictate bottom-seeking behavior rather than planktonic behavior.
The paralarvae that are ready to settle and take up a benthic life have to be changed both physically and mentally from their life in the plankton. Species of octopus paralarvae have been studied in groups. Red octopus paralarvae have been observed from an ROV (remotely operated underwater vehicle) at a depth of 500 ft. (150 m), hovering in mid water off Los Angeles in the Catalina Channel. Since the observed paralarvae were far below the plankton layer, they had probably achieved the right size for settlement and were on their way to the bottom, gradually drifting down en masse. Many adults were seen on the bottom at this location, and thousands of these paralarvae were seen together in a loose group. Based on the results of rearing experiments in the laboratory, the paralarval size may be the most important factor in determining whether an octopus is ready to settle or not. It is possible that these red octopuses were the
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