Octopus (genus)

About: Octopus (genus) is a research topic. Over the lifetime, 456 publications have been published within this topic receiving 7941 citations.

Personalities of octopuses (Octopus rubescens)

Abstract: Large individual differences are commonly found in the behavior of octopuses, even in standardized situations Octopus rubescens (n = 44) were tested in 3 situations (alerting, threat, and feeding) to quantify this variation A factor analysis of resulting behaviors isolated 3 orthogonal dimensions of their variability, Activity, Reactivity, and Avoidance, which accounted for 45% of the variance The similarity of these factors to dimensions of personality in humans and individual differences in animals suggests there may be commonalities in such variation across phyla

Crypsis, conspicuousness, mimicry and polyphenism as antipredator defences of foraging octopuses on Indo-Pacific coral reefs, with a method of quantifying crypsis from video tapes

Abstract: We tested the hypothesis that soft-bodied octopuses, which spend most of their lives in dens, remain highly cryptic as their primary defence against predation while they forage. We videotaped foraging octopuses on two widely dispersed Pacific coral reefs and developed a rigorous method to analyse the degree of crypsis from videotapes. Five ranks were assigned (two of «highly cryptic», one of «moderately cryptic», and two of «conspicuous») to assess each octopus's body pattern match to its background, using the criteria of brightness, colour, shape and skin patterning. The data do not support the hypothesis. In Tahiti, octopuses were highly cryptic only 54%, moderately cryptic 24% and conspicuous 22% of the time. In Palau, the respective calculations were 31%, 19% and 50%. A major feature of their behaviour was their remarkable ability to instantly change their body pattern, or phenotype, by direct neural control of the skin. Six chronic and nine acute categories of body patterns were observed. On average, octopuses changed their phenotype 2.95 times/minute, or 177 times per hour, based upon 7.5 hours of videotaped foraging. This rapid neurally controlled polyphenism was used most often to adjust their appearance as they foraged slowly across highly diverse substrates, thus implementing appropriate mechanisms of crypsis over each (e.g. general background resemblance, deceptive resemblance, disruptive coloration). However, when crawling rapidly, or swimming for short distances, octopuses often engaged a second antipredator tactic that was conspicuous: mimicking fishes or showing bold disruptive patterns that rendered them visibly different from an octopus. Nevertheless, sometimes they were simply conspicuous even when moving slowly, particularly in Palau, where the octopuses were larger, there was a high degree of mating, and fewer signs of predation were evident. The results suggest that, while foraging, the overall strategy is to use polyphenism to produce «apparent rarity» of any single phenotype (or search image) through mechanisms of crypsis, conspicuousness and mimicry, all of which are guided by keen vision in this marine invertebrate.

Understanding octopus growth: patterns, variability and physiology

Abstract: Octopuses are generally characterised by rapid non-asymptotic growth, with high individual variability. However, in situ octopus growth is not well understood. The lack of an ageing method has resulted in the majority of our understanding of octopus growth coming from laboratory studies. Despite not being applicable to cephalopods, Modal Progression Analysis (MPA) of length-frequency data is the most common method for examining in situ octopus growth. Recently, counting growth increments in beaks and vestigial shells, and quantifying lipofuscin in brain tissue, have all shown promise for the ageing octopus. Octopuses generally demonstrate two-phase growth in the laboratory, with physiological changes possibly associated with the switch between an initial rapid exponential phase and a slower power growth phase. Temperature and food ration and quality are key factors influencing the initial growth phase. Temperature, however, does not appear to affect the second phase in any consistent way, perhaps because maturity stage can influence the growth response. There may be basic differences in the mechanisms of octopus muscle growth compared with that of other cephalopods. Furthermore, higher relative maintenance energy expenditure, along with the low energy content of their prey, may account for the relatively slow growth of deep-sea octopuses compared to littoral species.