A multilevel approach to examining cephalopod growth usingOctopus pallidusas a model

Abstract

SUMMARYMany aspects of octopus growth dynamics are poorly understood, particularly in relation to sub-adult or adult growth, muscle fibre dynamics and repro-somatic investment. The growth of 5month old Octopus pallidus cultured in the laboratory was investigated under three temperature regimes over a 12week period: seasonally increasing temperatures (14-18°C); seasonally decreasing temperatures (18-14°C); and a constant temperature mid-way between seasonal peaks (16°C). Differences in somatic growth at the whole-animal level, muscle tissue structure and rate of gonad development were investigated. Continuous exponential growth was observed, both at a group and at an individual level, and there was no detectable effect of temperature on whole-animal growth rate. Juvenile growth rate (from 1 to 156days) was also monitored prior to the controlled experiment; exponential growth was observed, but at a significantly faster rate than in the older experimental animals, suggesting that O. pallidus exhibit a double-exponential two-phase growth pattern. There was considerable variability in size-at-age even between individuals growing under identical thermal regimes. Animals exposed to seasonally decreasing temperatures exhibited a higher rate of gonad development compared with animals exposed to increasing temperatures; however, this did not coincide with a detectable decline in somatic growth rate or mantle condition. The ongoing production of new mitochondria-poor and mitochondria-rich muscle fibres (hyperplasia) was observed, indicated by a decreased or stable mean muscle fibre diameter concurrent with an increase in whole-body size. Animals from both seasonal temperature regimes demonstrated higher rates of new mitochondria-rich fibre generation relative to those from the constant temperature regime, but this difference was not reflected in a difference in growth rate at the whole-body level. This is the first study to record ongoing hyperplasia in the muscle tissue of an octopus species, and provides further insight into the complex growth dynamics of octopus.

Effect of temperature increase on the embryonic development of Patagonian red octopusEnteroctopus megalocyathusin controlled culture

“…The high values of Q 10 observed indicate that E. megalocyathus embryos showed a high sensitivity to temperature, just as it had been observed in the embryos of O. mimus , probably because the embryos have limited ability to regulate their basal metabolism. Clarke and Fraser (2004) suggested that basal metabolism is particularly sensitive to temperature due to the energy demands of ectotherms to maintain basic functions, while Semmens, Doubleday, Hoyle and Pecl (2011) highlighted the fact that octopuses respond to temperature changes abruptly.…”

Effect of maternal temperature stress before spawning over the energetic balance of Octopus maya juveniles exposed to a gradual temperature change

“…In cephalopods, respiratory metabolism has a central role in the survival and physiological performance, due to the high demand of energy that those organisms have for growth (Petza et al, 2011;Semmens et al, 2011) and locomotion activity (Wells and Clark, 1996). Temperature is the main environmental factor that controls the respiratory metabolism in cephalopods; therefore, it is considered the most important factor controlling the energy turnover and the fitness of cephalopods (Mangold, 1983;Farías et al, 2009;Noyola et al, 2013b).…”

Octopus life history relative to age, in a multi-geared developmental fishery

“…Where the total weight of females rose sharply reaching maximum sizes (4000 g) far exceeding those of the males (∼2500 g) for animals +1 year. Increased investment in reproductive development significantly contributed to this additional weight in mature individuals, as demonstrated by GSI, thus supporting the existence of two-phased growth (Mangold, 1983;Semmens et al, 2011). However, a potential limitation on the suitability of SIA for brooding females, is the preliminary observation by Leporati and Hart (2015) that females may cease forming stylet increments at the onset of spawning.…”