The jumbo or Humboldt squid, Dosidicus gigas, is an important fisheries resource and a significant participant in regional ecologies as both predator and prey. It is the largest species in the oceanic squid family Ommastrephidae and has the largest known potential fecundity of any cephalopod, yet little is understood about its reproductive biology. We report the first discovery of a naturally deposited egg mass of Dosidicus gigas, as well as the first spawning of eggs in captivity. The egg mass was found in warm water (25 -278C) at a depth of 16 m and was far larger than the egg masses of any squid species previously reported. Eggs were embedded in a watery, gelatinous matrix and were individually surrounded by a unique envelope external to the chorion. This envelope was present in both wild and captive-spawned egg masses, but it was not present in artificially fertilized eggs. The wild egg mass appeared to be resistant to microbial infection, unlike the incomplete and damaged egg masses spawned in captivity, suggesting that the intact egg mass protects the eggs within. Chorion expansion was also more extensive in the wild egg mass. Hatchling behaviours included proboscis extension, chromatophore activity, and a range of swimming speeds that may allow them to exercise some control over their distribution in the wild.
We examined the oxygen consumption rates and activity levels of respiratory enzymes involved in the aerobic (citrate synthase [CS]) and anaerobic (octopine dehydrogenase [ODH]) metabolism of gonatid squids (Gonatus onyx and Gonatus pyrus) as a function of body size. The energy expenditure rates of gonatids (ranging from 2.51 to 8.79 micromol O(2) g(-1) h(-1) at 5 degrees C) are among the highest in Animalia when mass and temperature are taken into account. They reflect the low efficiency of jet propulsion and the animals' active life strategy as diel vertical migrants in the pelagic environment. Both metabolic rate and aerobic muscle potential (CS activity) were size independent across a size range of four orders of magnitude, which may be a result of their unusual body geometric allometry, extensive cutaneous respiration, and decreased energy-saving opportunities at larger sizes. Anaerobic metabolic potential (ODH activity) revealed a shift from positive scaling in juveniles to negative scaling among larger sizes. Juveniles are found in shallow water, where they are more susceptible to visually cued predators and require quicker size-specific escape responses and higher burst swimming capacities. Conversely, adults have reduced requirements for predator/prey interactions in the light-limited deep sea. Anaerobic metabolic scaling reflects an adaptive response to the changing physical and ecological demands across a depth gradient during this species's ontogenetic vertical migration.
Much of the CO 2 released by human activity into the atmosphere is dissolving into the oceans, making them more acidic. In this study we provide the first data on the short-and longterm impacts of ocean acidification on octopuses. We measured routine metabolic rate (RMR) of Octopus rubescens at elevated CO 2 pressure (PCO 2) with no prior acclimation and 1 or 5 wk of acclimation and critical oxygen pressure (P crit) after 5 wk of acclimation. Our results show that with no prior acclimation, octopuses had significantly higher RMRs in 1,500-matm PCO 2 environments than octopuses in 700-or 360-matm environments. However, after both 1 and 5 wk of acclimation there was no significant difference in RMRs between octopuses at differing PCO 2 , indicating that octopuses acclimated rapidly to elevated PCO 2. In octopuses acclimated for 5 wk at 1,500 matm PCO 2 , we observed impaired hypoxia tolerance, as demonstrated by a significantly higher P crit than those acclimated to 700 matm PCO 2. Our findings suggest that O. rubescens experiences shortterm stress in elevated PCO 2 but is able to acclimate over time. However, while this species may be able to acclimate to nearterm ocean acidification, compounding environmental effects of acidification and hypoxia may present a physiological challenge for this species.
Many cephalopods can rapidly change their external appearance to produce multiple body patterns. Body patterns are composed of various components, which can include colouration, bioluminescence, skin texture, posture, and locomotion. Shallow water benthic cephalopods are renowned for their diverse and complex body pattern repertoires, which have been attributed to the complexity of their habitat. Comparatively little is known about the body pattern repertoires of open ocean cephalopods. Here we create an ethogram of body patterns for the pelagic squid, Dosidicus gigas. We used video recordings of squid made in situ via remotely operated vehicles (ROV) to identify body pattern components and to determine the occurrence and duration of these components. We identified 29 chromatic, 15 postural and 6 locomotory components for D. gigas, a repertoire rivalling nearshore cephalopods for diversity. We discuss the possible functional roles of the recorded body patterns in the behavioural ecology of this open ocean species.
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