Slow swimming, fast strikes: effects of feeding behavior on scaling of anaerobic metabolism in epipelagic squid

Many pelagic fishes engage prey at high speeds supported by high metabolic rates and anaerobic metabolic capacity. Epipelagic squids are reported to have among the highest metabolic rates in the oceans as a result of demanding foraging strategies and the use of jet propulsion, which is inherently inefficient. This study examined enzymatic proxies of anaerobic metabolism in two species of pelagic squid, Dosidicus gigas and Doryteuthis pealeii (Lesueur 1821), over a size range of six orders of magnitude. We hypothesized that activity of the anaerobically poised enzymes would be high and increase with size as in ecologically similar fishes. In contrast, we demonstrate that anaerobic metabolic capacity in these organisms scales negatively with body mass. We explored several cephalopod-specific traits, such as the use of tentacles to capture prey, body morphology and reduced relative prey size of adult squids, that may create a diminished reliance on anaerobically fueled burst activity during prey capture in large animals

The Jumbo Squid,\u3cem\u3e Dosidicus gigas \u3c/em\u3e (Ommastrephidae), Living in Oxygen Minimum Zones I: Oxygen Consumption Rates and Critical Oxygen Partial Pressures

Dosidicus gigas is a large, metabolically active, epipelagic squid known to undertake diel vertical migrations across a large temperature and oxygen gradient in the Eastern Pacific. Hypoxia is known to cause metabolic suppression in D. gigas. However, the precise oxygen level at which metabolic suppression sets in is unknown. Here we describe a novel ship-board swim tunnel respirometer that was used to measure metabolic rates and critical oxygen partial pressures (Pcrit) for adult squids (2–7 kg). Metabolic rate measurements were validated by comparison to the activity of the Krebs cycle enzyme, citrate synthase, in mantle muscle tissue (2–17 kg). We recorded a mean routine metabolic rate of 5.91 μmol g−1 h−1 at 10 °C and 12.62 μmol g−1 h−1 at 20 °C. A temperature coefficient, Q10, of 2.1 was calculated. D. gigas had Pcrits of 1.6 and 3.8 kPa at 10 and 20 °C, respectively. Oxygen consumption rate (MO2) varied with body mass (M) according to MO2=11.57 M−0.12±0.03 at 10 °C. Citrate synthase activity varied with body mass according to Y=9.32 M−0.19±0.02

Slow Swimming, Fast strikes: Effects of Feeding Behavior on Acaling of Anaerobic Metabolism in Epipelagic Squid

Many pelagic fishes engage prey at high speeds supported by high metabolic rates and anaerobic metabolic capacity. Epipelagic squids are reported to have among the highest metabolic rates in the oceans as a result of demanding foraging strategies and the use of jet propulsion, which is inherently inefficient. This study examined enzymatic proxies of anaerobic metabolism in two species of pelagic squid, Dosidicus gigas and Doryteuthis pealeii (Lesueur 1821), over a size range of six orders of magnitude. We hypothesized that activity of the anaerobically poised enzymes would be high and increase with size as in ecologically similar fishes. In contrast, we demonstrate that anaerobic metabolic capacity in these organisms scales negatively with body mass. We explored several cephalopod-specific traits, such as the use of tentacles to capture prey, body morphology and reduced relative prey size of adult squids, that may create a diminished reliance on anaerobically fueled burst activity during prey capture in large animals

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ABSTRACT Many pelagic fishes engage prey at high speeds supported by high metabolic rates and anaerobic metabolic capacity. Epipelagic squids are reported to have among the highest metabolic rates in the oceans as a result of demanding foraging strategies and the use of jet propulsion, which is inherently inefficient. This study examined enzymatic proxies of anaerobic metabolism in two species of pelagic squid, Dosidicus gigas and Doryteuthis pealeii (Lesueur 1821), over a size range of six orders of magnitude. We hypothesized that activity of the anaerobically poised enzymes would be high and increase with size as in ecologically similar fishes. In contrast, we demonstrate that anaerobic metabolic capacity in these organisms scales negatively with body mass. We explored several cephalopod-specific traits, such as the use of tentacles to capture prey, body morphology and reduced relative prey size of adult squids, that may create a diminished reliance on anaerobically fueled burst activity during prey capture in large animals

Ecophysiological Influence on Scaling of Aerobic and Anaerobic Metabolism of Pelagic Gonatid Squids

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 μmol O2 g−1 h−1 at 5°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\u27 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\u27s ontogenetic vertical migration

An Ethogram of the Humboldt Squid \u3cem\u3e Dosidicus gigas \u3c/em\u3e Orbigny (1835) as Observed from Remotely Operated Vehicles

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

Natural Egg Mass Deposition by the Humboldt Squid (\u3cem\u3eDosidicus gigas\u3c/em\u3e) in the Gulf of California and Characteristics of Hatchlings and Paralarvae

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 (25–27°C) 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