Description: The functional properties of the haemocyanin ofVampyroteuthis infernalis (Cephalopoda: Vampyromorpha), measured at 5 °C, are reported and discussed in relation to hypoxia. The oxygen affinity of this haemocyanin (P50=0.47−0.55 kPa) is higher than any previously measured for a cephalopod. The high cooperativity (n50=2.20−2.23) and Bohr coefficient (−0.22) suggest a true transport function for this haemocyanin. This high-affinity haemocyanin, in conjunction with moderate gill diffusion capacity, provides a sufficient oxygen gradient from the environment to the blood to support the low routine oxygen consumption rate of V. infernalis.

Description: The metabolic demands of a rare paper nautilus, Argonauta nouryi, in the eastern tropical Pacific (ETP) are evaluated. After adjusting for temperature and size, the rates of oxygen consumption and of aerobic and anaerobic metabolic potential (as evidenced by citrate synthase and octopine dehydrogenase activities, respectively) of A. nouryi were much higher than those in holopelagic octopods that exhibit float-and-wait predation strategies. In fact, the rates were similar to those found in small epipelagic squids and benthic octopods. The critical oxygen partial pressure was 4.9 kPa at 20°C, suggesting that the strong oxygen minimum layer found at intermediate depths in the ETP may constrain the vertical distribution of A. nouryi to the upper few metres of the water column. We also report the occurrence of a chain of shelled females at the surface, in which each animal was attached, as if on the benthos, to the next individual in the chain. Although it may constitute an effective strategy to increase the rates of mate encounter in the vast open ocean, there may be an important ecological trade-off for such behaviour, namely the increase in visibility at the surface with concomitant attraction of predators.

Description: In the last few decades, numerous studies have investigated the impacts of simulated ocean acidification on marine species and communities, particularly those inhabiting dynamic coastal systems. Despite these research efforts, there are many gaps in our understanding, particularly with respect to physiological mechanisms that lead to pathologies. In this review, we trace how carbonate system disturbances propagate from the coastal environment into marine invertebrates and highlight mechanistic links between these disturbances and organism function. We also point toward several processes related to basic invertebrate biology that are severely understudied and prevent an accurate understanding of how carbonate system dynamics influence organismic homeostasis and fitness-related traits. We recommend that significant research effort be directed to studying cellular phenotypes of invertebrates acclimated or adapted to elevated seawater pCO2 using biochemical and physiological methods.

Description: The survival of oceanic organisms in oxygen minimum zones (OMZs) depends on their total oxygen demand and the capacities for oxygen extraction and transport, anaerobic ATP production and metabolic suppression. Anaerobic metabolism and metabolic suppression are required for daytime forays into the most extreme OMZs. Critical oxygen partial pressures are, within a range, evolved to match the minimum oxygen level to which a species is exposed. This fact demands that low oxygen habitats be defined by the biological response to low oxygen rather than by some arbitrary oxygen concentration. A broad comparative analysis of oxygen tolerance facilitates the identification of two oxygen thresholds that may prove useful for policy makers as OMZs expand due to climate change. Between these thresholds, specific physiological adaptations to low oxygen are required of virtually all species. The lower threshold represents a limit to evolved oxygen extraction capacity. Climate change that pushes oxygen concentrations below the lower threshold (∼0.8 kPa) will certainly result in a transition from an ecosystem dominated by a diverse midwater fauna to one dominated by diel migrant biota that must return to surface waters at night. Animal physiology and, in particular, the response of animals to expanding hypoxia, is a critical, but understudied, component of biogeochemical cycles and oceanic ecology. Here, I discuss the definition of hypoxia and critical oxygen levels, review adaptations of animals to OMZs and discuss the capacity for, and prevalence of, metabolic suppression as a response to temporary residence in OMZs and the possible consequences of climate change on OMZ ecology.

Description: The majority of squid families (Teuthoidea: Cephalopoda) exchange sodium for ammonium, creating a low-density fluid that imparts lift for neutral buoyancy. However, previous methods for measuring ammonium did not distinguish between NH4+ and various other amine compounds. The present study, using single column ion chromatography, reassessed the cation concentrations in several midwater cephalopod species. High NH4+ levels were confirmed for histioteuthid, cranchiid, and chiroteuthid and related squids. A strong relationship is reported between ammonium content and body mass in Histioteuthis heteropsis, suggesting a gradual accumulation of ammonium coincident with an ontogenetic migration to greater depths. The bathypelagic squids Bathyteuthis abyssicola and Bathyteuthis berryi, on the other hand, contained very little ammonium but rather contained large quantities of an as yet unidentified cation. The ecological significance of this compound is not yet known. Morphology in Bathyteuthid squids suggests that the unknown cation is contained intracellularly and so, unlike sequestered ammonia, does not diminish the space available for muscle tissue. Accordingly, protein measurements in B. berryi mantle muscle are on par with shallower-living muscular squids, and in situ submersible observations reveal strong locomotory abilities relative to other deep-water squids.

Description: 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.

Description: The rates of metabolism in animals vary tremendously throughout the biosphere. The origins of this variation are a matter of active debate with some scientists highlighting the importance of anatomical or environmental constraints, while others emphasize the diversity of ecological roles that organisms play and the associated energy demands. Here, we analyse metabolic rates in diverse marine taxa, with special emphasis on patterns of metabolic rate across a depth gradient, in an effort to understand the extent and underlying causes of variation. The conclusion from this analysis is that low rates of metabolism, in the deep sea and elsewhere, do not result from resource (e.g. food or oxygen) limitation or from temperature or pressure constraint. While metabolic rates do decline strongly with depth in several important animal groups, for others metabolism in abyssal species proceeds as fast as in ecologically similar shallow-water species at equivalent temperatures. Rather, high metabolic demand follows strong selection for locomotory capacity among visual predators inhabiting well-lit oceanic waters. Relaxation of this selection where visual predation is limited provides an opportunity for reduced energy expenditure. Large-scale metabolic variation in the ocean results from interspecific differences in ecological energy demand.

Description: Aim  One of the most recognized ecological paradigms on earth is the increase in species richness from the poles towards the equator. Here we undertake a comprehensive survey of the latitudinal gradients of species richness (LGSR) of coastal cephalopod fauna in the western (WA) and eastern margins (EA) of the Atlantic Ocean, and test climate and non-climate theories to explain the variation in diversity. Location  The coastal Atlantic Ocean. Methods  The diversity and geographical ranges of coastal cephalopods were investigated by means of an exhaustive survey of the primary literature, reports and on-line data bases. In order to test the productivity, ambient energy and area hypotheses, we investigated the relationship between diversity and net primary production (NPP), sea surface temperature (SST; measure of solar energy input) and continental shelf area, respectively. Results  LGSR of cephalopod molluscs are present at both Atlantic coasts, but are quite distinct from each other. Historical processes (rise of the Central American Isthmus, formation of ‘Mare Lago’ and glaciations) explained much of the shape and the zenith of LGSR. Contemporary climate and non-climate variables also each explained over 83% and 50% of the richness variation in WA and EA, respectively, and the best fitted models accounted for 〉 92% of the variance. By combining latitude with depth a strong Rapoport effect was observed in WA but not in EA. Main conclusions  Besides the evolutionary history, we demonstrate that the contemporary environmental gradients (SST and NPP), shelf area and extent of coral habitat can predict many of the diversity patterns. The longitudinal difference in Rapoport's bathymetric rule is attributed to western fauna specialization to shallow coral reef habitats and greater ecological tolerance of eastern fauna to upwelling ecosystem dynamics. A combined approach of historical biogeography and species–area–energy theories was essential to fully understand broad-scale variation in cephalopod biodiversity.