Dosidicus gigas (jumbo or Humboldt squid) is a semelparous, major predator of the eastern Pacific that is ecologically and commercially important. In the Gulf of California, these animals mature at large size (>55 cm mantle length) in 1–1.5 years and have supported a major commercial fishery in the Guaymas Basin during the last 20 years. An El Niño event in 2009–2010, was accompanied by a collapse of this fishery, and squid in the region showed major changes in the distribution and life‐history strategy. Large squid abandoned seasonal coastal‐shelf habitats in 2010 and instead were found in the Salsipuedes Basin to the north, an area buffered from the effects of El Niño by tidal upwelling and a well‐mixed water column. The commercial fishery also relocated to this region. Although large squid were not found in the Guaymas Basin from 2010 to 2012, small squid were abundant and matured at an unusually small mantle‐length (<30 cm) and young age (approximately 6 months). Juvenile squid thus appeared to respond to El Niño with an alternative life‐history trajectory in which gigantism and high fecundity in normally productive coastal‐shelf habitats were traded for accelerated reproduction at small size in an offshore environment. Both small and large mature squid, were present in the Salsipuedes Basin during 2011, indicating that both life‐ history strategies can coexist. Hydro‐acoustic data, reveal that squid biomass in this study area nearly doubled between 2010 and 2011, primarily due to a large increase in small squid that were not susceptible to the fishery. Such a climate‐driven switch in size‐at‐maturity may allow D. gigas to rapidly adapt to and cope with El Niño. This ability is likely to be an important factor in conjunction with longerterm climate‐change and the potential ecological impacts of this invasive predator on marine ecosystems.

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Vampire squid (Vampyroteuthis infernalis) are considered phylogenetic relics with cephalopod features of both octopods and squids. They lack feeding tentacles, but in addition to their eight arms, they have two retractile filaments, the exact functions of which have puzzled scientists for years. We present the results of investigations on the feeding ecology and behaviour of Vampyroteuthis, which include extensive in situ, deep-sea video recordings from MBARI's remotely operated vehicles (ROVs), laboratory feeding experiments, diet studies and morphological examinations of the retractile filaments, the arm suckers and cirri. Vampire squid were found to feed on detrital matter of various sizes, from small particles to larger marine aggregates. Ingested items included the remains of gelatinous zooplankton, discarded larvacean houses, crustacean remains, diatoms and faecal pellets. Both ROV observations and laboratory experiments led to the conclusion that vampire squid use their retractile filaments for the capture of food, supporting the hypothesis that the filaments are homologous to cephalopod arms. Vampyroteuthis' feeding behaviour is unlike any other cephalopod, and reveals a unique adaptation that allows these animals to spend most of their life at depths where oxygen concentrations are very low, but where predators are few and typical cephalopod food is scarce.

Gelatinous zooplankton hold key functions in the ocean and have been shown to significantly influence the transport of organic carbon to the deep sea. We discovered a gelatinous, flux‐feeding polychaete of the genus Poeobius in very high abundances in a mesoscale eddy in the tropical Atlantic Ocean, where it co‐occurred with extremely low particle concentrations. Subsequent analysis of an extensive in situ imaging dataset revealed that Poeobius sp. occurred sporadically between 5°S–20°N and 16°W–46°W in the upper 1000 m. Abundances were significantly elevated and the depth distribution compressed in anticyclonic modewater eddies (ACMEs). In two ACMEs, high Poeobius sp. abundances were associated with strongly reduced particle concentrations and fluxes in the layers directly below the polychaete. We discuss possible reasons for the elevated abundances of Poeobius sp. in ACMEs and provide estimations showing that a single zooplankton species can completely intercept the downward particle flux by feeding with their mucous nets, thereby substantially altering the biogeochemical setting within the eddy.

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Background The giant squid (Architeuthis dux; Steenstrup, 1857) is an enigmatic giant mollusc with a circumglobal distribution in the deep ocean, except in the high Arctic and Antarctic waters. The elusiveness of the species makes it difficult to study. Thus, having a genome assembled for this deep-sea–dwelling species will allow several pending evolutionary questions to be unlocked. Findings We present a draft genome assembly that includes 200 Gb of Illumina reads, 4 Gb of Moleculo synthetic long reads, and 108 Gb of Chicago libraries, with a final size matching the estimated genome size of 2.7 Gb, and a scaffold N50 of 4.8 Mb. We also present an alternative assembly including 27 Gb raw reads generated using the Pacific Biosciences platform. In addition, we sequenced the proteome of the same individual and RNA from 3 different tissue types from 3 other species of squid (Onychoteuthis banksii, Dosidicus gigas, and Sthenoteuthis oualaniensis) to assist genome annotation. We annotated 33,406 protein-coding genes supported by evidence, and the genome completeness estimated by BUSCO reached 92%. Repetitive regions cover 49.17% of the genome. Conclusions This annotated draft genome of A. dux provides a critical resource to investigate the unique traits of this species, including its gigantism and key adaptations to deep-sea environments.

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