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Cephalopods play a major role in marine food webs as both predators and prey. Although most of the Hg in cephalopods is present in the muscle, most studies on its accumulation by predators are based on concentrations in beaks. Here, using upper and lower beaks and buccal masses of Moroteuthopsis longimana, we evaluated the relationship between Hg concentrations in different cephalopod tissues. Hg concentrations in muscle tissue (329.9 ± 166.4 ng.g -1 dw) were ≈100-fold higher than in different sections of the upper (3.5 ± 1.4 ng.g -1 dw) and lower (3.5 ± 1.0 ng.g -1 dw) beaks. A positive linear relationship was found between the Hg in the beak wing and in the muscle. Hg concentrations in the wing are therefore a useful proxy for the total Hg body burden, and their analysis provides a means of assessing the levels, transport and fate of Hg in marine ecosystems., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Cephalopods represent an important pathway for mercury transfer through food webs. Due to the general difficulties in capturing oceanic squid, beaks found in the diet of top predators can be used to study their life-cycles and ecological role. Using upper beaks of the giant warty squid Moroteuthopsis longimana (major prey in the Southern Ocean), we describe a method to assess mercury concentrations along the life of cephalopods through the segmentary analysis of beak sections (i.e. tip of the rostrum and subsections along the hood). Distinct total mercury concentrations in the different subsections support that beaks can be used to study mercury levels in different periods of cephalopods' life-cycle. Mercury values in the anterior (1.3-7.9 μg kg -1 dw) and posterior (7.8-12.5 μg kg -1 dw) subsections of the hood reflect juvenile and adult stages, respectively. Furthermore, these results confirm that mercury bioaccumulates continuously throughout the individuals' life, with adults doubling their mercury concentrations to juveniles., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Sympatry can lead to higher competition under climate change and other environmental pressures, including in South Georgia, Antarctica, where the two most common octopod species, Adelieledone polymorpha and Pareledone turqueti, occur side by side. Since cephalopods are typically elusive animals, the ecology of both species is poorly known. As beaks of cephalopods are recurrently found in top predator's stomachs, we studied the feeding ecology of both octopods through the evaluation of niche overlapping and specific beak adaptations that both species present. A multidisciplinary approach combining carbon (δ 13 C) and nitrogen (δ 15 N) stable isotope signatures, mercury (Hg) analysis and biomaterials' engineering techniques was applied to investigate the beaks. An isotopic niche overlap of 95.6% was recorded for the juvenile stages of both octopod species, dropping to 19.2% for the adult stages. Both A. polymorpha and P. turqueti inhabit benthic ecosystems around South Georgia throughout their lifecycles (δ 13 C: -19.21 ± 1.87‰, mean ± SD for both species) but explore trophic niches partially different during adult life stages (δ 15 N: 7.01 ± 0.40‰, in A. polymorpha, and 7.84 ± 0.65‰, in P. turqueti). The beaks of A. polymorpha are less dense and significantly less stiff than in P. turqueti. Beaks showed lower mercury concentration relative to muscle (A. polymorpha - beaks: 0.052 ± 0.009  μg g -1 , muscle: 0.322 ± 0.088  μg g -1 ; P. turqueti - beaks: 0.038 ± 0.009  μg g -1 ; muscle: 0.434 ± 0.128  μg g -1 ). Overall, both octopods exhibit similar habitats but different trophic niches, related to morphology/function of beaks. The high Hg concentrations in both octopods can have negative consequences on their top predators and may increase under the present climate change context., (Copyright © 2019 Elsevier Ltd. All rights reserved.)