Cephalopod Species Research Articles

Holistic description of new deep sea megafauna (Cephalopoda: Cirrata) using a minimally invasive approach

BackgroundIn zoology, species descriptions conventionally rely on invasive morphological techniques, frequently leading to damage of the specimens and thus only a partial understanding of their structural complexity. More recently, non-destructive imaging techniques have successfully been used to describe smaller fauna, but this approach has so far not been applied to identify or describe larger animal species. Here, we present a combination of entirely non-invasive as well as minimally invasive methods that permit taxonomic descriptions of large zoological specimens in a more comprehensive manner.ResultsUsing the single available representative of an allegedly novel species of deep-sea cephalopod (Mollusca: Cephalopoda), digital photography, standardized external measurements, high-field magnetic resonance imaging, micro-computed tomography, and DNA barcoding were combined to gather all morphological and molecular characters relevant for a full species description. The results show that this specimen belongs to the cirrate octopod (Octopoda: Cirrata) genus Grimpoteuthis Robson, 1932. Based on the number of suckers, position of web nodules, cirrus length, presence of a radula, and various shell characters, the specimen is designated as the holotype of a new species of dumbo octopus, G. imperator sp. nov. The digital nature of the acquired data permits a seamless online deposition of raw as well as derived morphological and molecular datasets in publicly accessible repositories.ConclusionsUsing high-resolution, non-invasive imaging systems intended for the analysis of larger biological objects, all external as well as internal morphological character states relevant for the identification of a new megafaunal species were obtained. Potentially harmful effects on this unique deep-sea cephalopod specimen were avoided by scanning the fixed animal without admixture of a contrast agent. Additional support for the taxonomic placement of the new dumbo octopus species was obtained through DNA barcoding, further underlining the importance of combining morphological and molecular datasets for a holistic description of zoological specimens.

Thresholds of polarization vision in octopuses.

ABSTRACTPolarization vision is widespread in nature, mainly among invertebrates, and is used for a range of tasks including navigation, habitat localization and communication. In marine environments, some species such as those from the Crustacea and Cephalopoda that are principally monochromatic, have evolved to use this adaptation to discriminate objects across the whole visual field, an ability similar to our own use of colour vision. The performance of these polarization vision systems varies, and the few cephalopod species tested so far have notably acute thresholds of discrimination. However, most studies to date have used artificial sources of polarized light that produce levels of polarization much higher than found in nature. In this study, the ability of octopuses to detect polarization contrasts varying in angle of polarization (AoP) was investigated over a range of different degrees of linear polarization (DoLP) to better judge their visual ability in more ecologically relevant conditions. The ‘just-noticeable-differences’ (JND) of AoP contrasts varied consistently with DoLP. These JND thresholds could be largely explained by their ‘polarization distance’, a neurophysical model that effectively calculates the level of activity in opposing horizontally and vertically oriented polarization channels in the cephalopod visual system. Imaging polarimetry from the animals’ natural environment was then used to illustrate the functional advantage that these polarization thresholds may confer in behaviourally relevant contexts.

Does the invasive macro-algae Sargassum muticum (Yendo) Fensholt, 1955 offer an appropriate temporary habitat for mobile fauna including non indigenous species?

The fauna inhabiting the brown seaweed Sargassum muticum was studied on a spatial scale along the Normandy coast from the Normand-Breton Gulf to the Bay of Seine (English Channel) in both shallow sandy and rocky tidal pools during the springs 2018 and 2019. In this paper, we test the following hypothesis: do the areas with dense populations of S. muticum represent an appropriate habitat for dense motile fauna including other Non-Indigenous Species (NIS)? The ALEX (ALien biotic indEX) is used to ascertain whether or not S. muticum favours the establishment of other NIS in this new habitat. Results show that the epifaunal assemblage associated with S. muticum differs between the five sampling sites. However, the fauna at all five sites is dominated by arthropoda, especially the amphipods and isopods. In addition, five non indigenous species are observed inhabiting the brown seaweed (four amphipods: Aoroides longimerus, Aoroides semicurvatus, Monocorophium acherusicum, Monocorophium sextonae and one decapod: Hemigrapsus sanguineus). In spite of the presence of Non-Indigenous Species (NIS) associated with the invasive Sargassum, the ALEX yields a high Ecological Quality Status for all the sites. Nevertheless, the results suggest that S. muticum is a suitable habitat for many invertebrates especially amphipods and isopods, while also representing a potential source of food for several local fish and cephalopod species.

Persistent Organic Pollutants Burden, Trophic Magnification and Risk in a Pelagic Food Web from Coastal NW Mediterranean Sea.

The storage capacity, trophic magnification and risk of sixty-two POPs have been evaluated in a well-characterized pelagic food web (including phytoplankton, zooplankton, six fish, and two cephalopods species) from an impacted area in NW Mediterranean Sea. Our results show the high capacity of the planktonic compartment for the storage of polybrominated diphenyl ethers (PBDEs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), consistent with their estimated low trophic magnification factors (TMF) of 0.2-2.0 (PBDEs) and of 0.3-1.1 (PCDD/Fs). ∑PBDEs dominated in the zooplankton size-class 200-1000 μm (∼330 ng g-1 lw, median), whereas ∑PCDD/Fs accumulated preferentially in phytoplankton size-class 0.7-200 μm (875 pg g-1 lw, median). In contrast, polychlorinated biphenyls (PCBs) were preferentially bioaccumulated in the higher trophic levels (six fish species and two cephalopods) with TMFs = 0.8-3.9, reaching median concentrations of 4270 and 3140 ng g-1 lw (∑PCBs) in Atlantic bonito (Sarda sarda) and chub mackerel (Scomber colias), respectively. For these edible species, the estimated weekly intakes of dioxin-like POPs for humans based on national consumption standards overpassed the EU tolerable weekly intake. Moreover, the concentrations of nondioxin-like PCBs in S. sarda were above the EU maximum levels in foodstuffs, pointing to a risk. No risk evidence was found due to consumption of all other edible species studied, neither for PBDEs. The integrated burden of POPs in the food web reached ∼18 μg g-1 lw, representing a dynamic stock of toxic organic chemicals in the study area. We show that the characterized food web could be a useful and comprehensive "bioindicator" of the chemical pollution status of the study area, opening new perspectives for the monitoring of toxic chemicals in Mediterranean coastal waters.

Interannual variability of body size and beak morphology of the squid Ommastrephes bartramii in the North Pacific Ocean in the context of climate change

Oceanic squids are typical species that sensitive to the environment change. Previous studies on oceanic squids mainly focus on its annually fluctuated abundance under the background of climate change. The changes of individual morphological sizes, including body and beak, have been observed in recent years. In this study, Ommastrephes bartramii, an important cephalopod species in North Pacific Ocean, has been selected to analyze the annual morphological changes of body and beak under different scales of climate events. Geometric morphometrics was used to analyze the shape variations of both upper beak and lower beak. The possible phenotypic plasticity of body and beak was also discussed in different aspects. Body size showed different variations among different climatic years. The size at the maturity stage in 2015 (El Niño year) was much smaller than that in other years for both sexes. The centroid size representing the beak size showed the significant difference between two types of Pacific Decadal Oscillation phases. The shapes of upper and lower beaks showed significant differences between small-scale climatic patterns in which El Niño or La Niña event occurred, displaying different growth patterns.

The Cost of Fishing on Juveniles of Finfish and Shellfish: Assessment of Economic Impacts of Trawl Juvenile by-Catch along the Coast of North Andhra Pradesh, India

A study was carried out to assess the economic value of juveniles of commercially important species of finfish and shellfish caught as by-catch by multiday commercial trawlers operated off the coast of Visakhapatnam, north Andhra Pradesh from January 2014 to December 2015. Juveniles of twenty species (four species of cephalopods and sixteen species of finfish) were found to dominate the trawl by-catch. The landed juveniles of these 20 species formed 12,757.16 t and 286.86 million numbers per year and their contribution to the total landings of these species in trawl by-catch were 55.30% by weight and 57.03% by numbers. The highest percentage of quantities of juveniles (biomass) was found in trawl by-catch in the months of August and July in, 2014 and 2015 respectively. Among the juveniles, ribbonfish (Trichiurus lepturus) and goatfish (Upeneus vittatus) dominated, contributing together, on an average 11.60% by weight and 33.68% by numbers respectively. Using the bio-economic model, it was estimated that if the juveniles were allowed to grow up to length at first maturity; total annual economic gain would have been Rs. 273.21 crores (42.03 million USD) with biomass gain of 44,493.02 t per annum. The estimated total annual biomass would have increased 3.46 times with an increase in revenue by 4.20 times. Annual average loss due to fishing of juveniles was estimated to be Rs. 209.62 crores (32.25 million USD). The results of the present study suggested that sustainable harvest of these resources would have yielded maximum economic return to the fishers. With the help of stakeholders using a participatory approach, management measures such as increase of cod end mesh size of trawl to 40 mm from the present mesh size of 10–12 mm, use of square mesh for trawl cod ends, fishing effort restriction and awareness campaign on the detrimental impacts of catching juveniles needs to be implemented at the earliest for avoiding growth overfishing.

European cephalopods distribution under climate-change scenarios

In a context of increasing anthropogenic pressure, projecting species potential distributional shifts is of major importance for the sustainable exploitation of marine species. Despite their major economical (i.e. important fisheries) and ecological (i.e. central position in food-webs) importance, cephalopods literature rarely addresses an explicit understanding of their current distribution and the potential effect that climate change may induce in the following decades. In this study, we focus on three largely harvested and common cephalopod species in Europe: Octopus vulgaris, Sepia officinalis and Loligo vulgaris. Using a recently improved species ensemble modelling framework coupled with five atmosphere–ocean general circulation models, we modelled their contemporary and potential future distributional range over the twenty-first century. Independently of global warming scenarios, we observed a decreasing in the suitability of environmental conditions in the Mediterranean Sea and the Bay of Biscay. Conversely, we projected a rapidly increasing environmental suitability in the North, Norwegian and Baltic Seas for all species. This study is a first broad scale assessment and identification of the geographical areas, fisheries and ecosystems impacted by climate-induced changes in cephalopods distributional range.

A survey of arsenic, mercury, cadmium, and lead residues in seafood (fish, crustaceans, and cephalopods) from the south-eastern Mediterranean Sea.

Seafood is capable of bioaccumulating heavy metals (HM), making it a potentially major dietary source of HM for humans. Presently, little data exists on seafood from the eastern-most boundary of the Mediterranean Sea. This study aims to provide exposure insight of the Israeli population to HM through the consumption of locally caught seafood by assessing the levels of arsenic, mercury, cadmium, and lead in raw tissues of seafood. A wide survey of local fisheries was conducted providing 296 samples from 11 different species, including seven fish, two crustacean, and two cephalopod species. Total arsenic, cadmium, and lead were analyzed by graphite-furnace atomic absorption. Total mercury was measured by cold-vapor mercury analyzer. Arsenic speciation was performed by anion chromatography-inductively coupled plasma sector field mass spectrometry. Results suggested that the total arsenic concentrations were significantly higher in crustaceans and cephalopods than fish. Arsenic speciation revealed two samples that exceed 1 mg/kg of inorganic arsenic, whereas methylated arsenic was below the detection limit. Elevated mercury levels were detected in the commercial benthic species Mullus barbatus (red mullet), cadmium was detected in one-third of the samples, and lead detected in eight samples. Comparing the results to health guidelines, 99.4% of seafood tested in this study abide with acceptable levels of heavy metals in seafood, as defined by both Israeli and European Union guidelines.

Cerebrotypes in Cephalopods: Brain Diversity and Its Correlation With Species Habits, Life History, and Physiological Adaptations.

Here we analyze existing quantitative data available for cephalopod brains based on classical contributions by J.Z. Young and colleagues, to cite some. We relate the relative brain size of selected regions (area and/or lobe), with behavior, life history, ecology and distribution of several cephalopod species here considered. After hierarchical clustering we identify and describe ten clusters grouping 52 cephalopod species. This allows us to describe cerebrotypes, i.e., differences of brain composition in different species, as a sign of their adaptation to specific niches and/or clades in cephalopod molluscs for the first time. Similarity reflecting niche type has been found in vertebrates, and it is reasonable to assume that it could also occur in Cephalopoda. We also attempted a phylogenetic PCA using data by Lindgren et al. (2012) as input tree. However, due to the limited overlap in species considered, the final analysis was carried out on <30 species, thus reducing the impact of this approach. Nevertheless, our analysis suggests that the phylogenetic signal alone cannot be a justification for the grouping of species, although biased by the limited set of data available to us. Based on these preliminary findings, we can only hypothesize that brains evolved in cephalopods on the basis of different factors including phylogeny, possible development, and the third factor, i.e., life-style adaptations. Our results support the working hypothesis that the taxon evolved different sensorial and computational strategies to cope with the various environments (niches) occupied in the oceans. This study is novel for invertebrates, to the best of our knowledge.

A novel metabarcoding primer pair for environmental DNA analysis of Cephalopoda (Mollusca) targeting the nuclear 18S rRNA region.

Cephalopods are pivotal components of marine food webs, but biodiversity studies are hampered by challenges to sample these agile marine molluscs. Metabarcoding of environmental DNA (eDNA) is a potentially powerful technique to study oceanic cephalopod biodiversity and distribution but has not been applied thus far. We present a novel universal primer pair for metabarcoding cephalopods from eDNA, Ceph18S (Forward: 5′-CGC GGC GCT ACA TAT TAG AC-3′, Reverse: 5′-GCA CTT AAC CGA CCG TCG AC-3′). The primer pair targets the hypervariable region V2 of the nuclear 18S rRNA gene and amplifies a relatively short target sequence of approximately 200 bp in order to allow the amplification of degraded DNA. In silico tests on a reference database and empirical tests on DNA extracts from cephalopod tissue estimate that 44–66% of cephalopod species, corresponding to about 310–460 species, can be amplified and identified with this primer pair. A multi-marker approach with the novel Ceph18S and two previously published cephalopod mitochondrial 16S rRNA primer sets targeting the same region (Jarman et al. 2006 Mol. Ecol. Notes. 6, 268–271; Peters et al. 2015 Mar. Ecol. 36, 1428–1439) is estimated to amplify and identify 89% of all cephalopod species, of which an estimated 19% can only be identified by Ceph18S. All sequences obtained with Ceph18S were submitted to GenBank, resulting in new 18S rRNA sequences for 13 cephalopod taxa.

闽南渔场游泳动物优势种种群聚集特性

基于2016年4月和10月闽南渔场渔业资源的专项调查数据，运用相对性重要指数、平均拥挤度指数、聚块指数、Cassie指标、Mrisita指数等方法分析闽南渔场游泳动物优势种组成及其种群聚集特性，比较不同的季节、类群和种类及其相互间的聚集状态，探究种群聚集驱动因子，旨在发现闽南渔场游泳动物优势种种群聚集的特征、内在规律和形成机制。结果表明，闽南渔场游泳动物优势种共17种，其中鱼类6种、虾类3种、蟹类4种、头足类4种；鱼类中六指马鲅（Polydactylus se-xfilis）聚集强度最强，头足类中火枪乌贼（Loligo beka）聚集强度最强；虾类和蟹类中春季以哈氏仿对虾（Parapenaeopsis hardwickii）和拥剑梭子蟹（Portunus gladiator）的聚集强度最强，而秋季以鹰爪虾（Trachypenaeus curvirostris）和日本蟳（Charybdis japonica）的聚集强度最强；鱼类、虾类、蟹类和头足类中春季分别以二长棘犁齿鲷（Evynnis cardinali）、鹰爪虾、三疣梭子蟹（P. trituberculatus）和火枪乌贼的平均拥挤度最高，而秋季分别以带鱼（Trichiurus lepturus）、鹰爪虾、拥剑梭子蟹和杜氏枪乌贼（Loligo duvaucelii）的平均拥挤度最高；闽南渔场游泳动物优势种的平均拥挤度呈现出秋季高于春季，虾类、蟹类种群聚集强度大于鱼类、头足类的特点。;The relative importance index, mean crowding index, patchiness index, Cassie index and Mrisita index were used to analyze the composition and aggregation characteristics of the dominant species of nekton in Minnan Fishing Ground using the special investigation data of fishery resources in Minnan Fishing Ground in April and October 2016. The results showed that there were 17 dominant species of nektons in Minnan Fishing Ground, including 6 species of fish, 3 species of shrimp, 4 species of crab and 4 species of cephalopod. Polydactylus se-xfilis had the strongest aggregation intensity among fishes, and Loligo beka had the strongest aggregation intensity among cephalopods in spring and autumn. Parapenaeopsis hardwickii had the largest aggregation intensity among shrimps, and Portunus gladiator had the largest aggregation intensity among crabs in spring. Trachypenaeus curvirostris had the largest aggregation intensity among shrimps, and Charybdis japonica had the largest aggregation intensity among crabs in autumn. In spring, Evynnis cardinali, Trachypenaeus curvirostris, Portunus trituberculatus, Loligo beka had the highest mean crowding among fishes, shrimps, crabs and cephalopods, respectively. In autumn, Trichiurus lepturus, Trachypenaeus curvirostris, P. gladiator and Loligo duvaucelii had the highest mean crowding among fishes, shrimps, crabs and cephalopods, respectively. The average crowding of main dominant species of nekton in autumn was higher than that in spring, and the aggregation intensity of shrimp and crab was higher than that of fish and cephalopod in the Minnan Fishing Ground.

Prediction of Monophyletic Groups Based on Gene Order and Sequence Similarity in Organelle DNA

Organelle genomics has become its own field of study. Much information can be gleaned from the study of cell organelles. The differences in the genomes of organelles, such as the mitochondrion and the chloroplast are amenable to phylogenetic and cladistic studies. These differences include the genome sequence, GC%, genome length and gene order. The conserved nature of the organelle genomes and the gene inventory of both mitochondrial and chloroplast genomes also make this easier to accomplish. This paper includes a review of existing organelle genome software. These include gene annotation and genome visualization tools as well as organelle gene databases for both mitochondrion and plastid. A new R tool, available on github, called “Organelle DNA Lineages”, or ODL, was written to compare and classify organelle genomes based on their genome sequence and gene order. The software was run on the mitochondrial genomes of a set of 51 cephalopod species, delineating ten separate monophyletic groups, including argonauts, nautiluses, octopuses, cuttlefish, and six squid groups. This new tool can help enrich and expand the field of organelle genomics.

Research progress in fecundity study of Coleoidea (Cephalopoda)

Cephalopods are characterized by fast growth, short generation replacement and high abundance. These species live in all oceans of the world with the exception of the Black Sea, not only playing an important role in the trophic webs of the marine ecosystem but also being one of the most important fishery resources in the world. It is important to well study the fecundity of cephalopods, which can improve our understandings of their life history, and more importantly can promote to realize their population dynamics and recruitment processes. Herein, the fecundity of Coleoidea (Cephalopoda) was summarized in details, including the definitions and their determination methodologies, the values of fecundity among species, and the changeable characteristics of fecundity in relation to species body size, egg diameter and living habitats. The potential fecundity was one of the most popular approaches to determine the reproductive value, and represented the theoretical value that one species could produce during its lifecycle. Other approaches such as actual realized fecundity, effective fecundity, and relative fecundity were also used to estimate the fecundity of cephalopod species. It showed that there was species-specific fecundity for Coleoida species. The maximum potential fecundity was reported for <italic>Dosidicus gigas</italic>, and the minimum was reported for <italic>Pareledone turqueti</italic>. The fecundity of Coleoidea was generally found a linear relation to adult body size, indicating a larger body size with a higher fecundity value. At the guild level, there was a significantly negative relationship between the fecundity and egg size for both Octopoda and Teuthoidea. In contrast, there was a slightly positive relationship between the fecundity and egg size for Sepioidea. Generally, species living at lower latitudes exhibited a relatively higher fecundity, and those living at higher latitudes had a relatively lower fecundity. Meanwhile, such fecundity characteristics were also detected at the species level. Water temperature and primary production appeared to be the most important environmental factors that influenced the latitudinal trend of fecundity among the species. It is worthy to note that Coleoida species is semelparous reproduction and the fecundity is associated with the pattern and amount of energy allocation to reproduction. The reproductive investment strategy would determine the actual fecundity of a species and subsequently the biomass of recruitment, and hence studies on the potential reproductive investment will be an important area for better understanding of the fecundity characteristics of cephalopods. Increasingly, the importance of cephalopods has been recognized not only in their ecological roles as trophic indicators but also in their high abundance supporting global fisheries. Therefore, it is necessary to deeply understand the fecundity characteristics of cephalopods, which will largely increase our knowledge about their ecological roles and also assist the sustainable exploitation and the policy-making of resource assessment and management.

Cephalopods habitat and trophic ecology: historical data using snares penguin as biological sampler

In the Southern Ocean and adjacent waters, early stages of cephalopods play an important role in food webs as prey to top predators, but few is known regarding their biology and availability. Snares Penguin, Eudyptes robustus, is a top predator endemic to Snares Islands (New Zealand) that feed on cephalopods. As historical data on diet are rare for this species, Snares Penguins were used as biological samplers to evaluate the cephalopod component of its diet, where habitat and trophic level of cephalopods around the Snares Islands was assessed through stable isotope analysis. Moreover, ontogenic changes of juvenile squid were evaluated. Data collection were carried out during the breeding season 1986–87 and its analysis revealed that penguins fed on three juvenile cephalopod species: two squids (Nototodarus sloanii and Moroteuthopsis ingens) and one octopod (Octopus campbelli). Nototodarus sloanii was the most important species in frequency of occurrence and mass, whereas M. ingens was the most important in number. Juvenile squid species showed similar δ13C values, suggesting both occupied similar habitats on the Snares shelf, whereas juvenile O. campbelli showed lower δ13C values. Moreover, O. campbelli fed on higher trophic level (δ15N) prey relative to squid species. Lower diversity and larger sizes of cephalopods were found when compared with data from 2002. This study shows that Snares Penguin can be a good local biological sampler of juvenile cephalopods during their breeding season, providing both essential biogeographic information of cephalopod diversity and relevant historical information for the conservation of this endemic penguin species.

Some Deep-Sea Cephalopods from the Northeastern Mediterranean Sea (Mersin Bay, Turkey)

Deep-sea sampling was conducted by a commercial trawl in the International Waters of Mersin Bay between 14 and 17 May 2018. The sampling depth ranged between 274 and 641 meters. A total of 13 trawling operations were performed, and each trawling operation lasted approximately 4 hours. During the sampling, six of the deep-sea cephalopods species were caught. All specimens were preserved in ethyl alcohol and were deposited in the Museum of the Systematic, Faculty of Fisheries, Mersin University (Catalog no: MEUCC-18-11-2- MEUCC-18-11-7). A total of two cuttlefish species belonging to the families of Sepiidae were identified. The others were represented by the families of Sepiolidae, Octopodidae, Bathypolypodidae, and Ommastrephidae.

Detection of Biogenic Amines in Indian Fish and Fishery Products Consumed in Southeast Coast Region of India

ABSTRACT The aim of the present study was to assess the occurrence of seven biogenic amines (cadaverine, histamine, putrescine, tryptamine, tyramine, spermidine, and spermine) in 13 fresh fish, three crustaceans, and three cephalopod species, as well as six cured and dried fish products commonly consumed in the southeast coast region of India. The biogenic amines were analyzed by high performance liquid chromatography with a dansyl chloride derivatization. In the majority of the cases, the biogenic amine content was within the limits set at both national and international levels. The only exceptions were the histamine content of fresh Silago sihama, Lutjanus bohar, and L. johnii, cured and dried Rastrelliger kanagurta and the tyramine content of cured and dried Penaeus indicus. In these cases, lack of proper temperature handling was indicated, which highlights the importance of establishing and implementing proper handling procedures to ensure fish and fishery product safety for human consumption.

Ege Üniversitesi Su Ürünleri Fakültesi Müzesi (ESFM)’nin cephalopod envanteri

In this study, cephalopod individuals exemplified in scientific studies from 1988 to 2015 were registered and listed in the Ege University Faculty of Fisheries Museum (ESFM). Cephalopod species examined in the museum were obtained from the Marmara Sea, the Aegean Sea, the Mediterranean and Northern Cyprus waters. In this study, cephalopod individuals exemplified in scientific studies from 1988 to 2015 were registered and listed in the Ege University Faculty of Fisheries Museum (ESFM). These studies showed that Turkey seas surrounding the 46 species of sepiida orders from 58 pieces, the orders in Sepiolida 230, Teuthida orders of 106 pieces and order Octopoda total 146 storage in a jar. As a result of this study surrounding Turkey seas it has been identified 46 species of cephalopods. The cephalopod types found in the museum were first cleaned and fixed to the jars using the formalin fixation method, which is the most suitable of the 4 known fixation methods, and then the necessary information regarding the sampling was labeled on the jars and the ESFM museum registration was performed.

Mercury in the tissues of five cephalopods species: First data on the nervous system

Mercury (Hg), one of the elements most toxic to biota, accumulates within organisms throughout their lifespan and biomagnifies along trophic chain. Due to their key role in marine systems, cephalopods constitute a major vector of Hg in predators. Further, they grow rapidly and display complex behaviours, which can be altered by neurotoxic Hg. This study investigated Hg concentrations within 81 cephalopod specimens sampled in the Bay of Biscay, which belonged to five species: Eledone cirrhosa, Sepia officinalis, Loligo vulgaris, Todaropsis eblanae and Illex coindetii. Hg concentrations were measured in the digestive gland, the mantle muscle and the optic lobes of the brain. The digestive gland and the mantle were tissues with the most concentrated Hg among all species considered (up to 1.50 μg.g−1 dw), except E. cirrhosa. This benthic cephalopod had 1.3-fold higher Hg concentrations in the brain (up to 1.89 μg.g−1 dw) than in the mantle, while other species had 2-fold lower concentrations of Hg in the brain than in the mantle. Brain-Hg concentrations can be predicted from muscle-Hg concentrations for a given species, which facilitates the assessment of Hg toxicokinetics in cephalopods. In the most contaminated E. cirrhosa individual, the chemical form of Hg in its digestive gland, mantle muscle and optic lobes, was determined using High energy-Resolution X-ray Absorption Near Edge Structure (HR XANES) spectroscopy. In the digestive gland, 33 ± 11% of total Hg was inorganic Hg speciated as a dicysteinate complex (Hg(Cys)2), which suggested that the demethylation of dietary MeHg occurs in this organ. All Hg found in the mantle muscle and the optic lobes is methylated and bound to one cysteinyl group (MeHgCys complex), which implies that dietary MeHg is distributed to these tissues via the bloodstream. These results raised the questions regarding interspecific differences observed regarding Hg brain concentrations and the possible effect of Hg on cephalopod functional brain plasticity and behaviour.

Diet and life history reduce interspecific and intraspecific competition among three sympatric Arctic cephalopods

Trophic niche and diet comparisons among closely sympatric marine species are important to understand complex food webs, particularly in regions most affected by climate change. Using stable isotope analyses, all ontogenetic stages of three sympatric species of Arctic cephalopods (genus Rossia) were studied to assess inter- and intraspecific competition with niche and diet overlap and partitioning in West Greenland and the Barents Sea. Seven traits related to resource and habitat utilization were identified in Rossia: no trait was shared by all three species. High boreal R. megaptera and Arctic endemic R. moelleri shared three traits with each other, while both R. megaptera and R. moelleri shared only two unique traits each with widespread boreal-Arctic R. palpebrosa. Thus all traits formed fully uncrossing pattern with each species having unique strategy of resource and habitat utilization. Predicted climate changes in the Arctic would have an impact on competition among Rossia with one potential ‘winner’ (R. megaptera in the Barents Sea) but no potential ‘losers’.

A Rapid Colorimetric Assay for On-Site Authentication of Cephalopod Species.

A colorimetric assay, exploiting the combination of loop-mediated isothermal amplification (LAMP) with DNA barcoding, was developed to address the authentication of some cephalopod species, a relevant group in the context of seafood traceability, due to the intensive processing from the fishing sites to the shelf. The discriminating strategy relies on accurate design of species-specific LAMP primers within the conventional 5’ end of the mitochondrial COI DNA barcode region and allows for the identification of Loligo vulgaris among two closely related and less valuable species. The assay, coupled to rapid genomic DNA extraction, is suitable for large-scale screenings and on-site applications due to its easy procedures, with fast (30 min) and visual readout.