Stomach content analysis in cephalopods: past research, current challenges, and future directions

Ibáñez, Christian M.; Riera, Rodrigo; Leite, Tatiana S.; Díaz‐Santana‐Iturrios, Mariana; Rosa, Rui; Pardo‐Gandarillas, M. Cecilia

doi:10.1007/s11160-021-09653-z

Cited by 30 publications

(12 citation statements)

References 122 publications

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“…When considering changes in dietary compositions and relationships between prey preference and size of predators in the long-term period, the quantity and quality of food resources in month or year may lead to a restructuring of fisheries and marine ecosystems. Notably, although stomach content analysis is a universal technique for understanding dietary compositions for each species, detection, recognition, and counting the detached components of prey in the stomach contents remain critical challenges and unresolved weaknesses in this widely used and accepted methodology (Hyslop, 1980;Brown et al, 2012;Zacharia, 2017;Ibáñez et al, 2021). Particularly, I. argentinus crushes food with their beaks, and their digestion is fast, both resulting in a higher number of empty stomachs and unidentified fragments in the stomachs.…”

Section: Discussionmentioning

confidence: 99%

“…In addition to the small size of the cephalopods' statoliths being difficult to observe, cephalopods' statoliths may be more susceptible than fishes' otoliths to the gastric acid of the I. argentinus (Clarke, 1978). Furthermore, considering abundance estimation, unbiased indices, and phases of digestion to better characterize diets of abundant, data-poor species to avoid faculty or incomplete conclusion about their trophic roles is further necessary as a reasonable measures for dietary studies in cephalopods (Brown et al, 2012;Ibáñez et al, 2021).…”

Section: Discussionmentioning

confidence: 99%

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Dietary Shifts and Risks of Artifact Ingestion for Argentine Shortfin Squid Illex argentinus in the Southwest Atlantic

et al. 2021

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Cephalopods play an important role in both ecology and fisheries. Variations in the dietary compositions of squids with large populations further promote interactions between different trophic levels in marine ecosystems. Moreover, due to marine pollution, squids are also at risks of artifact ingestion, and there is limited understanding about the influence of artifacts on the feeding behavior of squids. We examined 296 stomachs of the Argentine shortfin squid Illex argentinus collected through commercial catches across the Southwest Atlantic from February to April of 2018 and 2019 to establish the monthly dietary compositions and risks of artifact ingestion. The results supported typical observations that the Argentine shortfin squids switched from a diet dominated by crustaceans at small sizes to consuming larger prey, predominantly fishes and/or cephalopods, at large sizes during their growth and southward migration. Significantly higher consumption of fishes was observed in recent years compared with that observed in other studies since 1992. The ingested artifacts examined were composed of plastic and non-plastic materials. Artifacts were observed in 19.9% of the total number of stomachs, with 20.5% of the empty stomachs containing artifact remains. The results indicate that although the main dietary compositions of the Argentine shortfin squid maintain the taxonomic groups of prey compositions, the dietary structure, i.e., composition percentage, is varying. The detection of artifacts suggests that environmental monitoring is needed in this region in order to manage and conserve the squid and safeguard aquatic food safety.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Dietary Shifts and Risks of Artifact Ingestion for Argentine Shortfin Squid Illex argentinus in the Southwest Atlantic

et al. 2021

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“…Cephalopods occupy key roles in marine ecosystems (Clarke, 1996;Piatkowski et al, 2001), and play pivotal roles in trophic webs by being positioned between lower trophic levels and top predators (Boyle & Rodhouse, 2005). Numerous studies have attempted to identify cephalopod diets, yet stomachs are often empty or prey are unidentifiable (Ibáñez et al, 2008(Ibáñez et al, , 2021. The high digestion rate and strong prey reduction by means of the beaks (Clarke, 1962) considerably reduce the ability of identifying prey (Boyle & Rodhouse, 2005) from stomach contents.…”

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confidence: 99%

Every hooked beak is maintained by a prey: Ecological signal in cephalopod beak shape

et al. 2022

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1. Beaks are among the few hard parts of coleoid cephalopods and are informative for species identification. Although mandible shape has been shown to be adaptive in many vertebrate taxa, it has been suggested that the shape of coleoid beaks does not bear any ecological signal. Yet, previous studies only explored beak shape in 2D and none have provided an in-depth investigation of the potential relationship with ecological variables such as habitat use or diet.2. The goal of the present study was to understand whether variation in cephalopod beak shape reflects ecology and/or is more driven by phylogenetic relatedness as suggested previously.3. We imaged 101 lower and 108 upper beaks in 3D using underwater photogrammetry and micro-CT scanning. Our 3D morphometric analysis conducted on 75 species of cephalopod shows that there is a significant but moderate phylogenetic signal. However, comparative phylogenetically informed analyses demonstrate that beak shape is also driven by ecology.4. We detected significant differences in beak shape between species inhabiting different habitats (pelagic, benthic or demersal) and of different trophic levels.Our results further suggest that beak shape variation can be summarized along a continuum between two main functions: fast closing versus hard biting.5. These results provide novel insights into the drivers of beak shape diversity in coleoid cephalopods and suggest that beak shape has evolved adaptively in relation to diet and habitat use.

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“…Ingestion rate (I) is expressed as g. ingested food (wet weight) considering the water content obtained after dry sampling at 60 °C for 48 h. In the case of fresh or frozen food the same method is used. A review of the stomach contents and ingestion rate in cephalopods by Ibáñez et al (Ibáñez et al, 2021) gives recommendations for obtaining data of ecological importance.…”

Section: Measuring Food Ingestion Ratementioning

confidence: 99%

Methodological considerations in studying digestive system physiology in octopus: limitations, lacunae and lessons learnt

2022

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Current understanding of cephalopod digestive tract physiology is based on relatively “old” literature and a “mosaic of data” from multiple species. To provide a background to the discussion of methodologies for investigating physiology we first review the anatomy of the cephalopod digestive tract with a focus on Octopus vulgaris, highlighting structure-function relationships and species differences with potential functional consequences (e.g., absence of a crop in cuttlefish and squid; presence of a caecal sac in squid). We caution about extrapolation of data on the digestive system physiology from one cephalopod species to another because of the anatomical differences. The contribution of anatomical and histological techniques (e.g., digestive enzyme histochemistry and neurotransmitter immunohistochemistry) to understanding physiological processes is discussed. For each major digestive tract function we briefly review current knowledge, and then discuss techniques and their limitations for the following parameters: 1) Measuring motility in vitro (e.g., spatiotemporal mapping, tension and pressure), in vivo (labelled food, high resolution ultrasound) and aspects of pharmacology; 2) Measuring food ingestion and the time course of digestion with an emphasis on understanding enzyme function in each gut region with respect to time; 3) Assessing transepithelial transport of nutrients; 4) Measuring the energetic cost of food processing, impact of environmental temperature and metabolic rate (flow-through/intermittent respirometry); 4) Investigating neural (brain, gastric ganglion, enteric) and endocrine control processes with an emphasis on application of molecular techniques to identify receptors and their ligands. A number of major knowledge lacunae are identified where available techniques need to be applied to cephalopods, these include: 1) What is the physiological function of the caecal leaflets and intestinal typhlosoles in octopus? 2) What role does the transepithelial transport in the caecum and intestine play in ion, water and nutrient transport? 3) What information is signalled from the digestive tract to the brain regarding the food ingested and the progress of digestion? It is hoped that by combining discussion of the physiology of the cephalopod digestive system with an overview of techniques and identification of key knowledge gaps that this will encourage a more systematic approach to research in this area.

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Stomach content analysis in cephalopods: past research, current challenges, and future directions

Cited by 30 publications

References 122 publications

Dietary Shifts and Risks of Artifact Ingestion for Argentine Shortfin Squid Illex argentinus in the Southwest Atlantic

Dietary Shifts and Risks of Artifact Ingestion for Argentine Shortfin Squid Illex argentinus in the Southwest Atlantic

Every hooked beak is maintained by a prey: Ecological signal in cephalopod beak shape

Methodological considerations in studying digestive system physiology in octopus: limitations, lacunae and lessons learnt

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