Life histories of Antarctic incirrate octopods (Cephalopoda: Octopoda)

Age Estimation in Sepia officinalis Using Beaks and Statoliths

Establishing the age of cephalopods is crucial for understanding their life history, which can then be used for assessment and management. This is particularly true for the common cuttlefish Sepia officinalis (Linnaeus, 1758), one of the most important resources for coastal fisheries. For this reason, an age analysis of S. officinalis was performed for the first time in the Mediterranean, using beaks and statoliths from 158 wild specimens (55-222 mm mantle length; 23-1382 g total weight) at different maturity stages (immature to mature). Growth increments were counted in the lateral wall of the upper beaks and the lateral dome of statoliths. In both cases, a good relationship was found between the counts and the sizes of the animals. The low values of coefficients of variation between the readings obtained for beaks (3.96 ± 1.87%) and statoliths (4.00 ± 1.89%) showed a high level of precision and accuracy in the readings. However, the analysis was simpler for beaks, which were all successfully analyzed, while it was more complex for statoliths, with 69% being lost due to rejection or overgrinding. Based on daily increments previously validated in statoliths, the beaks were cross-verified by comparing their counts with those from statoliths extracted from the same 83 specimens, obtaining a statistically significant relationship between the two counts, confirmed by the ANOVA test. Absolute growth rates that were assessed using both beaks and statoliths indicated that the two sexes had a higher growth rate at 122 and 182 days, which subsequently declined in older specimens. Due to the relative simplicity of its processing method, the beak was finally proposed as a suitable hard structure to study the age of S. officinalis. We also confirmed the good readability of increments in the lateral wall of the beak, which could be considered a valid alternative to the rostrum surface.

Genomic evidence for West Antarctic Ice Sheet collapse during the Last Interglacial

The marine-based West Antarctic Ice Sheet (WAIS) is considered vulnerable to irreversible collapse under future climate trajectories, and its tipping point may lie within the mitigated warming scenarios of 1.5° to 2°C of the United Nations Paris Agreement. Knowledge of ice loss during similarly warm past climates could resolve this uncertainty, including the Last Interglacial when global sea levels were 5 to 10 meters higher than today and global average temperatures were 0.5° to 1.5°C warmer than preindustrial levels. Using a panel of genome-wide, single-nucleotide polymorphisms of a circum-Antarctic octopus, we show persistent, historic signals of gene flow only possible with complete WAIS collapse. Our results provide the first empirical evidence that the tipping point of WAIS loss could be reached even under stringent climate mitigation scenarios.

Life History of the Arctic Squid Gonatus fabricii (Cephalopoda: Oegopsida) Reconstructed by Analysis of Individual Ontogenetic Stable Isotopic Trajectories

Cephalopods are important in Arctic marine ecosystems as predators and prey, but knowledge of their life cycles is poor. Consequently, they are under-represented in the Arctic ecosystems assessment models. One important parameter is the change in ecological role (habitat and diet) associated with individual ontogenies. Here, the life history of Gonatus fabricii, the most abundant Arctic cephalopod, is reconstructed by the analysis of individual ontogenetic trajectories of stable isotopes (δ13C and δ15N) in archival hard body structures. This approach allows the prediction of the exact mantle length (ML) and mass when the species changes its ecological role. Our results show that the life history of G. fabricii is divided into four stages, each having a distinct ecology: (1) epipelagic squid (ML < 20 mm), preying mostly on copepods; (2) epi- and occasionally mesopelagic squid (ML 20−50 mm), preying on larger crustaceans, fish, and cephalopods; (3) meso- and bathypelagic squid (ML > 50 mm), preying mainly on fish and cephalopods; and (4) non-feeding bathypelagic gelatinous females (ML > 200 mm). Existing Arctic ecosystem models do not reflect the different ecological roles of G. fabricii correctly, and the novel data provided here are a necessary baseline for Arctic ecosystem modelling and forecasting.

The significance of cephalopod beaks as a research tool: An update

The use of cephalopod beaks in ecological and population dynamics studies has allowed major advances of our knowledge on the role of cephalopods in marine ecosystems in the last 60 years. Since the 1960's, with the pioneering research by Malcolm Clarke and colleagues, cephalopod beaks (also named jaws or mandibles) have been described to species level and their measurements have been shown to be related to cephalopod body size and mass, which permitted important information to be obtained on numerous biological and ecological aspects of cephalopods in marine ecosystems. In the last decade, a range of new techniques has been applied to cephalopod beaks, permitting new kinds of insight into cephalopod biology and ecology. The workshop on cephalopod beaks of the Cephalopod International Advisory Council Conference (Sesimbra, Portugal) in 2022 aimed to review the most recent scientific developments in this field and to identify future challenges, particularly in relation to taxonomy, age, growth, chemical composition (i.e., DNA, proteomics, stable isotopes, trace elements) and physical (i.e., structural) analyses. In terms of taxonomy, new techniques (e.g., 3D geometric morphometrics) for identifying cephalopods from their beaks are being developed with promising results, although the need for experts and reference collections of cephalopod beaks will continue. The use of beak microstructure for age and growth studies has been validated. Stable isotope analyses on beaks have proven to be an excellent technique to get valuable information on the ecology of cephalopods (namely habitat and trophic position). Trace element analyses is also possible using beaks, where concentrations are significantly lower than in other tissues (e.g., muscle, digestive gland, gills). Extracting DNA from beaks was only possible in one study so far. Protein analyses can also be made using cephalopod beaks. Future challenges in research using cephalopod beaks are also discussed.

Trophic ecology drives trace element concentrations in the Antarctic octopod community

Despite the Antarctic Ocean being considered a pristine environment, elevated trace element concentrations have been reported in many marine organisms. The Antarctic Ocean is particularly vulnerable to climate change, which can also affect the bioaccumulation of trace element concentrations in biota. While Antarctic octopods are key components of the regional food webs as prey for a variety of predators (e.g., seals, fish, and seabirds), their contamination state by trace elements remains largely unknown. This study investigated the trace element concentrations in relation to the trophic ecology in Antarctic octopods. Stable isotope values (δ¹³C and δ¹⁵N) and trace element concentrations (Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, V, and Zn) were measured in eight different species (Adelieledone polymorpha, Pareledone aequipapillae, P. albimaculata, P. aurata, P. charcoti, P. cornuta, P. felix, and P. turqueti) sampled near Elephant Island, close to the Antarctic Peninsula. Stable isotopes of δ¹⁵N varied among species, with significant differences between A. polymorpha and P. aurata suggesting potential niche segregation. Trace element concentrations also differed among species and with sampling depth, which likely reflects their trophic ecology. The data presented in this study provides the first insight into the trace element concentrations for these endemic octopods in this vulnerable habitat and their stable isotope values.

The palaeobiology of belemnites - foundation for the interpretation of rostrum geochemistry

Belemnites are an extinct group of Mesozoic coleoid cephalopods with a fossil record ranging from the early Late Triassic [about 240 million years ago (Mya)] to the Cretaceous/Palaeogene boundary (65 Mya). Belemnites were widely distributed, highly abundant and diverse, and an important component of Mesozoic marine food webs. Their internal shells, specifically their low-Mg calcite rostra, have been used as palaeoenvironmental carbonate archives for the last 70 years. This is primarily due to the assumption that the rostrum calcite formed in equilibrium with the oxygen isotope composition of ambient sea water. Of prime importance for the reliable interpretation of isotope data derived from these biogenic carbonates is a robust reconstruction of the palaeobiology of their producers. Here we provide a critical assessment of published reconstructions of belemnite soft-body organization and their lifestyle and habitats. Different lines of evidence, including sedimentological, geochemical, morphological, and biomechanical data, point towards an outer shelf habitat of belemnites, for some taxa also including the littoral area. Belemnite habitat temperatures, oxygen content, salinities, and life span are constrained based on observations of the ecology and life history of modern coleoids. Belemnite habitat depth might have been largely controlled by food and temperature, with a temperature optimum between 10°C and 30°C. The distribution of modern coleoids is for most species restricted to well-oxygenated water masses and a salinity between 27 and 37 psu. The trophic position of belemnites as both predators and prey is documented by unique fossil finds of stomach contents and soft tissue preservation, such as jaws, hooks, and ink sacs. Belemnites were medium-sized predators in the epipelagic zone (not deeper than ∼200 m) hunting for crustaceans, other cephalopods, and fishes. Taxa with elongated rostra probably were fast and highly manoeuvrable swimmers. Forms with conical rostra represent slow but highly manoeuvrable swimmers, and forms with depressed rostra likely had a bottom-related life habit. Predators of adult belemnites were sharks, bony fishes, and marine reptiles. Belemnites, like most of the modern coleoids, were relatively short lived, most likely living only for 1-2 years. Understanding the biomineralization of belemnite rostra is highly relevant for an improved interpretation of their geochemistry. Here we confirm that belemnite rostra are composed of low Mg-calcite fibres, but they do not contain distinct types of laminae. These fibres are composed of two distinct calcite phases. One phase is a filigree network of tetrahedral organic-rich calcite and the second phase is represented by organic-poor calcite.