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The reproductive process in Octopus maya was analyzed to establish the amount of reactive oxygen species that the embryos inherit from females, during yolk synthesis. At the same time, respiratory metabolism, ROS production, and the expression of some genes of the antioxidant system were monitored to understand the ability of embryos to neutralize maternal ROS and those produced during development. The results indicate that carbonylated proteins and peroxidized lipids (LPO) were transferred from females to the embryos, presumably derived from the metabolic processes carried out during yolk synthesis in the ovary. Along with ROS, females also transferred to embryos glutathione (GSH), a key element of the antioxidant defense system, thus facilitating the neutralization of inherited ROS and those produced during development. Embryos are capable of neutralizing ROS thanks to the early expression of genes such as catalase (CAT) and superoxide dismutase (SOD), which give rise to the synthesis of enzymes when the circulatory system is activated. Also, it was observed that the levels of the routine metabolic rate of embryos are almost as high as those of the maximum activity metabolism, which leads, on the one hand, to the elevated production of ROS and suggests that, at this stage of the life cycle in octopuses, energy production is maximum and is physically limited by the biological properties inherent to the structure of embryonic life (oxygen transfer through the chorion, gill surface, pumping capacity, etc.). Due to its role in regulating vascularization, a high expression of HIf-1A during organogenesis suggests that circulatory system development has begun in this phase of embryo development. The results indicate that the routine metabolic rate and the ability of O. maya embryos to neutralize the ROS are probably the maximum possible. Under such circumstances, embryos cannot generate more energy to combat the free radicals produced by their metabolism, even when environmental factors such as high temperatures or contaminants could demand excess energy.

An essential requirement for biomedical devices is the capability of conformal adaptability on diverse irregular 3D (three-dimensional) nonflat surfaces in the human body that may be covered with liquids such as mucus or sweat. However, the development of reversible adhesive interface materials for biodevices that function on complex biological surfaces is challenging due to the wet, slippery, smooth, and curved surface properties. Herein, we present an ultra-adaptive bioadhesive for irregular 3D oral cavities covered with saliva by integrating a kirigami-metastructure and vertically self-aligning suction cups. The flared suction cup, inspired by octopus tentacles, allows adhesion to moist surfaces. Additionally, the kirigami-based auxetic metastructure with a negative Poisson\'s ratio relieves the stress caused by tensile strain, thereby mitigating the stress caused by curved surfaces and enabling conformal contact with the surface. As a result, the adhesive strength of the proposed auxetic adhesive is twice that of adhesives with a flat backbone on highly curved porcine palates. For potential application, the proposed auxetic adhesive is mounted on a denture and performs successfully in human subject feasibility evaluations. An integrated design of these two structures may provide functionality and potential for biomedical applications.

The East Asian common octopus (Octopus sinensis) is an economically important species among cephalopods. This species exhibits a strict dioecious and allogamous reproductive strategy, along with a phenotypic sexual dimorphism, where the third right arm differentiates into hectocotylus in males. However, our understanding of the molecular mechanisms that underlie sex determination and differentiation in this species remains limited. In the present study, we surveyed gene-expression profiles in the immature male and female gonads of O. sinensis based on the RNA-seq, and a total of 47.83 Gb of high-quality data were generated. Compared with the testis, we identified 8302 differentially expressed genes (DEGs) in the ovary, of which 4459 genes were up-regulated and 3843 genes were down-regulated. Based on the GO enrichment, many GO terms related to sex differentiation were identified, such as sex differentiation (GO: 0007548), sexual reproduction (GO: 0019953) and male sex differentiation (GO: 0046661). A KEGG classification analysis identified three conserved signaling pathways that related to sex differentiation, including the Wnt signaling pathway, TGF-β signaling pathway and Notch signaling pathway. Additionally, 21 sex-related DEGs were selected, of which 13 DEGs were male-biased, including Dmrt1, Foxn5, Foxj1, Sox30, etc., and 8 DEGs were female-biased, including Sox14, Nanos3, β-tubulin, Suh, etc. Ten DEGs were used to verify the expression patterns in the testis and ovary using the RT-qPCR method, and the results showed that the expression level shown by RT-qPCR was consistent with that from the RNA-seq, which confirmed the reliability of the transcriptome data. The results presented in this study will not only contribute to our understanding of sex-formation mechanisms in O. sinensis but also provide the foundational information for further investigating the molecular mechanisms that underline its gonadal development and facilitate the sustainable development of octopus artificial breeding.

BACKGROUND: The genes involved in cephalopod development and their association with hatching and survival during early life stages have been extensively studied. However, few studies have investigated the paralarvae transcriptome of the East Asian common octopus (Octopus sinen sis).
OBJECTIVE: This study aimed to identify the genes related to embryonic development and hatching in O. sinensis using RNA sequencing (RNA-seq) and verify the genes most relevant to different embryonic stages.
METHODS: RNA samples from hatched and 25 days post-hatching (dph) O. sinensis paralarvae were used to construct cDNA libraries. Clean reads from individual samples were aligned to the reference O. sinensis database to identify the differentially expressed genes (DEGs) between the 0- and 25-dph paralarvae libraries. Real-time quantitative polymerase chain reaction (RT-qPCR) was used to supplement the RNA-seq data for embryogenic developmental stages.
RESULTS: A total of 12,597 transcripts were annotated and 5,468 DEGs were identified between the 0- and 25-dph O. sinensis paralarvae, including 2,715 upregulated and 2,753 downregulated transcripts in the 25-dph paralarvae. Several key DEGs were related to transmembrane transport, lipid biosynthesis, monooxygenase activity, lipid transport, neuropeptide signaling, transcription regulation, and protein-cysteine S-palmitoyltransferase activity during the post-hatching development of O. sinensis paralarvae. RT-qPCR analysis further revealed that SLC5A3A, ABCC12, and NPC1 transcripts in 20 and/or 30 days post-fertilization (dpf) embryos were significantly higher (p < 0.05) than those in 10-dpf embryos.
CONCLUSIONS: Transcriptome profiles provide molecular targets to understand the embryonic development, hatching, and survival of O. sinensis paralarvae, and enhance octopus production.

In this report, passive elasticity properties of Octopus rubescens arm tissue are investigated using a multidisciplinary approach encompassing biomechanical experiments, computational modeling, and analyses. Tensile tests are conducted to obtain stress-strain relationships of the arm under axial stretch. Rheological tests are also performed to probe the dynamic shear response of the arm tissue. Based on these tests, comparisons against three different viscoelasticity models are reported.

UNASSIGNED: Octopuses are capable of complex arm movements. Unfortunately, experimental barriers and lack of a robust analysis method made it difficult to quantify the three-dimensional (3D) kinematics of soft, flexible bodies, such as the octopus arm. This information is not only crucial for understanding the posture of the animal\'s arm but also for the development of similarly designed soft, flexible devices.
UNASSIGNED: The primary goal of this work was to create a method to comprehensively quantify complex, 3D postures of octopus (Octopus Bimaculoides) arms in a manner that is conducive and translatable to octopus arm-inspired devices for health monitoring and rehabilitation.
METHODS: In this study, 3D underwater motion capture was used to collect kinematic data on both live octopuses and disembodied arms that still had neural activity. A new method was developed to define how arm curvature and regional segments were oriented relative to each other in 3D. This included identification of the bend within a segment along with the computation of the relative orientation between segments, thus permitting the complete quantification of complex arm motions.
RESULTS: By comparing vector-based and radius of curvature-based approaches to magnitude of curvature, it was clear that the vector-based approach was less dependent on the length of a segment and that its reported ranges of motion were translatable for outcome measures associated with clinical use. The new approach for the relative orientation of each segment of the octopus arm resulted in the capability of describing the octopus arm in many unique postures, such as straight, simple bending, and complex bending as it utilized the three rotational angles.
UNASSIGNED: This method and its application to octopus arms will yield new information that can be used to better communicate and track not only octopus arm movements but in the development of complex, segmented, soft-bodied devices that can be used in health monitoring and rehabilitation.

In this study, the expressions and distributions of methionine-enkephalin (Met-enk) and δ opioid receptor in the nervous system of Octopus ocellatus, and the immune regulatory mechanisms of Met-enk on O. ocellatus were explored. The distributions and expressions of Met-enk and δ opioid receptor were assessed by immunohistochemistry and enzyme-linked immunosorbent assay. UV-spectrophotometer, microplate reader, and flow cytometer were used to examine the effects of different concentrations of Met-enk on phagocytosis, antioxidant effects, and body surface mucus immunity of O. ocellatus hemocytes. The data were used to study the mechanisms of Met-enk immunity regulation in O. ocellatus. According to the results, the expression levels of Met-enk and δ opioid receptor in O. ocellatus lymphocytes were higher than those in hemocytes. The expression levels of Met-enk in the ganglia of O. ocellatus decreased in the following order: pedal ganglia > cerebral ganglia > visceral ganglia > optic ganglia > stellate ganglia. Moreover, the phagocytic activity of O. ocellatus hemocytes was enhanced with increasing Met-enk concentration. With increasing Met-enk concentration, the expressions of nitric oxide, total nitric oxide synthase, inducible nitric oxide synthase, catalase, hydrogen peroxide, myeloperoxidase, reduced glutathione, α-naphthy acetate esterase, and methionine aminopeptidases decreased in serums of O. ocellatus in the experimental group compared to the blank group. Similarly, the content of reduced glutathione in the hemocytes of O. ocellatus was also lower in the experimental group than in the blank group; however, the expressions of other substances were higher compared to the blank group. Furthermore, α-naphthy acetate esterase, myeloperoxidase, and hydrogen peroxide expressions in mucus immunity trials of the body surface were lower in the experimental group compared to the blank group. These results indicate that the distributions and expressions of Met-enk and δ opioid receptor in the nervous system of O. ocellatus were related to axoplasmic transport and immune regulation mechanisms. Met-enk participates in cellular immunity, humoral immunity, and mucus immunity in the form of neurotransmitters, thereby regulating the immune response of O. ocellatus.

There is evidence that indicates that temperature modulates the reproduction of the tropical species Octopus maya, through the over- or under-expression of many genes in the brain. If the oxygen supply to the brain depends on the circulatory system, how temperature affects different tissues will begin in the heart, responsible for pumping the oxygen to tissues. The present study examines the impact of heat stress on the mitochondrial function of the systemic heart of adult O. maya. The mitochondrial metabolism and antioxidant defense system were measured in the systemic heart tissue of female organisms acclimated to different temperatures (24, 26, and 30°C). The results show that acclimation temperature affects respiratory State 3 and State 4o (oligomycin-induced) with higher values observed in females acclimated at 26°C. The antioxidant defense system is also affected by acclimation temperature with significant differences observed in superoxide dismutase, glutathione S-transferase activities, and glutathione levels. The results suggest that high temperatures (30°C) could exert physical limitations on the circulatory system through the heart pumping, affecting nutrient and oxygen transport to other tissues, including the brain, which exerts control over the reproductive system. The role of the cardiovascular system in supporting aerobic metabolism in octopus females is discussed.

Understanding an animal\'s metabolic rate and thermal history is pivotal for ecological research. Recent studies have proposed the use of stable carbon and oxygen isotopes (δ13C and δ18O) in biogenic carbonates as proxies of metabolic rate and experienced temperature, respectively, to overcome the challenges of directly measuring these data in the field. Our study represents the first experimental investigation to develop δ13C and δ18O proxies in octopus. Octopus berrima hatchlings were raised in captivity, at varying water temperatures, for up to 110 days. O. berrima statoliths were then subsequently analysed for δ13C and δ18O values. The proportion of metabolically derived carbon, or respired carbon (Cresp), increased as the octopus grew (slope = 0.076, R2 = 0.72), suggesting an influence of somatic growth rate and body mass on δ13C values. Additionally, we identified an inverse correlation between δ18O values and environmental temperature (slope = -0.163, R2 = 0.91), which was subsequently used to develop a thermal reconstruction model. Our experiment aids in interpreting stable isotopic values in statoliths and their application as temperature and metabolic proxies in wild-caught octopus. Such proxies will increase our monitoring capabilities of these ecologically and commercially significant cephalopods and contribute to their conservation and effective management.