Octopod Species Research Articles

Using genomics and morphometrics to monitor data-poor and commercially exploited octopod populations

Over 150 species of benthic octopods have been described within the ‘catch-all’ Octopus genus (Family: Octopodidae) and yet, many Octopus species harvested by fisheries remain unidentified to species-level due to a lack of distinguishing traits. Within species, there is also limited information on how populations differ genetically and the level of connectivity between populations. Therefore, we sampled octopods from commercial fisheries in southeast Australia, in order to identify the species, examine the phylogeographic relationships among species and the level of population genetic structuring within species, as well as to look for any adaptive genetic variation. The mitochondrial gene, cytochrome oxidase subunit III (COIII), was sequenced in 346 octopods along with single nucleotide polymorphisms using double digest restriction site-associated DNA sequencing (ddRADseq). Morphometric traits were also measured in mature specimens. The southern keeled octopus (‘Octopus’berrima) and pale octopus (‘Octopus’pallidus) were identified using COIII data. For ‘Octopus’berrima, we found that some populations whilst being morphologically similar were genetically distinct. In contrast, ‘Octopus’pallidus populations were both morphologically and genetically distinct across the studied regions. Our results provide key information to better inform conservation and management decisions for developing octopod fisheries in southeast Australia and highlight the importance of genomics tools in the conservation management of commercially and recreationally important species.

Application of the thermal time model of embryonic development duration to the culture of octopod cephalopods

Data about the effect of temperature on the duration of embryonic development, or the incubation process, are relatively abundant for octopod cephalopods. Experimental data can be used to fit the thermal time classic model of development in order to predict the duration of the process and the range of temperatures within which development proceeds according to the model and with high survival (permissive range), with potential applications for basic research and production activities. The present work is aimed at fitting this classical model to fourteen data sources dealing with eleven species of octopods, seven of them not being previously analyzed, and discussing the constraints and applications of the model. As a result, it is possible to hold that the thermal time model of development duration suitably fits experimental data in octopods, and can be used to schedule hatching events in a production facility. Nevertheless, the range of temperatures tested in the literature is usually too limited to allow an appropriate estimation of the permissive range, so an extension of the temperature range to the known limits of each species is suggested. In addition, when the model is applied to whole spawnings with culture purposes, it is recommended to set the very first hatchings as the criterion for the end of the incubation. Further research is needed to ascertain if temperature fluctuations within and/or out of the permissive range can have implications for the parameterization of the model in octopod species.

Gene Recruitments and Dismissals in the Argonaut Genome Provide Insights into Pelagic Lifestyle Adaptation and Shell-like Eggcase Reacquisition.

The paper nautilus or greater argonaut, Argonauta argo, is a species of octopods which is characterized by its pelagic lifestyle and by the presence of a protective spiral-shaped shell-like eggcase in females. To reveal the genomic background of how the species adapted to the pelagic lifestyle and acquired its shell-like eggcase, we sequenced the draft genome of the species. The genome size was 1.1 Gb, which is the smallest among the cephalopods known to date, with the top 215 scaffolds (average length 5,064,479 bp) covering 81% (1.09 Gb) of the total assembly. A total of 26,433 protein-coding genes were predicted from 16,802 assembled scaffolds. From these, we identified nearly intact HOX, Parahox, Wnt clusters, and some gene clusters that could probably be related to the pelagic lifestyle, such as reflectin, tyrosinase, and opsin. The gene models also revealed several homologous genes related to calcified shell formation in Conchiferan mollusks, such as Pif-like, SOD, and TRX. Interestingly, comparative genomics analysis revealed that the homologous genes for such genes were also found in the genome of the shell-less octopus, as well as Nautilus, which has a true outer shell. Therefore, the draft genome sequence of Arg. argo presented here has helped us to gain further insights into the genetic background of the dynamic recruitment and dismissal of genes to form an important, converging extended phenotypic structure such as the shell and the shell-like eggcase. Additionally, it allows us to explore the evolution of from benthic to pelagic lifestyles in cephalopods and octopods.

Comparative brain structure and visual processing in octopus from different habitats

Octopods are masters of camouflage and solve complex tasks, and their cognitive ability is said to approach that of some small mammals. Despite intense interest and some research progress, much of our knowledge of octopus neuroanatomy and its links to behavior and ecology comes from one coastal species, the European common octopus, Octopus vulgaris. Octopod species are found in habitats including complex coral reefs and the relatively featureless mid-water. There they encounter different selection pressures, may be nocturnal or diurnal, and are mostly solitary or partially social. How these different ecologies and behavioral differences influence the octopus central nervous system (CNS) remains largely unknown. Here we present a phylogenetically informed comparison between diurnal and nocturnal coastal and a deep-sea species using brain imaging techniques. This study shows that characteristic neuroanatomical changes are linked to their habits and habitats. Enlargement and division of the optic lobe as well as structural foldings and complexity in the underlying CNS are linked to behavioral adaptation (diurnal versus nocturnal; social versus solitary) and ecological niche (reef versus deep sea), but phylogeny may play a part also. The difference between solitary and social life is mirrored within the brain including the formation of multiple compartments (gyri) in the vertical lobe, which is likened to the vertebrate cortex. These findings continue the case for convergence between cephalopod and vertebrate brain structure and function. Notably, within the current push toward comparisons of cognitive abilities, often with unashamed anthropomorphism at their root, these findings provide a firm grounding from which to work.

Separating species of North Pacific bathyal octopods of Graneledone Joubin, 1918

Separating species of North Pacific bathyal octopods of Graneledone Joubin, 1918

Cephalopoda (Mollusca) of the Colombian Caribbean Sea

The cephalopod fauna in Colombian Caribbean waters is poorly known. This work gives an overview of the species found in the area. For elaborating this list, the most relevant natural history collections where the material of the area’s is material is deposited were consulted, identifications were verified compared with type material and original descriptions and redescriptions. In the Colombian Caribbean Sea 48 cephalopod species are present in different environments, represented in 17 families and 33 genera. There is one Spirula, seven sepiolids, 21 squids, and 19 octopod species. Most animals are from shallow coastal waters.

Born With Bristles: New Insights on the Kölliker’s Organs of Octopus Skin

The entire skin surface of octopus embryos, hatchlings and juveniles bears scattered tufts of tiny chitinous setae within small pockets, from which they can be everted and retracted. Known as Kölliker’s organs (KO), they disappear before the subadult stage. The function of these structures during the early life of the octopus is unknown, despite having been first described nearly two centuries ago. To investigate these organs further, general trends in size of KO distribution and density were analyzed in hatchlings and juveniles of 17 octopod species from all oceans, representing holobenthic, holopelagic and meropelagic modes of life. The size of the KO is fairly constant across species, unrelated to mode of life or hatchling size. The density of KO is similar on ventral and dorsal body surfaces, but hatchlings of smaller size tend to have a higher density of KO on the aboral surface of the arms. Analysis of a series of post-hatchingOctopus vulgarisshows KO size to be constant throughout ontogeny; it is therefore a consistent structure during the octopus early life from planktonic hatchling to benthic juvenile. New KO are generated on the skin of the arm tips during the planktonic period and initial benthic lives of juveniles. Their density, on both the mantle and arms, gradually decreases as the octopus grows. In older benthic juveniles, the KO degrades, losing its setae and the base of its follicle becomes exposed as a nearly circular stump of muscle. It is estimated that fully everted KO increase the body surface area by around two-thirds compared to when the KO are retracted. This modular mechanism of body surface extension and roughness probably influences flow-related forces such as drag and propulsion of the moving surface of the young octopus while it is of small size with a relatively large surface area. In addition, the distribution of these organs on the aboral surface of the arms of the octopus and their birefringent properties suggest a role in camouflage. Further research is needed to test these hypotheses of KO function in live animals.

Ontogenetic variation of trophic habitat for sympatric benthic octopods in East China Sea derived from isotopic analysis on beaks

Sympatry is commonly observed in marine species, and always accompanied by high competition. Octopus consists of large amount of species and also widely distributed in the neritic area of the sea. As typical benthic species, octopus tend to live in the similar habitat with less movement during its lifetime. It is important to understand the trophic ecology of sympatric octopod species, which play an irreplaceable role in marine ecosystem. In this study, four neritic octopus species in the East China Sea (Amphioctopus fangsiao, Amphioctopus ovulum, Octopus minor and Octopus sinensis) were chose, we used stable isotope analysis (SIA) to analyze the variation of δ13C and δ15N derived from beak to assess the trophic variation among species and maturity stages. O. sinensis has the largest body and beak size than other species, and this species also had highest mean δ13C, δ15N value among species. The result of ANOVA showed that significant differences existed among four species for isotopic values. The overlaps among species were also calculated by standard ellipse area (SEAc). Isotopic overlap was decreased from immature stage to mature stage. The trophic niches were shrunk from immature to mature for all the four octopods species except for A. ovulum, which presented an expansion tendency. Trophic overlaps between specific two species in different groups were also calculated with distribution and mean values based on Bayesian model. The highest and lowest isotopic overlap occurred between O. minor and A. ovulum in immature group, A. fangsiao and O. sinensis in mature group, respectively. The four octopods species had very different trophic niches during ontogeny.

Nocturnal Solitary Sneakers Versus Diurnal Social Explorers – Brain Evolution in Octopods

Octopods are masters of camouflage, solving complex tasks, expressing emotion and their cognitive ability is said to approach that of some small mammals. Despite intense interest and some research progress, much of our knowledge of octopus neuroanatomy and its links to behaviour and ecology comes from one coastal species, the European common octopus, Octopus vulgaris a largely nocturnal coastal dweller. Octopod species are found in habitats including complex coral reefs to the relatively featureless deep mid-water. There they encounter different selection pressures, may be nocturnal or diurnal and mostly solitary or partially social. How these different ecologies and behavioural differences influence the octopus central nervous system (CNS) or brain remains largely unknown. Here we present a phylogenetically-informed comparison between diurnal and nocturnal coastal and a deep-sea species using brain imaging techniques. This study shows that characteristic neuroanatomical changes are linked to their life modes and ecological niches. Octopods are voracious visual predators and we demonstrate enlargement and division of the optic lobe as well as structural foldings and complexity in the underlying CNS. It appears these modifications are linked to behavioural adaptation (diurnal versus nocturnal; social versus solitary) and ecological niche (reef versus deep sea), but phylogeny may play a part also. The difference between solitary and social life is mirrored within the brain including the formation of multiple compartments, or gyri, in the vertical lobe. This brain region has previously been linked to cognitive capability and is likened to the vertebrate cortex. Some of the life-mode related modifications described here are convergent with similar progressions of complexity found within the vertebrates. These findings continue the case for convergence between cephalopod and vertebrate brain structure and function. Notably, within the current push towards comparisons of cognitive abilities, often with unashamed anthropomorphism at their root, these findings provide a firm grounding from which to work.

Life history traits of the deep-sea pelagic cephalopods Japetella diaphana and Vampyroteuthis infernalis

The pelagic cephalopods Japetella diaphana and Vampyroteuthis infernalis are charismatic and widely distributed members of deep pelagic ecosystems. Their habitat temperatures, metabolic rates, feeding and reproductive strategies all together suggest that the pace of life in these species is reduced when compared to neritic octopod species, but information on longevity, growth rates and age estimations are absent to date. To estimate the pace of life in pelagic octopods, this study investigated size at maturity, reproductive strategy, and the number of growth-increments in the upper beak lateral walls (LWS) of J. diaphana (an octopod) and V. infernalis (a vampyromorph). Daily deposition of growth increments in hard body structures (e.g., beaks and stylets) has been validated experimentally in some temperate and tropical octopods, but remains unquantified and not yet validated for most deep-sea and high-latitude cephalopods. We used a diverse assemblage of specimens ranging from early juveniles to adults for both species. Mature J. diaphana had a mantle length (ML) of 53–144 mm and a body mass (BM) of 18–235 g. A brooding female of J. diaphana captured at 1352 m in the Gulf of California was carrying 1419 eggs in pre-organogenetic stage that measured ~2.5 mm in diameter. The size range of mature V. infernalis was ML 66–122 mm and BM 34–286 g. The number of growth increments in the beaks ranged from 21 to 207 in J. diaphana and from 89 to 375 in V. infernalis. If the growth increments are formed daily, like in tropical octopod species, age estimates are incongruent with the low metabolic rates and reproductive strategies of the two species. These observations suggest that growth increments may require more than one day to be formed. To better understand the life histories of invertebrates in the largest but least studied habitat on the planet, age and growth validation studies are critical.

Antarctic octopod beaks as proxy for mercury concentrations in soft tissues

As the role of mercury is poorly known in Southern Ocean biota, the total mercury (T-Hg) concentrations were evaluated in upper/lower beaks, digestive gland, gills and mantle muscle of Adelieledone polymorpha and Pareledone turqueti, two of the most abundant octopod species around South Georgia. Beaks had the lowest T-Hg concentrations (A. polymorpha: [T-Hg]Upper = 27.2 ± 12.9 ng∙g−1 and [T-Hg]Lower = 27.5 ± 20.0 ng∙g−1; P. turqueti: [T-Hg]Upper = 34.6 ± 13.9 ng∙g−1 and [T-Hg]Lower = 56.8 ± 42.0 ng∙g−1), followed by gills and muscle. The highest values were recorded in the digestive gland (A. polymorpha: 251.6 ± 69.7 ng∙g−1; P. turqueti: 347.0 ± 177.0 ng∙g−1). Significant relationships were found between the concentrations of T-Hg in the beaks and muscle of A. polymorpha (T-Hg in muscle is 10 times higher than in beaks). This study shows that beaks can be used as proxy for T-Hg in muscle for some octopod species, and a helpful tool for estimating total Hg body burden from beaks.

A biogeographic framework of octopod species diversification: the role of the Isthmus of Panama.

The uplift of the Isthmus of Panama (IP) created a land bridge between Central and South America and caused the separation of the Western Atlantic and Eastern Pacific oceans, resulting in profound changes in the environmental and oceanographic conditions. To evaluate how these changes have influenced speciation processes in octopods, fragments of two mitochondrial (Cytochrome oxidase subunit I, COI and 16S rDNA) and two nuclear (Rhodopsin and Elongation Factor-1α, EF-1α) genes were amplified from samples from the Atlantic and Pacific oceans. One biogeographical and four fossil calibration priors were used within a relaxed Bayesian phylogenetic analysis framework to estimate divergence times among cladogenic events. Reconstruction of the ancestral states in phylogenies was used to infer historical biogeography of the lineages and species dispersal routes. The results revealed three well-supported clades of transisthmian octopus sister species pair/complex (TSSP/TSSC) and two additional clades showing a low probability of species diversification, having been influenced by the IP. Divergence times estimated in the present study revealed that octopod TSSP/TSSC from the Atlantic and Pacific diverged between the Middle Miocene and Early Pliocene (mean range = 5–18 Ma). Given that oceanographic changes caused by the uplift of the IP were so strong as to affect the global climate, we suggest that octopod TSSP/TSSC diverged because of these physical and environmental barriers, even before the complete uplift of the IP 3 Ma, proposed by the Late Pliocene model. The results obtained in this phylogenetic reconstruction also indicate that the octopus species pairs in each ocean share a recent common ancestor from the Pacific Ocean.

Redescription of Amphioctopus ovulum (Sasaki, 1917) (Cephalopoda : Octopodidae) and comparative morphological analyses among three species of violet-ringed octopods

Amphioctopus ovulum (Sasaki, 1917) is a small to moderate-sized octopus, which can be identified by the iridescent violet ring present in the dark ocellus on the web between the bases of arms II and III. Comprehensive taxonomic review is required to fully characterise this species because the syntypes are missing and the description is insufficiently complete for modern octopod taxonomy. In this study, the species A. ovulum is redescribed with morphological and morphometric characters of 18 specimens collected from the coastal waters of China. The distribution of A. ovulum extends from the Gulf of Thailand, through Cambodia, Vietnam, Philippines, through the South China Sea and the East China Sea to Japan. The swollen terminal organ diverticulum and long spermatophores make it possible to distinguish A. ovulum clearly from A. rex and A. neglectus, species with similar morphological characters of violet rings. Moreover, three species of violet-ringed octopods were clearly differentiated by sequences of the partial mitochondrial genes COI and COIII. Three monophyletic clades resolved in phylogenetic trees. Amphioctopus rex and A. neglectus clustered into a sister taxon, and clustered with the remaining Amphioctopus species.

Show your beaks and we tell you what you eat: Different ecology in sympatric Antarctic benthic octopods under a climate change context

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 (δ13C) and nitrogen (δ15N) 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 (δ13C: −19.21 ± 1.87‰, mean ± SD for both species) but explore trophic niches partially different during adult life stages (δ15N: 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.

Show us your beaks and we tell you what you eat: Different ecology in sympatric Antarctic benthic octopods under a climate change context

Show us your beaks and we tell you what you eat: Different ecology in sympatric Antarctic benthic octopods under a climate change context

Octopods of the Canary Islands. New records and biogeographic relationships

ABSTRACTTwo octopod species are reported from the Canary Islands (eastern Atlantic Ocean) for the first time: the deep sea four-horn octopus, Pteroctopus tetracirrhus (Delle Chiaje, 1830) and the gelatinous giant octopus, Haliphron atlanticus Steenstrup, 1861. Both female specimens were caught in Tenerife. Haliphron atlanticus is described from fresh remains found floating close to the southwest coast and the second species, P. tetracirrhus, is described from a specimen captured in a shrimp trap at 200 m depth on the southeastern coast of Tenerife. With these two additions the revised and updated list of octopod species of the Canary Islands now comprises eight families and 18 species, all of them incirrate octopods. The zoogeographic relationships of octopod species from other Atlantic regions, including the Mediterranean Sea, were studied. The likely directions of faunal flows were inferred based on affinity indices, showing that Mauritania could be the most probable source of the octopod species of the Canary Islands and the rest of the Macaronesian archipelagos.

Complete mitochondrial genome and the phylogenetic position of the pelagic octopus Tremoctopus violaceus (Mollusca: Tremoctopodidae)

Tremoctopus violaceus is a small species of pelagic octopods which inhabit in subtropical and tropical open oceans. The mitogenome of T. violaceus is 16,015 base pairs (bp) in length and contained 13 protein-coding genes, two rRNA genes, and 22 tRNA genes. Sequence analysis showed that the overall base composition is 31.5% for A, 40.47% for T, 7.79% for C, and 20.24% for G. The newly characterized complete mitochondrial genome of T. violaceus will provide essential data for further studies of this endangered species.

Comparison of the genetic relationship between nine Cephalopod species based on cluster analysis of karyotype evolutionary distance.

Karyotype analysis was carried out on gill cells of three species of octopods using a conventional air-drying method. The karyotype results showed that all the three species have the same diploid chromosome number, 2n=60, but with different karyograms as 2n=38M+6SM+8ST+8T, FN (fundamental number)=104 (Cistopus chinensis Zheng et al., 2012), 2n=42M+6SM+4ST+8T, FN=108 (Octopus minor (Sasaki, 1920)) and 2n=32M+16SM+12T, FN=108 (Amphioctopus fangsiao (d’Orbigny, 1839–1841)). These findings were combined with data from earlier studies to infer the genetic relationships between nine species via cluster analysis using the karyotype evolutionary distance (De) and resemblance-near coefficient (λ). The resulting tree revealed a clear distinction between different families and orders which was substantially consistent with molecular phylogenies. The smallest intraspecific evolutionary distance (De=0.2013, 0.2399) and largest resemblance-near coefficient (λ=0.8184, 0.7871) appeared between O. minor and C. chinensis, and Sepia esculenta Hoyle, 1885 and S. lycidas Gray, 1849, respectively, indicating that these species have the closest relationship. The largest evolutionary gap appeared between species with complicated karyotypes and species with simple karyotypes. Cluster analysis of De and λ provides information to supplement traditional taxonomy and molecular systematics, and it would serve as an important auxiliary for routine phylogenetic study.

Macro and microscopic structure of the digestive system of Octopus vulgaris From Alexandria water on the Mediterranean Sea

The present work deals with the macroscopic and microscopic anatomy of Octopus vulgaris from Alexandria water on the Mediterranean sea. The digestive system is formed of the buccal mass, oesophagus, crop, stomach, caecum, intestine and rectum. The associated glands included the anterior and posterior salivary glands, liver and digestive duct appendages (Pancreas). In the present study, the structure of the buccal mass, with the upper and lower jaws has been described. Also the radular teeth, which are specific for their morphology and considered of taxonomic evidence for different octopod species, have been described. The oesophagus enters the crop on its right side approximately one third of the way from its anterior end. Musculature and lining epithelium of the two regions have been studied. The stomach is a region where the grinding of food occurs so that its lining epithelium is covered by thick layer of cuticle. The caecum is a coiled organ which lies below the stomach and has primary and secondary leaflet-like structures. Secretory cells are found between the columnar cells which form the lining epithelium. The intestine is a long tube, which is followed by short rectum, and has internal folds with scattered mucous cells between the columnar epithelial cells. The rectum has no mucous cells and its lining epithelium is covered with a thin layer of cuticle. The anterior salivary glands are smaller in size than the posterior ones and have two types of secretory cells like the posterior salivary glands. The digestive gland is a large grayish cigar-shaped organ, consisting of two fused lobes. It has two types of cells, big vaculated cells and small triangular ones. The pancreas lies around the two digestive ducts and forms a small wedge-shaped appendages, each is formed of a single layer of short columnar cells.

Early Mode of Life and Hatchling Size in Cephalopod Molluscs: Influence on the Species Distributional Ranges.

Cephalopods (nautiluses, cuttlefishes, squids and octopuses) exhibit direct development and display two major developmental modes: planktonic and benthic. Planktonic hatchlings are small and go through some degree of morphological changes during the planktonic phase, which can last from days to months, with ocean currents enhancing their dispersal capacity. Benthic hatchlings are usually large, miniature-like adults and have comparatively reduced dispersal potential. We examined the relationship between early developmental mode, hatchling size and species latitudinal distribution range of 110 species hatched in the laboratory, which represent 13% of the total number of live cephalopod species described to date. Results showed that species with planktonic hatchlings reach broader distributional ranges in comparison with species with benthic hatchlings. In addition, squids and octopods follow an inverse relationship between hatchling size and species latitudinal distribution. In both groups, species with smaller hatchlings have broader latitudinal distribution ranges. Thus, squid and octopod species with larger hatchlings have latitudinal distributions of comparatively minor extension. This pattern also emerges when all species are grouped by genus (n = 41), but was not detected for cuttlefishes, a group composed mainly of species with large and benthic hatchlings. However, when hatchling size was compared to adult size, it was observed that the smaller the hatchlings, the broader the latitudinal distributional range of the species for cuttlefishes, squids and octopuses. This was also valid for all cephalopod species with benthic hatchlings pooled together. Hatchling size and associated developmental mode and dispersal potential seem to be main influential factors in determining the distributional range of cephalopods.