Argonauta Argo Research Articles

Analytical justifications of constructive parameters of bionic colters for vertical soil treatment

Bionic coulters imitate natural forms and functions, which help reduce energy costs for soil tillage. The aim of the research was to justify the design and structural parameters of turbo discs (coulters) for vertical tillage based on the principles of bionic reverse engineering. Using this method, an equation for the shape of the turbo discs (coulters) was derived, which was obtained by approximating the shell of the argonaut (Argonauta argo). The equation takes into account the main structural parameters of the turbo discs: diameter Dd, cutout height Hm, wave height Hw, number of cutouts n, and spiral coefficient k. As a result of analytical studies on the interaction process between a solid disc and plant residues, the optimal diameter value was determined to be Dd=460 mm under the condition of submerging stems with a thickness of 10-20 mm to a depth of 80 mm. The analytical studies confirmed that the presence of cutouts on the disc prevents stem deflection and ensures better stem capture. In analysing the obtained dependencies using the Wolfram Cloud software package, the optimal values for the cutouts were determined: cutout height Hm=40 mm, number of cutouts n=8. The presence of waves on the disc surface ensures that the interaction with plant residues is independent of their position on the field surface and creates conditions for vertical soil tillage. It was found that, to minimize specific cutting resistance and maximize the degree of soil fragmentation, the optimal wave parameters for the coulter are a wave height of Hw=24.4 mm. The justified parameters of the coulters provide the best balance between soil fragmentation efficiency and reduction in energy consumption for soil tillage. The obtained results can be used to adapt existing agricultural machinery to the new structural parameters of coulters to improve its efficiency.

Species Delimitation of Argonauta Paralarvae Reveals an Extensive Morphological Variability in the Northern Humboldt Current System

Argonauts or paper nautiluses are pelagic octopod cephalopods with a cosmopolitan distribution in tropical and subtropical waters around the world. Unlike other species of octopus, these are characterized by the fact that the female has a shell that serves as the breeding chamber for the eggs. Over time, this structure has been used as a taxonomic diagnostic character, causing problems in the systematics of this genus, with around 50 synonymies reported. Only two species, Argonauta argo and A. nouryi, have been reported in the Northern Humboldt Current System; however, there is taxonomic uncertainty regarding these species, which is reflected in the paralarvae (the first stage of life after hatching). In the paralarvae, the chromatophore patterns are considered to be conservative and reliable taxonomic characteristics. The objective of this study is to demonstrate the extensive variability in the chromatophore arrangement of Argonauta paralarvae in the Northern Humboldt Current using DNA barcoding and five species delimitation models. Our results include up to 11 different paralarvae morphotypes according to the pattern of chromatophores (number and arrangement) and 2 shell morphotypes. Species delimitation methods divided the 13 Argonauta morphotypes into two consensus molecular taxonomic units (MOTUs), A. argo and A. nouryi. Additionally, the results revealed an extensive morphological variability in the paralarvae and female shells of A. nouryi, demonstrating the importance of molecular data in studies involving species with different life stages, especially when this extensive morphological variability obscures conventional analyses.

Ammonoid extinction versus nautiloid survival: Is metabolism responsible?

Abstract Understanding the mechanism of selective extinction is important in predicting the impact of anthropogenic environmental changes on current ecosystems. The selective extinction of externally shelled cephalopods at the Cretaceous-Paleogene (K-Pg) mass extinction event (ammonoids versus nautiloids) is often studied, but its mechanism is still debated. We investigate the differences in metabolic rate between these two groups to further explore the causes of selective extinction. We use a novel metabolic proxy—the fraction of metabolic carbon in the stable carbon isotope ratio of shell material (Cmeta)—to determine metabolic rate. Using this approach, we document significant differences in Cmeta among modern cephalopod taxa (Nautilus spp., Argonauta argo, Dosidicus gigas, Sepia officinalis, and Spirula spirula). Our results are consistent with estimates based on oxygen consumption, suggesting that this proxy is a reliable indicator of metabolic rate. We then use this approach to determine the metabolic rates of ammonoids and nautiloids that lived at the end of the Cretaceous (Maastrichtian). Our results show that the nautiloid Eutrephoceras, which survived the K-Pg mass extinction event, possessed a lower metabolic rate than co-occurring ammonoids (Baculites, Eubaculites, Discoscaphites, and Hoploscaphites). We conclude that the lower metabolic rate in nautiloids was an advantage during a time of environmental deterioration (surface-water acidification and resulting decrease in plankton) following the Chicxulub asteroid impact.

How Rare Are Argonautoidea Octopuses in the Mediterranean? New Data from Stranding Events, Stomach Contents and Genetics

The present paper represents the first all-encompassing study on all Mediterranean holopelagic octopods belonging to Argonautoidea (Argonauta argo, Ocythoe tuberculata, Tremoctopus gracilis, Tremoctopus violaceus). Argonautoidea octopuses were collected by different sampling methods in the Strait of Messina and southern Tyrrhenian Sea. The aim of this paper was to improve knowledge, using information from different data sources, such as the study of stranded individuals or accidental caught specimens, as well as the analysis of stomach content of large pelagic fishes. Moreover, we investigated their taxonomic profile through the amplification of the mitochondrial cytochrome c oxidase subunit I (COI). Overall, 47 fresh holopelagic octopods were collected, including valuable records of rare males. Moreover, 330 Argonautoidea octopuses were found in the stomachs of 800 predators. The results provided evidence that these cephalopods are more abundant than thought in the past. The molecular approach supported the ecological results with interesting insights. The similarity-based identifications and tree-based methods indicated that three females could be identified as Tremoctopus violaceus in agreement with their morphological classifications. The sequences obtained from the two T. gracilis individuals were clustered with the sequences of Tremoctopus violaceus from the Gulf of Mexico and were differentiated from the sequences attributed to T. gracilis and T. robsoni. The study represents a valuable contribution to the genetic characterization of Mediterranean individuals of the genera Tremoctopus, Argonauta and Ocythoe.

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.

New Record of the Pelagic Octopods Argonauta argo (Linnaeus, 1758) off the Shore of the Northern Tip of the Gulf of Aqaba in Jordan

A few specimens of the pelagic octopod Argonauta argo (Linnaeus, 1758) were found after they were washed up by currents along the northern beach of the Gulf of Aqaba in Jordan. This article describes this record and provides a review of the species’ sightings worldwide and their importance as prey in maintaining an ecological balance.

Stranding record of the common paper nautilus Argonauta argo on the coast of Yoichi Bay, Hokkaido in the autumn of 2021

Stranding record of the common paper nautilus <i>Argonauta argo</i> on the coast of Yoichi Bay, Hokkaido in the autumn of 2021

The full mitochondrial genome sequence of the greater argonaut Argonauta argo (Cephalopoda, Argonautoidea) and its phylogenetic position in Octopodiformes

The greater argonaut Argonauta argo is a species of the paper nautilus (Argonautidae), which is a family in Octopoda. In this paper, we report its full mitogenome sequence, which was obtained from a specimen collected in the Japan Seas near Oki Island, Shimane Prefecture, in Japan. The sequence was determined using the NGS Illumina HiSeq platform. With its 37 genes, the mitogenome shows a typical metazoan and Octopoda genomic structure, and similar to the mitogenome of the previously reported congener, A. hians. To confirm A. argo phylogenetic position in Octopoda, we conducted maximum likelihood phylogenetic analysis, using a data set including publicly available 17 Octopodiformes, five Decapodiformes, three Nautiloids and two outgroup Conchiferans. The result confirmed the affinity of Argonautidae to Tremoctopus, and the sister group position of this clade against the rest of incirrate Octopods. The mitogenome and phylogeny of A. argo reported here will be useful for future studies involving this enigmatic species, including on the reacquisition of external calcified shell structures in mollusks.

Stranding record of the common paper nautilus Argonauta argo on the coast of Yoichi Bay, Hokkaido in the autumu of 2020

Stranding record of the common paper nautilus <i>Argonauta argo</i> on the coast of Yoichi Bay, Hokkaido in the autumu of 2020

When nature continues to surprise: observations of the hectocotylus of Argonauta argo, Linnaeus 1758

In this paper, a live hectocotylus, found inside a stranded female Argonauta argo shell, allowed us to describe the behaviour of this copulatory arm and add new information on its morphology. The hectocotylus penile filament is contained in a special membranous pocket or sac, almost completely transparent, extending from the apex of the basal part to about one-third of the central section. The hectocotylus assumes a folded position to protect the penile filament in the membranous sac. This is probably extracted only when copulation occurs. Our observations seem to suggest that the shell may have the secondary function of storing and protecting the hectocotyli received by males until the copulation. The observations confirmed the high vitality and endurance of the hectocotylus after detachment from the A. argo male.

NAUTILUS BERCANGKANG RAPUH DARI TELUK TOMINI KABUPATEN PARIGI MOUTONG SULAWESI TENGAH, INDONESIA

Nautilus bercangkang rapuh termasuk dalam kelas Cephalopoda, famili Argonautidae. Tujuan dari penelitan ini adalah untuk mengidentifikasi jenis Nautilus bercangkang rapuh yang ditemukan di perairan Teluk Tomini Kabupaten Parigi Moutong. Sampel paper Nautilus ditangkap pada kedalaman 1000 m. Hasil penelitian memperlihatkan bahwa sampel yang berhasil dikoleksi selama bulan Maret hingga bulan Desember hanya sebanyak 6 spesimen pada kedalaman 70-80 m, dengan 4 spesimen yang bertelur dan 2 spesimen tanpa telur. Dari 6 spesimen yang ditemukan, diketahui ada 2 jenis yaitu Argonauta argo dengan rerata panjang cangkang= 34,05 mm, lebar cangkang= 22,20 mm dan lebar aperture= 11,15 mm. A. argo memiliki 8 tentakel dengan 4 tentakel panjang dan 2 pendek. Warna cangkangnya lebih cerah dari cangkang A. hians, cangkangnya lebih pipih dengan dua baris duri kecil yang sangat berdekatan di sepanjang sisi dorsal dan halus, sepanjang sisi ventral ujung tebal dan meruncing. Serta A. hians yang memiliki rerata panjang cangkang 47,02 mm, lebar cangkang 33,07 mm dan lebar aperture 21,30 mm, memiliki duri yang lebih besar dan tumpul, di sepanjang sisi dorsal yang lebar, sepanjang sisi lateral aperture melebar dan tidak membentuk seperti sayap. Garis rusuk yang terdapat di sisi lateral lebih tebal dan renggang. Jenis Nautilus bercangkang rapuh yang ditemukan di Teluk Tomini, yaitu A. argo dan A. hians.

Presence of Argonauta argo and Ocythoe tuberculata in Madeira Archipelago

Five new records are presented on the presence of two rare cephalopod species (Argonauta argo (Linnaeus, 1758) and Ocythoe tuberculata (Rafinesque, 1814)) in the waters of the Autonomous Region of Madeira, Portugal. Increased collaboration with fishermen has made it possible to significantly add to the number of records in the region, and further collaboration may provide key insights into the ecology of these rare cephalopod species.

Stranding record of the common paper nautilus Argonauta argo on the coast of Yoichi Bay, Hokkaido in the autumn 2018

Stranding record of the common paper nautilus Argonauta argo on the coast of Yoichi Bay, Hokkaido in the autumn 2018

Stranding record of the common paper nautilus Argonauta argo on the coast of Yoichi Bay, Hokkaido, in the autumn of 2016

Stranding record of the common paper nautilus Argonauta argo on the coast of Yoichi Bay, Hokkaido, in the autumn of 2016

Belemnite biomineralization, development, and geochemistry: The complex rostrum of Neohibolites minimus

Belemnites, a group of extinct coleoid cephalopods, were important components of Mesozoic marine ecosystems. Their calcitic rostra are extensively used in biostratigraphy and geochemistry. The preservation state of the rostra is a crucial factor for the interpretation of their geochemical data. However, their preservation is difficult to assess, since no modern cephalopod forms calcitic rostra. The biomineralization process of the rostrum, which functioned as an internal skeleton, is poorly understood for most species. This also applies for the epirostrum, a late ontogenetic extension of the rostrum which is only present in some belemnite species. The primary structure and function of this character are still being debated controversially.We have investigated the microstructure, stable isotope (δ13C, δ18O), and elemental composition (Mg/Ca, Sr/Ca, Fe/Ca, Mn/Ca) of both, ortho- and epirostra of the belemnite species Neohibolites minimus (Early Cretaceous, Albian). For comparison, we studied argonauts (Argonauta argo). These recent octopuses build a calcitic shell. Ortho- and epirostra of N. minimus show microstructural and geochemical differences. Cathodoluminescence-microscopy and the microstructures of belemnites and argonauts indicate that blue/orange luminescent growth lines in the studied belemnites are largely a primary biomineralization phenomenon and not solely due to diagenesis. Based in part on analogy to argonaut shell, we suggest that the inner part of the belemnite epirostrum is a continuation of an originally organic apical line. The development and evolution of the epirostrum as a potential sexually selected character is discussed. Well-preserved epirostrum calcite has higher element/Ca ratios than the calcite of the orthorostrum, suggesting a vital effect affecting these values. We further found evidence for vital effects on the stable isotope signatures due to metabolic and kinetic fractionation.Our findings suggest a complex mineralization process of the studied rostra. Different microstructures with distinctive geochemical signatures occur in a single belemnite species. Vital effects played an important role in the rostrum geochemistry, complicating the application of the rostra as paleoclimatic archives.

The Canary record of the evolution of the North Atlantic Pliocene: New 40Ar/39Ar ages and some notable palaeontological evidence

Abstract Two new 40Ar/39Ar ages (*) and previously published K/Ar ages of basaltic pillow lava flows are coeval with closely-related fossiliferous marine layers, allowing us to establish the beginning (5.8; 5.0; 4.8 Ma at Ajui, Fuerteventura Island and 4.8 ± 0.03 Ma (2σ)* at Tamaraceite) and a middle stage (4.20 ± 0.18 Ma (2σ)* at La Esfinge in Gran Canaria Island) of Early Pliocene marine deposits in the Canary Islands. Here the presence of tropicopolitan fossils (Megaselachus megalodon, Janthina typica) suggests the influence of a possible Central American Circumtropical Current during the Pliocene and in the North Atlantic basin. The presence of both Janthina typica and the Argonauta argo also indicate the occurrence of tropical storms in the area of the Canary Islands around that time. In addition, the pillow lava flow at La Esfinge overlies a submarine pyroclastic layer containing Ostrea offreti that was preserved in its life position, a fossil from the terminal Miocene and commonly found on the south eastern Iberian Peninsula. At La Cruz on Fuerteventura Island, a dune formed above marine deposits lies beneath a palaeosol and a basaltic lava flow that was K/Ar dated at 2.9 Ma. Near El Marmol in Gran Canaria the corresponding palaeosol lies between lava flows K/Ar dated at 3 Ma. Based on these observations, we argue in this paper that the first appearance of the Canary Current, the eastern boundary current of the North Atlantic sub-tropical gyre, occurred between 4.2 Ma and 2.9 Ma ago. This was followed by a major sea level drop (of about 40 m) and the formation of a first fossil-bearing palaeosol which indicate that major climate change that took place around 2.95–2.82 Ma.

Taxonomy and biology of the argonauts (Cephalopoda: Argonautidae) with particular reference to Australian material

Argonauts (Argonautidae: Cephalopoda) are a family of pelagic octopuses that inhabit tropical and temperate oceans of the world. Argonauts are most commonly recognised by the beautiful white shells of females (known as “paper nautiluses”) that wash up on beaches throughout the world. Historically, taxonomic delineation of the group has relied on features of these shells—structures not homologous to true molluscan shells and prone to extreme variability. As a consequence, more than 50 species names have been coined worldwide to date. This study constitutes the first thorough examination of argonauts from Australian waters. All argonaut material housed in Australian museums was examined using modern octopus taxonomic methodology and compared to material from key museums throughout the world. Three argonaut species are identified from Australian waters: Argonauta nodosus, Argonauta hians and Argonauta argo. All species can be separated based on morphological characters of males and females, and features of the shells of females. Detailed diagnoses, synonymies, maximum size records, distributional records, nomenclature corrections and biological information are included for each species. Details of the east Pacific Argonauta nouryi, the only other species recognised worldwide, are included for comparative purposes.

Mass strandings of the common paper nautilus Argonauta argo along the coast of Yoichi Bay, Hokkaido, in the autumn of 2012

Mass strandings of the common paper nautilus <i>Argonauta argo</i> along the coast of Yoichi Bay, Hokkaido, in the autumn of 2012

CEFALÓPODES CAPTURADOS PELA PESCA COMERCIAL DE TALUDE NO SUDESTE E SUL DO BRASIL

The development of demersal fishing in slope areas off southern Brazil (21o - 34o S) accelerated since the year 2000 as a result of commercial operations conducted by national and chartered bottom longliners, potters, gillnetters and trawlers. These operations were continuously monitored by observers as part of scientific research program carried out by the Fisheries Study Group (CTTMar - UNIVALI) in collaboration with Brazilian Government. Besides the assessment of the main stocks, efforts have been concentrated on assessing the impact generated by fishing on non-target organisms and on deep-water ecosystem as a whole. In this context, this work lists cephalopod fauna caught by both trawling and gillnetting between 2001 and 2003. Only the argentinean squid Illex argentinus was included between trawlers target-species, specially during the winter of 2001. Other 15 species, included in the orders Spirulida (1), Sepiolida (1), Teuthida (6) and Octopodida (5), were caught as by-catch of trawling operations. Particularly abundant in some fishing trips were the squid Pholidoteuthis adami and Histioteuthis corona corona, and the octopus Vosseledone charrua. Gillnet fishing directed towards the monkfish between 2001 and 2002 caught, besides the argentinean squid, two octopods including the pelagic Argonauta argo.

Phylogenetic Relationships among Major Species of Japanese Coleoid Cephalopods (Mollusca: Cephalopoda) Using Three Mitochondrial DNA Sequences

Phylogenetic relationships among 36 species of major coleoid cephalopods from Japanese waters were studied using partial sequences of three mitochondrial genes, 16S rDNA, 12S rDNA, and cytochrome c oxidase subunit I gene. Octopoda and Decapoda were monophylic groups. Within Sepioidea, Sepiadariidae and Sepiolidae were not closely related to Sepiidae, but rather related to Teuthoidea. Sepiidae with a distinct calcareous shell formed a single cluster. Myopsida was closely related to Oegopsida. Within Octopoda, Opisthoteuthis depressa and Argonauta argo diverged earlier than Octopodiidae. The common octopuses in Japanese waters were separated into three clusters. The first cluster occupied a basal position, and includes large-sized octopuses, such as Enteroctopus dofleini and Octopus (Paroctopus) conispadiceus from the continental shelf and upper slope. The second cluster consisted of long-armed octopuses, such as O. ornatus, O. minor, and O. sasakii. The third cluster contained small- to medium-sized octopus, such as Amphioctopus fangsiao, A. areolatus, O. cyaneus, and O. vulgaris, in which several species possess ocelli on the web. The second cluster formed the sister group to the third cluster.