Tremoctopus Violaceus Research Articles

Morphological Characteristics and DNA Barcoding of the Rare Blanket Octopus Tremoctopus violaceus (Cephalopoda: Tremoctopodidae) in the Adriatic Sea

Tremoctopods are epipelagic argonautoid octopods characterized by their expanded dorsal webs and strong sexual size dimorphism, with dwarfed males. The scarcity of taxonomic features attributed to this genus presents a challenge, and there is growing evidence of species misidentification in Tremoctopus genus on a molecular level. In this study, we investigated four female specimens of blanket octopus Tremoctopus violaceus caught by purse seine fishing in the Central Eastern Adriatic Sea in 2019. Individuals had smooth, firm and muscular bodies, dark bluish purple on the dorsal and iridescent silvery on the ventral side, with dorsal mantle lengths of 113, 82, 80 and 78 mm. The constructed phylogenetic trees based on the 16S ribosomal RNA and cytochrome c oxidase subunit I sequences of investigated Adriatic specimens and publicly available sequences showed strong support for the T. violaceus clade, consisting of individuals collected from the Adriatic Sea, Mediterranean Sea and Atlantic Ocean, with the exclusion of Indo-Pacific clade most probably corresponding to T. gracilis. To fully understand the life-history traits of Tremoctopus species, future research should focus on DNA-based methods for correct species identification combined with morphological characters, geographic distribution and ecological information.

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.

New record of a female violet blanket octopus (Tremoctopus violaceus, delle Chiaje, 1830) in the Strait of Messina, southern Italy

ABSTRACT In the present note an adult female of Tremoctopus violaceus delle Chiaje, 1830, is recorded from the Strait of Messina. Species of the family Tremoctopodidae are widely distributed in tropical oceans, but rare in coastal waters. The morphological characteristics coincide with those described by other authors. Necroscopic examination performed did not reveal any peculiar pathology. Morphometrical characteristics, photos and general information are given, expanding the knowledge about these rare cephalopods in Mediterranean basin.

New Records of Rare Species of Marine Invertebrates in the Eastern Mediterranean, Syria

Conducting further research and exerting more effort into field studies will aid the detection and recording of new, rare species of invertebrates in the Mediterranean and allow the examination of their biological and environmental characteristics. This article provides information on four species of sea crab (one of which is alien), two species of sea star, one species of sea urchin and two species of octopus, which have all been documented for the first time in Syrian waters. Samples were collected by fishing nets from a coastal area at medium depths (20–630 meters) from Ras al-Basit, Lattakia and Banias during 2020 and 2021. These species are: Actaea savignii (H. Milne Edwards, 1834); Dromia personata (Linnaeus, 1758);Geryon longipes (A. Milne-Edwards, 1882); Homola barbata (Fabricius, 1793); Peltaster placenta (Müller and Troschel, 1842); Chaetaster longipes (Bruzelius, 1805); Sphaerechinus granularis (Lamarck, 1816); Tremoctopus violaceus (Delle Chiaje, 1830);Ocythoe tuberculate (Rafinesque, 1814). Documenting the presence of these rare species is very important from an environmental and scientific perspective, and recording more of them requires coordination with the marine fishing sector in Syria. KEYWORDS Cephalopods, crustaceans, echinoderms, marine biodiversity, non-indigenous species,zoobenthos

First Integrative Morphological and Genetic Characterization of Tremoctopus violaceussensu stricto in the Mediterranean Sea.

Simple SummaryFour rare species are recognized within the genus Tremoctopus (Cephalopoda: Octopoda), i.e., T. gelatus, T. gracilis, T. robsoni, and T. violaceus. The accurate identification of organisms is a fundamental prerequisite to deepen our knowledge of the biology and ecology of a species. In this study, for the first time, an integrative morphological and genetic approach was undertaken to confirm the identity of specimens of the genus Tremoctopus collected in Mediterranean waters. Sequences of two mitochondrial genes were generated and analyzed from three Mediterranean females, allowing ascribing all the samples to the species T. violaceus sensu stricto. For the first time, barcoding sequences have been obtained from the presumed type locality of the species. This information is of particular importance for this rare species; it has been complemented with the detailed descriptions of morphometric and biological features, as well as beaks analyses for the age estimation of the samples.An integrative approach based on morphological and genetic analyses was undertaken for the first time to confirm the species identification of Mediterranean samples belonging to the genus Tremoctopus. Sequences of two mtDNA genes (cytochrome c oxidase subunit (COI) and 16S) were generated for the first time from Mediterranean samples. Both the similarity-based identifications and tree-based methods indicated that three females can be identified as Tremoctopus violaceus sensu stricto in agreement with their morphological classifications. All Mediterranean sequences clustered with the sequences of Tremoctopus violaceus from the Gulf of Mexico and were clearly differentiated from the sequences attributed to T. gracilis and T. robsoni. The chromatic pattern of the web and some features of gill filaments, arms formula, stylets, radulae, beaks, and stomach contents were given for all the samples; 105,758, 20,140, and 11,237 oocytes were estimated in the mature, immature, and developing samples, respectively. The presence of four spermatangia inside the cavity of the maturing female suggested the ability of this species to mate before reaching full maturity with more partners. Age investigation using beaks, performed for the first time in T. violaceus and within the genus gave results consistent with the different sizes and maturity conditions of the samples.

The first record of Tremoctopus violaceus sensu stricto Delle Chiaje,1830 in southwestern Gulf of Mexico gives a hint of the taxonomic status of Tremoctopus gracilis.

Knowledge on species taxonomic identity is essential to understand biological and biogeographical processes and for studies on biodiversity. Species the genus Tremoctopus have been confused in the past and are inconsistently identified. To clarify of the taxonomic diagnosis Tremoctopus violaceus Delle Chiaje, 1830, an evaluation of morphological and meristic characters, as well as morphometric indices and genetic analyses, was undertaken. The analyzed octopod was an opportunistically collected mature female of 640 mm in total length, with a mantle length of 135 mm and a total weight of 1.02 kg. Evidence of autotomy as a defensive mechanism for protecting the egg mass is presented. The 16S haplotype sequenced from this specimen represents the first one publicly available for this species from the Gulf of Mexico. The genetic divergence between this haplotype and those reported from the Pacific Ocean is representative of interspecific variation in other taxa, which suggests that “T. violaceus” in the Pacific Ocean (KY649286, MN435565, and AJ252767) should be addressed as T. gracilis instead. Genetic evidence to separate T. violaceus and T. gracilis is presented. The studied specimen from the Gulf of Mexico represents the westernmost known occurrence of T. violaceus and the first record from the southwestern Gulf of Mexico.

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.

Uncommon pelagic and deep-sea cephalopods in the Mediterranean: new data and literature review

Compared to their shelf-living relatives, the biology and ecology of most pelagic and deep-sea cephalopods is currently rather unknown owing to the difficulties to catch them. To cover the lack of information on these cephalopods, scientists have to make use of the limited and fragmentary data gathered from different sources such as sporadic captures, strandings or stomach contents of their predators. Here, we give some biological and ecological information on eleven uncommon pelagic and deep-sea cephalopods collected during more than fifteen years of fisheries surveys in the western Mediterranean Sea. The cephalopods investigated include two epipelagic octopuses (Ocythoe tuberculata and Tremoctopus violaceus), one deep-sea cirrate octopus (Opisthoteuthis calypso), the sepiolid Stoloteuthis leucoptera and seven teuthoid species inhabiting preferentially mesopelagic and bathypelagic waters (Abraliopsis morisii, Ancistrocheirus lesueurii, Brachioteuthis riisei, Chiroteuthis veranyi, Chtenopteryx sicula, Onychoteuthis banksii and Taonius pavo). Although all of these species are either cosmopolitan or present a wide distribution in other oceans, they are nevertheless relatively rare in catches, and therefore remain poorly known. The finding of T. pavo represents the first record of this cephalopod in the Mediterranean.

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This study presents new information on the feeding habits of the Atlantic spotted dolphins, Stenella frontalis, in the Western South Atlantic. Nine stomach contents of S. frontalis incidentally caught in fishing operations conducted by the gillnet fleet based on main harbour of Cananéia (25°00'S; 47°55'W), southeastern Brazil, were analyzed. These specimens were captured between 2005 and 2007. A total of 1 422 cephalopod beaks, 147 otoliths and three crustaceans were recovered from the stomach contents. The dolphins assessed preyed on at least eight different fish species of the families Trichiuridae, Carangidae, Sparidae, Merluccidae, Engraulidae, Sciaenidae, Congridae and Scombridae, five cephalopod species of the families Loliginidae, Sepiolidae, Tremoctopodidae and Thysanoteuthidae, and one shrimp species of the Penaeidae family. Based on the analysis of the Index of Relative Importance (IRI), the Atlantic cutlassfish, Trichiurus lepturus, was the most important fish species represented. Of the cephalopods, the squid Doryteuthis plei was by far the most representative species. Several items were reported for the first time as prey of the S. frontalis: Xiphopenaeus kroyeri, Tremoctopus violaceus, Semirossia tenera, Merluccius hubbsi, Pagrus pagrus and Paralonchurus brasiliensis. S. frontalis presented teuthophagous and ichthyofagous feeding habits, with apparent predominance of the first, and preyed mainly on pelagic and demersal items.

Taxonomic Study of Shallow-Water Octopuses (Cephalopoda: Octopodidae) in Japan and Adjacent Waters using Mitochondrial Genes with Perspectives on Octopus DNA Barcoding

ABSTRACT A recent study revised the generic level taxonomy of the family Octopodidae, and several species groups that were previously included in Octopus are now recognized as independent genera. However, knowledge regarding phylogenetic relationships among taxa in the family Octopodidae is still poor. The phylogenetic relationships of shallow-water benthic octopus species in Japan and adjacent waters were examined in the present study using mitochondrial DNA cytochrome c oxidase subunits I and III (COI and COIII, respectively) sequence data, and the taxonomic statuses of the octopus species were compared to those derived by morphological identification. We obtained COI (657 bp) and COIII (464 bp) sequences from 45 taxa assigned to 34 species of seven genera. Samples used were voucher specimens stored in the National Museum of Nature and Science, Tokyo. Sequences of the genes of both Haliphron atlanticus and Tremoctopus violaceus from GenBank were included as outgroup taxa. Additionally, sequences of the ...

Feeding habits of the blue shark (Prionace glauca) off the coast of Brazil

Stomachs from 222 blue sharks collected along the Brazilian coast were analyzed - 116 from the northeastern region and 106 from the southern region. A total of 51 prey taxa were identified. The most important prey items in the southern region were Mysticeti whales, teleosteans, the gempylid Ruvettus pretiosus and the nomeid Arioma bondi. Cephalopods were more diverse, with dominance of vertical migrants Histioteuthis spp., Cranchiidae and the epipelagic octopus Ocythoe tuberculata. In the northeastern region, blue sharks consumed mainly teleosteans, including the alepisaurid Alepisaurus ferox and the gempylid Gempylus serpens. Among cephalopods, Histioteuthis spp. and the epipelagic octopus Tremoctopus violaceus were the dominant items. Predation upon schooling prey was occasional, as observed on Arioma bondi. Birds also were consumed in both regions; Puffinus gravis was the fifth most frequent item in the northeastern region. During the reproductive migration cycle, blue sharks likely prey in the thermocline, which is deeper in the northeastern region and closer to the surface in the southern region.

Tremoctopus violaceus uses Physalia tentacles as weapons : Jones, E. C. (U.S. Bureau of Commercial Fisheries, Biol. Lab., Honolulu, Hawaii). Science, 139, 766, 1963

Tremoctopus violaceus uses Physalia tentacles as weapons : Jones, E. C. (U.S. Bureau of Commercial Fisheries, Biol. Lab., Honolulu, Hawaii). Science, 139, 766, 1963

Tremoctopus violaceus Uses Physalia Tentacles as Weapons

Immature octopods (Tremoctopus violaceus) have been found with numerous fragments of tentacles of the coelenterate Physalia attached to the suckers of their dorsal arms. The probable method of acquisition, the evidence of adaptation for holding the tentacles, and the possibility that the octopod uses these coelenterate tentacles as offensive and defensive weapons are discussed.

II. Some Observations upon the Structure of two new Species of Hectocotyle, parasitic upon Tremoctopus violaceus, D.Ch., and Argonauta Argo, Linn.; with an Exposition of the Hypothesis that these Hectocotylae are the Males of the Cephalopoda upon which the

II. Some Observations upon the Structure of two new Species of Hectocotyle, parasitic upon Tremoctopus violaceus, D.Ch., and Argonauta Argo, Linn.; with an Exposition of the Hypothesis that these Hectocotylae are the Males of the Cephalopoda upon which the