Showing posts sorted by date for query SQUID. Sort by relevance Show all posts

Thursday, November 27, 2025

Vampires in the deep: An ancient link between octopuses and squids

A 'genomic living fossil' reveals how evolution of octopuses and squids diverged more than 300 million years ago

University of Vienna

In a study now published in iScience, researchers from the University of Vienna (Austria), National Institute of Technology - Wakayama College (NITW; Japan), and Shimane University (Japan) present the largest cephalopod genome sequenced to date. Their analyses show that the vampire squid has retained parts of an ancient, squid-like chromosomal architecture, and thus revealing that modern octopuses evolved from squid-like ancestors.

The vampire squid (Vampyroteuthis sp.) is one of the most enigmatic animals of the deep sea. With its dark body, large eyes that can appear red or blue, and cloak-like webbing between its arms, it earned its dramatic name – although it does not suck blood, but feeds peacefully on organic detritus. "Interestingly, in Japanese, the vampire squid is called "kōmori-dako", which means 'bat-octopus'", says one of three lead PIs of this project, Masa-aki Yoshida, Shimane University. Yet its outward appearance hides an even deeper mystery: despite being classified among octopuses, it also shares characteristics with squids and cuttlefish. To understand this paradox, an international team led by Oleg Simakov from the University of Vienna, together with Davin Setiamarga (NITW) and Masa-aki Yoshida (Shimane University), has now decoded the vampire squid genome.

A glimpse into deep-sea evolution

By sequencing the genome of Vampyroteuthis sp., the researchers have reconstructed a key chapter in cephalopod evolution. "Modern" cephalopods (coleoids) – including squids, octopuses, and cuttlefish – split more than 300 million years ago into two major lineages: the ten-armed Decapodiformes (squids and cuttlefish) and the eight-armed Octopodiformes (octopuses and the vampire squid). Despite its name, the vampire squid has eight arms like an octopus but shares key genomic features with squids and cuttlefish. It occupies an intermediate position between these two lineages – a connection that its genome reveals for the first time at the chromosomal level. Although it belongs to the octopus lineage, it retains elements of a more ancestral, squid-like chromosomal organization, providing new insight into early cephalopod evolution.

An enormous genome with ancient architecture

At over 11 billion base pairs, the genome of the vampire squid is roughly four times larger than the human genome – the largest cephalopod genome ever analyzed. Despite this size, its chromosomes show a surprisingly conserved structure. Because of this, Vampyroteuthis is considered a "genomic living fossil" – a modern representative of an ancient lineage that preserves key features of its evolutionary past. The team found that it has preserved parts of a decapodiform-like karyotype while modern octopuses underwent extensive chromosomal fusions and rearrangements during evolution. This conserved genomic architecture provides new clues to how cephalopod lineages diverged. "The vampire squid sits right at the interface between octopuses and squids," says the senior author Oleg Simakov from the Department of Neurosciences and Developmental Biology at the University of Vienna. "Its genome reveals deep evolutionary secrets on how two strikingly different lineages could emerge from a shared ancestor."

Octopus genomes formed their own evolutionary highway

By comparing the vampire squid with other sequenced species, including the pelagic octopus Argonauta hians, the researchers were able to trace the direction of chromosomal changes over evolutionary time. The genome sequence of Argonauta hians ("paper nautilus"), a "weird" pelagic octopus whose females secondarily obtained a shell-like calcified structure, was also presented for the first time in this study. The analysis suggests that early coleoids had a squid-like chromosomal organization, which later fused and compacted into the modern octopus genome – a process known as fusion-with-mixing. These irreversible rearrangements likely drove key morphological innovations such as the specialization of arms and the loss of external shells. "Although it is classified as an octopus, the vampire squid retains a genetic heritage that predates both lineages," adds second author Emese Tóth, University of Vienna. "It gives us a direct look into the earliest stages of cephalopod evolution."

Revisiting cephalopod evolution

The study provides the clearest genetic evidence yet that the common ancestor of octopuses and squids was more squid-like than previously thought. It highlights that large-scale chromosomal reorganization, rather than the emergence of new genes, was the main driver behind the remarkable diversity of modern cephalopods.

About the University of Vienna:

For over 650 years the University of Vienna has stood for education, research and innovation. Today, it is ranked among the top 100 and thus the top four per cent of all universities worldwide and is globally connected. With degree programmes covering over 180 disciplines, and more than 10,000 employees we are one of the largest academic institutions in Europe. Here, people from a broad spectrum of disciplines come together to carry out research at the highest level and develop solutions for current and future challenges. Its students and graduates develop reflected and sustainable solutions to complex challenges using innovative spirit and curiosity.

Journal

iScience

DOI

10.1016/j.isci.2025.113832

Article Title

Giant genome of the vampire squid reveals the derived state of modern octopod karyotypes

Article Publication Date

21-Nov-2025

Tuesday, November 25, 2025

The ingenuity of white oval squid camouflage brought to light

New study documents the full palette of camouflaging behaviors that white oval squid selects from when hiding from predators.

Okinawa Institute of Science and Technology (OIST) Graduate University

White oval squids camouflage elements — image:
An overview of the different camouflage components that the white oval squid, or shiro-ika, employ when assembling their camouflage strategy. A-D) are coloration patterns, E-M) are postures, I-M) are states of movement. The squids can mix and match these elements depending on their environment and have been observed to coordinate components with adjacent squids to enhance their collective camouflage.
view more
Credit: Nakajima et al., 2025.

White oval squid (Sepioteuthis lessoniana sp. 2), known locally as shiro-ika, are medium-sized squids naturally distributed in the Indian and western Pacific oceans, flittering in and out of a wide range of different habitats – from shallow seagrass beds, over coral reefs, to depths of 100m along coastal environments. In such biodiverse zones, the squids encounter predators of all sizes and shapes, from seabirds flying overhead to sharks, tuna, and other cephalopods prowling under the sea.

Such a variety of threats calls for a large repertoire of survival strategies. Researchers from the Okinawan Institute of Science and Technology (OIST) have previously discovered how shiro-ika change color when moving between different shades of substrate – and now, the same team has painted a full picture of how the cephalopod employs a sophisticated range of camouflaging strategies to adapt to different environments and threats. “The wide variety of visual strategies used by the squid is surprisingly complex, especially considering that squid have traditionally been regarded as spending most of their lives in the open water column,” explains former OIST Visiting Researcher Dr. Ryuta Nakajima, “This discovery suggests that squid have a deeper behavioral relationship with the ocean floor than previously thought.”

The natural predators of shiro-ika often have sharp but monochrome vision that is tuned to spot symmetry in the otherwise asymmetric substrates in reefs. To counter this, the squid selects color patterns are highly irregular to perfectly match their surroundings – whether they are mimicking algae-covered rocks, blending into the shadows under rocks, or turning transparent to stay invisible against sandy seagrass beds.

The team also described a specific coloration pattern dubbed ‘disruptive’, which, like the dazzle-patterns that were painted on warships during WW1, is not meant to conceal the squid but might instead confuse predators about the true shape, size, and location of the squid, making it easier for them to escape in a pinch. “The squids' ability to change their appearance is stunning,” adds Dr. Wee Hin Boo from the Institute of Climate Change at the National University of Malaysia, who contributed to the research. “By analyzing the underlying mathematical patterns in their behavior, we were able to confirm the different strategies they use to vanish into the background. It was a fascinating challenge to quantify what the eye sees.”

As part of their strategy, the squids select different arm positions to minimize symmetry, like casting them off to the side or letting them flop chaotically in front. And a well-known defensive strategy of oval squid is schooling, forming groups of up to 200 individuals. OIST researcher Dr. Zdenek Lajbner continues: “We found that the squids synchronize their camouflaging strategies, like stacking on top of one another to masquerade as a rock, showing the ability to coordinate their camouflage.”

“These squid have recently been observed in the Mediterranean Sea, which they’ve entered through Suez Canal. As they appear in more varied ecosystems, their diverse camouflaging strategies become increasingly relevant to science,” says former OIST researcher Dr. Michael Kuba, who’s now at the University of Naples Federico II in Italy. Dr. Nakajima adds that “shiro-ika is a commercially important species in Okinawa, yet its annual catch has declined by 98%. I hope this study will provide valuable insights into the ecological interdependence between squid and their ecosystem, ultimately contributing to the development of more effective conservation strategies.”

The squid featured in this study are part of the successful research aquaculture project led by Dr. Lajbner at OIST, which has shown the feasibility of raising healthy and active squid over several generations – something which has proven exceedingly difficult for cephalopods in general. Dr. Lajbner summarizes: “Oval squid are a viable candidate for future research into cephalopod cognition, as well as a potential model animal for studying visual perception and motor control through the central nervous system. It’s a remarkable animal.”

Different camouflaging strategies employed by white oval squid, or shiro-ika. A) Two squids create an overlapping effect by merging their chromatic components. B) Three animals stacked next to a rock. C) Hiding under a live rock while blending into the surroundings. D) Disruptive camouflage pattern with fins resting over the substrate, resulting in a gradual transition from substrate to the disruptive pattern. E) Two animals with mottled patterns, hiding between a branch and a rock. F) Two stacked animals with dark, mottled patterns that obscure their contours. G) Hiding next to an algae-covered rock with a mottled color pattern and raised arms to blend in.

Credit

Nakajima et al., 2025.

A photograph of a white oval squid hiding by a clump of algae in a research tank.

Credit

Nakajima et al., 2025.