Sayaka Mitoh, a Ph.D. candidate at Nara Women’s University in Japan, was looking through her lab’s extensive collection of sea slugs a few years ago when she came across a horrifying sight. Elysia marginata, a sea slug reared in captivity in the lab, was missing its head.
The creature’s severed head was moving around the tank, devouring algae as if being a bodyless slug wasn’t strange, Ms. Mitoh saw when she glanced into its tank to get a better look. This was even more startling.
The sea slug appeared to have disintegrated the tissue surrounding its neck and severed its own head, which was further indication that the wound was self-inflicted, according to Ms. Mitoh. Animals frequently perform autotomy, also known as self-amputation. Many animals are able to eject a body part, like a tail, which helps them avoid being eaten. No animal had ever been seen throwing its full body, though.
Ms. Mitoh, who researches the characteristics of sea slug life histories, stated, “I was genuinely amazed and shocked to see the head moving. The slug “would perish soon without a heart and other critical organs,” she continued. But within three weeks, it not only continued to exist, but also completely rebuilt its destroyed body.
This led Ms. Mitoh and her colleagues to conduct a number of tests to ascertain the mechanism(s) and motivation(s) underlying some sea slugs’ self-guillotine behavior. They found that Elysia marginata and a closely similar species, Elysia atroviridis, deliberately decapitate themselves in order to promote the creation of a new body. The findings of their tests were published on Monday in Current Biology. The researchers believe that these sea slugs abandon their bodies when they become infected with internal parasites, though more research is required to confirm this.
Several groups of Elysia marginata and Elysia atroviridis were observed during the course of the animals’ lives by Ms. Mitoh and her team. Although many of the sea slugs they saw did so—some even did it twice—not all of them did. Both species’ bodies could regenerate from their heads, but their headless bodies did not. However, those abandoned bodies responded to stimuli for several months before starting to rot.
The sea slugs’ autotomy-induced head wounds healed in just one day. It typically took a week for organs like the heart to repair. The majority of the sea slugs underwent regeneration in less than three weeks.
Sea slug regeneration is something we’ve known about for a while, but this finding truly goes beyond our expectations, according to Terry Gosliner, senior curator of invertebrate zoology at the California Academy of Science.
Dr. Gosliner, who has uncovered almost one-third of all species of sea slugs known to exist, hypothesizes that these sea slugs’ amazing biological abilities may be related to their remarkable capacity for regeneration.
Elysia atroviridis and Elysia marginata are frequently referred to as “solar-powered sea slugs.” They are one of a select few slug species that can internalize chloroplasts from the algae they consume. This enables the slugs to survive, at least in part, on the sugars that are produced by photosynthesis in the chloroplasts.
This capability, called kleptoplasty, may be what enables these sea slugs to endure for extended periods of time without their bodies.
It is believed that autotomy solely serves as a defense mechanism in the majority of creatures, including some sea slugs. However, the scientists discovered proof that it can also be used to get rid of inside parasites. The researchers discovered intracellular parasites within every Elysia atroviridis that split their heads. They were also successful in expelling their infected bodies by discarding them, regenerating parasite-free forms. There were no parasites discovered in any of theElysia marginata.
Whatever their intended use, these sea slugs’ capacity for regeneration is “amazing,” according to Kenro Kusumi, an Arizona State University biologist who specializes in reptile regeneration. Dr. Kusumi asserts that the in issue sea slugs possess all the qualities that make creatures capable of intricate regeneration desirable. For instance, the “breakage plane down their necks that allows for a smooth break” is present in these sea slugs. Near the base of their tail, a lot of lizards, including geckos, have a fracture plane similar to this.
Dr. Kusumi remarked that it is “very fascinating to witness so many characteristics of regeneration in the animal kingdom coming together in one creature.
The ability of Elysia marginata and Elysia atroviridis to sever their own heads and regenerate their bodies is still largely unknown, but Ms. Mitoh and other researchers believe that a better understanding of this peculiar phenomenon could one day result in advancements in regenerative medicine and other fields.
Ms. Mitoh will continue observing her beloved sea slugs behead themselves until the solar-powered slugs’ secrets are revealed. Although it’s unpleasant work, somebody needs to do it.
What distinguishes several Elysia sea slug species?
Elysia chlorotica is a tiny marine snail with a length of 5 cm. It inhabits the shallow seas off North America’s east coast. This odd slug resembles a leaf. Green color! When the sun is out, it opens up as if to take in the rays. How is that even doable? Feeding on filamentous algae like Vaucheria littorea, Elysia chlorotica consumes them. The chloroplasts of the algae’s photosynthetic cells, which enable Elysia to exploit the byproducts of photosynthesis to sustain itself, are only partially destroyed during digestion. This is an instance of chloroplastic symbiosis, often known as kleptoplasty or chloroplast theft [1]. Chlorophyll, a pigment that absorbs light during photosynthesis and gives the sea slug its green color, is present in these chloroplasts. They can be found in his greatly branching digestive tract’s cells. Elysia chlorotica exhibits leaf-like vein-like features, which is why it resembles a green leaf. Since multiple closely related species exhibit the same behavior, this characteristic appears to be unique to this family.
Generally speaking, a lot of marine species keep the chlorophyll cells they ingest from their prey, such as green, red, or brown algae. After incorporating them into their digestive system, they put them to use for themselves. Predation enables the stock to be regenerated, though often for a little time. Photosynthetic organisms that symbiose exhibit the most stable association. Corals, which are structured colonies of polyps, exhibit this (see Corals: Ocean engineers are under threat). Symbiotic zooxanthellae, a type of photosynthetic microalgae from the genus Symbiodinium, are found in their tissues.
The situation is completely different for the sea slug Elysia chlorotica, though. Chloroplasts were obtained by the mollusc throughout its development, or when it changed from larval to adult form. The sea slug’s chloroplasts continue to function after that. As a result, Elysia chlorotica appears to consume algae only at the beginning of its life, after which it completely relies on photosynthesis for energy. Research has demonstrated that Elysia chlorotica can use photosynthesis to incorporate CO2 into its organic matter in the presence of light and CO2. However, there is still debate regarding whether or not sea slugs need chloroplasts to survive.
In plants, proteins made in the cytoplasm must be permanently imported into the chloroplast. It is consequently rather troubling that the chloroplasts trapped in the sea slug’s digestive tract can continue photosynthesis for months. Sequencing of the host, symbiont, and host genomes of the algae revealed that the animal had gained key genes for photosynthesis by horizontal gene transfer from the nucleus of the algae. The plastid then receives the proteins that have been thusly encoded [2]. Thus, a horizontal gene transfer between the host nucleus and that of the symbiont has occurred in the instance of this sea slug along with predation, or the consumption of a green alga. This arrangement is the source of a metabolic innovation known as “green animals,” which may perform photosynthesis for several months as a result of the host tissues’ chloroplasts continuing to function [1].
What makes the ruffled sea slug unique?
Like many nudibranchs, Glaucus atlanticus has finger-like cerata that it uses to store and use stinging cells, or nematocysts, from its prey (Portuguese man of war).
Other species, like the Pyjama slug Chromodoris quadricolor, might advertise their repulsive chemical taste using their eye-catching colors.
The body of the lettuce sea slug (Elysia crispata) is covered in ruffles that resemble lettuce. In order to photosynthesize sugars, this slug, like other Sacoglossa, engages in a process known as kleptoplasty in which it takes chloroplasts from the algae it consumes. The lettuce sea slug’s ruffles give it more surface area, which increases the amount of light its cells can absorb.
The majority of their time is spent in the sand, where head-shield slugs like the Chelidonura varians use their shovel-shaped heads to dig. In the course of burrowing, the shield also prevents sand from penetrating the mantle.
Have sea slugs hearts?
According to Annie Roth for the New York Times, some sea slugs can remove their heads in a few of weeks before growing new bodies.
The research was presented this week in the journal Current Biology and describes how the heads of Elysia marginata and Elysia atroviridis sea slugs separate from their bodies and move away. The researchers claim that these headless creatures resumed eating algae after a few hours as if nothing had happened. The Times reports that the researchers believe the sea slugs’ gruesome tactic may be a means of getting rid of parasites.
According to Susan Milius of Science News, flatworms and sea squirts are two other animals that exhibit such high regeneration. But these animals have simpler bodies, according to Science News. While flatworms and sea squirts don’t have hearts to begin with, sea slugs can regenerate essential organs like the heart.
Oddly enough, Christa Leste-Lasserre of New Scientist says that the headless bodies can also endure for a few months while their hearts continue to beat. However, the decapitated bodies never sprout heads, as Sayaka Mitoh, a scientist at Nara Women’s University in Japan and a co-author of the article, explains to New Scientist. The brain and teeth, or radula, are located in the head, and she claims that they may be irreplaceable.
In studies, only approximately a third of the sea slugs who chopped off their own heads were able to regrow their bodies. Additionally, scientists noticed that the self-amputating sea slugs frequently included copepods, which are parasitic crustaceans. According to New Scientist, because the older slugs in the experiment didn’t survive the separation, regrowing a body from the neck down is a young slug’s game.
According to Mitoh, this decision can seem foolish.
The older ones, though, would eventually pass away regardless, and they might have a chance to live and regenerate a body free of parasites.
According to Science News, the slugs’ green hue and leaf-shaped bodies may be the reason why their severed heads can live on their own. The Elysia genus of slugs is known for stealing the green colored photosynthesis engines from the algae they consume, earning themselves the moniker “solar-powered sea slugs,” according to the Times.
According to Science News, the slugs can maintain these biological components, known as chloroplasts, alive for weeks or months. Slugs have an inexpensive supply of food in the form of the sugars that chloroplasts produce from sunlight. According to Mitoh, the creature’s digestive glands are believed to be “spread all over the body surface, including the head,” which is crucial for the severed slug heads.
What sea slug is the rarest?
Introducing the Glaucus Atlanticus, a rare and unusual species of nudibranch.
Due to its fantastical appearance, this remarkable sea slug is frequently referred to as a “Blue Dragon.”
Even though it barely reaches a maximum length of 1 inch, the Glaucus Atlanticus must rank among the ocean’s most eye-catching organisms.
The pelagic Blue Dragon is not typically found living on the sea floor like other varieties of nudibranchs do. Actually, they hang around on the water’s surface upside down for the majority of their time.
Glaucus Atlanticus feeds on jellyfish and relies on the waves and currents to survive. Even while Blue Dragons have delicate bodies that seem enjoyable to touch, they could be hazardous.
The Blue Dragon uses the sting cells they store from the jellies they eat to defend itself from scavengers!
Why was the Elysia chlorotica finding so extraordinary?
The sea slug Elysia chlorotica provides a rare chance to research how a novel function—photosynthesis—evolved in a sophisticated multicellular host. Vaucheria litorea, a heterokont algal prey species, is harvested by Elysia chlorotica for its plastids (nuclei missing). The “stolen plastids” are vital for animal growth and are kept alive for several months in digestive tract cells. It was believed that significant horizontal gene transfer (HGT) from the animal nucleus to the nucleus of the alga, followed by the expression of algal genes in the gut to produce vital proteins with plastid-destined, was the basis for the long-term preservation of photosynthesis in this sea slug. The HGT concept was initially supported by analyses of target genes and proteins, but more recent genome-wide data show inconsistent results. In order to test the HGT theory, we produced considerable genome data from the E. chlorotica germ line (egg DNA) and from V. litorea. Our thorough analyses fall short in showing proof of HGT from algae into the sea slug germ line. However, polymerase chain reaction (PCR) investigations of genomic DNA and cDNA from various individual E. chlorotica reveal that the mature slug has algal nuclear genes (or gene fragments). We hypothesize that these nucleic acids may originate from extrachromosomal DNAs that are made accessible to the animal through interaction with the alga, or they may be found there. These findings put to rest a long-standing question and indicate that HGT may not be the key factor sustaining photosynthesis in E. chlorotica over an extended period of time. In light of this, it appears that sea slug photosynthesis is maintained without endangering the animal germ line by introducing a large number of foreign genes.
Elysia chlorotica’s photosynthetic process:
Elysia chlorotica, often known as the emerald green sea slug or the eastern emerald elysia, is a species of sea slug that belongs to the Sacoglossa order and the family Elysiidae. It was one of the earliest animals in the animal kingdom to be believed to be able to produce chlorophyll, a pigment present in practically all photosynthetic plants that use sun energy to convert carbon dioxide into carbohydrates. Members of this species resemble broad, wavy, green leaves with heads that resemble snails. They live in the inlets and shallow salt marshes along the Atlantic coast of North America, from Florida to Nova Scotia. They can reach a length of 16 cm during the course of their 910-month lifespan (0.42.4 inches).
It appears that Elysia chlorotica acquires its capacity for photosynthetic activity by the transient incorporation of chloroplasts (photosynthesizing organelles within plants) from Vaucheria litorea, a yellow-green alga it consumes, into cells lining its digestive track. For up to several months, chloroplasts and other plastids—small structures involved in the synthesis and storage of food—can continue to photosynthesize nutrition for the animals. However, since individuals can endure prolonged periods of darkness, it is unknown how much E. chlorotica depends on the ability of the chloroplasts it carries into its body for photosynthetic energy (possibly through digesting their stored plastids). The genes from V. litorea are likewise assimilated into the genetic framework of E. chlorotica, however the animal does not seem to have these genes turned on.