What percentage of genome do slugs and scallops have in common?

What percentage of genome do slugs and scallops have in common?

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We can know genetic distance of thousands of species. The OTT tree of life gives genetic distance for nearly all species. Is there a resource to compare the genomes of any sequenced animals to know the percentage of DNA they have in common? I wanted to know for slugs and scallops.


In reproductive biology, a hermaphrodite ( / h ɜːr ˈ m æ f r ə d aɪ t / ) is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes. [1] [2] [3] Many taxonomic groups of animals (mostly invertebrates) do not have separate sexes. [4] In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which either partner can act as the female or male. For example, the great majority of tunicates, pulmonate snails, opisthobranch snails, earthworms, and slugs are hermaphrodites. Hermaphroditism is also found in some fish species and to a lesser degree in other vertebrates. Most plants are also hermaphrodites. A species having different sexes, male and female, is called gonochoric, which is the opposite of hermaphrodite. [5] [6] [7]

Historically, the term hermaphrodite has also been used to describe ambiguous genitalia and gonadal mosaicism in individuals of gonochoristic species, especially human beings. The word intersex has come into usage for humans, since the word hermaphrodite is considered to be stigmatizing, [8] [9] [10] [11] as well as "scientifically specious and clinically problematic." [12] There have been no identified cases of a human reproducing as both male and female, [13] and there are no hermaphroditic species among mammals, birds, or insects. [14] However hermaphroditism is said to occur in one or two insect species. [15]

A rough estimate of the number of hermaphroditic animal species is 65,000. [16] The percentage of animal species that are hermaphroditic is about 5% in all animal species, or 33% excluding insects. (Although the current estimated total number of animal species is about 7.7 million, the study, which estimated the number, 65,000, used an estimated total number of animal species, 1,211,577 from "Classification phylogénétique du vivant (Vol. 2)" - Lecointre and Le Guyader (2001)). Most hermaphroditic species exhibit some degree of self-fertilization. The distribution of self-fertilization rates among animals is similar to that of plants, suggesting that similar processes are operating to direct the evolution of selfing in animals and plants. [16]

The 2% Difference

If you find yourself sitting close to a chimpanzee, staring face to face and making sustained eye contact, something interesting happens, something that is alternately moving, bewildering, and kind of creepy. When you gaze at this beast, you suddenly realize that the face gazing back is that of a sentient individual, who is recognizably kin. You can't help but wonder, What's the matter with those intelligent design people?

Chimpanzees are close relatives to humans, but they're not identical to us. We are not chimps. Chimps excel at climbing trees, but we beat them hands down at balance-beam routines they are covered in hair, while we have only the occasional guy with really hairy shoulders. The core differences, however, arise from how we use our brains. Chimps have complex social lives, play power politics, betray and murder each other, make tools, and teach tool use across generations in a way that qualifies as culture. They can even learn to do logic operations with symbols, and they have a relative sense of numbers. Yet those behaviors don't remotely approach the complexity and nuance of human behaviors, and in my opinion there's not the tiniest bit of scientific evidence that chimps have aesthetics, spirituality, or a capacity for irony or poignancy.

What accounts for those differences? A few years ago, the most ambitious project in the history of biology was carried out: the sequencing of the human genome. Then just four months ago, a team of researchers reported that they had likewise sequenced the complete chimpanzee genome. Scientists have long known that chimps and humans share about 98 percent of their DNA. At last, however, one can sit down with two scrolls of computer printout, march through the two genomes, and see exactly where our 2 percent difference lies.

Given the outward differences, it seems reasonable to expect to find fundamental differences in the portions of the genome that determine chimp and human brains — reasonable, at least, to a brainocentric neurobiologist like me. But as it turns out, the chimp brain and the human brain differ hardly at all in their genetic underpinnings. Indeed, a close look at the chimp genome reveals an important lesson in how genes and evolution work, and it suggests that chimps and humans are a lot more similar than even a neurobiologist might think.

DNA, or deoxyribonucleic acid, is made up of just four molecules, called nucleotides: adenine (A), cytosine (C), guanine (G), and thymine (T). The DNA codebook for every species consists of billions of these letters in a precise order. If, when DNA is being copied in a sperm or an egg, a nucleotide is mistakenly copied wrong, the result is a mutation. If the mutation persists from generation to generation, it becomes a DNA difference — one of the many genetic distinctions that separate one species (chimpanzees) from another (humans). In genomes involving billions of nucleotides, a tiny 2 percent difference translates into tens of millions of ACGT differences. And that 2 percent difference can be very broadly distributed. Humans and chimps each have somewhere between 20,000 and 30,000 genes, so there are likely to be nucleotide differences in every single gene.

To understand what distinguishes the DNA of chimps and humans, one must first ask: What is a gene? A gene is a string of nucleotides that specify how a single distinctive protein should be made. Even if the same gene in chimps and humans differs by an A here and a T there, the result may be of no consequence. Many nucleotide differences are neutral — both the mutation and the normal gene cause the same protein to be made. However, given the right nucleotide difference between the same gene in the two species, the resulting proteins may differ slightly in construction and function.

One might assume that the differences between chimp and human genes boil down to those sorts of typographical errors: one nucleotide being swapped for a different one and altering the gene it sits in. But a close look at the two codebooks reveals very few such instances. And the typos that do occasionally occur follow a compelling pattern. It's important to note that genes don't act alone. Yes, each gene regulates the construction of a specific protein. But what tells that gene when and where to build that protein? Regulation is everything: It's important not to start up genes related to puberty during, say, infancy, or to activate genes that are related to eye color in the bladder.

In the DNA code list, that critical information is contained in a short stretch of As and Cs and Gs and Ts that lie just before each gene and act as a switch that turns the gene on or off. The switch, in turn, is flicked on by proteins called transcription factors, which activate certain genes in response to certain stimuli. Naturally, every gene is not regulated by its own distinct transcription factor otherwise, a codebook of as many as 30,000 genes would require 30,000 transcription factors — and 30,000 more genes to code for them. Instead, one transcription factor can flick on an array of functionally related genes. For example, a certain type of injury can activate one transcription factor that turns on a bunch of genes in your white blood cells, triggering inflammation.

Accurate switch flickers are essential. Imagine the consequences if some of those piddly nucleotide changes arose in a protein that happened to be a transcription factor: Suddenly, instead of activating 23 different genes, the protein might charge up 21 or 25 of them — or it might turn on the usual 23 but in different ratios than normal. Suddenly, one minor nucleotide difference would be amplified across a network of gene differences. (And imagine the ramifications if the altered proteins are transcription factors that activate the genes coding for still other transcription factors!) When the chimp and human genomes are compared, some of the clearest cases of nucleotide differences are found in genes coding for transcription factors. Those cases are few, but they have far-ranging implications.

The genomes of chimps and humans reveal a history of other kinds of differences as well. Instead of a simple mutation, in which a single nucleotide is copied incorrectly, consider an insertion mutation, where an extra A, C, G, or T is dropped in, or a deletion mutation, whereby a nucleotide drops out. Insertion or deletion mutations can have major consequences: Imagine the deletion mutation that turns the sentence "I'll have the mousse for dessert" into "I'll have the mouse for dessert," or the insertion mutation implicit in "She turned me down for a date after I asked her to go boweling with me." Sometimes, more than a single nucleotide is involved whole stretches of a gene may be dropped or added. In extreme cases, entire genes may be deleted or added.

More important than how the genetic changes arise — by insertion, deletion, or straight mutation — is where in the genome they occur. Keep in mind that, for these genetic changes to persist from generation to generation, they must convey some evolutionary advantage. When one examines the 2 percent difference between humans and chimps, the genes in question turn out to be evolutionarily important, if banal. For example, chimps have a great many more genes related to olfaction than we do they've got a better sense of smell because we've lost many of those genes. The 2 percent distinction also involves an unusually large fraction of genes related to the immune system, parasite vulnerability, and infectious diseases: Chimps are resistant to malaria, and we aren't we handle tuberculosis better than they do. Another important fraction of that 2 percent involves genes related to reproduction — the sorts of anatomical differences that split a species in two and keep them from interbreeding.

That all makes sense. Still, chimps and humans have very different brains. So which are the brain-specific genes that have evolved in very different directions in the two species? It turns out that there are hardly any that fit that bill. This, too, makes a great deal of sense. Examine a neuron from a human brain under a microscope, then do the same with a neuron from the brain of a chimp, a rat, a frog, or a sea slug. The neurons all look the same: fibrous dendrites at one end, an axonal cable at the other. They all run on the same basic mechanism: channels and pumps that move sodium, potassium, and calcium around, triggering a wave of excitation called an action potential. They all have a similar complement of neurotransmitters: serotonin, dopamine, glutamate, and so on. They're all the same basic building blocks.

The main difference is in the sheer number of neurons. The human brain has 100 million times the number of neurons a sea slug's brain has. Where do those differences in quantity come from? At some point in their development, all embryos — whether human, chimp, rat, frog, or slug — must have a single first cell committed toward generating neurons. That cell divides and gives rise to 2 cells those divide into 4, then 8, then 16. After a dozen rounds of cell division, you've got roughly enough neurons to run a slug. Go another 25 rounds or so and you've got a human brain. Stop a couple of rounds short of that and, at about one-third the size of a human brain, you've got one for a chimp. Vastly different outcomes, but relatively few genes regulate the number of rounds of cell division in the nervous system before calling a halt. And it's precisely some of those genes, the ones involved in neural development, that appear on the list of differences between the chimp and human genomes.

That's it that's the 2 percent solution. What's shocking is the simplicity of it. Humans, to be human, don't need to have evolved unique genes that code for entirely novel types of neurons or neurotransmitters, or a more complex hippocampus (with resulting improvements in memory), or a more complex frontal cortex (from which we gain the ability to postpone gratification). Instead, our braininess as a species arises from having humongous numbers of just a few types of off-the-rack neurons and from the exponentially greater number of interactions between them. The difference is sheer quantity: Qualitative distinctions emerge from large numbers. Genes may have something to do with that quantity, and thus with the complexity of the quality that emerges. Yet no gene or genome can ever tell us what sorts of qualities those will be. Remember that when you and the chimp are eyeball to eyeball, trying to make sense of why the other seems vaguely familiar.

Horizontal Gene Transfer: Sorry, Darwin, It’s Not Your Evolution Any More

Horizontal gene transfer (HGT), sometimes called lateral gene transfer (LGT), is a profound recent discovery in genetics: Genome mapping has shown that bacteria can acquire genes from the bacteria around them –that is, horizontally — rather than from a previous generation (vertical transfer), as when a parent cell divides into two daughter cells. They can transfer multiple segments of DNA at once to fellow species members.

But that was hardly the critical finding. This is: Because bacteria are found everywhere and are comparatively simple, they can move newly acquired genes between life forms in the other domains of life. They can produce heritable changes with no recent common ancestor. For example,

— Some researchers have reported that a massive network of recent gene exchange connects bacteria from around the world, 󈫺,000 unique genes flowing via HGT among 2,235 bacterial genomes,” providing the bacteria with genetic information they didn’t inherit from their parent cells, including antibiotic resistance.

Microbes were fighting natural antibiotics this way, we are told, from long before humans learned how to invent them. Bacteria from 30,000 years ago that resist today’s antibiotics have been found in permafrost (underground frost that never melts). A generalized antibiotic resistance may have been traded between types of bacteria long ago, including some that subsequently got frozen for millennia.

— Bacteria were assumed to need long, intact strings of DNA to integrate. But it turns out that they can also use discarded DNA. A 2013 PNAS paper notes:

Our surroundings contain large amounts of strongly fragmented and damaged DNA, which is being degraded. Some of it may be thousands of years old. Laboratory experiments with microbes and various kinds of DNA have shown that bacteria take up very short and damaged DNA from the environment and passively integrate it in their own genome. Furthermore this mechanism has also been shown to work with a modern bacteria’s uptake of 43,000 years old mammoth DNA.

One is reminded of mechanics who visit wrecking yards to locate reuseable spare parts.

— Sometimes the microbes’ methods of harvesting genes are more sophisticated than we might expect. Bacteria that grow on crustaceans can absorb fragments containing more than 40 genes, using a small “spear.” Researcher Melanie Blokesch describes that number as “an enormous amount of new genetic information.” That may explain why antibiotic resistance sets in so quickly.

Bacteria just do not play by Darwin’s rules.

Neither, it turns out, do plants, animals, or fungi, not when bacteria shuttle between them, absorbing, carrying, and delivering genes that get incorporated into other genomes.

Scientific American observes that HGT from bacteria to more complex life forms (eukaryotes) is more common than formerly believed:

Muller and his colleagues scanned the genomes of 149 eukaryotes, and found acdS-like genes in 65 of them — 61 in fungi and 4 in parasitic microorganisms called oomycetes, including Phytophthora infestans, the microbe responsible for the Irish potato famine. After analysing the organisms’ genetic family trees, the researchers determined that the most likely explanation was that three different kinds of bacterium had donated the gene to the fungi and oomycetes in a total of 15 different horizontal-gene-transfer events.

— In another study, ferns were found to have adapted to low light via HGT from moss-like hornworts from which they diverged 400 million years ago:

“We’re actually seeing more and more incidence of horizontal gene transfer in plants”… However neochrome was transferred, it seems to have occurred at just the right moment in ferns’ evolutionary history.

— The giant Rafflesia flower has stolen genes from plants it parasitizes. Genes may even be shared among plants with only a distant ancestral relationship.

— Animals do it too. Bacteria are known to use horizontal gene transfer by injecting toxins into rival cells. And some species of ticks and mites (relatives of spiders) have been found to acquire these toxins to get rid of the bothersome bacteria.

— The bdelloid rotifer (pictured above) holds the record for HGT (as of 2013). It dispenses with sex, and at least 8 percent of its genes are considered likely to have been acquired by HGT.

— An article in prestigious Scientist tells us, “Scientists show that horizontal transfer of a particular DNA sequence among a diverse range of vertebrates is more widespread than previously believed.”

The results can be surprising. In one gene sequence, cows are closer to snakes than elephants, with shared parasites as a possible vector.

— One finding could affect lab research: Bacterial DNA pass traits from mouse mother to offspring, which means, among other things that when we study lab mice, we must account for the possibility that inherited bacteria and their genes could influence the trait under study–as opposed to assuming that the Darwinian mechanism of vertical common ancestry is the only possible source of genes.

— Lastly, in one remarkable case, an invertebrate stole more than a plant’s genes: Sea slugs were known to steal chloroplasts from algae (kleptoplasty) since the 1970s. But one question was how the chloroplasts lasted so much longer in the slug than in the algae. A recent finding:

“This paper confirms that one of several algal genes needed to repair damage to chloroplasts, and keep them functioning, is present on the slug chromosome,” Pierce says. “The gene is incorporated into the slug chromosome and transmitted to the next generation of slugs.” While the next generation must take up chloroplasts anew from algae, the genes to maintain the chloroplasts are already present in the slug genome, Pierce says.

“There is no way on earth that genes from an alga should work inside an animal cell,” Pierce says. “And yet here, they do. They allow the animal to rely on sunshine for its nutrition. So if something happens to their food source, they have a way of not starving to death until they find more algae to eat.”

The slug did not “evolve” this trait, it hijacked it. One researcher has commented, “The process of evolution just isn’t what many evolutionary biologists think it is.”

But surely bacteria could not transfer DNA to humans, considering how complex we are? Yes they can, apparently,according to a recent article in the Scientist.

— For example, we are told in Aeon Magazine, “… in Japan, some people’s gut bacteria have stolen seaweed-digesting genes from ocean bacteria lingering on raw seaweed salads.”

Lead author Alastair Crisp from the University of Cambridge, UK, said: “This is the first study to show how widely horizontal gene transfer (HGT) occurs in animals, including humans, giving rise to tens or hundreds of active ‘foreign’ genes. Surprisingly, far from being a rare occurrence, it appears that HGT has contributed to the evolution of many, perhaps all, animals and that the process is ongoing, meaning that we may need to re-evaluate how we think about evolution.”

Alastair Crisp and Chiara Boschetti of Cambridge University, and their colleagues, have been investigating the matter. Their results, just published in Genome Biology, suggest human beings have at least 145 genes picked up from other species by their forebears. Admittedly, that is less than 1 percent of the 20,000 or so humans have in total. But it might surprise many people that they are even to a small degree part bacterium, part fungus and part alga.

Dr Crisp and Dr Boschetti came to this conclusion by looking at the ever-growing public databases of genetic information now available. They did not study humans alone. They looked at nine other primate species, and also 12 types of fruit fly and four nematode worms. Flies and worms are among geneticists’ favourite animals, so lots of data have been collected on them. The results from all three groups suggest natural transgenics is ubiquitous.

So we are a long way from when biochemist Christian de Duve (1917-2013), grudgingly admitted the significance of horizontal gene transfer, noting that it “… has been recognized as a major complication when attempting to use molecular data to reconstruct the tree of life.” 1

It certainly has, because where HGT is in play, there just isn’t a tree of life. Even popular science writers are beginning to recognize the significance of this fact. New Scientist‘s Mark Buchanan writes: “Just suppose that Darwin’s ideas were only a part of the story of evolution. Suppose that a process he never wrote about, and never even imagined, has been controlling the evolution of life throughout most of the Earth’s history.”

No need to suppose, actually it’s here. But HGT isn’t “controlling the evolution of life.” It is simply breaking Darwinism’s monopoly on accounting for it.

Some ask, why is HGT bad news for Darwin? Can’t Darwinism simply co-opt it? No. Admittedly, some hope it can, sort of. In Aeon Magazine, science writer Ferris Jabr suggests,

The fact that horizontal gene transfer happens among eukaryotes does not require a complete overhaul of standard evolutionary theory, but it does compel us to make some important adjustments…

Ferris, it really does require a complete overhaul.

He goes on to defend Darwinism by personifying the gene:

We did not invent gene transfer DNA did. Genes are concerned with one thing above all else: self-perpetuation. If such preservation requires a particular gene to adapt to a genome it has never encountered before – if riding a parasite from one species to another turns out to be an extremely successful way of guaranteeing perpetuity – so be it. Species barriers might protect the integrity of a genome as a whole, but when an individual gene has a chance to advance itself by breaching those boundaries, it will not hesitate.

No, no, no. Genes can travel but they have no minds and no desires. When the Dawkinsian metaphysic of the vertical “selfish gene” is used to assign properties of minds to genes, it becomes not only questionable but ridiculous. What Jabr mainly demonstrates is how difficult it is for people raised on Darwin (and Dawkins) to maintain a science-based view of evolution in the face of evident non-Darwinian evolution.

Speaking of Richard Dawkins: For over a century, Darwinism was the “must be” explanation, the only “scientific one.” As Dawkins put it (p. 287, Blind Watchmaker, 1986):

My argument will be that Darwinism is the only known theory that is in principle capable of explaining certain aspects of life. If I am right it means that, even if there were no actual evidence in favour of the Darwinian theory (there is, of course) we should still be justified in preferring it over all rival theories.

But Darwinism is not “the only known theory that is in principle capable of explaining certain aspects of life.” Claims that were formerly merely preferred must be tested against HGT. True, some of the example findings given above may need revision or replacement. But many more will likely turn up, as research uncovers HGT in many genomes.

Anything HGT does, Darwinian evolution did not do. As more and more pieces are carved out of Darwin’s territory, just think of the impact on the vast project of “Darwinizing the culture.”

One report boldly alludes to Darwin’s plight:

It’s a firmly established fact straight from Biology 101: Traits such as eye color and height are passed from one generation to the next through the parents’ DNA.

But now, a new study in mice by researchers at Washington University School of Medicine in St. Louis has shown that the DNA of bacteria that live in the body can pass a trait to offspring in a way similar to the parents’ own DNA.

The latter explanation involves a major change in thinking because it suggests that traits affected by bacteria can pass from mothers to their offspring in the same manner as traits affected by mouse DNA.

As a major change in thinking, HGT is very bad news for Darwinism.

So we find ourselves in an odd situation: Yes, there is some evidence for evolution, but it provides no help to the publicly funded, widely believed, court-enforced Darwinian theory stoutly defended in media as “evolution.”

And things will get stranger still when we look at epigenetics. For now, just suppose a sharply diminished Darwin.

(1) Christian de Duve, “Mysteries of Life” , in Bruce L. Gordon and William A. Dembski, The Nature of Nature: Examining the Role of Naturalism in Science (Wilmington, DE: ISI Books, 2011), p. 348.

There Is Plastic In Your Fish

Microplastics can be ingested by marine species such as shellfish. The ingestion of marine plastics . [+] carrying concentrated toxins has the potential to bioaccumulate up the food chain and enter the human diet.

Photo used with permission. GRID-Arendal, cartographer Maphoto/Riccardo Pravettoni,

Overwhelming research shows that cutting back on red meat and increasing our intake of high-quality seafood is beneficial to our health. Fish is high in Omega-3 fatty acids which are essential fats, meaning the body cannot produce them on its own and they must be sourced from the food we eat. Omega-3 fatty acids are beneficial to heart health, are instrumental in preventing stroke and may help control a host of other health conditions. However, the flip side of eating more fish is a tiny problem 5 millimeters or less in diameter: microplastics.

Pieces of microplastic, pictured with a 1-cent piece for scale. Plastics consumed by marine life . [+] often end up in the human food chain. (Photo by Bernd Wüstneck/picture alliance via Getty Images)

picture alliance via Getty Images

Tiny pieces of plastic called microplastics (a distinction based on size alone) are found in the ocean. Ceaselessly broken down by the elements over time, larger pieces of plastic become smaller and smaller. Microplastics are small enough to be ingested by sea animals, including those that end up on our plates. 70 years of manufacturing plastic later, we are finally starting to see where it all ends up when we toss it.

According to a 2017 UN report, there are more than 51 trillion microplastic particles in the sea, more than 500 times the number of stars in the Milky Way. Unlike plastic bags, fishing gear and other macroplastic waste, microplastics are so insidious because they are invisible to us. Research into microplastics and their effects is still in its infancy.

Where are microplastics found?

Microplastics are found everywhere in the ocean, floating at the surface, mixed in with the water column and some are denser than water and sink to the seafloor. Plastics have been discovered thousands of feet down in the deepest reaches of the ocean. Even the arctic and Antarctica have become dumping grounds for these tiny plastics. Plastic polymers contain additives such as pigments, plasticizers, heat and UV stabilizers, fillers, and flame retardants such as polybrominated diphenyl ethers (PBDEs). These additives can leach into surrounding water and potentially cause problems for environmental and human health.

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How plastics enter the food web, a visual representation of how plastics move through the marine . [+] environment.

Photo used with permission. GRID-Arendal, cartographer Maphoto/Riccardo Pravettoni,

How do they affect marine life?

Not a whole lot is understood about microplastics and their environmental effects yet. We have manufactured plastics for many decades, however the first US legislation to address microplastics went into effect for the first time at the tail-end of 2015, with The Microbead-Free Waters Act of 2015. The act targets rinse-off products such as toothpaste and bodywash, however manufacture of some products containing microbeads was allowed to continue until summer of 2019.

Current research suggests that the chemicals used in the manufacture of plastics can leach out and become ingested by marine life. Plastics are petrochemicals, meaning they are produced from petroleum and natural gas. Traveling from the digestive tract to the circulatory system and surrounding tissues. And ocean-dwellers aren’t the only ones chowing down on plastic. Microplastics are found in fresh water too. Carp and tilapia are two freshwater species that were found to ingest microplastics.

When microplastics exist in the ocean, they accumulate pollutants such as PCBs and pesticides that prefer to stick to plastic when it’s around (this is called ‘adsorbing’). The pollutants are also concentrated in this way.

Filter feeders such as clams, mussels, scallops and oysters draw in and filter out particles in seawater. A study of microplastic ingestion in clams suggests that microplastics can damage the gills of shellfish. A recent study of microplastics in the deep sea found plastic particles in every single filter feeder that was studied.

New research found that chemical leaching from microplastics is also affecting our tiniest friends- marine photosynthetic algae, which play a role in producing the oxygen that we rely on to live. Plastic pollution was found to interfere with the growth, photosynthesis and oxygen production of the most abundant photosynthetic bacteria group in the ocean, Prochlorococcus.

What does this mean for all of the seafood lovers out there?

At this point in time more research is needed to understand exactly how ingested microplastics may affect human health. It is known that humans are in fact eating these tiny plastic particles, but fish aren’t the only source. Bottled water, beer, honey, sea salt and tea bags have all been exposed as microplastic carriers, just to name a few. We don’t yet know how these plastics may affect us and in what amounts they may or may not be harmful. So should we just stop eating seafood to avoid potentially eating plastic? Bottom line, questions and knowledge gaps still remain so the amount of risk one is willing to take will determine this.

According to the United Nations Environment Programme (UNEP), at current rates of pollution, there . [+] will likely be more plastic in the sea than fish by 2050. (Photo by Dan Kitwood/Getty Images)

New Research Finds Garlic Kills Slugs

September 12, 2003 -- It was worshipped by the ancient Egyptians, was said to keep vampires at bay, and is good for keeping you healthy. Scientists from the University of Newcastle upon Tyne have now found the pungent herb garlic could win the costly worldwide war against slugs and snails as an environmentally friendly pesticide.

The findings are published in the current edition of the academic journal, Crop Protection. Lead researcher Dr Gordon Port will speak about the effective alternatives to chemical pesticides, with special reference to slugs, at approximately 11am at the BA Festival of Science TODAY, Friday September 12 2003.

Laboratory tests on nine potential molluscicides &ndash the technical term for substances that kill slugs and snails - revealed that a highly refined garlic product (ECOguard produced by ECOspray Ltd.) was one of the most effective killers.

The research was carried out at the request of the crop growing industry and sponsored by the Horticultural Development Council and the Department for Environment, Food and Rural Affairs. It provides scientific proof of garlic's pest controlling properties, and should help businesses developing new treatment products for widespread use.

The scientists, Ingo Schüder and Gordon Port from Newcastle University's School of Biology, suspect garlic may have an adverse affect on the creatures' nervous systems but say it is difficult to say exactly why they die without further investigation.

Garlic has long been used in 'companion planting' strategies for hundreds of years. Monks used to site garlic next to their vegetable crops to keep unwanted pests away.

Slugs and snails cause millions of pounds worth of damage as they munch their way through food crops and plants, particularly those in cool, temperate climates like those of the UK, Northern Europe and North West America. Even more millions of pounds are spent trying to control them - the estimated overall cost to the UK is around £30m.

Growers are increasingly seeking alternative solutions to traditional pesticides, however, as ever-tightening regulations governing the use of chemicals may mean that some products could be withdrawn.

Garlic is already being used in some products as a mollusc repellent but this research takes it a step further. Earlier work by Newcastle University also found that garlic kills slug eggs laid in the soil.

The Newcastle University scientists looked at how applying a liquid containing garlic extract to soil affected slugs and snails' movement through it. They also measured damage to a Chinese cabbage leaf. Garlic largely prevented the leaf from being eaten and killed a very high percentage of the creatures.

Tests also revealed that ureaformaldehyde, a chemical used in the manufacture of chipboard, was a very effective molluscicide.

Lead researcher Dr Gordon Port said:

"Nobody has really found a definitive solution to the problem of slugs and snails. There are lots of products on the market but the real difficulty is actually getting to them in the field. They are very well adapted to their habitat, live hidden away in the soil, and are coated with layer of mucus that can help protect them from substances.

"Farmers and growers have difficulty controlling them with conventional bait pellets, which are particularly ineffective in very wet or very dry weather. Poison baits can also be toxic to other creatures living in the soil, as well as birds and mammals such as shrews and field mice.

"We need to find new environmentally and cost-effective ways of controlling molluscs, and garlic could be our answer. The tests show that it is certainly a potent chemical where slugs and snails are concerned and if used appropriately we know it's mostly harmless to man because it is used as a cooking ingredient.

"We need to carry out more tests to find out its commercial potential. We want to find out how garlic affects other creatures living in the soil, the right concentration to use, how it affects the taste of food once it has been used on crops, and many other things.

Dr Port added the findings may be welcomed by organic gardeners looking for alternatives to pesticides. He said: "The research suggests that a home-made recipe of crushed garlic bulbs mixed with water could work on small-scale gardens."

Story Source:

Materials provided by University Of Newcastle Upon Tyne. Note: Content may be edited for style and length.


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Beaumont, A.R. & Zouros, E., 1991. Genetics of scallops. In Scallops: biology, ecology and aquaculture (ed. S.E. Shumway), pp. 585-624. Amsterdam: Elsevier. [Developments in Aquaculture and Fisheries Science, no.21.]

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Beaumont, A.R., 2005. Genetics. In Scallops: biology, ecology and aquaculture 2nd edn, (ed. S.E. Shumway and J. Parsons). Amsterdam: Elsevier (in press).

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Davies, I.M. & Paul, J.D., 1986. Accumulation of copper and nickel from anti-fouling compounds during cultivation of scallops (Pecten maximus L.) and pacific oysters (Crassostrea gigas Thun.). Aquaculture, 55, 93-102.

Fegley, S.R., MacDonald, B.A. & Jacobsen, T.R., 1992. Short-term variation in the quantity and quality of seston available to benthic suspension feeders. Estuarine, Coastal and Shelf Science, 34, 393-412.

Fish, J.D. & Fish, S., 1996. A student's guide to the seashore. Cambridge: Cambridge University Press.

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Gibson, F.A., 1956. Escallops (Pecten maximus L.) in Irish waters. Scientific Proceedings of the Royal Dublin Society, 27, 253-271.

Gould, E. & Fowler, B.A., 1991. Scallops and pollution. In Scallops: biology, ecology and aquaculture (ed. S.E.Shumway), pp. 495-515. Amsterdam: Elsevier. [Developments in Aquaculture and Fisheries Science, no.21.]

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Hall-Spencer, J.M. & Moore, P.G., 2000c. Scallop dredging has profound, long-term impacts on maerl habitats. ICES Journal of Marine Science, 57, 1407-1415.

Hall-Spencer, J.M., 1998. Conservation issues relating to maerl beds as habitats for molluscs. Journal of Conchology Special Publication, 2, 271-286.

Hall-Spencer, J.M., Grall, J., Moore, P.G. & Atkinson, R.J.A., 2003. Bivalve fishing and maerl-bed conservation in France and the UK - retrospect and prospect. Aquatic Conservation: Marine and Freshwater Ecosystems, 13, Suppl. 1 S33-S41.

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" The Big Picture!" by Mr C

    10 Classes, 8 of which are still alive today, 2 are just fossils (we will only look at 3 of the Classes):
      ________________________________: Clams, Oysters, Mussels, Scallops etc.

    DID YOU KNOW. The Molluscs are the second largest Phylum (abundance of species) next

    II Body Plan/Structure: (General Characteristics of all Molluscs)

    • Molluscs demonstrate a ____________________________ symmetrical body plan
    • They have the three true germ layers:
      • __________________________
      • __________________________
      • __________________________
      • They have true coeloms
        1. The coelom has been reduced to a special body cavity that just surrounds the organs. This cavity is called a _______________________ and contains a special type of blood called ____________________________. Since the __________________________________ is not found in __________________________________ of any kind it is considered an _______________________________________________________________
      • The Molluscs all have a true ___________________________________ with a _______________, ________________________ and _______________
      • The following features are common to all Molluscs:
        1. A muscular ___________________: The foot is used for locomotion
        2. A ____________________: The shell is largely consisting of ____________________________________. Some Molluscs have very reduced _______________, and others, like slugs have lost their ___________ all together
        3. A ____________________: This is a fold of outer skin which lines the ____________________ and covers the rest of the body
        4. A ________________________________: The internal organs including the gut, kidneys, heart(s), and reproductive organs
        5. _________________: These are specialized organs used for respiration (and sometimes feeding).
        6. A ___________________: This is a unique to the Phylum Mollusca and is a rasping “______________________” organ with hard ______________. It is very different in all of the Molluscs and serves many functions from __________________ algae off rocks as in the Gastropods, to a _______________________________ as in the Cephalopods

      Class Bivalvia (Greek: bi = “two”, valvia = “shells”)

      DID YOU KNOW. The giant clam, Tridacna gigas, is the largest Bivalve in the world. Some

      have been measured to weigh up to 227 kg (

      500 pounds), as much as 1.2 m across

      4 feet) and have an average lifespan of

      • All Bivalves have a ____________ that is divided into two halves called_____________
      • The two _______________ are connected at one edge by a strong _________________________ that holds the two valves _______________
      • There are one or two _____________________________________ that connect the two __________________ together and when they are contracted the two valves come _____________________, closing the Bivalve
      • In Bivalves the __________________ takes on the form of a thin _______________________ that surrounds the body just underneath the shell. The mantle is responsible for creating the ________________.
      • In some bivalves the part of the ___________________ that is exposed to the outside of the body has _______________ to form two __________________ used for filter feeding
      • Often there is a large ____________________________ which is where _____________ can be found
      • The _______________ are used for respiration and feeding
      • Bivalves do have a ________________, but it has been laterally flattened
      • They do not have a ________________
      • Bivalves lack a head even though they demonstrate __________________ symmetry, and in fact, do not have a ________________
      • They have an _____________________________________________ which means that the “blood” just bathes the organs and is not contained within ____________________________

      III. Feeding:

      • Bivalves are _____________________________
      • Water circulates through the ________________________________ where microscopic food particles are trapped by the ________________
      • The gills are ______________________ and the _______________ move the food towards the _____________ where it is taken into the _______________________
      • The food is digested in the _____________________ and then passed out through the _____________ into the _____________________________
      • Some Bivalves live buried in the sand and have evolved to have two ________________
      • In this case one siphon ______________________________ and food is filtered out by the ______________
      • Once the water has passed over the gills the Bivalve contracts its ____________________________________ and the water (along with waste from the anus) is passed out of the Bivalve from the other siphon

      DID YOU KNOW. The Geoduck (pronounced gooey-duck) is one of the longest living

      organisms in the animal kingdom and can live up to 160 years. Scientists believe this is because of their feeding mechanism. They burrow very deep into the sand and send their long siphons to the surface of the sand to collect water and food. This process not only protects them from predators but also helps prevent the wear and tear of having to move.

      • Respiration occurs in the same way that feeding does
      • Water is taken into the ____________________________ (can be through a siphon) and passes over the _________________
      • ______________________ is taken into the ______________ from the water and _________________________________ is released from the __________ into the water
      • Bivalves have an _____________________________________________
      • This means that they do not have any _________________________ which would store the “blood”
      • Instead the “blood” (called ________________________) bathes the organs
      • As oxygen and food particles are taken up by the ________________ they are passed into the _________________________ which acts to transport the ___________________ and _____________________ to the rest of the body
      • A _______________ pumps the ______________________ to ensure that circulation occurs (even if it is not through blood vessels)
      • Most of the waste material exits the anus and is then released out of the Bivalve through the __________________________ (or siphon if present)

      VII. Response:

      • Though Bivalves demonstrate ____________________symmetry they lack a _________
      • Instead they have ______________________________ of very simple ______________________ which control the ______________ and ____________________________________
      • Though having such simple _________________________________________ (especially compared to other Molluscs), Bivalves can still sense and respond to the senses of:
        1. ____________________
        2. ____________________
        3. ____________________
        4. ____________________

      DID YOU KNOW. The Scallops have one of the most complex sensory organs of all of the

      Bivalves. They have hundreds of eyes on the fringe of the mantle that have lenses and retinas, however, as complex as these eyes are they can still only detect light or dark.

      VIII. Movement:

      • Bivalves are ______________________, but do have the ability to move
      • Most often Bivalves use their muscular _____________ for movement
      • The muscular ________________ is used to help the Bivalve ______________________ into the sand or move along the bottom of the ocean
      • Other Bivalves such as Cockles have an extremely muscular ____________ which allows them to quickly “leap” from danger
      • Razor shells use their ____________ to burrow extremely fast into the sand
      • Another form of movement is only seen in the Scallops. They use their incredibly strong _____________________________________ to rapidly open and close their valves to actually swim away from predators

      DID YOU KNOW. The scallops that we eat at restaurants are actually the adductor

      muscles of the organism called a Scallop. The reason that these muscles are so large in Scallops is because they use them to forcefully open and close their valves allowing them to actually swim away from their predators.

      • Most Bivalves species contain both _____________ and ____________________ forms that are separate from each other, though some hermaphroditic species do exist
      • Most often sexual reproduction occurs by ______________________________________ where ______________ is released by the ______________ into the water and _____________ are released by the _________________ into the water
      • The fertilized egg will become a _______________________________ that will grow to become the adult Bivalve
      • There are numerous ecological roles that Bivalves fill
      • Many Bivalves are food for thousands of different species of animals (including us)
      • They help to recycle sediment back into the environment
      • They help to filter the water
      • One major harmful ecological role that Bivalves play involves pollution. Since they are filter feeders much of the pollution that they filter feed becomes trapped in their tissues. When other organisms feed on those toxic Bivalves they often become sick and die.

      DID YOU KNOW. Mussels produce an incredibly strong “superglue” that helps them cling to

      surfaces during rough seas. This “superglue” is called byssus. Researchers have discovered the gene that Mussels use to create byssus and have since been able to produce the material using genetically modified yeast cells. This is a great leap in scientific research as byssus could be used for many things including dentistry, medicine and industry.

      Comparative Reproduction

      Spermiogenesis of Aquasperm

      Aquasperm are produced by scaphopods, monoplacophorans, the chaetoderms (Aplacophora), and the majority of bivalves, chitons , patellogastropods and vetigastropods. The early spermatids of aquasperm have a relatively small spherical nucleus that contains a patchwork of heterochromatin ( Fig. 1(C) ). Early in spermiogenesis the chromatin becomes homogeneously distributed within the nucleus and takes on a fine granular appearance ( Fig. 1(D) ). The granules are about 20 nm in diameter and this change in chromatin appearance has signalled a transition in proteins associated with the DNA of the nucleus. Up until the early spermatid stage the DNA is associated with histones and these are gradually replaced with protamines that are sperm nuclear basic proteins ( Chiva et al., 2011 ). This change in nuclear proteins is necessary for chromatin condensation and a major change in shape of the nucleus. Within the cytoplasm of early spermatids, mitochondria surround the nucleus, a flagellum begins to form from one of the centrioles, and a Golgi body is present. In species where proacrosomal vesicles have not formed in spermatocytes, these now appear ( Fig. 1(C) ) although in some species a larger single proacrosomal vesicle develops from Golgi secretions. As the spermatid matures the chromatin in the nucleus further condenses because the granules become reorganized as coarse granules often about 60 nm in diameter ( Fig. 1(E) ). These larger granules are brought about by further substitution of histones by protamine ( Chiva et al., 2011 ). Therefore, the nucleus is now mainly composed of DNA and protamine. In the final stage of spermiogenesis the coarse granules usually coalesce into the fully condensed form of the nucleus of the mature spermatozoon ( Fig. 1(F) ). This process is brought about by the protamine being chemically dephosphorylated. In chitons, however, the chromatin becomes twisted into fibres before final condensation. The process of chromatin condensation usually results in a gradual change in shape of the nucleus. Whilst the nucleus may remain more or less spherical in some species, in others it becomes cylindrical, conical or bullet-shaped.

      During spermiogenesis the acrosome develops from either the single proacrosomal vesicle, or more usually by fusion of the small proacrosomal vesicles into a single vesicle. An exception to this is found in the bivalve families Trigonoidea and Unionoidea where the vesicles do not fuse, the acrosomal complex of the mature spermatozoon consisting of several anteriorly positioned vesicles ( Healy, 1989 ). In most species the acrosome forms in the presumptive posterior region of the spermatozoon. As the spermatid matures and changes shape, the developing acrosome migrates to the anterior pole of the nucleus ( Fig. 1(E) ) where it assumes its final form often becoming cap-shaped or conical ( Fig. 1(F) ). This can involve elongation and differentiation of the acrosomal contents, as well as the development of a posterior invagination that creates a subacrosomal space filled with fine granular or fibrillar material. An exception to where the acrosome develops is found in the bivalve group Anomalodesmata. In these bivalves the acrosome forms anteriorly then migrates to the posterior of the late spermatid to become located within the mid-piece ( Healy et al., 2008 ).

      As the nucleus matures and changes shape, the amount of cytoplasm in the spermatid decreases and the mitochondria begin to fuse together. This results in an increase in their size and a decrease in their number to between four and seven. As this happens the fusing mitochondria along with the pair of centrioles migrate to the future posterior pole of the nucleus ( Fig. 1(D) ). Here the larger spherical to oval mitochondria, which have well developed cristae, surround the orthogonally arranged centrioles in tight proximity to the nucleus to form the developing mid-piece of the spermatid. One centriole (the proximal) becomes anchored in a small depression of the nucleus (posterior nuclear fossa), whilst the flagellum, which has the normal 9+2 arrangement of microtubules, continues to develop from the distal centriole to form the tail.

      Author information

      Pedro Antonio Pérez-Mancera and Inés González-Herrero: These authors have contributed equally to this work.


      Laboratorio 13, Instituto de Biología Molecular y Celular del Cáncer (IBMCC), CSIC/Universidad de Salamanca, Campus Unamuno, 37007, Salamanca, Spain

      Pedro Antonio Pérez-Mancera, Inés González-Herrero, María Pérez-Caro, Noelia Gutiérrez-Cianca, Manuel Sánchez-Martín & Isidro Sánchez-García

      Servicio de Anatomía Patológica, Universidad de Salamanca, Campus Unamuno, 37007, Salamanca, Spain

      Area de Reproducción Animal, Centro de Investigación y Tecnología, Ctra de la Coruña km 5.9, 28040, Madrid, Spain

      Alfonso Gutiérrez-Adán & Belén Pintado

      Departamento de Medicina, Universidad de Salamanca, Campus Unamuno, 37007, Salamanca, Spain

      Watch the video: 10 Παράξενες Αράχνες Που θα σε Τρομάξουν (July 2022).


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