Paint Colors Designed By Neural Network, Part 2

Have you ever seen a Lybia crab? Often called boxer crabs, or pom-pom crabs, these tiny crustaceans are easily identified by a unique behavior: they hold anemones on their claws to defend themselves from predators, keeping the anemones small enough to wield by limiting their food intake. But how do they get the anemones in the first place? Researchers think they have an answer: by stealing one from another crab, and then splitting it in half to create two identical clones—one for each claw.

Two graduate students, Yisrael Schnytzer and Yaniv Giman, set out to discover how the Lybia crabs acquire their anemones. They spent years observing and collecting crabs (Lybia leptochelis, specifically) from the Red Sea. Given that Lybia crabs are exceptionally well-camouflaged and only a few centimeters across, this was no easy task, but they managed to observe or collect more than 100 individuals.

Every specimen Schnytzer and Giman found was in possession of a pair of anemones, and each anemone belonged to the genus Alicia. Interestingly, the anemones themselves were not found living by themselves; they were only found already living on the claws of Lybia crabs. The researchers decided to study some of the crabs in a laboratory, to see if more observation would solve the mystery of how they acquired their anemones to begin with.

In the lab, the researchers conducted several experiments, the first of which was to take one anemone away from a crab. When left with just one anemone, the crab solved the problem by splitting the remaining anemone into two. The two halves of the anemone would then regenerate into two identical clones, one for each claw, over the course of several days.

The second experiment involved removing both anemones from one crab and placing it in a tank with a crab that still had both its anemones. The result: the two crabs would fight, with the anemone-less crab usually succeeding in stealing one anemone from the other crab. These fights did not tend to result in injuries to the crabs themselves, and once each crab was in possession of one anemone, both crabs would split their anemone into halves to create a pair of clones.

In addition to these experiments, Schnytzer and Giman examined the genes of the anemones found on the wild crabs. Every crab collected from the wild was holding a pair of identical clones. This might mean that anemone theft is rampant among Lybia crabs in the Red Sea, and that it might be the main way that these crabs acquire their anemones.

At any rate, it is clear that the crabs are frequently splitting anemones in two, inducing asexual reproduction in another species and potentially limiting that species’ genetic diversity in the process—a rarity outside the human world.

Based on materials provided by PeerJ and ScienceDaily

Journal reference: Yisrael Schnytzer, Yaniv Giman, Ilan Karplus, Yair Achituv. Boxer crabs induce asexual reproduction of their associated sea anemones by splitting and intraspecific theft. PeerJ, 2017; 5: e2954 DOI: 10.7717/peerj.2954

Image credit: Yisrael Schnytzer

Submitted by volk-morya

Perfect magnets

My tummy is blushing now. 

People Were Asked: ‘What’s The Coolest Thing Most People Don’t Know About Their Own Body?’

This image hurts my brain more than the original debate ever did. Brains are dumb.

Timelapse of Europa & Io orbiting Jupiter, shot from Cassini during its flyby of Jupiter

Galaxies: Types and morphology

A galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter. Galaxies range in size from dwarfs with just a few hundred million (108) stars to giants with one hundred trillion (1014) stars, each orbiting its galaxy’s center of mass.

Galaxies come in three main types: ellipticals, spirals, and irregulars. A slightly more extensive description of galaxy types based on their appearance is given by the Hubble sequence. 

Since the Hubble sequence is entirely based upon visual morphological type (shape), it may miss certain important characteristics of galaxies such as star formation rate in starburst galaxies and activity in the cores of active galaxies.

Ellipticals

The Hubble classification system rates elliptical galaxies on the basis of their ellipticity, ranging from E0, being nearly spherical, up to E7, which is highly elongated. These galaxies have an ellipsoidal profile, giving them an elliptical appearance regardless of the viewing angle. Their appearance shows little structure and they typically have relatively little interstellar matter. Consequently, these galaxies also have a low portion of open clusters and a reduced rate of new star formation. Instead they are dominated by generally older, more evolved stars that are orbiting the common center of gravity in random directions.

Spirals

Spiral galaxies resemble spiraling pinwheels. Though the stars and other visible material contained in such a galaxy lie mostly on a plane, the majority of mass in spiral galaxies exists in a roughly spherical halo of dark matter that extends beyond the visible component, as demonstrated by the universal rotation curve concept.

Spiral galaxies consist of a rotating disk of stars and interstellar medium, along with a central bulge of generally older stars. Extending outward from the bulge are relatively bright arms. In the Hubble classification scheme, spiral galaxies are listed as type S, followed by a letter (a, b, or c) that indicates the degree of tightness of the spiral arms and the size of the central bulge.

Barred spiral galaxy

A majority of spiral galaxies, including our own Milky Way galaxy, have a linear, bar-shaped band of stars that extends outward to either side of the core, then merges into the spiral arm structure. In the Hubble classification scheme, these are designated by an SB, followed by a lower-case letter (a, b or c) that indicates the form of the spiral arms (in the same manner as the categorization of normal spiral galaxies). 

Ring galaxy

A ring galaxy is a galaxy with a circle-like appearance. Hoag’s Object, discovered by Art Hoag in 1950, is an example of a ring galaxy. The ring contains many massive, relatively young blue stars, which are extremely bright. The central region contains relatively little luminous matter. Some astronomers believe that ring galaxies are formed when a smaller galaxy passes through the center of a larger galaxy. Because most of a galaxy consists of empty space, this “collision” rarely results in any actual collisions between stars.

Lenticular galaxy

A lenticular galaxy (denoted S0) is a type of galaxy intermediate between an elliptical (denoted E) and a spiral galaxy in galaxy morphological classification schemes. They contain large-scale discs but they do not have large-scale spiral arms. Lenticular galaxies are disc galaxies that have used up or lost most of their interstellar matter and therefore have very little ongoing star formation. They may, however, retain significant dust in their disks.

Irregular galaxy

An irregular galaxy is a galaxy that does not have a distinct regular shape, unlike a spiral or an elliptical galaxy. Irregular galaxies do not fall into any of the regular classes of the Hubble sequence, and they are often chaotic in appearance, with neither a nuclear bulge nor any trace of spiral arm structure.

Dwarf galaxy

Despite the prominence of large elliptical and spiral galaxies, most galaxies in the Universe are dwarf galaxies. These galaxies are relatively small when compared with other galactic formations, being about one hundredth the size of the Milky Way, containing only a few billion stars. Ultra-compact dwarf galaxies have recently been discovered that are only 100 parsecs across.

Interacting

Interactions between galaxies are relatively frequent, and they can play an important role in galactic evolution. Near misses between galaxies result in warping distortions due to tidal interactions, and may cause some exchange of gas and dust. Collisions occur when two galaxies pass directly through each other and have sufficient relative momentum not to merge.

Starburst

Stars are created within galaxies from a reserve of cold gas that forms into giant molecular clouds. Some galaxies have been observed to form stars at an exceptional rate, which is known as a starburst. If they continue to do so, then they would consume their reserve of gas in a time span less than the lifespan of the galaxy. Hence starburst activity usually lasts for only about ten million years, a relatively brief period in the history of a galaxy.

Active galaxy

A portion of the observable galaxies are classified as active galaxies if the galaxy contains an active galactic nucleus (AGN). A significant portion of the total energy output from the galaxy is emitted by the active galactic nucleus, instead of the stars, dust and interstellar medium of the galaxy.

The standard model for an active galactic nucleus is based upon an accretion disc that forms around a supermassive black hole (SMBH) at the core region of the galaxy. The radiation from an active galactic nucleus results from the gravitational energy of matter as it falls toward the black hole from the disc. In about 10% of these galaxies, a diametrically opposed pair of energetic jets ejects particles from the galaxy core at velocities close to the speed of light. The mechanism for producing these jets is not well understood.

The main known types are: Seyfert galaxies, quasars, Blazars, LINERS and Radio galaxy.

source

images: NASA/ESA, Hubble (via wikipedia)

Jupiter’s south pole, taken by Cassini

Drone with grabbing claw arms can lift 44 pounds

Prodrone’s latest creation could lift a four-year-old child, and uses its 5-axis metal claws to perch on fences like a bird.

Video