New Material: Research Shows That Genetic Material Of Crustaceans Can Be Used To Make Silk

For thousands of years, people have been amazed at the complexity of spiders' solid silk webs and valued the luxury and softness of silks spun by silkworms. Other insect species, such as bees and flies, also produce silk. But few people, even biologists, know that all kinds of crustaceans can also produce such multifunctional and valuable protein fibers. Now, two graduate students believe that these little-known silk producers deserve due attention.

The two cooperated to collect and analyze the genetic material of dozens of crustaceans called amphipods, some of which can be used to make silk. One of the students, Brittany from the Florida Museum of Natural History Cummings， A family tree has been pieced together, revealing that the group has independently developed silk production for many times - an example of so-called convergent evolution. The other is Siena from the University of California, Santa Barbara McKim， She found that at least one amphibian produces this fiber, and its gene is the same as that of the silkworm.

Last week, at the annual meeting of the Society of Comprehensive and Comparative Biology held in Seattle, both of them reported their findings, including data showing that some amphipods lost their ability to manufacture silk and formed strange physical conditions or appendages.

Jonathan Allen, an invertebrate zoologist at William Mary College, was not involved in this work. He said that this study shows that the evolution of silk has many purposes, which may promote the diversity of lifestyle and body shape. "The subsequent loss of silk production led to even more strange changes."

At the meeting, McKim described the use of scientific literature more than a century ago to determine which crustaceans make silk. She reported that silk may have evolved at least six times among crustaceans, among which bipeds, swimming crabs (also known as species shrimp) and tanaids (small shrimps living in salt water and fresh water) have two origins respectively.

Some silk biologists attending McKinley's lecture were surprised. Angela Alicea, postdoctoral researcher of spider silk at Akron University Serrano said, "I didn't know that crustaceans could make silk.".

Even among biologists, amphipods are often ignored, or worse, mistaken for weird looking shrimp. Bean shaped, usually no larger than cherry, they are very rich in oceans, rivers, lakes and ponds, and are the main food for fish, other invertebrates and even whales. So far, McKim and Cummings have focused on snaketails, the most diverse amphipods. Several species of sea snakes are silk plants. In addition, many species have undergone tremendous changes, from the enlargement of claws and antennae to the reduction and loss of head and back end, or both.

It was these strange snake crowns that attracted Cummings to study silk in amphipods. About 20 years ago, other researchers believed that the diversity of Serpentidae originated from members of this branch, which includes 21 families, and evolved silk glands, long antennae and grasping legs.

Cummings and McKim collected amphipods from British Columbia to southern California and South America. She also examined preserved specimens shipped to her coastal areas in the Atlantic, Caribbean and Antarctica. These creatures make silk for different purposes. Some use it to bind sand and feces, sometimes to make soft protective tubes in mud, or hard tubes for pumping water to collect food. One even built filamentous "rods" at the ends of the spines of sea urchins, which were used as supports when they stretched out their tentacles to catch food. (The spines provide protection for sea urchins and amphipods.) Some people use their silk to create movable fences. Their bodies swim in the silk tubes and beat their antennae to move around.

Together, they collected genetic material from newly captured amphipods representing seven snake tails. So far, they have cataloged the active genes of nine species. Cummings reported at the meeting that these early data provided some surprising clues for amphibian evolution.

Researchers believe that all the manufacturers of silk tubes are gathered together, and all the species that no longer manufacture silk tubes belong to another branch of the amphibian family tree. However, Cummings' preliminary analysis shows that the generation and development of silk have been repeated, and may have disappeared for many times. The earliest species of amphipods that use silk to make hoses. Some of them lost their ability to produce silk, but without any pipes, they tightly grasped rocks, shells and other surfaces.

She reported that at some time, silk production evolved again, but these species built hard pipes, so they could live in faster flowing water. Recently, some of these species have once again used their silk production ability to exchange for life that can live and depend on freely in these faster waters. "The story she wants to tell is not as simple as it first seems," Allen said.

A more in-depth analysis of crustacean silk may one day have practical applications. Researchers have used spider silk in biomedicine and engineering, as sutures and scaffolds for regenerative tissue. By studying its properties, researchers are learning how to make equally sturdy synthetic materials.

　　Alicea Serrano said: "Amphibians live in the marine environment, so this silk has some unique features," which enable it to play a role in salt water. ". "Maybe we can use these materials to make our own materials."

McKim only paid attention to silk producing organisms and compared the active genes of some of their legs. These legs can produce silk, while their other legs do not have silk glands. She reported that two active genes for silk producing bipedal legs were found in the silkworm. She said at the meeting that this discovery "makes us believe that the genes they use are very similar to those of moths". But why and how to produce these similar genes - which are unlikely to be traced back to a common ancestor - "is the reason why I can't sleep all night."