The animals described in this chapter are called bone-eating worms, which belong to the animal phylum. The gate also contains other worms we know well, such as earthworms and leeches. But bone-eating worms are far from these distant relatives, in many ways, such as the body structure of adult worms, the patterns of growth and development, and the way they make a living. Most notably, they fix themselves somewhere as adults, a way of life that is biologically called a fixed life. For hermaphrodites, a fixed, immovable lifestyle on the ocean floor poses a problem that neither partner can find the other half to mate. So, in animals with this lifestyle, how do sperm combine with eggs?
Currently, the most common solution is "sperm diffusion", which allows it to meet the female's egg within a certain range. There are also similar solutions on land, such as pollen transmission of flowering plants and conifers. Tiny pollen particles use external forces, such as wind, rain or the spread of insects, bats, or birds, to reach the female ovules. The vast majority of entrenched animals in the water excrete sperm into the water, giving them the opportunity to float to the egg to bind to the egg. The eggs, on the other hand, remain in the mother's body and are not excreted until after fertilization. There are also animals that discharge both sperm and unfertilized eggs into the water, allowing the eggs to be fertilized in the water.
There are a few hermaphrodite, fixed animals that have evolved a way for sperm to bind to eggs without the aid of uncertain water outflows. Bone-eating worms are one of these, taking advantage of extreme gender differences. In the fixed area of bone-eating worms, only adult females can be observed. The female has a protective shell formed by a hard, transparent catheter, and the inner wall of the catheter is attached to a swarm of tiny males. When they are still larvae, they cling to the female and quickly reach sexual maturity when they are very small, and then use the short rest of their lives to make sperm and provide eggs for fertilization. These tiny suitors, though attached to their mates, survive on their own stored energy, unlike the male sea ghost fish. Such arrangements are beneficial for both females and males because they protect the males and allow them to lay sperm near the egg, while for females, they can obtain sperm at any time. Tiny, independently surviving males are not parasites, they simply supply each other with sperm and do not need to pay any price for it. Males reach sexual maturity at a very small size, with minimal morphological development, and at a young age, and their life is short, which, like the spiders, octopuses, and sea ghost fish mentioned earlier, are a more extreme version of adaptive evolution. In any case, bone-eating worms add new highlights to this type of research, and their stories are worth telling.
Research on bone-eating worms started relatively late. In February 2002, a team of marine biologists from the Monterey Bay Aquarium Research Institute used a remote-controlled submersible to find a rotting gray whale carcass at 2893 meters under the sea, which later became known as "Whale 2893". The body sank quietly at the bottom of Monterey Canyon, about 31,000 meters from California's central coast. The gray whale didn't die long ago, its skeleton still had flesh and soft tissues on it, and it was crowded with encroachers. Where the bones are bare, there is a group of tiny solid worms, which look uncommon, and are fixed deep in the bones. Their skinny worm-like bodies are wrapped in slender, transparent tubes and stand upwards, topped with 4 bright red pinnate tentacles. The biologists responsible for studying these new discoveries on the voyage were two roberts verrijanhawk and Shana Godfredi from the Monterey Bay Aquarium Institute, and one was Greg Rouse, who was working at the South Australian Museum at the time, and later at the Scripps Institute of Oceanography in La Jolla, California. They had never seen this strange worm before, so the three scientists decided to find out what kind of creature it was and what its place in the animal kingdom. Two years later, they published an article in the prestigious journal Science naming a new genus, osteivore worms (Latin for Osedax), meaning they feed on bones, and the worms of this genus are called bone-eating worms.
Geneticists divide this genus into the phylum Oftes, Polychaetes, the family Siberga, where the marine tubular worms are located. This family includes some large tubular worms found in hot or cold springs in the deep sea (e.g., chlamydia), as well as elongated frenulate worms that live on muddy, oxygen-deficient deep sea bottoms, and a small number of scleropods that live on decaying organic matter, such as wood or rope. What they have in common is that they live in a closed tube of a suitable size, made of opaque shell or transparent slime-like substance, tightly attached to other objects. Although the new bone-eating worm genus has many similarities with other tubular worms, researchers soon discovered that their morphological, physiological, and ecological traits differ from those of other worms as adults. Most relevant to the content of this chapter is that the previously mentioned "Whale 2893" appears to be full of female insects, and no males are seen.
Usually tubular worms are densely packed, with males and females together, and their appearance is very similar. Some tubular worms can determine gender by the location of the reproductive foramen. Furthermore, females may be slightly larger and thicker than males, but in reality there is little other way to distinguish them except for the internal reproductive glands. No males were found in bone-eating worm colonies at the time, and it wasn't until the researchers removed the females from their fixed bones and placed them under a microscope to find the missed males. These males are extremely small, like larvae, and attach in large numbers to the inner wall of the female tube. This extreme gender difference surprised the researchers. That's why they named the groundbreaking scientific journal article "Bone-Eating Worms: Bone-Eating Marine Worms with Pygmy Males," reflecting their unique bone-eating abilities and the extremely small size of males.
Excerpt from "The Mismatched Pair: The Gender Culture of the Animal Kingdom"
[United States] Daphne Fairbairn | Xu Luohao, Li Fang, translated | Shanghai Culture Publishing House Phoenix Yili
Some unusual extreme animal differences
A great theme
A fascinating natural history
An eye-opening popular science book
Although we say that men are from Mars and women are from Venus, the gender differences between humans are still not comparable to the sex differences of animals...
Males may be several times the size of females or 1 in 10,000 females.
Where these unusual extreme animal sex differences are rooted can be learned from this unique book.
This unique, ambitious, and engaging book, with its gender differences in themes, is a remarkable achievement for the average reader to learn about animal behavior, physiology, life history, and evolution. Reading this book is a treat. — Alan J. Moore, Distinguished Professor, University of Georgia
This is a fascinating natural history that describes some unusual examples of extreme animal sex differences that are eye-opening. —Mark Elgar, Professor of Evolutionary Biology at the University of Melbourne
About the Author
Daphne Fairbairn is a professor of biology and author at the University of California, who has authored numerous scientific articles on animal sex differences and co-editor of Gender, Size, and Gender Roles.
Synopsis
The book Mismatched Pair: The Gender Culture of the Animal Kingdom explores extreme gender differences in the animal kingdom. If you want to understand why adult male elephant seals weigh four times as much as adult female elephant seals, and why female blanket octopuses are so huge compared to tiny male mates... This fascinating book is just for you. Daphne Fairbairn not only introduces us to some special animals, but also provides some explanations for biological evolution, as to why males are much larger (or much smaller) than females of their species.
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