What is a sea cucumber?

An ordinary sea cucumber. Sea cucumber is a marine invertebrate that lives on the bottom of the sea. Their name comes from their unusual rectangle, which is similar to a fat cucumber. Although people occasionally eat sea cucumbers, these chubby, insect-like marine creatures have nothing to do with their fruit of the same name (if you expect a crisp and refreshing food, they will not be very appetizing salad ingredients).

There are about 1250 species of sea cucumbers, all of which belong to the class Holothuria. This class belongs to echinoderms, including many other famous marine invertebrates, such as starfish, sea urchins and sand elements. According to National Geographic, according to the National Wildlife Federation,

The size of sea cucumbers ranges from about three quarters of an inch (65,438+0.9 cm) to over 6 feet (65,438+0.8 m), and they are found all over the world, from shallow coastal waters to the deepest trench in the ocean. According to the research of the Paleontology Museum (UCMP) at the University of California, Berkeley, regardless of the depth, their main habitat is at the bottom of the sea, usually partially buried in sand.

Related: Like all other echinoderms, seven strange facts about the ocean.

Sea cucumbers are also radially symmetrical. However, sea cucumbers don't arrange their five arms in a circle like starfish or sand yuan, but there are five rows of tiny feet from their mouths to * * *, and their bodies extend vertically downward. According to woods hole oceanographic institution, their tubular feet are mainly used to fix creatures with weak limbs on the seabed. Sea cucumbers cross the seabed by changing the water pressure on their feet; They increase the amount of water on their feet to stretch them and release water to shrink them.

What does sea cucumber eat? When these creatures wander around slowly, they will scoop up everything, including sand, with an extra 20 to 30 feet of pipes around their mouths. They mainly feed on tiny algae and marine life, which are broken down into smaller and smaller pieces, similar to the way earthworms break down organic matter in gardens. According to the National Oceanic and Atmospheric Administration (NOAA), the sand ingested by sea cucumbers directly passes through their systems and is discharged from the other end in the form of sandy feces.

Related: Watch this giant sea cucumber excrete spiral feces.

Sea cucumber and sand will discharge by-products beneficial to marine ecosystem, especially coral reefs. 20 1 1 A study published in the Journal of Geophysical Research found that the natural digestion process of sea cucumber makes its excrement have a relatively high (or alkaline) pH value, which means that the water around the sea cucumber habitat is protected by ocean acidification to some extent. Sea cucumber also secretes calcium carbonate, which is the main component of coral formation, and ammonia is the fertilizer to promote coral growth.

Anatomy and reproduction of sea cucumber Sea cucumber has a relatively simple internal anatomical structure, which consists of three main parts: digestion. According to the description in the book Nature Focus (20 10), this animal has the ability to breathe and reproduce.

According to UCMP, although sea cucumbers have no bones, many kinds of sea cucumbers have a basic skeleton consisting of tiny calcium carbonate flakes loosely distributed under the skin. According to the research of Southeast University of Alaska, some species can arrange their bone plates, thus making their bodies stiff. The digestive tract of "KDSP" and "KDSP" consists of a long intestinal wound between the mouth and * * *, which is about two to three times the length of sea cucumber. According to the World Health Organization, occasionally, if disturbed or stressed, sea cucumbers will be excreted from the whole digestive system, but they can grow substitutes in just a few weeks.

Photo 1 A total of 6 dolphin fish. (Shutterstock)6 Figure 2 California sea cucumber. Six photos of Stichopus japonicus. 3(Shutterstock)6 photos of Graffi sea cucumber 4. Shutterstock)6 Picture 5 A bright red sea cucumber. 6 Elephant trunk fish sea cucumber (sea cucumber) Picture 6. According to the research of Southeast University of Alaska, the respiratory system of sea cucumber consists of two respiratory trees on both sides of digestive tract. According to National Geographic, water enters the human body through the roots of two Y-shaped trees in * * *, and oxygen enters the body cavity through a thin film.

Most sea cucumbers reproduce sexually through in vitro fertilization. This means that the male releases * * * into the water, and the female releases her eggs into the water, hoping that several eggs will collide with * * *. These animals must release thousands of * * * and egg cells to increase the chances of fertilization.

Sea cucumber larvae drift with the current until they are big enough to attach to the seabed.

Scientists have identified at least 16 species of sea cucumbers, which can also reproduce. According to an article published in the journal Ecology and Evolution on 20 17, there are two ways of asexual reproduction. Every half-divided sea cucumber will regenerate its lost organs and basically become a clone of primitive animals.

People eat a lot of sea cucumbers. The International Union for Conservation of Nature and Natural Resources (IUCN) has listed several sea cucumbers (such as brown sea cucumber and yellow heterorod sea cucumber) as fragile or endangered species. However, most species are considered as the least concerned species, or there are not enough data to accurately evaluate the species population. According to a report of the Food and Agriculture Organization of the United Nations (FAO) in 20 10,

Except for some populations in temperate waters in the northern hemisphere, sea cucumbers are caught in large quantities. According to Cool Green Technology, most of the harvested animals are exported to Asian markets, where sea cucumbers are regarded as delicacies.

In some areas, such as Papua New Guinea, overfishing of sea cucumbers has completely destroyed the local population. According to the U.S. Department of Justice, most sea cucumbers are traded on the black market.

Related: The man was arrested for selling soft sea cucumbers worth $6.5438+0.7 million.

And was fined 6,543,800 yuan. FAO has issued a global guide for sustainable fishing of sea cucumbers. These guidelines have become laws in some countries, but many places have no resources to implement them. As scientists learn more about sea cucumbers, FAO has revised the guidelines accordingly.

Other resources:

Have you seen sea cucumber recently? Find the sea cucumber species you meet on the marine species identification portal. Learn more about sea cucumber from XL Catlin seascape survey. Watch another strange and rare sea cucumber swimming video of Monterey Bay Aquarium Research Institute.