When it comes to spiders, everyone is familiar with it, but when it comes to “sea spiders”, many people are not familiar with it, or even heard of it for the first time.
Sea spiders and spiders both belong to the phylum Chelicerina of the phylum Arthropods. They are homologous and close relatives, but they are not in the same class. They belong to the class Sea Aranea and the class Arachnida respectively. Compared with the round belly of most spiders, the sea spider’s belly is just a small protrusion, so that at a glance, it seems that there are no other parts of the body except legs.
Currently, there are more than 1,300 known species of sea spiders in the world, distributed in most sea areas around the world, with the largest distribution in Antarctic waters. The lower the water temperature, the higher the dissolved oxygen content. The higher oxygen content and low temperature environment can reduce the metabolism rate of organisms. Therefore, sea spiders in Antarctic waters are dozens of times larger than those in ordinary seas, forming a Extra large body structure.
The sea spider is also known as the “Mesopod”, and the name also shows that its legs have a strong sense of presence. Sea spiders generally have 8 legs, but some have 10 or even 12 legs. The leg length ranges from 5 mm to 25 cm. Each leg has 4 segments and is very soft and can be bent and stretched to adapt to different environments. For example, the legs of sea spiders in the intertidal zone are mainly used to adhere to other organisms and are relatively short and thick; while the sea spiders in the deep sea have slender legs and better movement coordination because they need to hunt for food.
Due to the heavy proportion of their legs, sea spiders look extremely slender and have almost no meat, which allows them to live a very carefree life in the sea without natural enemies. Moreover, most of the life activities of sea spiders are completed by the legs. The legs have the respiratory system, digestive system, circulatory system, etc., and even the reproductive system is also on the legs.
The legs of sea spiders are covered with many tiny holes, which allow them to obtain oxygen efficiently and breathe. In addition, the heart and intestines of sea spiders also extend to the legs in the form of blind tubes. The intestines are also responsible for the tasks related to the digestive and circulatory systems. In order to maintain oxygen transportation and blood circulation, sea spiders’ hearts beat at a rate of 90 to 180 times per minute. The resulting high blood pressure will promote circulation in the legs or near the trunk, which also allows them to digest and blood more efficiently. Cycles have unique survival advantages in nature.
In addition to breathing, digesting and transporting blood, sea spiders’ legs can also “give birth”.
After in vitro fertilization between a male sea spider and a female sea spider, the male sea spider will pick up the fertilized eggs, place them in a part of the leg called an egg-carrying foot, store them, and allow them to hatch. With no natural predators, it doesn’t take long for the hatchlings to be able to live on their own.
Sea spiders not only have magical long legs, but also have strong adaptability and self-repair capabilities. Some researchers put sea spiders captured in Antarctic waters into environments with different water temperatures to observe their self-adjustment capabilities. The results of the study show that sea spiders can live well in different temperatures. Researchers from Germany’s Humboldt University and other institutions also discovered that sea spiders have miraculous regeneration abilities – unlike other arthropods that can only regenerate legs and feet, they can also regenerate some important parts of the body, including the hindgut, anus, Muscle tissue and some reproductive organs. The discovery could help further advance regenerative medicine research and even help develop certain therapies to treat amputated human limbs.
As marine creatures, the food of sea spiders is usually the body fluids of other soft-bodied invertebrates in the ocean, or polyzoans and bryozoans, such as sponges, bryozoans, etc. The way of hunting is to suck prey into the body through the tubular mouthparts and then digest it. It is worth mentioning that when the sea spider cannot even catch small creatures such as sponges and bryozoans, it will also eat the leftovers of the previous marine ecosystem, such as animal carcasses and marine garbage, as if A “sea scavenger”.
The oldest and most complete sea spider fossil to date was discovered by Oxford University paleontologist Derek Swent and colleagues in Herefordshire, England. The discovery of this fossil shows that sea spiders, as a unique creature, appeared about 450 million years ago. At that time, dinosaurs had not yet been born. Later, after experiencing several mass extinctions of life on earth, sea spiders have always maintained their original shapes and structures. This kind of survival strength is really shocking.