Protostome

Définitions de « protostome »

Protostome - Nom commun

• (Zoologie) Animal bilatérien caractérisé par une embryogenèse au cours de laquelle la bouche est le premier orifice à se former.

  Dans le règne animal, l'escargot, exemple frappant de protostome, voit sa bouche se développer avant toute autre ouverture corporelle dès les premiers stades de l'embryogenèse.

Évolution historique de l’usage du mot « protostome » depuis 1800

Citations contenant le mot « protostome »

• Looking at about 5,000 different genes, for approximately 70%, the protostome branch had more unique changes supporting it than the deuterostome branch did. That means the animals on the protostome branch share lots of unique changes to their DNA – and so this branch is very well supported by the DNA evidence. The close relationship between vertebrates and echinoderms, in contrast, is supported by much weaker evidence – they share relatively few unique DNA changes.

• "Here is an animal that is the poster child for early protostomes, and it develops just like a deuterostome," says Mark Martindale, a developmental biologist at the University of Hawaii in Honolulu. “We’ve been using the name protostome for 100 years, and now it’s clear that it doesn’t mean anything.”

• Surprisingly, the researchers found that these worms, which are protostomes, share many gene families and gene arrangements with the deuterostomes, the group that includes the vertebrates. For example, they share genes that are involved in multicellularity and maintenance of the body's internal environment. They also share a common system for controlling head development; the same mechanism that controls vertebrate head patterning also controls the development of ribbon worm heads and horseshoe worm feeding tentacles. Other protostome groups, such as insects, have lost some of these genetic features.

• There might be a need to rename the protostome class of animals. There are tiny differences in how embryos develop in the different branches in the tree of life, which can lead to monumental changes in adults. When an embryonic ball of cells develops two indentations instead of one, the organism will develop a separate mouth and anus contrary to the single opening that jellyfish and sea anemones have. In 1908, animals with both a mouth and anus were divided into two groups. The protostomes formed their mouth first, the anus second. In the other animals, the mouth formed after the anus.

• Most of the organisms that we see today are bilaterally symmetrical. Such animals are categorised under primary two groups. Humans and other vertebrate animals belong to the deuterostomes, while creatures like bugs and crabs fall under the protostome category.

Traductions du mot « protostome »

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