Lancelets contain many organs and organ systems that are homologous to those of modern fish, but in a more primitive form. Therefore, they provide a number of examples of possible evolutionary exaptation. For example, the gill-slits of lancelets are …

2024年8月20日 · Lancelets, or amphioxi, are tiny, fish-like marine organisms that belong to the subphylum Cephalochordata, in the class Leptocardii. They get their name ‘lancelets’ due to their slender, elongated body that tapers to a point at both ends, resembling the shape of …

Lancelets are distributed throughout the world along tropical and temperate coasts. They inhabit soft bottoms ranging from sand to coarse shelly sand or gravel in shallow coastal water. Lancelets lie buried beneath this substrate, often with their mouths protruding above the surface, allowing them to take in water laden with food.

2018年5月11日 · lancelet, name for small, fishlike lower chordate (see Chordata [1]), also called amphioxus; it shows many affinities with the vertebrates. There are about 30 lancelet species, most belonging to the genus Brachiostoma (formerly Amphioxus).

Scientists consider lancelets the closest living relatives to vertebrates (VER-teh-brehts), or animals with a backbone. The two groups share traits such as the organization of the main body muscles into separate segments and the organization of the blood vessels. Lancelets also have a structure that is a simple form of the liver of vertebrates.

Cephalochordates (also called acraniates or lancelets) possess key features that characterize them as chordates. Those characters include the notochord, dorsal nerve cord, branchial basket, and a post anal tail with fins. It is generally believed that cephalochordates are the closest living relatives to the vertebrates.

Lancelets are suspension feeders that extract small particles suspended in the water. The mouth is covered by an oral hood, the edges of which form the buccal cirri. The cephalochordate commonly is buried in the substrate and positions its mouth above the surface of the sand.

Although there is no brain or cranium, growing evidence suggests that the vertebrate brain evolved from a portion of the nerve cord in a lancetlike ancestor. Blood flows forward along the ventral side and backward along the dorsal side, but there is no distinct heart.

The lancelets, also known as Cephalochordata or Leptocardii, are a group of primitive chordates which were formerly called Amphioxus. It includes Pikaia. Lancelets are the modern survivors of an ancient chordate lineage, with a fossil record dating back to the Cambrian period. The lancelets are usually said to be the sister group of the craniates.

Lancelet (amphioxus), in particular, represents the most basally divergent living cephalochordate that diverged from urochordates and vertebrates 550 million years ago and retains a body plan and morphology most similar to fossil Cambrian chordates (1, 4).