Branchiostoma is one of the few living genera

Genera

Genera is a commercial operating system and development environment for Lisp machines developed by Symbolics. It is essentially a fork of an earlier operating system originating on the MIT AI Lab's Lisp machines which Symbolics had used in common with LMI and Texas Instruments...

 of lancelet

Lancelet

The lancelets , also known as amphioxus, are the modern representatives of the subphylum Cephalochordata, formerly thought to be the sister group of the craniates. They are usually found buried in sand in shallow parts of temperate or tropical seas. In Asia, they are harvested commercially as food...

s (order

Order (biology)

In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 Amphioxiformes). It is the type genus of family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Branchiostomidae

Branchiostomidae

Branchiostomidae is the family that includes most of the lancelets, which are tiny chordates without a true spine but only a flexible notochord....

.
These small vaguely eel- or snake-like animals are close relatives of vertebrate

Vertebrate

Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...

s. The scientific name means "gill-mouth", referring to their anatomy

Anatomy

Anatomy is a branch of biology and medicine that is the consideration of the structure of living things. It is a general term that includes human anatomy, animal anatomy , and plant anatomy...

 – unlike vertebrates, they do not have a true head

Head

In anatomy, the head of an animal is the rostral part that usually comprises the brain, eyes, ears, nose and mouth . Some very simple animals may not have a head, but many bilaterally symmetric forms do....

 (with a skull

Skull

The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...

 capsule, eye

Eye

Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptors in conscious vision connect light to movement...

s, nose

Nose

Anatomically, a nose is a protuberance in vertebrates that houses the nostrils, or nares, which admit and expel air for respiration in conjunction with the mouth. Behind the nose are the olfactory mucosa and the sinuses. Behind the nasal cavity, air next passes through the pharynx, shared with the...

, a well-developed brain

Brain

The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...

 etc.), but merely a mouth adjacent to the gill

Gill

A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...

-slits, with the slightly enlarged anterior end of the dorsal nerve cord

Dorsal nerve cord

The dorsal nerve cord is one of the embryonic features unique to chordates, along with a notochord, a post-anal tail and pharyngeal slits. The dorsal nerve cord is a hollow cord dorsal to the notochord.It is formed from a part of the ectoderm that rolls, forming the hollow tube, compared to other...

 above and in front of them.

Like all lancelets, they are filter feeder

Filter feeder

Filter feeders are animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feeding are clams, krill, sponges, baleen whales, and many fish and some sharks. Some birds,...

s that hide in the sediment

Sediment

Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....

 most of the time. The genus inhabits coastal waters e.g. of the North Atlantic.

Species

• Branchiostoma belcheri
• Branchiostoma californiense
• Branchiostoma capense
• Branchiostoma caribaeum
• Branchiostoma clonaseum
• Branchiostoma floridae
  Branchiostoma floridae
  Branchiostoma floridae is a lancelet of the genus Branchiostoma. The genome of this species has been sequenced, revealing that among the chordates, the morphologically simpler tunicates are actually closer related to vertebrates than lancelets....
  
  
• Branchiostoma lanceolatum
  Branchiostoma lanceolatum
  Branchiostoma lanceolatum or amphioxus is a lancelet in the subphylum Cephalochordata. It is a marine invertebrate found in soft substrates in shallow seas. It is used as a model organism to study the development of vertebrates...
  
  
• Branchiostoma minucauda
• Branchiostoma moretonensis
• Branchiostoma valdiviae
• Branchiostoma virginiae

Lancelet biodiversity

Biodiversity

Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions...

 is not very well studied; other as of yet undescribed species (perhaps including cryptic species) might await discovery.

External links

• Branchiostoma