from The American Heritage® Dictionary of the English Language, 4th Edition
- n. See lancelet.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. The lancelet
from the GNU version of the Collaborative International Dictionary of English
- n. A fishlike creature (Amphioxus lanceolatus), two or three inches long, found in temperature seas; -- also called the lancelet. Its body is pointed at both ends. It is the lowest and most generalized of the vertebrates, having neither brain, skull, vertebræ, nor red blood. It forms the type of the group Acrania, Leptocardia, etc.
from The Century Dictionary and Cyclopedia
- n. The lancelets, the typical genus of the family Amphioxidæ, whose body is compressed and tapers to a point at each end: a synonym of Branchiostoma (which see). See also cut under lancelet.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. small translucent lancet-shaped burrowing marine animal; primitive forerunner of the vertebrates
In fact, the very name amphioxus is from Greek words meaning "both-pointed," with reference to the two ends.
In passing from the primitive chordates, such as amphioxus, into the vertebrate subphylum, one passes from an unspecialized nerve cord to one in which the anterior end has developed into the brain.
This poor beastie is an amphioxus, though a more apposite appellation might have been "anxious".
The same mitochondrial DNA sequences placed echinoderms - which include starfish and sea urchins - in closer proximity to the vertebrates than amphioxus even though, being a chordate, we would expect amphioxus to be closer (Ref 2).
In going from amphioxus to jawless fish to jawed fish to land vertebrates we see an increase in complexity of the clotting cascade:
All of them are potentially testable via molecular clocks and whole-genome studies on a variety of protoverebrates we need the amphioxus genome, apparently due out this year and vertebrates, as well as reconstruction of the common ancestral proteins.
This is not dissimilar to the trypsin/prophenyloxidase system, in amphioxus, where a trypsin activates an enzyme prophenyloxidase to make gluggy melanin at wound sites 17.
The chordate amphioxus in modern taxonomy, Branchiostoma and its relatives, a protovertebrate that looks a bit like a minature eel, does clot its haemolymph.
Presence of prophenoloxidase in the humoral fluid of amphioxus Branchiostoma belcheri tsingtauense.
A tadpole-like beastie similar to the chordate amphioxus.
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