Of the about three dozen or so species of lancelet
that exist, the one examined by the study's authors was found during a marine survey off the coast of Scotland in 2011.
Hidden ancient diversification in the circumtropical lancelet
Asymmetron lucayanum complex.
"But the surprising thing that emerged was that while the lancelet
has not evolved a great deal from its ancestors, it is strikingly similar at the gene level to humans.
The team scoured the lancelet
genome for precursors to a class of genes known as variable-region, or V-region, genes.
The present study is concerned with two cephalochordates representing different genera: namely, the Florida amphioxus, Branchiostoma floridae Hubbs, 1922, and the Bahamas lancelet
, Asymmetron lucayanum Andrews, 1893.
The cephalochordates are represented by the lancelets
(also known as amphioxus in old literature), with about 29 valid species in two genera: Branchiostoma and Epigonychthys (Poss & Boschung 1996).
adults, the preoral hood extends anteriorly from the right metapleural fold, and the right series of somites develop half a segment posterior to the left series (Schubert et al., 2001).
In the present study, the relationships between the movement and morphological parameters of a lancelet
and fish spermatozoa and their effects on sperm swimming speed were examined using the measured values obtained from spermatozoa having different morphologies.
Fine structural study of the cortical reaction and formation of the egg coats in a lancelet
(=amphioxus), Branchiostoma floridae (phylum Chordata: subphylum Cephalochordata = Acrania).
Searches based on domain organization were used to identify genes encoding usherin-like proteins in the genomes of chordates (including the tunicate Ciona savignyi and the lancelet
Branchiostoma floridae), the echinoderm Strongylocentrotus purpuratus, as well as in the limpet Lottia gigantea and the polychaete Capitella (Table 1).
Contrary to its similarity to vertebrates in basic body structures, the lancelet
(amphioxus) develops a nervous system with many unique features.
For example, Lacalli and West (1993) propose that the distinctive multipolar cells of echinoderm circumoral ciliary bands are homologous with similar neurons in the ciliary bands of the hemichordate tomaria, as well as with those in the dorsal nerve cord of ammocoete larvae of the lancelet