Tracing the origin of fish immunoglobulins.

We have studied the origin of immunoglobulin genes in fish. There are two evolutionary lines of bony fish, Actinopterygii and Sarcopterygii. The former gave rise to most of the current fish and the latter to the animals that went to land.

Immunoglobulins genes in Neoceratodus forsteri and Protopterus annectens explain the origin of the immunoglobulins of the animals that passed ashore.

Sarcopterygian fishes are a taxon of bony fishes. They include lungfish and coelacanths (six species of lungfish and two species of coelacanths). Evolutionary adaptations arose with these fish, such as the appearance of lungs and paired lobed fins that help them move over the bottom of the sea.

Gouania willdenowi is a teleost fish without immunoglobulin genes.

Immunoglobulin (Ig) genes encode antibodies in jawed vertebrates. They are essential elements of the adaptive immune response. Ig exists in soluble form or as part of the B cell membrane antigen receptor (BCR).

Immunoglobulin T genes in Actinopterygii.

In teleost fishes, there are three immunoglobulin isotypes named immunoglobulin M (IgM), D (IgD), and T (IgT). IgT was the last to be described in teleost fishes, and it is specific to them. From recent fish genomes, we identified and studied the immunoglobulin heavy chain genes in Actinopterygii.