Primitive Chordates

The hemichordate, Dolichoglossus kowalevskii, and the cephalo-chordate, Branchiostoma (Amphioxus), contain sialic acids, mostly as AT-glycolylneuraminic acid. In urochordates, including one urochordate larva, sialic acids could not be detected (Warren, 1963). The urochor- 

The structures of the polysialogangliosides have been elucidated by Ishizuka et aL (1972). Most of the sialic acid is N-acetylneuraminic acid. Also identified is N-acetyl-8-O-acetylneuraminic acid (Ishizuka et a/., 1970 Seiter, 1970 McCluer and Agranoff, 1972). 

Yiamouyiannis and Dain, 1968 Avrova, 1968 1971). Most, if not all, of the sialic acid is N-acetylneuraminic acid (Eldredge et aL, 1%3). 

In the oviduct mucoprotein of the toad, Bufo arenarunty four species of sialic acids were detected N-acetyl-, N,4-0-diacetyl-, and two species of A-glycolylneuraminic acids (DeMartinez and Olavarria, 1973). 

Histochemical studies have revealed the presence of sialic acid in cephalic glands of several reptilian species, Ameiva ameiva (Lacertilia, Teiidae), Micrurus corallinus corallinus (Ophiadea, Elapidae), and o/Zi-rops jararaca (Ophiadia, Viperidae) (Lopes and Valeri, 1972 Lopes et al.y 1973 1974). 

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Pavao, M. S. (2002). Structure and anticoagulant properties of sulfated glycosaminoglycans from primitive Chordates. An. Acad. Bras. Cien. 74,105-112. 

Lamellarins were originally extracted from a marine prosobranch mollusk Lamdlaria sp. and subsequently from primitive chordate ascidians (tunicates) [23]. These ascidian species, knovm to produce many bioactive metabolites, likely represent the original producer of lamellarins because these organisms are presumed to be the dietary source of the Lamdlaria mollusks. Lamellarins have been isolated from different tunicates, including recently from the Indian ascidian Didemnum obscurum... 

III trials in Europe) [70]. The biomedical potential of the ascidian metabolites has resulted in these primitive chordates. As part of our ongoing chemical and biological studies on Okinawan marine organisms, we investigated an ascidian Lissoclinum sp. collected off the coast of Hateruma Island. A lipophilic extract of the ascidian showed that it could inhibit the division of fertilized sea urchin eggs. 

We can find evidence for such gross replication errors by comparing the DNA of a primitive organism with that of its more complex relatives. Although there is no necessary relationship between the amount of DNA that an organism has and its complexity, there are examples that fit with naive expectations. One is provided by the lancelet, a small animal found on beaches around the world. This looks snperficially like a small fish, but it is not a fish, or even a vertebrate, as it has no backbone. It is a primitive chordate, which means that it is an invertebrate member of the phylum that includes the vertebrates as its... 

Fig. 2.6 Evidence for gene duplication in human DNA. Four human chromosomes contain three or four each of a series of four genes similar to a series of four genes in the DNA of the lancelet, a primitive chordate...

The early discovery of scymnol in a primitive chordate led to repeated mention of the probable evolutionary significance of this bile alcohol. Sobotka (7) called scymnol the phylogenetic precursor of the bile acids. Both Haslewood (3) and Fieser and Fieser (1) cite the suspicion of Windaus et al. (212)... 

The appearance of bilateral symmetry (two halves which are mirror images of each other) was an important evolutionary breakthrough. The most primitive bilaterally symmetrical animals are the flatworms (phylum Platyhelminthes). Platyhelminthes gave rise to the coelo-mates, which have a coelom, or internal body cavity. The coelomates split into two evolutionary lines, the proto-stomes (molluscs, annelids, and arthropods) and the deuterostomes (echinoderms and chordates). A few phyla, such as the phylum Bryozoa, are intermediate between the two lines. Of the nearly 20,000 species of bry-ozoans known, only 3,500 are stUl living. 

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