The emergence of Vertebrata was accompanied by two rounds of whole-genome duplications. This enabled paralogous genes to acquire novel functions with high evolutionary potential, a process suggested to occur mostly by changes in gene regulation, rather than in protein sequences. In the case of Hox gene clusters, such duplications favored the appearance of distinct global regulations. To assess ...

There is now good evidence that in the Vertebrata peripheral nerves exert an important trophic effect on the regeneration of the structures which they innervate (Millot, 1931; Needham, J. 1942; Hamburger, 1944). In invertebrates the nervous system is not always necessary; Millot (1931, p. 117) concluded that in types where regenerative powers are comparatively limited (e.g. Mollusca, some Nemer...

It is well known that Carl Schmidtf was tlie first to discover in tlie Ascidian the presence of a principle previously known to exist only in plants, viz. cellulose, and to show that it was a constituent of the animal tissue. The researches of Kolliker and Lowig, j of Scliacht,? and of Huxley || have established this important fact. The occurrence of this substance, however, was limited to a co...

Three known bromophenols, 2,3-dibromo-4,5-dihydroxybenzylaldehyde (1), 2,2',3-tribromo-3',4,4',5-tetrahydroxy-6'-hydroxymethyldiphenylmethane (2) and bis(2, 3-dibromo-4,5-dihydroxylbenzyl) ether (3), and one new one, 5,5″-oxybis(methylene)bis (3-bromo-4-(2',3'-dibromo-4',5'-dihydroxylbenzyl)benzene-1,2-diol) (4), were isolated from an extract of the red alga, Vertebrata lanosa. The antioxidant ...

The hagfish, a group of extant jawless fish, are known to lack true vertebrae and, for this reason, have often been excluded from the group Vertebrata. However, it has yet to be conclusively shown whether hagfish lack all vertebra-like structures, and whether their somites follow developmental processes and patterning distinct from those in lampreys and gnathostomes. Here we report the presence...

We present information about new records of 11 species chondrichthyans in the southern Gulf Mexico, adding specimens and occurrence Mexican waters. The second record Bathytoshia centroura, Mustelus sinusmexicanus, Mobula hypostoma Squalus clarkae for Mexico is presented, as well marine areas Lagoon Alvarado system corresponding to Hexanchus vitulus, Heptranchrias perlo, Scyliorhinus retifer cub...