GENE MAPPING IN XENOPUS (ANURA PIPIDAE)

Muscle opacity (mo), a new mutant gene in Xenopus laevis, linked to the rusty locus

A new developmental mutant is described in Xenopus laevis (Amphibia, Anura): muscle opacity (mo). Homozygotes die at larval stage 48. The underlying defect, visible at stage 47, is a degeneration of cephalic musculature. The mo gene is linked to the rusty locus, with a map distance of 6.1%.

Two transitions of haemoglobin expression in Xenopus: from embryonic to larval and from larval to adult

Electrophoretic analyses of haemoglobin and globin phenotypes in families of Xenopus borealis and Xenopus l. laevis revealed two developmental haemoglobin transitions during ontogeny. The first transition occurs at the developmental stage when tadpoles begin to feed. It is characterized by the decline of embryonic-specific globins in favour of novel, tadpole-specific globins (X. borealis) correlated to changes in the haemoglobin pattern. We suppose that this switch results from the replacement of a primitive, ventral blood island-dependent erythrocyte population by tadpole erythrocytes from other erythropoietic sites. Several other globin chains and haemoglobins are present in both young tadpoles and throughout larval life. The second, well-known transition occurs during metamorphosis, where all tadpole haemoglobins are replaced by adult haemoglobins composed of entirely different globin chains.