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Lake Tana, located in the north-western highlands of Ethiopia, contains a unique assemblage of cyprinid fishes. In addition to the only known intact species flock of large (max. 100 cm forklength (FL)) Labeobarbus species, the lake harbours three small (<10 cm FL) Barbus species: B. humilis Boulenger, 1902, B. pleurogramma Boulenger, 1902 and B. tanapelagius de Graaf, Dejen, Sibbing and Osse, 2000. Phylogenetic relationships of the small Barbus species of Lake Tana were investigated using the mtDNA cytochrome b gene. All small Barbus species occurring in Lake Tana are part of the 'small African diploid' groups identified by Tsigenopoulos et al. (2002). Barbus pleurogramma, only reported in Lake Tana, and populations of the morphologically similar species, B. paludinosus Peters, 1852, collected in rivers and lakes throughout Ethiopia, comprised a monophyletic group with separate clades congruent with drainage basins. Barbus pleurogramma could well be a cryptic species rather than synonymous to B. paludinosus as previously suggested. The genetic divergence between B. humilis and B. tanapelagius was very low, and without lineage sorting of haplotypes. This is probably due to recent (<16 000 years ago) evolution of the pelagic, zooplanktivorous B. tanapelagius from the benthic, omnivorous B. humilis after the formation of Lake Tana.

The Zfcth1 gene is, as the previously cloned carp cth1 gene, related to the mammalian TIS 11 family of primary response genes and encodes a protein with two putative CCCH zinc fingers. This report describes the RNA expression of this gene during oogenesis and early embryogenesis up to gastrulation in the zebrafish (Danio rerio). Maternal cth1 message is present in the ovary of 1-month-old fish and of adult fish in oocytes at all stages of maturation. In the youngest oocytes the message is localized in the cytoplasm all around the nucleus, in larger oocytes the message becomes restricted to the future animal pole of the embryo, and in mature oocytes the expression is sharply localized in the cortical layer under the micropyle. After ovulation the cth1 messenger spreads over the cytoplasmic cap and is distributed over the blastomeres during subsequent cleavages. In subsequent stages maternal expression of cth1 gradually disappears. From early epiboly stages onward embryonic cth1 expression is localized to the germ ring and the hypoblast cells in the central part of the embryonic shield. In the shield, cth1 expression largely overlaps with the area of gooscoid expression in the first involuting cells. In stages after 70% of epiboly cth1 expression diminishes and soon can no longer be detected in the embryo. Next to a developmental role in cell fate determination we propose a function for cth1 during oocyte maturation.

A carp caudal cDNA of 1.3 kb was cloned after screening an early segmentation stage cDNA library with a probe produced by PCR using conserved homeobox sequences as primers and genomic DNA as template. The homeobox gene was called carp-cdxl. The gene appears highly similar to other vertebrate caudal homologs, especially the zebrafish gene cdx(Zf-cad). The possible relationship to homeobox genes within the Hox-C gene complexes is discussed. A weak expression of the gene, detected by in situ hybridization, was found shortly before gastrulation (at 25% epiboly) in cells likely to have a posterior fate. During gastrulation expression became stronger. At the early segmentation stage, cells of the neural keel in the area of the prospective spinal cord expressed the gene. During the progression of segmentation, expression retracted in a caudal direction. The tailbud expressed the gene throughout, but the somites lost expression shortly after their formation. Only the most lateral mesoderm cells maintained expression in the trunk area. Carp-cdxl was also expressed in the endoderm. At 24 h after fertilization the gene was only expressed in the tailbud. At 48 h, no expression could be detected. The expression pattern suggests a function for carp-cdxl in gastrulation and patterning along the anterior-posterior axis of the embryo.