Big and slow: phylogenetic estimates of molecular evolution in baleen whales (suborder mysticeti).

Baleen whales are the largest animals that have ever lived. To develop an improved estimation of substitution rate for nuclear and mitochondrial DNA for this taxon, we implemented a relaxed-clock phylogenetic approach using three fossil calibration dates: the divergence between odontocetes and mysticetes approximately 34 million years ago (Ma), between the balaenids and balaenopterids approximately 28 Ma, and the time to most recent common ancestor within the Balaenopteridae approximately 12 Ma. We examined seven mitochondrial genomes, a large number of mitochondrial control region sequences (219 haplotypes for 465 bp) and nine nuclear introns representing five species of whales, within which multiple species-specific alleles were sequenced to account for within-species diversity (1-15 for each locus). The total data set represents >1.65 Mbp of mitogenome and nuclear genomic sequence. The estimated substitution rate for the humpback whale control region (3.9%/million years, My) was higher than previous estimates for baleen whales but slow relative to other mammal species with similar generation times (e.g., human-chimp mean rate > 20%/My). The mitogenomic third codon position rate was also slow relative to other mammals (mean estimate 1%/My compared with a mammalian average of 9.8%/My for the cytochrome b gene). The mean nuclear genomic substitution rate (0.05%/My) was substantially slower than average synonymous estimates for other mammals (0.21-0.37%/My across a range of studies). The nuclear and mitogenome rate estimates for baleen whales were thus roughly consistent with an 8- to 10-fold slowing due to a combination of large body size and long generation times. Surprisingly, despite the large data set of nuclear intron sequences, there was only weak and conflicting support for alternate hypotheses about the phylogeny of balaenopterid whales, suggesting that interspecies introgressions or a rapid radiation has obscured species relationships in the nuclear genome.

Diversity and duplication of DQB and DRB-like genes of the MHC in baleen whales (suborder: Mysticeti).

The molecular diversity and phylogenetic relationships of two class II genes of the baleen whale major histocompatibility complex were investigated and compared to toothed whales and out-groups. Amplification of the DQB exon 2 provided sequences showing high within-species and between-species nucleotide diversity and uninterrupted reading frames consistent with functional class II loci found in related mammals (e.g., ruminants). Cloning of amplified products indicated gene duplication in the humpback whale and triplication in the southern right whale, with average nucleotide diversity of 5.9 and 6.3%, respectively, for alleles of each species. Significantly higher nonsynonymous divergence at sites coding for peptide binding (32% for humpback and 40% for southern right) suggested that these loci were subject to positive (overdominant) selection. A population survey of humpback whales detected 23 alleles, differing by up to 21% of their inferred amino acid sequences. Amplification of the DRB exon 2 resulted in two groups of sequences. One was most similar to the DRB3 of the cow and present in all whales screened to date, including toothed whales. The second was most similar to the DRB2 of the cow and was found only in the bowhead and right whales. Both loci showed low diversity among species and apparent loss of function or altered function including interruption of reading frames. Finally, comparison of inferred protein sequence of the DRB3-like locus suggested convergence with the DQB, perhaps resulting from intergenic conversion or recombination.

Hydatidiform moles at Waikato Women's Hospital, 1971-85.

A retrospective study was made of 61 patients who had hydatidiform moles diagnosed at Waikato Women's Hospital, from 1971 to 1985. The incidence of molar pregnancy was 1 in 700 deliveries. Following the introduction of the National Trophoblastic Disease Register in 1980, the use of a standard surveillance schedule greatly improved the completeness of follow-up. To date, of 29 patients followed-up by serum beta hCG monitoring, 3/20 (15%) classic moles and 0/9 partial moles have required chemotherapy for persistent trophoblastic activity. No cases of histologically proven postmolar choriocarcinoma were recorded.