An assessment of the natural marking patterns used for photo-identification of common minke whales and white-beaked dolphins in Icelandic waters

Natural marks occurring in cetaceans are used to measure population parameters, social structure and movements. However, the changeable nature of these marks can originate bias in these estimates. The aim of this work was to calculate abundance and prevalence of 28 mark types observed in common minke whales and white-beaked dolphins photographed in Icelandic waters for 11 years (2002–2013) in order to identify reliable markings which could be suitable for capture-mark-recapture studies. In the common minke whale subsample the most prevalent occurring marks were cookie-cutter shark bite, notch and lamprey bite, and herpes-like lesions and blisters were the most abundant. White-beaked dolphins had notch, fin patches and fine scrape as the most prevalent, and black mark and fine scrape were the most abundant. Loss and gain rates were also estimated resulting in eight mark types with no losses in common minke whales including fin outline and injury marks. In white-beaked dolphins there were 13 mark types with null loss rate among which there were notch, distinct notch and amputation. Our findings confirm that fin and injury marks are among the most accurate features to use for capture-mark-recapture studies as noted for other cetacean species. We also suggest including cookie-cutter shark bites for common minke whales and fin patches for white-beaked dolphins due to their low loss rate. These two mark types were amongst the most prevalent in both species, so their addition will be pivotal in increasing the power of analysis conducted using photo-identification data obtaining more accurate population estimates.

Marked mitochondrial DNA sequence heterogeneity in single CD34+ cell clones from normal adult bone marrow

Somatic mitochondrial DNA (mtDNA) mutations accumulate with age in postmitotic tissues but have been postulated to be diluted and lost in continually proliferating tissues such as bone marrow (BM). Having observed marked sequence variation among healthy adult individuals' total BM cell mtDNA, we undertook analysis of the mtDNA control region in a total of 611 individual CD34+ clones from 6 adult BM donors and comparison of these results with the sequences from 580 CD34+ clones from 5 umbilical cord blood (CB) samples. On average, 25% (range, 11% to 50%) of individual CD34+ clones from adult BM showed mtDNA heterogeneity, or sequence differences from the aggregate mtDNA sequence of total BM cells of the same individual. In contrast, only 1.6% of single CD34+ clones from CB showed mtDNA sequence variation from the aggregate pattern. Thus, age-dependent accumulation of mtDNA mutations appears relatively common in a mitotically active human tissue and may provide a method to approximate the mutation rate in mammalian cells, to assess the contribution of reactive oxygen species to genomic instability, and for natural “marking” of hematopoietic stem cells; our data also have important implications for the aging process, forensic identifications, and anthropologic conclusions dependent on the mtDNA sequence.