Dataset Information

A trade-off between thickness and length in the zebra finch sperm mid-piece.

ABSTRACT: The sperm mid-piece has traditionally been considered to be the engine that powers sperm. Larger mid-pieces have therefore been assumed to provide greater energetic capacity. However, in the zebra finch Taeniopygia guttata, a recent study showed a surprising negative relationship between mid-piece length and sperm energy content. Using a multi-dimensional approach to study mid-piece structure, we tested whether this unexpected relationship can be explained by a trade-off between mid-piece length and mid-piece thickness and/or cristae density inside the mitochondrial helix. We used selective plane illumination microscopy to study mid-piece structure from three-dimensional images of zebra finch sperm and used high-resolution transmission electron microscopy to quantify mitochondrial density. Contrary to the assumption that longer mid-pieces are larger and therefore produce or contain a greater amount of energy, our results indicate that the amount of mitochondrial material is consistent across mid-pieces of varying lengths, and longer mid-pieces are simply proportionately 'thinner'.

SUBMITTER: Mendonca T

PROVIDER: S-EPMC6083248 | biostudies-literature | 2018 Jul

REPOSITORIES: biostudies-literature

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A trade-off between thickness and length in the zebra finch sperm mid-piece.

Mendonca Tania T Birkhead Tim R TR Cadby Ashley J AJ Forstmeier Wolfgang W Hemmings Nicola N

Proceedings. Biological sciences 20180725 1883

The sperm mid-piece has traditionally been considered to be the engine that powers sperm. Larger mid-pieces have therefore been assumed to provide greater energetic capacity. However, in the zebra finch <i>Taeniopygia guttata</i>, a recent study showed a surprising negative relationship between mid-piece length and sperm energy content. Using a multi-dimensional approach to study mid-piece structure, we tested whether this unexpected relationship can be explained by a trade-off between mid-piece ...[more]

PMID: 30051869

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Project description:Most of our understanding of the fundamental processes of mutation and recombination stems from a handful of disparate model organisms and pedigree studies of mammals, with little known about other vertebrates. To gain a broader comparative perspective, we focused on the zebra finch (Taeniopygia castanotis), which, like other birds, differs from mammals in its karyotype (which includes many micro-chromosomes), in the mechanism by which recombination is directed to the genome, and in aspects of ontogenesis. We collected genome sequences from three generation pedigrees that provide information about 80 meioses, inferring 202 single-point de novo mutations, 1,174 crossovers, and 275 non-crossovers. On that basis, we estimated a sex-averaged mutation rate of 5.0 × 10-9 per base pair per generation, on par with mammals that have a similar generation time. Also as in mammals, we found a paternal germline mutation bias at later stages of gametogenesis (of 1.7 to 1) but no discernible difference between sexes in early development. We also examined recombination patterns, and found that the sex-averaged crossover rate on macro-chromosomes (1.05 cM/Mb) is again similar to values observed in mammals, as is the spatial distribution of crossovers, with a pronounced enrichment near telomeres. In contrast, non-crossover rates are more uniformly distributed. On micro-chromosomes, sex-averaged crossover rates are substantially higher (4.21 cM/Mb), as expected from crossover homeostasis, and both crossover and non-crossover events are more uniformly distributed. At a finer scale, recombination events overlap CpG islands more often than expected by chance, as expected in the absence of PRDM9. Despite differences in the mechanism by which recombination events are specified and the presence of many micro-chromosomes, estimates of the degree of GC-biased gene conversion (59%), the mean non-crossover conversion tract length (~23 bp), and the non-crossover to crossover ratio (6.7:1) are all comparable to those reported in primates and mice. The conservation of mutation and recombination properties from zebra finch to mammals suggest that these processes have evolved under stabilizing selection.

Dataset Information

A trade-off between thickness and length in the zebra finch sperm mid-piece.

Publications

A trade-off between thickness and length in the zebra finch sperm mid-piece.

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