scholarly journals Convergent evolution of sperm gigantism and the developmental origins of sperm size variability inCaenorhabditisnematodes

Evolution ◽  
2016 ◽  
Vol 70 (11) ◽  
pp. 2485-2503 ◽  
Author(s):  
Anne Vielle ◽  
Nicolas Callemeyn-Torre ◽  
Clotilde Gimond ◽  
Nausicaa Poullet ◽  
Jeremy C. Gray ◽  
...  
Keyword(s):  
Convergent Evolution ◽  
Developmental Origins ◽  
Size Variability ◽  
Sperm Size

scholarly journals Convergent evolution of sperm gigantism and the developmental origins of sperm size variability in Caenorhabditis nematodes

2016 ◽  
Author(s):  
Anne Vielle ◽  
Nicolas Callemeyn-Torre ◽  
Clotilde Gimond ◽  
Nausicaa Poullet ◽  
Jeremy C. Gray ◽  
...  
Keyword(s):  
Sperm Competition ◽  
Convergent Evolution ◽  
Paternal Care ◽  
Early Stage ◽  
Size Variation ◽  
Egg Cell ◽  
Evolutionary Origins ◽  
Integrative View ◽  
Size Variability ◽  
Sperm Size

AbstractSperm cells provide crucial, if usually diminutive, ingredients to successful sexual reproduction as the source of centrioles and half the diploid genome. Despite this essential conserved function, sperm competition and coevolution with female traits can drive spectacular change in size and shape of these motile cells. Here we characterize four repeated instances of convergent evolution of sperm gigantism in Caenorhabditis nematodes using phylogenetic comparative methods on 26 species. Species at the extreme end of the 50-fold range of sperm-cell volumes across the genus have sperm capable of comprising up to 5% of egg-cell volume, representing severe attenuation of the magnitude of anisogamy. Exploring potential genetic and developmental determinants of Caenorhabditis sperm size variation, we uncover significant differences in mean and variance of sperm size among genotypes, between sexes of androdioecious species, as well as within and between individuals of identical genotypes. We demonstrate that the developmental basis of sperm size variation, both within and between species, becomes established during an early stage of sperm development, i.e. at the formation of primary spermatocytes while subsequent meiotic divisions contribute little further sperm size variability. These findings provide first insights into the developmental determinants of inter-and intraspecific sperm size differences in Caenorhabditis. Together, our results provide a novel integrative view on the developmental and evolutionary origins of Caenorhabditis sperm size variation. We hypothesize that life history and/or ecological differences among species favoured the evolution of alternative sperm competition strategies toward either many smaller sperm or fewer larger sperm, with gigantic sperm potentially providing a means of paternal care via gametic provisioning or as a potent vehicle for sexual conflict over offspring development.

scholarly journals Delayed trait development and the convergent evolution of shell kinesis in turtles

2018 ◽  
Vol 285 (1888) ◽  
pp. 20181585 ◽  
Author(s):  
Gerardo A. Cordero ◽  
Kevin Quinteros ◽  
Fredric J. Janzen
Keyword(s):  
Convergent Evolution ◽  
Shell Shape ◽  
Developmental Origins ◽  
Life Stages ◽  
Shell Formation ◽  
Developmental Constraints ◽  
Structural Alterations ◽  
Box Turtles ◽  
Embryonic Life ◽  
Phenotypic Diversification

Understanding developmental processes is foundational to clarifying the mechanisms by which convergent evolution occurs. Here, we show how a key convergently evolving trait is slowly ‘acquired’ in growing turtles. Many functionally relevant traits emerge late in turtle ontogeny, owing to design constraints imposed by the shell. We investigated this trend by examining derived patterns of shell formation associated with the multiple (at least 8) origins of shell kinesis in small-bodied turtles. Using box turtles as a model, we demonstrate that the flexible hinge joint required for shell kinesis differentiates gradually and via extensive repatterning of shell tissue. Disproportionate changes in shell shape and size substantiate that this transformation is a delayed ontogenetic response (3–5 years post-hatching) to structural alterations that arise in embryogenesis. These findings exemplify that the translation of genotype to phenotype may reach far beyond embryonic life stages. Thus, the temporal scope for developmental origins of adaptive morphological change might be broader than generally understood. We propose that delayed trait differentiation via tissue repatterning might facilitate phenotypic diversification and innovation that otherwise would not arise due to developmental constraints.

Morphometric variability in round goby Neogobius melanostomus (Perciformes: Gobiidae) from the Sea of Azov

2017 ◽  
Vol 26 (2) ◽  
pp. 392-405 ◽  
Author(s):  
O.A. Diripasko ◽  
T.A. Zabroda
Keyword(s):  
Round Goby ◽  
Joint Effect ◽  
Neogobius Melanostomus ◽  
Sea Of Azov ◽  
Morphometric Characters ◽  
One Dimensional ◽  
The Sea Of Azov ◽  
Size Dependent ◽  
Size Variability ◽  
Males And Females

A total of 38 morphometric characters of the round goby Neogobius melanostomus melanostomus (Pallas, 1814) were studied in its native range in the Sea of Azov. The aim was to assess joint effect of sexual dimorphism and size variability on overall variability within groups of samples (populations) using appropriate methods of traditional statistical analysis (one-dimensional and multivariate statistics). Sex and size-dependent variability was studied based on model samples of males and females of different size. Most of the studied morphometric characters of round goby from the Sea of Azov demonstrated statistically significant sex- and size-dependent in-group variability. The pattern of the variability suggests that, for a comparison of round goby from different sea regions and between populations, separate samples of males and females within the range 9–13 cm SL should be examined in order to minimise the effect of the size and sex factors. The approach of searching for the most informative size range could be useful not only for further studies of infraspecific variation but for comparisons between morphologically close gobiin species.

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