The genome sizes of ostracod crustaceans correlate with body size and phylogeny

Within animals a positive correlation between genome size and body size has been detected in several taxa but not in others, such that it remains unknown how pervasive this pattern may be. Here we provide another example of a positive relationship, in a group of crustaceans whose genome sizes have not previously been investigated. We analyze genome size estimates for 46 species across Class Ostracoda, including 29 new estimates made using Feulgen image analysis densitometry and flow cytometry. Genome sizes in this group range ~80-fold, a level of variability that is otherwise not seen in crustaceans with the exception of some malacostracan orders. We find a strong positive correlation between genome size and body size across all species, including after phylogenetic correction. We additionally detect evidence of XX/XO sex determination in all three species of myodocopids where male and female genome sizes were estimated. On average, genome sizes are larger but less variable in myodocopids than in podocopids, and marine ostracods have larger genomes than freshwater species, but this appears to be explained by phylogenetic inertia. The relationship between phylogeny, genome size, body size, and habitat is complex in this system, and will benefit from additional data collection across various habitats and ostracod taxa.