# Comparing Small and Large Genomes Within Monogonont Rotifers

## TL;DR

This study compares genome sizes in monogonont rotifers and finds that larger genomes correlate with body size and metabolic rate, but not due to repetitive elements.

## Contribution

The study expands genome data for rotifers and identifies protein count increases with genome size, not repetitive elements.

## Key findings

- Genome size estimates correlate with body size and respiration rate in monogonont rotifers.
- Genome size variation is not driven by repetitive elements or duplications.
- Larger genomes contain more predicted proteins, many with unknown functions.

## Abstract

Genome size is an important correlate of many biological features including body size, metabolic rate, and developmental rate and can vary due to a variety of mechanisms, including incorporation of repetitive elements, duplication events, or reduction due to selective constraints. Our ability to understand the causes of genome size variation is hampered by limited sampling of many nonmodel taxa, including monogonont rotifers. Here, we used high-throughput Nanopore sequencing and flow cytometry to estimate genome sizes of nine species of monogonont rotifers representing seven families, including three representatives of Superorder Gnesiotrocha. We annotated the genomes and classified the repetitive elements. We also compared genome size with two biological features: body size and metabolic rate. Body sizes were obtained from the literature and our estimates. Oxygen consumption was used as a proxy for metabolic rate and was determined using a respirometer. We obtained similar genome size estimates from genome assemblies and flow cytometry, which were positively correlated with body size and size-specific respiration rate. Importantly, we determined that genome size variation is not due to increased numbers of repetitive elements or large regions of duplication. Instead, we observed higher numbers of predicted proteins as genome size increased, but currently many have no known function. Our results substantially expand the taxonomic scope of available genomes for Rotifera and provide opportunities for addressing genetic mechanisms underlying evolutionary and ecological processes in the phylum.

Graphical Abstract