Analysis of the Persistence and Particle Size Distributional Shift of Sperm-Derived Environmental DNA to Monitor Jack Mackerel Spawning Activity

Environmental DNA (eDNA) analysis holds great promise
as an efficient
and noninvasive method to monitor not only the distribution of organisms
but also their spawning activity. In eDNA analysis-based monitoring
of spawning activity, the detection of sperm-derived eDNA is a key
point; however, its characteristics and dynamics are completely unknown.
The present study focuses on the persistence and particle size distribution
(PSD) of eDNA derived from the sperm of Japanese jack mackerel. First,
we investigated the time-dependent degradation and the PSD of sperm-derived
eDNA by artificially adding sperm to seawater. Next, we kept fish
in tanks and examined the changes in eDNA concentration and PSD before
and after spawning. The results of two experiments showed that the
degradation of sperm-derived eDNA proceeded rapidly, with PSD shifting
to a smaller size regardless of the DNA region (Cyt b or ITS1). Additionally, it was shown that the nuclei and mitochondria
released from sperm through degradation had a size distribution that
was not simply dependent on each organelle size. These results will
contribute to elucidating the characteristics and dynamics of eDNA
specifically during the spawning season and to further developing
eDNA analysis as a powerful tool for the monitoring of spawning activity.