Ontogeny of eDNA shedding during early development in Chinook Salmon (Oncorhynchus tshawytscha)

Abstract

Knowledge of the timing of major life history events in aquatic species is important for informing conservation and resource management planning. Accordingly, surveys of environmental DNA (eDNA) have been performed to determine the efficacy of eDNA for providing information on life history events, primarily focusing on the timing of events associated with spawning, and these studies have proved successful. However, spawning represents only one part of the life history, and therefore, information on eDNA shedding during other life history stages is needed to fill gaps in knowledge. Here, we explored eDNA shedding during early life history (from fertilized eggs until near yolk sac absorption) in Chinook Salmon (Oncorhynchus tshawytscha) at three biomasses in a laboratory environment. We found that fertilized eggs shed little eDNA prior to hatching. Hatching coincided with a spike in eDNA, and we observed a significant and positive relationship between eDNA concentration and the number of hatched eggs. The concentration of eDNA shed by larvae after hatching was not consistent across post‐hatch sampling days, suggesting developmental and behavioral changes associated with larval ontogeny may affect eDNA shedding rate. These results indicate that eDNA data may be used to identify hatch timing and verify successful reproduction in oviparous aquatic fishes. The application of eDNA to early life history broadens the capacity of eDNA‐based methods for assessing population status and trends.

Temperature Controls eDNA Persistence across Physicochemical Conditions in Seawater

“…Aqueous eDNA is DNA that is dissolved in solution or associated with larger suspended particles, such as cells, organelles, or aggregates . Animal eDNA may be shed into the environment through several processes, and the shedding rate depends on factors like biomass, metabolic rate, ontogeny, and activity. − Once shed from an animal, eDNA changes from intracellular to subcellular states. − eDNA degrades at rates influenced by physicochemical and biotic factors, and the relative influence of these factors may depend on its state. ,− Before completely degrading into short fragments that molecular methods cannot detect, marine eDNA can be transported away from its source by ocean currents. , Determining how the persistence of eDNA is controlled by physicochemical conditions is vital to constraining when and where it was shed from a source organism. This knowledge is essential to define the spatiotemporal resolution of the ecological information derived from eDNA quantification and sequencing.…”

Environmental DNA (eDNA) detects temporal and habitat effects on community composition and endangered species in ephemeral ecosystems: A case study in vernal pools

“…This should include broadened sampling of intra‐annual and diel temporal variation, which can be high in vernal pools (Solomeshch et al, 2007). Third, monitoring should be compared among taxa that vary in life histories to help understand taxon‐specific drivers and discrepancies of negative and positive discovery rates (Carrasco‐Puga et al, 2021; Ostberg & Chase, 2022; Ritter et al, 2019; Takeuchi et al, 2019). Finally, globally, much work is needed to optimize sample processing methods, reference databases, and informatics pipelines to better enable the widespread use of eDNA for biological monitoring (Pawlowski et al, 2021).…”

“…Third, monitoring should be compared among taxa that vary in life histories to help understand taxon-specific drivers and discrepancies of negative and positive discovery rates (Carrasco-Puga et al, 2021;Ostberg & Chase, 2022;Ritter et al, 2019;Takeuchi et al, 2019).…”

Environmental DNA dynamics during embryonic development in the rare minnow Gobiocypris rarus

“…For specificity of the primer set of the rare minnow, the specificity was tested by cross‐amplification on several closely related species in the laboratory, a further test for the specificity in the wild is need. In addition, genetic material from ruptured or decomposing eggs could release into the water column (Ostberg & Chase, 2021), thus we speculate that dead egg may be a source for eDNA prior to egg hatching, which may affect the interpretation of eDNA quantitation in the wild. Therefore, further research is needed to provide sufficient evidence to confirm the relationship between the number of hatched fish and eDNA concentrations under in vivo and in vitro conditions.…”