Invasive Alien Species (IAS) are considered a key threat to global biodiversity. Environmental DNA (eDNA) sampling has emerged as a valuable tool for IAS detection and surveillance. The Chinese Mitten Crab (Eriocheir sinensis) is a high-risk IAS that can tolerate both fresh and salt water due to its catadromous life cycle. The Marine Institute (Ireland) began testing for E. sinensis DNA when monitoring for possible vectors of crayfish plague. Several TaqMan assays have been trialled for detecting E. sinensis, two of which have been used successfully in other countries (Canada and Denmark). Whilst several live specimens have been caught in Waterford Harbour since 2006, no E. sinensis DNA has been detected in Irish waters to-date. To evaluate reasons for these negative results, research was undertaken to investigate if the salinity of water influences the eDNA shedding and persistence of this species. Sensitivity testing was carried out on the two species-specific assays currently used by the Marine Institute for E. sinensis detection. Shedding and decay rates were determined through a series of tank trials, whereby a single female Chinese Mitten crab was placed in a fresh or brackish water tank for a number of hours. Assay sensitivity was determined using synthetic target DNA (gBlock). We found that DNA shedding rate was six times higher in brackish than freshwaters (DNA shedding= 3.12x10-6 vs 6.42x10⁻7 DNA copies/µL/hour). eDNA decay exhibited expected exponential degradation at both salinities. Decay constants were 0.108hr-1 (brackish) and 0.045hr-1(fresh water). The Danish assay (Knudsen et al., (2019) was more sensitive than the Canadian (Chevrinais et al., (2023), with the ability to detect DNA concentration as low as 106.6 DNA copies/μL, in comparison to 192.5 DNA copies/μL. Our results indicate that salinity could affect eDNA detection of E. sinensis, with a higher chance of detection in brackish waters. The results of this study will be used to inform management of E. sinensis in Ireland, by indicating priority locations to sample (based on salinity) and maximise DNA amplification (by using Danish assay).
Mitten Impossible: investigating the use of environmental DNA (eDNA) as a detection tool for Chinese Mitten Crab Eriocheir sinensis
Giulia Mariani;
2025-01-01
Abstract
Invasive Alien Species (IAS) are considered a key threat to global biodiversity. Environmental DNA (eDNA) sampling has emerged as a valuable tool for IAS detection and surveillance. The Chinese Mitten Crab (Eriocheir sinensis) is a high-risk IAS that can tolerate both fresh and salt water due to its catadromous life cycle. The Marine Institute (Ireland) began testing for E. sinensis DNA when monitoring for possible vectors of crayfish plague. Several TaqMan assays have been trialled for detecting E. sinensis, two of which have been used successfully in other countries (Canada and Denmark). Whilst several live specimens have been caught in Waterford Harbour since 2006, no E. sinensis DNA has been detected in Irish waters to-date. To evaluate reasons for these negative results, research was undertaken to investigate if the salinity of water influences the eDNA shedding and persistence of this species. Sensitivity testing was carried out on the two species-specific assays currently used by the Marine Institute for E. sinensis detection. Shedding and decay rates were determined through a series of tank trials, whereby a single female Chinese Mitten crab was placed in a fresh or brackish water tank for a number of hours. Assay sensitivity was determined using synthetic target DNA (gBlock). We found that DNA shedding rate was six times higher in brackish than freshwaters (DNA shedding= 3.12x10-6 vs 6.42x10⁻7 DNA copies/µL/hour). eDNA decay exhibited expected exponential degradation at both salinities. Decay constants were 0.108hr-1 (brackish) and 0.045hr-1(fresh water). The Danish assay (Knudsen et al., (2019) was more sensitive than the Canadian (Chevrinais et al., (2023), with the ability to detect DNA concentration as low as 106.6 DNA copies/μL, in comparison to 192.5 DNA copies/μL. Our results indicate that salinity could affect eDNA detection of E. sinensis, with a higher chance of detection in brackish waters. The results of this study will be used to inform management of E. sinensis in Ireland, by indicating priority locations to sample (based on salinity) and maximise DNA amplification (by using Danish assay).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
