Thus, if the species of concern is rare, then the estimation of detection probabilities should be conducted in a larger controlled system that can simulate the rarity of the organism in its natural setting. For an organism inhabiting a lotic system, the use of artificial streams or raceways may be necessary. Alternatively, the estimation of detection probabilities may be unattainable for an endangered organism due to its rarity; thus, the use of a surrogate species may be necessary. Second, aquarium trial experiments of African jewelfish failed to detect eDNA from a 1-L water sample at a density of 13 fish/m3. In the present study, water sample taken at this density should always detect African jewelfish; thus, aquarium experiments appear to have underestimated the detection of African jewelfish eDNA. There are a variety of potential explanations for the discrepancy in detection probabilities including behavioral and environmental ; regardless, our study demonstrated the complexities of extrapolating eDNA detection probabilities from a controlled to a natural environment. Our results and those of Dı ´az-Ferguson et al. indicate that detection probabilities for African jewelfish can be imperfect and vary spatially or temporally in response to local environmental conditions. As such, presence-absence data derived from eDNA-based methods where the density of African jewelfish is low will be negatively biased and could have profound implications when determining the leading edge of invasion for this species if imperfect detection is not taken into account. Potential biases associated with incomplete detection could be alleviated by formally estimating detection probabilities under an occupancy modeling framework; alternatively, the filtration of hundreds of liters of water may be required to detect African jewelfish at low densities with a desired level of confidence. The epididymis is responsible for sperm concentration, transport and storage, but also promotes maturation by adding various proteins to the sperm surface. Sperm maturation depends on the expression and secretion of proteins and glycoproteins by the epididymal epithelium, from the caput towards the cauda. These multiple and sequential interactions between the sperm surface and secreted proteins in the epididymal lumen are essential for the ability of mammalian sperm to fertilize BYL719 oocytes. The use of monoclonal antibodies to study molecules expressed in male reproductive organs has contributed to our understanding of sperm maturation and the formation of a functional male gamete.