Use of optimized conventional and advanced sperm quality diagnostic tools to establish reproductive data in wild-caught redclaw crayfish (Cherax quadricarinatus)

The Australian redclaw crayfish has great potential for aquaculture intensification and global market expansion. However, traditional production methods, subfertility, and high embryo mortality could curtail industry growth. Successful embryonic and post-embryonic development also depends on the paternal genetic contribution. Direct assessment of sperm quality can potentially determine the status of male fertility in decapod crustaceans. This study evaluated redclaw crayfish sperm quality using optimized conventional and advanced functional tools. Sexually mature male redclaw ( n = 33) were collected from Ross River Dam in North Queensland, Australia, and subjected to electroejaculation to yield spermatophores for sperm quality assessment. Sperm concentration and count (haemocytometer), morphology (phase contrast), viability (Hoechst 33342/PI), DNA fragmentation (TUNEL), and total potential fertile sperm concentration (TPFSC) were determined. Spermatozoa had an elliptical shape of varying sizes and a presumptive fertilization-spike structure. The mean ± SEM sperm viability, DNA fragmentation, concentration, and TPFSC were 65.2 ± 3.9 %, 17.2 ± 2.5 %, 42.5 ± 5.1 × 10 4 cells/mL, and 23.6 ± 3.4 × 10 4 cells/mL, respectively. Spermatophore weight showed a positive association with sperm concentration ( p = 0.001 ) and total potential fertile sperm concentration (TPFSC; p < 0.001 ), and a negative association with sperm DNA fragmentation ( p = 0.022 ). Conversely, sperm viability showed no significant relationship with spermatophore weight ( p = 0.188 ) but was negatively associated with body mass ( p = 0.010 ). In conclusion, this study reported the first quantitative data on sperm morphometry and functional traits, validated species-specific diagnostic tools for sperm quality assessment, and provided insight into the relationships between sperm quality parameters and body or spermatophore weights. Our approach may inform the selection of fertile male broodstock and enhanced strategies for sperm harvesting in order to facilitate selective breeding programs for commercial redclaw aquaculture. • Baseline reproductive data for wild-caught redclaw crayfish were established for the first time using optimized conventional and advanced sperm quality diagnostic tools. • This study revealed relatively high sperm DNA fragmentation, low sperm viability, and considerable variability in sperm quality among redclaw males. • This study found that heavier spermatophores had higher sperm concentration, less DNA damage, and improved total potential fertile sperm concentration (TPFSC). • A putative fertilization-spike, not previously documented in Parastacidae , was identified in redclaw crayfish spermatozoa, highlighting a potential structural feature that warrants further investigation. • A technique for the collection of spermatophores by electroejaculation and extraction of spermatozoa without enzymatic or chemical treatments or mechanical shearing was developed for redclaw crayfish.