Spatial variations in ectoparasite Pseudione galacanthae prevalence in the squat lobster Grimothea gregaria in Argentine Patagonia

The bopyrid Pseudione galacanthae is an ectoparasite of the squat lobster Grimothea gregaria (Munida gregaria). This study aimed to analyze the spatial variations in the prevalence of P. galacanthae in Argentine Patagonia and the potential drivers shaping this variability. To analyze this crustacean/crustacean parasitic relationship, bottom trawl net hauls, a CTD cast, and zooplankton samplings were performed in 10 locations between 43.6° and 47.7°S. Squat lobsters were assigned to 1 of 2 morphotypes (gregaria or subrugosa), sexed, and measured, and the branchial chambers were examined in search of bopyrids. Correlation analyses were performed to identify whether environmental variables (sea bottom salinity, SBS), sea bottom temperature, depth, and calanoid copepods abundance) or population traits (median of size distribution and density of squat lobsters) were related to P. galacanthae prevalence. The gregaria morphotype was dominant in the south of San Jorge Gulf (SJG), whereas the subrugosa morphotype was more abundant in the other locations. No significant differences were observed in P. galacanthae prevalence between sexes or morphotypes. Spatial variations in prevalence were observed, reaching 15.2% in the south of SJG. P. galacanthae prevalence was correlated only with SBS. We hypothesized that the highest prevalence of P. galacanthae could be related to the presence of a tidal frontal system in the south of SJG, which could favor parasite larval retention. The prevalence reported here is the highest for bopyrid parasites in squat lobster species and reveals that this interaction could have a detrimental impact on G. gregaria populations at local scale.