Rhizocephalan barnacles are infamous crustacean parasites due to their effects on host behavior and morphology. As parasitic castrators, rhizocephalans co-opt the reproductive investments of their hosts, suggesting that they may in turn affect the host nutritive quality. As one aspect of nutrition, fatty acids (FA) play vital physiological roles in organisms and their consumers, and differences in host FA compositions imposed by rhizocephalans could highlight their impact.
Here, we investigated the influence of parasitism on host lipid content and FA composition by the rhizocephalan Sylon hippolytes infecting the dock shrimp Pandalus danae . We collected visibly infected and uninflected P. danae from the docks of Friday Harbor Laboratories, Friday Harbor, WA, USA. We dissected the abdomen tissue, hepatopancreas, and externae from one subset of the shrimp (n = 20) and left the remaining shrimp (n = 24) whole, analyzing the samples for lipid content using gravimetry and for FA composition using gas chromatography-mass spectrometry.
Lipid content did not differ between Sylon -infected and uninfected shrimp for whole shrimp, abdomen tissue, nor hepatopancreas. Permutational multivariate analysis of variance (PERMANOVA) showed a significant difference in FA composition by Sylon -infection status and by tissues when dissected, but significant differences by infection status were not detected within tissues. Whole shrimp were also significantly different in FA composition by infection status, as shown by PERMANOVA, likely driven by the distinctive FA compositions of externae.
Taken together, these results suggest that while Sylon affects the FA composition of whole shrimp, potentially altering nutrition, that the shrimp may compensate for parasitism by having similar fatty acid compositions and lipid contents in the tissues of Sylon -infected and uninfected shrimp. As Sylon can reach high prevalence in Pandalus shrimps, it will be important to determine whether similar patterns are found in other, commercially important pandalids, as well as for other nutritional measures.