Trace element and metal sequestration in vitellaria and sclerites, and reactive oxygen intermediates in a freshwater monogenean, Paradiplozoon ichthyoxanthon

Abstract

Exposure to metals and other trace elements negatively affects infection dynamics of monogeneans, including diplozoids, but, physiological mechanisms linked to exposure have yet to be documented. In this study sequestration of trace elements and reactive oxygen intermediate production in the monogenean, Paradiplozoon ichthyoxanthon, was demonstrated. During dissection of host fish, Labeobarbus aeneus, the gills were excised and assessed for P. ichthyoxanthon, which were removed and frozen for fluorescence microscopy or fixed for transmission electron microscopy. Trace elements were sequestered in the vitellaria and sclerites in P. ichthyoxanthon, and the presence of reactive oxygen intermediates was observed predominantly in the tegument of the parasite. Trace elements and metals identified and ranked according to weight percentages (wt%) in the vitellaria were Cu > C > Au > O > Cr > Fe > Si while for the sclerites C > Cu > O > Au > Fe > Cr > Si were identified. For most element detected, readings were higher in the vitellaria than the sclerites, except for C and O which were higher in sclerites. Specifically for metals, all levels detected in the vitellaria were greater than in sclerites. Based on the proportion of trace elements present in the vitellaria and sclerites it appears that most trace elements including metals were sequestered in the vitellaria. The results of reactive oxygen intermediate production in the tegument of the parasite suggests either trace element accumulation takes place across the tegument or results from the action of the host’s immune response on the parasite. The results serve as the first demonstration of trace element sequestration and reactive oxygen intermediates in a freshwater monogenean parasite.

Trace element biomineralisation in the carapace in male and female Argulus japonicus

“…japonicus it would appear that eggshells do not function in a similar manner given the negative signal produced by the eggshell ( Fig 3G ). Instead, the findings of the present study are similar to those observed for the monogenean Paradiplozoon ichthyoxanthon treated with Phen–Green where similar orange signal was observed and indicated a negative reaction for the presence of metals in eggshells [ 25 ]. Degger et al [ 22 ] indicated that trace element and metal sequestration in the eggshells of S .…”

“…japonicus showed that N, O, Na, Mg, Al, Cl, K, Ca, Cr, Fe, Cu and Zn are present. In particular, elements such as Al, Cr, Fe, Cu and Zn become incorporated in the carapace, which is similar to other marine and terrestrial invertebrates [ 7 , 8 , 10 , 12 , 13 ] and hard structures as in other ectoparasites [ 25 ]. Furthermore, this shows that A .…”

“…Samples were subdivided for sectioning (n = 4) and whole mounts (n = 6). For sectioning two female and two male parasites were imbedded in optimal cutting temperature (OCT) compound (Sakura Finetek, California, United States of America) and frozen in liquid nitrogen until the compound turned white [ 25 ]. The blocks in the moulds were then stored at -80 °C until sectioning.…”

“…In ectoparasites, comparatively fewer studies have investigated trace element depuration in members of this group. Gilbert and Avenant-Oldewage [ 25 ] found that in the monogenean, Paradiplozoon ichthyoxanthon , trace elements and metals were associated with the vitellaria and sclerites of the parasite, but unlike endoparasite platyhelminthes, the eggshells of this monogenean did not sequester trace elements and metals.…”

Architecture of Paradiplozoon homoion: A diplozoid monogenean exhibiting highly-developed equipment for ectoparasitism

“…were published to date [ 36 – 38 ]. A recent study visualised the trace element accumulation sites in Paradiplozoon adults [ 39 ].…”