Are attachment organs of ectoparasites related to phylogeny?

What is it about?

We addressed a nuclear topic in biology: to which extent morphological similarity reflects a common evolutionary history as opposed to convergence in response to similar selective forces. Surprisingly this has seldom been tested in host-parasite systems. We studies the anchors of 14 species of Ligophorus, which represents a genus of monogenean gill parasites. Anchors are instrumental for attachment to the host and therefore to survival. Using geometric morphometrics, we mapped the phylogeny of these species onto morphospaces of shape ans size of the anchors. The results suggested that common descent played a major role in determining the shape and, to a lesser degree in the size of anchors in Ligophorus spp. Evidence for phylogenetic signal was more compelling for the ventral anchors, than for the dorsal ones, which could reflect different functional roles in attachment to the gills.

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Why is it important?

The present study delivers a common framework to address effectively the relationships among morphology, phylogeny and other traits, such as host specificity or niche occupancy in Monogenea and other ectoparasites. We could trace for the first time in monogeneans paths of morphological evolution in anchor shape. Anchors with narrow anchors and long shafts were considered to be ancestral relative to those possessing shorter shafts and longer roots.