Meeting Abstract
Tardigrade feeding apparatus is a complex cuticular structure with considerable taxonomic significance. It can be schematically divided into four parts: buccal ring, buccal tube, stylet system, and muscular pharynx. Basically it functions as a sucking organ in which the two piercing stylets are used to detach food from substrates and to penetrate plant cell or animal walls, while the pharynx sucks the organic matter via a cylindrical tube. This kind of feeding apparatus represents an autapomorphy of Tardigrada, but its origin is still unknown. Tardigrades belong to Panarthropoda, even though their feeding apparatuses share some characters with those of some Cycloneuralia. Our aim was to study the possible evolutionary origin and transformation of the feeding apparatuses of tardigrades. We compared new data on buccal-pharyngeal apparatus morphology obtained by SEM, CLSM, and energy-dispersive X-ray spectroscopy analyses with previous data. In addition, using software for evolutionary biology analyses, we traced back the characteristics of the feeding apparatus structures along the tardigrade phylogenetic tree obtained by molecular analyses. Although several tardigrade taxa are poorly studied (especially the marine Arthrotardigrada that generally seem to present a higher number of plesiomorphies), with the present analyses we were able to identify the possible plesiomorphic and homoplastic traits of tardigrade feeding apparatuses, and to find convergent characters among different evolutionary lineages. This analysis allowed also to establish a more specific relationship between tardigrade diet and feeding apparatus anatomy.
