Morphology and ultrastructure of the pharynx in Solenofilomorphidae (Acoela).
The homology of pharynges within the mostly pharynx-less Acoela has been a matter of discussion for decades. Here, we analyze the pharynges of three members of the Solenofilomorphidae, Myopea sp. and two species of the genus Solenofilomorpha, by means of light and transmission electron microscopy. Special focus is placed on the ultrastructure of the pharyngeal musculature, epidermis surrounding the mouth, pharyngeal epithelium, and junction with the digestive parenchyma. The main goal of this study was to evaluate the usefulness of certain characters for broader comparisons within the Acoela. Among the three species, characters relating to position of the mouth, presence and elaboration of sphincter muscles, presence of pharyngeal glands, and ultrastructure of epitheliosomes proved to be variously species- and genus-specific. The arrangement of pharyngeal muscles and their connection with body wall musculature, ultrastructure of receptor cells, and morphology of a nonciliated glandular region in the posterior pharynx, in contrast, appear to be characteristic of the family Solenofilomorphidae and thus of predominant interest for comparisons with other acoel families.
Todt
Christiane
C
Department of Biological Sciences, University of Maine, Orono, Maine 04469, USA. christiane@todt.or.at
Tyler
Seth
S
D000818:Animals; D000078404:Epidermal Cells; D004817:Epidermis / Q000033:anatomy & histology; D004848:Epithelium / Q000033:anatomy & histology; D005753:Gastric Mucosa / Q000033:anatomy & histology / Q000166:cytology; D046529:Microscopy, Electron, Transmission; D008954:Models, Biological; D009055:Mouth / Q000033:anatomy & histology / Q000166:cytology / Q000648:ultrastructure; D010609:Pharyngeal Muscles / Q000033:anatomy & histology / Q000166:cytology; D010614:Pharynx / Q000033:anatomy & histology* / Q000166:cytology / Q000648:ultrastructure*; D010802:Phylogeny; D012469:Salivary Glands / Q000033:anatomy & histology / Q000166:cytology; D013045:Species Specificity; D014419:Turbellaria / Q000033:anatomy & histology* / Q000145:classification / Q000166:cytology