The skate spiracular organ develops from a unique neurogenic placode, distinct from lateral line placodes

Abstract

The spiracular organ is an epithelial pouch or tube lined with mechanosensory hair cells, found embedded in the wall of the spiracle/spiracular chamber (remnant of the first pharyngeal cleft) in many non-teleost jawed fishes. It is innervated via a branch of the anterior lateral line nerve and usually considered a specialised lateral line organ, although it most likely functions as a proprioceptor for jaw movement. It is homologous to the paratympanic organ: a hair cell-lined epithelial pouch embedded in the wall of the middle ear (which evolved from the spiracular chamber) of birds, alligators and Sphenodon. A previous fate-mapping study showed that the chicken paratympanic organ and its afferent neurons originate from a molecularly distinct placode immediately dorsal to the geniculate (first epibranchial) placode. Here, DiI fate-mapping in a cartilaginous fish (little skate, Leucoraja erinacea) shows that the spiracular organ derives from a previously unrecognised neurogenic placode immediately dorsal to the geniculate placode and molecularly distinct from lateral line placodes. These findings further support the developmental and evolutionary independence of this unique jawed-vertebrate mechanosensory organ from the lateral line system.

pIGLET : Safe harbor landing sites for reproducible and efficient transgenesis in zebrafish

“…4, G and H). Consistent with TBX3 expression in diverse ganglion populations in zebrafish and mice (60)(61)(62)(63), we observed prominent reporter activity of Hs_ enh9B wt :min-mCherry in ventral anterior lateral line ganglia (Fig. 4G).…”

pIGLET: Safe harbor landing sites for reproducible and efficient transgenesis in zebrafish

“…4G, H). Consistent with TBX3 expression in diverse ganglion populations in zebrafish and mice [60][61][62][63] , we observed prominent reporter activity of Hs_enh9B wt :min-mCherry in ventral anterior lateral line ganglia (Fig. 4G).…”