Retinoic acid disrupts anterior ectodermal and endodermal development in ascidian larvae and postlarvae

Area of Science:

• Developmental Biology
• Chordate Evolution
• Molecular Signaling

Background:

• Vertebrate development shows anterior truncation with excess all-trans retinoic acid (RA).
• The role of RA in non-vertebrate chordate development is less understood.

Purpose of the Study:

• Investigate the effects of exogenous retinoic acid (RA) on ascidian (Herdmania curvata) development.
• Determine if RA causes similar anterior defects as observed in vertebrates.

Main Methods:

• Culturing Herdmania curvata embryos and postlarvae in the presence of all-trans retinoic acid (RA).
• Observing and documenting morphological changes and developmental defects.

Main Results:

• RA exposure during axis formation resulted in shortened larval trunks in H. curvata.
• RA treatment led to the loss of juvenile pharyngeal structures, suggesting anterior endoderm respecification.
• Chemosensory function in RA-treated larvae remained intact despite morphological changes.

Conclusions:

• Retinoic acid (RA) plays a significant role in ascidian anterior development, particularly pharyngeal formation.
• RA-induced pharyngeal loss in ascidians mirrors effects in cephalochordates, suggesting a conserved ancestral role.
• RA may have been involved in pharyngeal development in the ancestral chordate, with this function lost in vertebrates.