Corneal splitting in the developing lamprey Petromyzon marinus L. eye

Area of Science:

• Comparative anatomy
• Vertebrate ophthalmology
• Developmental biology

Background:

• The adult lamprey cornea comprises dermal (spectacle) and scleral components, separated by a mucoid layer.
• Lamprey corneal development in larval (ammocoete) stages is comparable to other lower vertebrates.

Purpose of the Study:

• To investigate the developmental process of the lamprey cornea from the larval (ammocoete) to the adult stage.
• To elucidate the structural changes and layer formation during lamprey corneal metamorphosis.

Main Methods:

• Histological examination of lamprey corneas at different developmental stages.
• Microscopic analysis of corneal tissue structure, including epithelial and stromal components.
• Observation of cellular and extracellular matrix organization during transformation.

Main Results:

• The larval dermal cornea features a stratified columnar epithelium and a stroma with orthogonal collagen.
• During transformation, the dermal cornea epithelium becomes stratified squamous, and its inner stroma separates from the scleral cornea.
• A distinct mucoid layer forms between the dermal (spectacle) and scleral corneas, persisting in adults.

Conclusions:

• Lamprey corneal development follows a pattern similar to other lower vertebrates.
• Metamorphosis involves significant structural reorganization, including epithelial changes and layer differentiation.
• The formation of the mucoid layer is a key event in establishing the adult corneal structure and function.