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Updated: Aug 19, 2026
Pharmacological and Functional Genetic Assays to Manipulate Regeneration of the Planarian Dugesia japonica
Published on: August 31, 2011
Comparative study of eye defective worm 'menashi' and regenerating wild-type in planarian, Dugesia ryukyuensis
Yukiko Sato1, Kazuya Kobayashi, Midori Matsumoto
1Department of Biology, Keio University, Hiyoshi 4-1-1, Kohoku-ku, Yokohama 223-8521, Japan.
Abstract:
Inbreeding of the sexualized planarian, Dugesia ryukyuensis, produces eye-defective worms, menashi, in the F1 population. To study the effects of this mutation on the eye, we observed the eye-region of menashi using electron microscopy and compared it with the regenerating eye in wild-type worms. The intact eye of wild-type planarians consisted of a few pigment cells and a number of visual cells. Pigment cells containing spherically-shaped electron-dense melanosomes contacted each other and enclosed rhabdomes of visual cells. Rhabdomes had numerous tubular microvilli extending radially and touching the pigment cells. However, in menashi, various lengths of tubular microvilli were irregularly distributed near the pigment cells, which contained numerous electron-lucent premelanosomes, and no adhesive structures were found between the pigment cells. The premelanosomes of menashi were equal in size to those seen after 2 days of regeneration in wild-type planarians and were similar in maturation to those found after 3 days of regeneration in wild-type planarian. These results suggest that menashi is defective in the mechanism(s) of developing pigment granules and constructing visual cells. These findings also suggest that pigment cells in menashi are defective in the mechanism(s) involved with cell adhesion.
Insights
A mutation in Dugesia ryukyuensis planarians, called menashi, causes eye defects. Electron microscopy revealed abnormal pigment granules and disrupted cell adhesion in menashi eyes compared to wild-type.
Area of Science:
- Developmental biology
- Cell biology
- Regenerative medicine
Background:
- Planarian eyes are crucial for regeneration and survival.
- Mutations can reveal underlying genetic mechanisms of development.
- The Dugesia ryukyuensis model system allows for genetic studies of regeneration.
Purpose of the Study:
- To investigate the cellular basis of eye defects in the 'menashi' mutant planarian.
- To compare the ultrastructure of 'menashi' eyes with regenerating wild-type planarian eyes.
- To identify specific cellular and molecular defects underlying the mutation.
Main Methods:
- Electron microscopy of the eye region in 'menashi' and wild-type planarians.
- Comparative analysis of pigment cell and visual cell structures.
- Observation of regenerating eyes in wild-type planarians for comparison.
Main Results:
- 'Menashi' pigment cells contain immature premelanosomes instead of mature melanosomes.
- Abnormal, irregularly distributed microvilli were observed in 'menashi' visual cells.
- Lack of adhesive structures between pigment cells in 'menashi' was noted.
- Premelanosome size and maturation in 'menashi' resemble early regeneration stages in wild-type.
Conclusions:
- The 'menashi' mutation disrupts pigment granule development and visual cell formation.
- Pigment cell adhesion mechanisms are impaired in 'menashi' planarians.
- These defects provide insights into the genetic control of eye development and regeneration in planarians.
