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- Title
Umbrella of Mastigias papua (Scyphozoa: Rhizostomeae: Mastigiidae): hardness and cytomorphology with remarks on colors.
- Authors
YUKI HAMAGUCHI; AKANE IIDA; JUN NISHIKAWA; EUICHI HIROSE
- Abstract
Mastigias papua, known as the golden (or spotted) jellyfish, is an epipelagic jellyfish widely distributed in the warm waters of the West Pacific. This jellyfish has a brownish body, owing to zooxanthellae, and white spots. We measured the maximum force to pierce the umbrella, which averaged 94-144 mm in diameter, to evaluate the hardness of M. papua, and returned a range of 0.14-0.45 N. Correlation analyses indicate that when the M. papua medusa grows (i.e., becomes heavier), the umbrella becomes larger in diameter, as well as thicker and harder within the size range we examined. However, a significant relationship between the hardness of the umbrellar apex and the thickness of the umbrella was not obtained. White spots are comprised of loose aggregates of mesogleal cells containing reflective granules. Since the white spots and the transparent parts were not significantly different in hardness, the spots were unlikely to strengthen the umbrella. The primary function of the spots may be the shading of solar radiation. Most of the zooxanthellae are located in mesogleal cells, and often beneath the exumbrellar epidermis. Therefore, light shading by white spots may be unnecessary for the zooxanthellae in mesogleal cells.
- Subjects
HARDNESS; UMBRELLAS; ZOOXANTHELLA; WHITE spot syndrome virus
- Publication
Plankton & Benthos Research, 2021, Vol 16, Issue 3, p221
- ISSN
1880-8247
- Publication type
Article
- DOI
10.3800/pbr.16.221