Fimbriaphyllia ancora

Shikina, Shinya, Chiu, Yi-Ling, Chung, Yi-Jou, Liu, Tai-Yu, Lee, Yan-Horn, Mita, Masatoshi & Chang, Ching-Fong, 2023, Fig. 12 in Tuerkayana rotundum, Zoological Studies 62 (38), pp. 141-149 : 3-5

Fimbriaphyllia ancora releases positively buoyant eggs

At 7:30 pm, 25 May 2011, one day after the predicted spawning date, spawning of F. ancora was observed in aquaria ( Fig. 1A ). Dozens to hundreds of pinkish eggs were released through the mouths of F. ancora polyps, and slowly floated to the surface ( Fig. 1B ), demonstrating that the eggs are positively buoyant. Microscopic observation of eggs found that they had no symbiotic algae. Unfertilized eggs underwent cell death approximately 12 h after spawning.

Features and time course of early development

No fertilization membrane surrounded fertilized eggs ( Fig. 2A and A’). The first cleavage was observed at ~1–2 hpf. The cleavage furrow initiated at the animal pole, and heart-shaped zygotes were observed. Cleavage was holoblastic, and embryos reached the 16–64-cell stage at 3–6 hpf ( Fig. 2B and B’, Table 1). Blastomeres divided in a more or less organized manner, and became flattened embryos (prawnchip stage) at 7–12 hpf ( Fig. 2C and C’, Table 1). After the bowl-shaped stage, spherical blastulae were formed at 14–16 hpf, and embryos were observed moving slowly, using cilia ( Fig. 2D and D’, Table 1). Initially lipid droplets in fertilized eggs were small and evenly distributed ( Fig. 2 A’), while those after the blastula stage were relatively large and distributed around the center ( Fig. 2 D’). Invagination was observed histologically at 26 hpf ( Fig. 2E and E’, Table 1). Formation of ectoderm and endoderm commenced around 32 hpf, and mesoglea, a gelatinous extracellular matrix, began to appear between the two layers ( Fig. 2F and F’, Table 1). At this point, larvae were no longer at the surface of the beakers, but were drifting slowly in the middle or at the bottom. Swimming planulae were observed at ~48 hpf ( Fig. 2G and H ; Table 1), and oral pores and pharynxes were histologically confirmed ( Fig. 2 G’ and H’). Mucus secretion was also observed at this stage. Larval settlement and metamorphosis on glass beakers or plastic culture plates was rarely observed during the entire course of observation. Some swimming planulae were maintained in glass beakers for more than 3 months.

Changes in lipid and sugar contents

Lipid component analysis by HPTLC demonstrated that eggs (0 hpf) are rich in WEs ( Fig. 3A ). Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were the major phospholipid components. Concentrations of those lipids, particularly WE in planulae at 48 hpf were significantly less than those of eggs. No further decrease of these lipid levels was observed in planulae from 48 hpf to 168 hpf ( Fig. 3A ). Sugar content analysis revealed that eggs are rich in glycogen, and that the glycogen concentration increased significantly during development ( Fig. 3B ). Free glucose was not detected in samples that we analyzed ( Fig. 3B ).

Figures

Fig. 1. Fimbriaphyllia ancora spawning in an aquarium. A: A female colony releasing pinkish eggs. B: Picture of the aquarium with spawning F. ancora. Note the released eggs floating at the surface (arrows).

Fig. 2. Early development of F. ancora, as assessed microscopically and histologically. External and histological views of unfertilized eggs (A and A’), 16–32 cell stage (B and B’), prawnchip stage (C and C’), early blastula stage (D and D’), mid gastrula stage (E and E’), late gastrula stage (F and F’), planula at 64 hpf (G and G’), and planula at 128 hpf (H and H’). All scale bars = 100 μm.

Fig. 3. Changes in lipid and sugar levels during early development of F. ancora. A: Changes in lipid levels. Lipids were extracted from released unfertilized eggs (0), early planulae at 48 hpf (48), and a planula at 168 hpf (168) and analyzed by high-performance thin-layer chromatography. WE, wax ester; PC, phosphatidylcholine; PE, phosphatidylethanolamine. B: Changes in glycogen and glucose levels. Sugars were extracted from released unfertilized eggs (0), gastrula at 32 hpf (32), planulae at 64 hpf (64), planulae at 128 hpf (128), and concentrations of glycogen and glucose were determined. Data are shown as the mean ± SE (n = 3 experiments). Groups with different letters are statistically different (p <0.05).