Figure 1.
Compound microscope images of the embryo development of Lophelia pertusa.
(A) oocyte; (B) 1st cleavage; (C) 2-cell; (D) 4-cell; (E) 8-cell; (F) 16-cell morula; (G) 32-cell morula; (H) 64-cell blastula. First cleavage is equal and holoblastic, followed by radial cleavage. A slight shift of blastomeres sometimes made cleavage appear pseudo-spiral. Scale bar 100 µm.
Figure 2.
SEM images of Lophelia pertusa early development.
(A) SEM image of an oocyte; (B) morula stage embryo; (C) Two days old embryo with indentation that possibly represents forming of the hollow blastula from morula stage; (D) late blastula showing sparse cilia coverage.
Figure 3.
Light microscopy images of Lophelia pertusa embryos and larvae sampled at day 6 to 57 after spawning.
Around day 6–7, embryos became piriform (A), followed by the formation of an indentation (*) indicating gastrulation sometime during day 6–8 (B). From day 10 larvae showed high plasticity, constantly shape-shifting (C–H). Scale bar = 100 µm. Larval age: A = 6; B = 7; C = 14; D = 22; E = 28; F–G = 44; H = 57 days old.
Figure 4.
Scanning Electron Micrographs of Lophelia pertusa embryos and larvae.
Image (A) shows a 6 days old ciliated embryo where each cell bears a cilium for locomotion. No oral pore or specialized structures are visible on the embryos at this stage; (B) A 4.5 weeks (31 days) old planula. The larva is fully and densely ciliated, and specialized structures are now visible. Larger pores are scattered over the surface, i.e. openings of mucus cells, and the oral pore facing downwards; (C–D) Close-ups of the body surface of 4.5 weeks old larvae; (C) ciliated ectoderm with mucus visible as web-like structures around the mucus cell openings; (D) mucus cell openings with webs of mucus. The white arrow marks out what appears to be a cnidocil, the trigger of a cnidocyst (a small bent cilium).
Figure 5.
Timeline for the embryonic and larval development.
Embryos reached the 64-cell blastula stage after 48 h. First cilia appeared day 3, and embryos were swimming blastulae day 5. During gastrulation (day 6–8) embryos were mainly still, rotating slowly around the oral-aboral axis, and resumed swimming after gastrulation was completed. An oral pore became visible when larvae were c. 2 weeks old, and the mouth became protractable and adjustable at c. 20 days. Bottom probing behavior was first observed when larvae were 3 weeks old and peaked at 4–5 weeks. Nematocysts appeared when larvae were 30 days old and if nematocysts are used for primary anchoring, this could indicate that larvae are competent to settle at this time. Larval longevity was c. 8 weeks, the longest lived larvae being 57 days old.
Figure 6.
Size measurements of Lophelia pertusa larvae (≥10 days) from the Tjärnö and Trondheim laboratories.
Larval length (A), length to width ratio (B), and volume of larvae from separate larval cultures at Tjärnö during the spawning 2013 (C). Lines are regression lines and the x-axis shows larval age in days after spawning. Batch sp23jan was fed on day 41.
Table 1.
Lophelia pertusa larval swimming speed.
Table 2.
Analysis of Lophelia pertusa larval genotypes.