. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Cohort Figure 2. Density of unfertilized eggs (a) and eggs and larvae (b) for three cohorts of Pteraster tesselatus. (a) Two estimates of density: open bars are for eggs with jelly coats; dark bars are for eggs only, assuming the jelly to be neutrally buoyant. The value on each bar represents the mean for 10 eggs. Error bars are 1 (b) Ontogenetic changes in density from eggs and two larval stages for three cohorts. The bars represent the means for eggs with jelly coats (e). hatched gastrulae (g). and bilobed larvae (b).
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Cohort Figure 2. Density of unfertilized eggs (a) and eggs and larvae (b) for three cohorts of Pteraster tesselatus. (a) Two estimates of density: open bars are for eggs with jelly coats; dark bars are for eggs only, assuming the jelly to be neutrally buoyant. The value on each bar represents the mean for 10 eggs. Error bars are 1 (b) Ontogenetic changes in density from eggs and two larval stages for three cohorts. The bars represent the means for eggs with jelly coats (e). hatched gastrulae (g). and bilobed larvae (b). All sample sizes were lOeggsor 10-12 larvae. Error bars are 1 The dotted line shows the density of seawater at °C and 28f?< salinity. The Reynolds numbers (Re) were £ for all eggs and < for all passively moving larvae, so we used the low-Re equation for terminal velocity and solved for the density of the egg or larva (see , 31, equation I. p. 340). We treated eggs as spheres and larvae as prolate spheroids; in the latter case we included a shape-correction term (see 32). We measured the diameter of each egg and the thickness of the jelly coat on a microscope with a 4x objective, after the egg rising time was measured. A suspension of India ink was added to reveal the edge of the translucent jelly coat. The length and width of gastrulae and larvae at their widest point were measured after larval swimming times were measured. Each larva was then deciliated by placing it in double-strength seawater for 10-15 s, then immediately rinsed three times in normal-strength seawater. This method has been used to collect cilia from echinoderm larvae and does not kill the larva; in fact, cilia are regenerated in a matter of hours ( 33; Emlet. pers. obs.). After the deciliated larvae were equilibrated in seawater at 28%c, we placed them individually in the chamber and measured their passive rising or sinking rates. The seawater in the chamber was at
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
