. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ECHINOTHURIOID DEVELOPMENT, REVISITED 17. Figure 1. Early embryonic stages ofAsthenosoma ijimai. a. Sixteen-cell stage embryos randomly oriented, show that all cells are approximately the same diameter after the fourth cleavage. Scale bar. 1 mm. b. SEM of a , lobate blastula. Arrowheads mark pits in ectoderm. Scale bar, 1 mm. c. Close-up SEM of ectodermal pit marked by right arrow in b. Scale bar, 25 nm. d. Section of a 21,5-h blastula shows yolky cytoplasm in the blastocoel and ectodermal pits (arrowheads). Same scale
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ECHINOTHURIOID DEVELOPMENT, REVISITED 17. Figure 1. Early embryonic stages ofAsthenosoma ijimai. a. Sixteen-cell stage embryos randomly oriented, show that all cells are approximately the same diameter after the fourth cleavage. Scale bar. 1 mm. b. SEM of a , lobate blastula. Arrowheads mark pits in ectoderm. Scale bar, 1 mm. c. Close-up SEM of ectodermal pit marked by right arrow in b. Scale bar, 25 nm. d. Section of a 21,5-h blastula shows yolky cytoplasm in the blastocoel and ectodermal pits (arrowheads). Same scale as b. in M sodium acetate buffer (pH ) at room tem- perature (Harris and Shaw, 1984) and preserved in 70% EtOH at 4°C. The preserved specimens were dehydrated through a graded ethanol series, dried at the critical point (Hitachi HCP-1 drier) with liquid CO: as a transitional fluid, and sputter-coated with gold (Eiko IB-3 ion coater). Observations were made with a Hitachi HHS-2R SEM. To examine the inside of larvae with SEM, specimens were embedded in polyester wax and sectioned by micro- tome to expose a particular cross section. These specimens were incubated in absolute ethanol at 40°C for 12 h to remove wax (Armstrong and Parenti, 1973) and then subjected to critical point drying as described above. Clearing lan>ae Live larvae ofAsthenosoma are opaque orange-yellow (Amemiya and Tsuchiya, 1979), and it was impossible to see internal structures in these or in fixed, preserved spec- imens. However, larvae could be rendered translucent by clearing with solutions of benzyl benzoate and benzyl al- cohol mixed in ratios of 2:1, 1:1, or 1:2, depending on the desired refractive index. Fixed larvae were first de- hydrated to 100% EtOH, then transferred into the clearing solution where the remaining EtOH was allowed to evap- orate. Upon clearing, larval dimensions remained the same, and no osmotic effects were discerned. To search for calcareous deposits, cleared larvae w
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
