. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ECHINOTHUR1OID DEVELOPMENT. REVISITED 25. Figure 9. Skeletal development in various, cleared stages of larvae of Asthenosoma ijimai. All larvae are viewed from the dorsal side in partially polarized light, a. A 63-h larva shows no evidence of calcareous skeletal elements. Scale bar, mm. b. Two specimens show the very first signs of skeletal development. One calcareous element is associated with each para-arm. The specimen on the right was an additional calcareous element centrally located between the para-arms. Sa
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ECHINOTHUR1OID DEVELOPMENT. REVISITED 25. Figure 9. Skeletal development in various, cleared stages of larvae of Asthenosoma ijimai. All larvae are viewed from the dorsal side in partially polarized light, a. A 63-h larva shows no evidence of calcareous skeletal elements. Scale bar, mm. b. Two specimens show the very first signs of skeletal development. One calcareous element is associated with each para-arm. The specimen on the right was an additional calcareous element centrally located between the para-arms. Same scale as a. c. A larva with continued skeletal development. Each calcareous element associated with a para-arm has formed a plate-like ossicle and shows substantial or initial formation of a rod attached to the plate. Other calcification centers have also begun. Same scale as a. d. Close-up of plate-like ossicle and rod from right posterior para-arm of a h larva. Scale bar. 100 ^m. e. Another plate-like ossicle and rod from a 101-h larva. Same scale as d. f. Central plate-like ossicle without an associated rod from a 101-h larva. Scale bar, 100 ^m. g. A 101-h larva with manv calcification sites. Same scale as a. Asthenosoma ijimai as that of a highly modified pluteus larva. The two pair of bilaterally symmetrical para-arms arising from posterior and dorsal parts of embryo, each one containing a calcareous, fenestrated skeletal element, appear to be vestigial larval arms. We reject an alternative interpretation that the fenestrated rods are juvenile spines, because the spines form in association with plates that are separate elements (Gordon, 1926a, b). Because the skeletal elements are fenestrated, we interpret the para- arms as reduced post-oral and postero-dorsal arms (the. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfect
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
