. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ONTOGENY AND HOMOLOGIES 23. Figure 1. (A) Amphiurastimpsonii: early (Stage 2) unhatched embryo mm dd showing large yolk mass and protruding terminal arm plate and small adoral shield spine. Specimen not plasma-ashed to remove integument. (B, C) Amphiura stimpsonii: ventral interradial body wall removed to show advanced brooded embryo in the bursa. Note gaps between jaws of adult (double arrowhead in B) and lack of primary rosette on disk of embryos (in C). (D) Amphiura filiformis: newly settled (Stage 2) juvenile m
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ONTOGENY AND HOMOLOGIES 23. Figure 1. (A) Amphiurastimpsonii: early (Stage 2) unhatched embryo mm dd showing large yolk mass and protruding terminal arm plate and small adoral shield spine. Specimen not plasma-ashed to remove integument. (B, C) Amphiura stimpsonii: ventral interradial body wall removed to show advanced brooded embryo in the bursa. Note gaps between jaws of adult (double arrowhead in B) and lack of primary rosette on disk of embryos (in C). (D) Amphiura filiformis: newly settled (Stage 2) juvenile mm dd, with relatively large adoral shield spine. Plasma-ashed specimen. Abbreviations: d, adoral shield spine; t. terminal arm plate: x. disk of embryo; y. yolk mass; z, arm of embryo. In a specimen mm dd with 19 AS (Fig. 2D) the adoral shield spine moves from the adoral shield to the "distal oral plate" (sensu Hendler, 1978) that is. distal to a suture line (visible in Fig. 2C) that bisects the jaw. This remarkable transition is a consequence of marked allo- metric growth of the oral and adoral shields in specimens to mm dd (and probably of the oral plate mus- cle-attachment surfaces as shown for Amphioplus abdi- tus in Hendler. 1978: Fig. 6). Due to differential growth rates of these jaw elements, the first ventral arm plates move from a superficial to an internal position on the disk, and the proximal end of the plate sinks into the oral gap (not shown in Fig. 2, but see Hendler, 1978: Fig. 5). As ontogenesis proceeds, the adoral shield spines show negative allometric growth. The infradental papillae change from a spinelike to a blocklike shape, and move from the dental plate to the tips of the oral plates by the time individuals reach mm dd with !' In early stages the oral slits are lightb of teeth and oral papillae (infradental culiform buccal scales) that are attacht to the ventral edge of the jaw. As Amphiura g. surface of the jaw bulges ventr
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
