. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. OPHIUROID SKELETAL DEVELOPMENT B 85 PER. FIGURE 5. Portion of the disc, in ventral view, for different stages of development: A, 21 arm-segment stage; and B, >30 arm-segment stage. Abbreviations as in Figures 1 to 4; and AP represents accessory papillae; GS, genital scale; TS, tentacle scale. Scale line is mm. Dotted lines separate DOP and POP. As each new arm segment is added a ventral arm-plate appears before the lateral arm-plates and arm spines, and a dorsal arm-plate finally forms to cap the segment. The arm-plat
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. OPHIUROID SKELETAL DEVELOPMENT B 85 PER. FIGURE 5. Portion of the disc, in ventral view, for different stages of development: A, 21 arm-segment stage; and B, >30 arm-segment stage. Abbreviations as in Figures 1 to 4; and AP represents accessory papillae; GS, genital scale; TS, tentacle scale. Scale line is mm. Dotted lines separate DOP and POP. As each new arm segment is added a ventral arm-plate appears before the lateral arm-plates and arm spines, and a dorsal arm-plate finally forms to cap the segment. The arm-plates and spines take a form characteristic of the adult by the 17 arm- segment stage. Rudiments of the oral shields and madreporite do not appear until the third arm-segment begins to form (by five months). They form in situ on the oral surface of the disc, proximal to the interradial-1 series (Fig. 3). Even so, the stone and pore canals associated with the madreporite are present before the two arm-segment stage. By eight months there are four arm-segments, and radial shields appear at the base of the arm, on the ventral surface of the disc. An exact chronology cannot be assigned for subsequent skeletal developments, as they were deduced using a growth series organized from material in field collec- tions (Table I; Figs. 3, 4, and 5). There is no important change in the armature of the disc until the 5 arm-segment stage, when pairs of infradental papillae appear distal to the dental plates (Fig. 3). The most striking superficial change at this time is the addition of minute scales on the ventral surface of the disc, which separate the oral shields and interradial-1 plates. Interradial-2 plates erupt be- tween the radials, isolating the radial plates from the interradial-1 on the dorsal surface of the disc (Figs. 3, 4, and 5). The central primary plate and the radial plates continue to grow until the disc diameter is 5 mm and then diminish in size with further growth. This allome
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
