. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 80 R. R. OLSON ET Figure 1. Scanning electron micrograph of a fractured gastrula of Phyllacanlhus imperialis showing mesenchyme cells (ME) aggregated around the base of the archenteron. Note the small hlastocoel (BC). Figure 2. One-day-old embryo showing rudiments of post-oral arms (POA) and blastopore (B). Figure 3. Two-day-old larva. PDA, posterodorsal arms; TF, tube foot; POL. preoral lobe. Figure 4. Anterior view of 3- to 4-day-old larva. The preoral lobe has undergone torsion nearly 45° to the left from its orienta
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 80 R. R. OLSON ET Figure 1. Scanning electron micrograph of a fractured gastrula of Phyllacanlhus imperialis showing mesenchyme cells (ME) aggregated around the base of the archenteron. Note the small hlastocoel (BC). Figure 2. One-day-old embryo showing rudiments of post-oral arms (POA) and blastopore (B). Figure 3. Two-day-old larva. PDA, posterodorsal arms; TF, tube foot; POL. preoral lobe. Figure 4. Anterior view of 3- to 4-day-old larva. The preoral lobe has undergone torsion nearly 45° to the left from its orientation in a typical pluteus. CB, ciliary band. tures and the general opacity of the preoral lobe. Scanning electron micrographs of arm rods showed them to be fen- estrated approximately 1 mm in length with a lattice-like plate at the base (Fig. 17). The larvae of P. imperial'is swim in a typical echinopluteus fashion with the anterior- posterior axis oriented vertically and the posterior directed downwards much like the orientation of a falling bad- minton shuttlecock (Fig. 13). Metamorphosis and description oj juvenile urchin Metamorphosis of the echinopluteus includes the for- mation of juvenile structures such as tube feet, spines, and pedicellaria, and the resorption of larval tissues. In the majority of echinoids with an echinopluteus larvae, the first appearance of juvenile structures is within the vestibule, which is an invagination that forms on the left side of the larva. In cidaroids, there is no vestibule (Emlet, 1988). but juvenile structures develop on the left side of the echinopluteus in the same general location as on other echinoid larvae. The onset of metamorphosis can be ob- served when juvenile structures are visible on the exterior of an echinopluteus larva. These juvenile structures are called the "echinus ; Settlement and metamorphosis of P. imperialis larvae began 4 days after fertilization. Larvae settled by attaching themselves to the
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
