. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. CHAETOPTERUS LARVAL ONTOGENY 323 Ocelli: 2; one lateral pair Reference*: Henry (1986) fig. 3b-c; Bonch-Bruevich and Malakhov (1987) fig. 1 By this stage gastrulation is complete, forming a tripartite gut. A ventrally opening ciliated stomodeum is visible an- teriorly. The more medial stomach occupies about half the volume of the larva, and a much smaller intestine is located just anterior to the pygidium. The anus opens dorsally. The gut is functional at this time, as evidenced by algal particles in the stomach. A pair of st
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. CHAETOPTERUS LARVAL ONTOGENY 323 Ocelli: 2; one lateral pair Reference*: Henry (1986) fig. 3b-c; Bonch-Bruevich and Malakhov (1987) fig. 1 By this stage gastrulation is complete, forming a tripartite gut. A ventrally opening ciliated stomodeum is visible an- teriorly. The more medial stomach occupies about half the volume of the larva, and a much smaller intestine is located just anterior to the pygidium. The anus opens dorsally. The gut is functional at this time, as evidenced by algal particles in the stomach. A pair of stiff lateral hooked bristles, com- posed of hooked cilia, take the place of the lateral hooked cilia (Henry, 1986). A distinct trochal band is not present at this stage. Stage L3—3-30 days (Fig. 2d-i): Size: 180-320 X 90-180 /am Ciliary structures: apical tuft present; mesotroch present; lateral bristles persist Ocelli: early: 2; one lateral pair: late: 4; one lateral pair and one medial pair References: early: Cazaux (1965) pit. 2. fig. 5; late: Cazaux (1965) pit. 3, fig. 6; Enders (1909) pit. II. fig. 9 Earl\ period, 3-10 days. In this period the relative size of the stomach enlarges to occupy most of the larva. A more distinct pygidial papilla forms. A distinct trochal band is first visible at the level of the intestine, here referred to as a mesotroch, following the terminology of Okada (1957). The lateral bristles of Stage L2 persist. In histological sections the neuropil of the cerebral gan- glion is visible anterior and dorsal to the stomodeal opening (Fig. 3a, b). At this stage other neural tissues were not visible in section, although a ventral nerve network has been reported in slightly younger specimens examined with transmission electron microscopy (Bonch-Bruevich and Malakhov, 1987). The stomodeum itself has three dorsal diverticulae and opens to the stomach through a pharyngeal valve in the midposterior floor of the stomodeal cavity (Fig. 3b). The midgut endoderm
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
