. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ASEXUAL REPRODUCTION IN PYGOSP1O 43. Figure 1. Scanning electron micrographs of adult Pygospio elegans. (A) Head and anterior thorax including the reduced first setiger. (B) Thorax, showing both anterior setigers with capillary neurochaetae and posterior setigers with neurochaetae that are hooded hooks. (C) Abdomen, characterized by branchiate setigers and a double dorsal ciliary band. (D) Tail and pygidium. b = branchus, c = cirrus, d = dorsal ciliary band, h = hooded hook, n = nuchal organ, cp = capillary chaetae, p = palp
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ASEXUAL REPRODUCTION IN PYGOSP1O 43. Figure 1. Scanning electron micrographs of adult Pygospio elegans. (A) Head and anterior thorax including the reduced first setiger. (B) Thorax, showing both anterior setigers with capillary neurochaetae and posterior setigers with neurochaetae that are hooded hooks. (C) Abdomen, characterized by branchiate setigers and a double dorsal ciliary band. (D) Tail and pygidium. b = branchus, c = cirrus, d = dorsal ciliary band, h = hooded hook, n = nuchal organ, cp = capillary chaetae, p = palp, pr = prostomium. t = tuft of cilia. Scale bar = 100 /am. was the most common form of fission observed in the present study. The maximum number of fragments observed per division was six, and regeneration in all fragments followed the same basic pattern. Table I provides a list of the structures that were observed during regeneration and the time at which the regenerated structures were first ob- served. On day 1, transverse fission began as a muscular con- striction in the body wall, usually in the abdominal region located at a point about two-thirds along the length of the worm. Constriction of the body wall continued until the gut separated and the two fragments, each anchored to the substrate v/a mucous, pulled apart. The anterior fragment consisted of the head, thorax, and most of the abdomen (about 25 or more pairs of branchiae), while the posterior fragment consisted of the tail, pygidium, and usually about five or fewer branchiate abdominal setigers. The epidermis healed quickly and formed a smooth surface the same day as division occurred (Fig. 2a). On day 2, the blastema of both the anterior and posterior fragments showed a small amount of new tissue with tiny, scattered tufts of cilia on an other- wise smooth epidermis (Fig. 2b). Regeneration on day 3 is characterized by rapid develop- ment of the blastema and formation of lost body regions (Table 1). As the anterio
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
