. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 6 FIGURES 5-6. Pscitdopolydora paucibranchiata: 5) early 3-setiger larva in ventral view; 6) early 3-setiger larva in dorsal view. to a ciliated larva that rotates slowly in the sac. The youngest embryo removed from a capsule measured 102 /* at the widest point. Large yolky macromeres surrounded by micromeres are the only noticeable features. There is no evidence of ciliation (Fig. 2). At the end of 24 hours, the pre-setiger larvae are 130 ^ in length (Figs. 3—4-). The central region is filled with yolk. Two broad ventral ci
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 6 FIGURES 5-6. Pscitdopolydora paucibranchiata: 5) early 3-setiger larva in ventral view; 6) early 3-setiger larva in dorsal view. to a ciliated larva that rotates slowly in the sac. The youngest embryo removed from a capsule measured 102 /* at the widest point. Large yolky macromeres surrounded by micromeres are the only noticeable features. There is no evidence of ciliation (Fig. 2). At the end of 24 hours, the pre-setiger larvae are 130 ^ in length (Figs. 3—4-). The central region is filled with yolk. Two broad ventral ciliated patches are present. The prototroch has developed and is formed of two ciliated bands on either side of the anterior end. The anteriormost band is tran- sitory but the posterior band continues to develop and is retained throughout the larval life. The mouth has developed and is heavily ciliated. The telotroch is a ring of seven isolated patches of cilia. There are two eyes located dorsally. There is no evidence of segmentation. EARLY 3-SETiGER LARVAE (Figs. 5—6). Another 24 hours is required for devel- opment of the first three setigerous segments when the larvae measure 190 /A in length. The central yolk mass is prominent but the larvae have feeble swimming abilities when released from the egg capsules. The two ventral ciliated patches are gone. The prototroch has continued to develop and now ventrally merges with the cilia of the vestibule which has deepened. A broad neurotroch is forming posterior to the mouth. Cilia of the telotroch have lengthened. There is a dorsal gap in the telotroch. Four eyes are present; the inner pair is rounded; while the lateral pair is cup-shaped. Two ciliated areas on either side of the head represent presumptive nuchal ciliation. There are two dorsal median chromatophores. One is located at about the level of setiger 1, while the second is on the anal segment. Two small patches of irides- cent pigment occur ventrally on the anal segm
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
