Title: American malacological bulletin
Identifier: americanmal4519861987amer (find matches)
Year: 1983 (1980s)
Authors: American Malacological Union
Subjects: Mollusks; Mollusks
Publisher: (Hattiesburg, Miss. ?) : (American Malacological Union)
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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84 AMER. MALAC. BULL. (4) (1986)
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Fig. 3. Sperm of C. fluminea filtered from aquarium water and stained with acridine orange. Horizontal field width = 50 ^m. Fig. 4. Early embryo of C. fluminea surrounded by gelatinous envelope (g). Horizontal field width = 400 ^m. Fig. 5. Trochophore larva of C. fluminea about 20 hours after spawning. Larva was removed from gills of parent clam, liberated from gelatinous envelope and suspended in water. Arrow indicates direction of movement, a = apical tuft. Horizontal field width = 150 ^m. Fig. 6. Movement of the apical tuft of C. fluminea trochophore. Horizontal field width = 55 /xm. Trochophores. Early trochophore larvae developed after 14 hours (Fig. 5). Cilia were not evident at 14 hours on trochophores that were removed from parental gills, liberated from the gelatinous envelope, and suspended in water, although particles moving in currents around the larvae were observed. Short cilia covering the apical surface were ap- parent after 17 hours, and at 18 hours much of the surface of the larvae was covered with cilia. Trochophores were im- mobile while retained on the gills, although larvae that were suspended in water rotated as a result of ciliary activity. Apical tuft. At 18 hours, trochophores developed an apical ciliary tuft which appeared as a spike-like projection after 20 hours (Fig. 5). When suspended in water, larvae swam with the tuft pointing in the direction of movement. Trochophores removed from the gills flexed and curled the tuft (Fig. 6). Although the tuft initially appeared to be a single, spike-like structure (Fig. 7), photomicrographs magnified approximately 320 x showed that the tuft was composed of individual cilia (Fig. 8). Straight-hinged larvae. Straight hinged larvae (veligers) were first observed at 37 hours and became most prevalent 49 hours after spawning (Fig. 9). The spike-like tuft was re- tained throughout the straight-hinged larval stage, and ex- tended from the velum. As with the trochophores, larvae that were motionless in the gills became motile when manually freed from the gelatinous material covering the gills, and swam with the velum extended in the direction of movement. Pediveligers. Pediveligers bearing a spike-like tuft on the velum and a ciliated foot were first released from parental clams at 100 hours after spawning. Some pediveligers re- mained on the gills of parent clams for 125 hours before release. The gelatinous material surrounding the larvae became less thick and less viscous throughout the period of release. Juveniles. Released pediveligers shed their vela (meta- morphosed) to juveniles at 112 hours (about 5 days) after spawning. Of 21 young clams observed at 112 hours, 67% bore only a foot, 24% bore only a velum, and 9% bore a foot and a velum. All larvae were without vela at six days after spawning. Juveniles were characterized by dark spots on the

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