File:American malacological bulletin (1986) (18157398681).jpg

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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KING ET AL: CORBICULA SPAWNING AND DEVELOPMENT 85
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Fig. 7. Apical tuft of C. fluminea trochophore. Horizontal field width = 20 ^m. Fig. 8. Individual cilia of the apical tuft of C. fluminea trochophore observed using phase contrast microscopy. Horizontal field width = 40 ^m. Fig. 9. Straight-hinged (veliger) larva of C. fluminea 37 hours after spawning bearing a velum (v) and apical tuft (t). Horizontal field width = 380 ^m. Fig. 10. Juvenile C. fluminea about one month after release from parent, g = gills; s = spot; f = foot. Horizontal field width = 330 /<m. body (Fig. 10), and gills were visible through the shell. The mean shell length of juveniles at metamorphosis was 221 (s.d. +/- 10 fjim). Shell length increased significantly after one week (two-sample t-test, t = 10.886; P < 0.001), to 256 nm (s.d. +/- 20 nm). Juveniles became coated with decay- ing algae and detritus after one to two weeks of culture, and high mortality occurred after three weeks. Remaining juve- niles survived for about two months after metamorphosis although little shell growth was observed. A summary of early development of laboratory- spawned C. fluminea is illustrated in Figure 11. The times stated for each developmental stage are based on observa- tions of embryos removed from gills of parent clams, and represent the number of hours after spawning when each stage was first observed, however, as development pro- gressed, gills of parent clams contained brooding embryos at different developmental stages. Adult clams continued to grow after releasing larvae, and six months after the spawning event, developing eggs and sperm were visible in gonad smears. FEEDING ACTIVITY OF LARVAE Particles were visible moving around released larvae as a result of currents produced by the ciliary activity of the velum. Released pediveligers that were exposed to fluores- cent latex microspheres contained fluorescent particles within the gut. Larvae brooded on the gills of parent clams showed no gut fluorescence. DISCUSSION GROWTH OF ADULT CORBICULA FLUMINEA Culture of C. fluminea in the laboratory has been at- tempted by many investigators using a variety of diets, includ- ing strained spinach (Britton and Morton, 1982), and algae, such as Chlamydomonas, Ankistrodesmus (Foe and Knight, 1985), Anabaena, Scenedesmus (Lauritsen, 1985), and Chlorella (Foe and Knight, 1985; Lauritsen, 1985). The diatom Skeltonema costatum, fed to clams in the present study, is known to support growth of marine bivalves in intensive culture (Epifanio, 1975). Further investigations of optimal physical and chemical culture conditions as well as nutritional requirements are needed to develop algal diets and culture techniques that support maximum growth of Corbicula in the laboratory. Growth of clams in this study demonstrates that C. fluminea is able to tolerate salinities fluctuating from 0 to 8 ppt. Evans ef al. (1979) reported that C. fluminea was able to survive exposures of 10 to 14 ppt salinity without prior

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