File:American malacological bulletin (1986) (18152786142).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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D'ASARO: EGG CAPSULES OF SMALL MARINE PROSOBRANCHS 193 axis (Figs. 2g, h and 3a). The rounded side (distal to the spawner) in some specimens had folds in the surface layer. The proximal side, which served as an escape aperture, sloped from the apical ridge to a broad basal area. In a few specimens, the basal area tapered to a point like most cap- sules of Ft. catesbyana or Zebina browniana (Orbigny, 1842). Surface texture of the layer through which veligers escape was different from the remaining capsule. When viewed apically, a distinct inner lamina and a zone with less dense albumen surrounding the embryos were visible. Sectioned capsules showed a layered outer envelope in which the outer lamina was actually a matrix surrounding an optically dense inner lamina (Fig. 4d). Within the optically dense lamina, the embryos in thin, clear albumen were surrounded by a substantial, granular lamina that separated them from the sur- rounding vesicular zone. In this species, the vesicles were larger than those of R. catesbyana previously described. As the embryos developed, the granular lamina expanded toward the optically dense lamina. Capsular dimensions are presented in Table 3. Egg capsules contained four or five large embryos that hatched as planktotrophic veligers in 11 days. Zebina browniana (Orbigny, 1842) (USNM 836981) Specimens collected from southern Florida during April and May, 1985, paired and began to spawn immediately after collection. One or two egg capsules were consistently deposited in two locations: on the culture dishes (inverted under the cover or between the cover and the side) and on the under side of Halodule leaves heavily encrusted with epiphytes. This species appeared to prefer to deposit cap- sules under an object. Zebina browniana has typical rissoinid egg capsules quite similar to Rissoina catesbyana and R. bryerea, only larger (see Table 3), enclosing a single, yellow-white, yolk-
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