. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 274 J. BUCKLAND-NICKS. Figure 9. of closed hull cupule (HC) of Lepidochitona fcrnaldi egg. showing reduction typical of brooders. Regular series of micropores is visible in intercupule area (arrowheads). Scale bar = 20 ^m. Figure 10. egg showing elongate microvillus (arrow), extending from one of a series of micropores in the intercupule region (arrowheads). Scale bar = 2 ^m. Figure 11. of Chaetopleiira apiculaia egg showing spinous hull. Scale bar = 100 i*m. Figure 12. of spine of ma
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 274 J. BUCKLAND-NICKS. Figure 9. of closed hull cupule (HC) of Lepidochitona fcrnaldi egg. showing reduction typical of brooders. Regular series of micropores is visible in intercupule area (arrowheads). Scale bar = 20 ^m. Figure 10. egg showing elongate microvillus (arrow), extending from one of a series of micropores in the intercupule region (arrowheads). Scale bar = 2 ^m. Figure 11. of Chaetopleiira apiculaia egg showing spinous hull. Scale bar = 100 i*m. Figure 12. of spine of mature egg of C. apiculaia. Spines are effectively closed, blocking sperm entry. Scale bar = 20 nm. Figure 13. of spines of mature egg ofC. apiculaia viewed from the base, showing that they are hollow internally (arrowheads). Note sperm visible only on external surface (S). Scale bar = 40 /im. the highly reduced form found in the majority of chitons differs markedly from the large, more typical molluscan acrosome found in the primitive Lepidopleurina (Hodg- son el 1988). Furthermore, there may be key differ- ences in the structure of acrosomes in open and closed cupule species. In the open cupule species Tonicella li- neata. sperm penetration of hull and vitelline layer ap- parently involves sequential exhaustion of two Golgi-de- rived granules in the acrosome (Buckland-Nicks el ai. 1988). The apical granule is used up during passage through the hull, whereas the basal granule is used up during passage through the vitelline layer. Any exposed area of the hull, but apparently not the hull cupules them- selves, can be penetrated by the sperm; although the ma- jority of sperm are attracted inside the hull cupules. Con- versely, in closed cupule species, I have not found sperm penetrating the hull anywhere except in the region of mi- cropores, which enable the sperm to bi-pass the hull and gain direct access to the vitelline layer; although it is not certain yet that sper
Size: 1750px × 1428px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
