The escape of veligers from the egg capsules of Nassarius obsoletus and Nassarius trivittatus (gastropoda, prosobranchia)
Pechenik, Jan A.
MetadataShow full item record
Many species of prosobranch gastropod deposit their eggs in tough capsules affixed to hard substrates. Generally, there is a small opening near the top of such capsules, occluded by a firm plug (operculum) which must be removed before the veligers can escape. Although the removal of the operculum is generally attributed to embryonic secretion of enzymes, there is little experimental support for this sugsestion. In the limited experiments which have been reported, all dealing with species that emerge as juvenile snails, no attempt was made to determine the properties of the hatching substance, or the timing of its production. My research has dealt with the escape of veligers from the egg capsules of two related species, Nassarius obsoletus and N. trivittatus. Their egg capsules are quite similar in size, number of eggs contained, general morphology, and the thickness of the material plugging the opening at the top. Both hatch as swimming veligers, after about one week of encapsulated. development. By adding fresh plug material to small volumes of sea-water containing veligers obtained prior to, or at known times after their normal hatching, I have demonstrated conclusively the essentially chemical nature of operculum removal for these two species. In addition, the hatching substance was found to be produced in a short pulse, to be functionally short-lived, and to be species-specific in its action for the two species considered. There is no evidence that the secretion of the hatching substance is stimulated by short pulses of light or increased temperature; the capsules of N. obsoletus contain many more embryos than are needed to successfully remove the plug, so that complete synchrony of hatching substance production by all individuals within a capsule is probably not necessary. Lastly, the observed rates at which N. obsoletus veligers leave their egg capsules were compared with those predicted from an equation assuming random movement of individuals. A close agreement was found, the capsules losing 98% of their residents within 45 to 55 minutes of the first escape. Thus, the location of the exit by an individual is probably by chance.
Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology [and the Woods Hole Oceanographic Institution] June 1975
Showing items related by title, author, creator and subject.
Green, Sarah A. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1992-02)The work presented in this thesis consists of three parts. The first is a photophysical study of the mechanism of fluorescence quenching by stable nitroxyl radicals, which are becoming an important analytical tool for ...
Comprehensive study of a heavy fuel oil spill : modeling and analytical approaches to understanding environmental weathering Lemkau, Karin L. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2012-06)Driven by increasingly heavy oil reserves and more efficient refining technologies, use of heavy fuel oils for power generation is rising. Unlike other refined products and crude oils, a large portion of these heavy oils ...
Hoyt, Joshua King (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1986-05)The Flying Fish is an autonomous, streamlined, gravity driven underwater vehicle of high speed (15 knots) vertical excursions to depths of 6000 meters. This prototype uses short baseline acoustic interferometry to guide ...