No description available.

Thesis (Ph. D.)--Johns Hopkins University, 1916. / Vita. Half-title: Part II, Gastropods and discussion of results. "Reprinted from Carnegie institution of Washingtonn Publication number 385 ... 1928." "Literature list for Miocene mollusks from tropical America": p. 42-48.

Thesis (M.S.)--University of Wisconsin--Madison, 1961. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 60-66)

Thesis (Ph. D.) - University of North Carolina, 1961. / Bibliography: leaves 41-46.

Inaug.-diss.--Halle-Wittenberg.

The columellar muscle of both limpets and coiled shell gastropods is of the paramyosin smooth type. Collagen forms an integral part of the musculature constituting about 35% of the tissue. In limpets, muscle organisation is typical of a muscular hydrostat. Tightly packed blocks of muscle, dense arrays of cross-linked collagen, large muscle cells (9 µm diameter) and thick filaments (70 nm diameter, 30 µm long) produce a tough, relatively rigid but powerful muscle. In coiled shell gastropods, muscle organisation is intermediate between a muscular and a fluid hydrostat. Finer muscle cells (6 µm diameter), thick filaments (60 nm diameter) and a loose intercellular network of collagen interspersed with fluid vesicles are features of a more pliable and extensible muscle. In addition, ultrastructural differences, such as larger numbers of mitochondria and sarcolemmal invaginations distinguish the tarsal from the columellar muscle in both limpets and coiled shell gastropods. About 25% of muscle cells in most species examined, contain a novel arrangement of thin filaments with periodic electron-dense regions. These are similar in appearance to intrafusal cells and stress-fibres of non-muscle cells. Structural analysis of isolated filaments, optical diffraction and SDS gel electrophoresis confirm the, large dimensions and the paramyosin nature of the thick filaments. Microdensitometry of the gel proteins confirms the high proportion of collagen present. No significant differences in muscle ultrastructure were found between limpets from different tidal heights. Muscle attachment areas are shown to be species-specific and positively correlated to tenacity and wave exposure. The muscle attachment mechanism is similar to that described for other molluscs. It consists of a special epithelial layer and a mucous-like material at the muscle-shell interface that possibly has an adhesive function. Although the ultrastructure of Patella is very similar to that of the anterior byssus retractor of Mytilus, its mechanical behaviour is not. The muscle has a narrow working range where maximum tensions and "catch-like" contractions develop. This narrow length range is co-incident with the in situ length at which clamping occurs. It is suggested that the large component of collagen has an important influence over the mechanical behaviour of the muscle during clamping, by cross-linking in a manner similar to that described for some echinoderm connective tissues.

A subtidal site at Saturnina Island was sampled quantitatively to determine the seasonal and depth related trends of gastropod populations. The resulting density estimates were used to characterize the assemblage using diversity, niche-breadth, and cluster analyses. The relationship between gastropod abundance and diatom density, as estimated from colonization of glass microscope slides, was investigated One experiment, which was conducted at the site, was designed to determine whether the macrophytic algae still attracted the numerically dominant snail after the algae had been either cleaned with hydrogen peroxide, or killed by immersion in 50° C. seawater. Most species attained their maximum development after recruitment in spring or early summer. The greatest number of species was found at the shallowest station that was sampled, and abundances tended to decrease with depth with most species. Most of the snails had dispersion patterns that were similar to those of the two dominant species Marqarites costalis and Lacuna marmorata. Ninety-five percent of all the individuals collected were found to belong to five species. This high degree of numerical dominance severely affected the results of the diversity and the cluster analyses. Analyses of frequency vs. mean abundance, and niche-breadths revealed detailed information concerning the distributions of the gastropods that was not readily obtainable from graphs of mean density per quadrat. Diversity, species richness, the total abundance of gastropods, and the densities of several species were correlated to the abundance of diatoms. Several species were also found to contain diatoms among their gut contents. Several other factors, including parasitism, predation, low salinity-high temperature water, and competition are discussed as factors, which, in addition to diatom abundance, may have affected the gastropod dispersion patterns. / Science, Faculty of / Botany, Department of / Unknown

The chloride ion concentration of blood, urine, and foot muscle, blood and muscle water content, and blood and urine osmotic pressure, were measured in summer and winter adapted populations of the prosobranch limpet Collisella persona, over a range of salinities from 25% to 125% SW (100% SW = 480 mEq Cl⁻/L). Blood, urine, and foot muscle Cl⁻ were not regulated in all salinities tested. Blood Cl⁻ was generally hypoionic and urine isoionic to the experimental sea water concentrations. Muscle Cl⁻ did not reach a level greater than one-half of equivalent blood or sea water values in all salinities tested. However, muscle and blood values were similar, if muscle Cl⁻ were expressed in terms of extracellular water. Extracellular volume remained relatively unchanged and showed only a 7% increase in salinities ranging from 50% to 125% SW. Seasonal differences were apparent in muscle Cl⁻, with winter values higher than summer values by 20-25 mEq/kg tissue, in salinities ranging from 75% to 125% SW. However, this could be accounted for by the slightly larger (4-8%) extracellular space recorded from winter animals. Summer and winter adapted limpets were osmoconformers in salinities ranging from 25% to 125% SW. Summer animals had blood hyperosmotic, and urine isosmotic to the experimental sea water concentrations. Winter limpets had blood hyperosmotic to 75% SW, and isosmotic in 25% and 125% SW. Urine was hyposmotic to 25% and 75% SW, and isosmotic in 125% SW. Summer blood was hyperosmotic to winter blood, although summer and winter urine remained isosmotic. In addition, for both summer and winter animals, blood was hyperosmotic to urine. The foot muscle water content of winter adapted limpets returned to the control value in 50% to 125% SW, between 48 hours and 1 week. Over the same time period, summer animals only regulated muscle water in 50% and 75% SW. Blood water content remained relatively unchanged for both summer and winter adapted limpets, and showed a 4% decrease over a salinity range from 25% to 125% SW. There were no significant seasonal differences in blood water content. Seasonal differences recorded during the present study, in particular the comparatively large variation in measurements from summer animals, were attributed to seasonal changes in salt and water permeability, or metabolic rate. In addition, an attempt was made to relate the physiological responses recorded from limpets in the laboratory, to the survival of limpets in the field. / Science, Faculty of / Zoology, Department of / Graduate

Aspects of the Pisaster-Tegula interaction are re-examined. Reproductive portions of T. funebrallis populations are shown to be immune to seastar predation through a combination of predator preference for larger snails and a withdrawal behavior that favors the escape of smaller snails after capture by a seastar . Experimental addition of p. ochraaceus in winter causes changes in the intertidal distribution of T. funebralis similar to those observed during the summer increase in seastar numbers. It is suggested that these results supplant the hypothesis that lowered prereproductive mortality influences formation and maintenance of vertical size gradients in the lower intertidal .

No description available.