Life Sciences Commons^™

Shore-Level Size Gradients In Tegula Funebralis (A. Adams) : Seasonal Changes Influenced By Interaction Of Predator Preference And Prey Behavior, Daniel Victor Markowitz

University of the Pacific Theses and Dissertations

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 .

Population Ecology Of The Littoral Fringe Gastropod Littorina Planaxis In Northern California, Russell James Schmitt

University of the Pacific Theses and Dissertations

Life history patterns of individual organisms are the result of natural selection and should be correlated with particular physical and biological characteristics of habitats in which they live. The littoral fringe is known to be the most severe physical habitat in the intertidal zone, and it is expected that organisms in it should have population characteristics associated with selective response to physical adversity rather than biological interaction. Ecological studies of populations of Littorina planaxis were made in the Dillon Beach and Bodega Head areas. The study localities differed principally in extent of wave exposure rather than geographical location.

Larval Development And Feeding Ecology Of Hermissenda Crassicornis (Eschscholtz) And Aeolidia Papillosa (Linnaeus), Leslie G. Williams

University of the Pacific Theses and Dissertations

Thompson (1967) defines three developmental types for Opisthobranchia with representative nudibranchs in each category. The types are: 1.) planktotrophic larvae which are obligatory plankton feeders prior to progressive metamorphosis, 2.) lecithotrophic larvae which may feed on the plankton, but do not need to do so in order to metamorphose, 3.) direct development which results in hatching of a post veliger, benthic juvenile.

Tardy (1970) feels that Thompson's Type 3 development is artificial. Thus, he incorporates direct development into the lecithotrophic developmental type. Tardy then proposes a classification of metamorphic types based on larval shell type (Thompson, 1961) and on larval …

Structure And Function Of The Alimentary Tract Of Batillaria Zonalis And Cerithidea Californica, Style-Bearing Mesogastropods, Andrew Locke Driscoll

University of the Pacific Theses and Dissertations

This study describes the structure and function of the alimentary tracts of B. zonalis and C. californica with particular emphasis on the stomach and style sac region. Both species were found to be generally similar to other styles bearing mesogastropods in that they have little or no development of glandular tissue in the esophageal region and a functional style is present in the stomach. The stomachs of both species are specialized to transport and digest a continuous supply of detritus by means of complex ridges, grooves and ciliary currents. C. californica appears more highly specialized for feeding on fine, highly …