Life Sciences Commons^™

A Response Surface Investigation Of The Larval Tolerances Of Three Spionid Polychaetes To Temperature, Salinity And Food Concentration, Alan Louis Hillyard

University of the Pacific Theses and Dissertations

Response surface techniques were used to investigate the tolerances of the planktonic larvae of three spionid polychaetes to a variety of temperature and salinity combinations. Two of the spionids were morphologically very similar members of the genus Boccar.dia., B. proboscidea and B. columbiana which occupy nearly identical geographic ranges. The other was Polydora giardi a common coinhabitant with B. columbiana. In addition a third independent parameter, food concentration, was added to the study of B. columbiana and P. giardi.

The larvae of the two Boccardia species were extremely euryhaline, in marked contrast to those of Polydora giardi which were confined …

The Ecology And Reproductive Cycle Of Pygospio Elegans Claparède (Polychaeta: Spionidae) From Tomales Bay, California, Debrah Lapp Armitage

University of the Pacific Theses and Dissertations

Pygospio elegans Claparede (1863) is a relatively small, inconspicuous intertidal Spionid polychaete (10 to 15 mm in length) having approximately 50 to 60 body segments. The species occurs in high intertidal sand flats along the central California coast.

Pygospio elegans is one of three species of the genus Pygospio, with the other being, P. california Hartman (1936) which is found only along the central California coast and P. dubia Munro (1930), from Antarctic seas. P. elegans is the most cosmopolitan of the three species (Clay, 1967; Light, 1978). The species has been recorded from both sides of the Atlantic Ocean; …

The Population Dynamics And Recruitment Pattern Of The Phoronid, Phoronopsis Viridis, Victoria Rolanda Starczak

University of the Pacific Theses and Dissertations

A dominant organism on intertidal Pacific Coast sandflats is the lophophorate Phoronopsis viridis Hilton. This suspension feeder builds a stiff, sandy tube, 3 mm wide and up to 20 cm long and usually lying within 6 cm of the surface (Johnson 1967a). Phoronopsis viridis is found over large areas and tidal ranges of sandflats in aggregate densities of over 21,000 phoronids per m² (Ronan 1978). On Lawson's Flat, the location of the present study, the areas of highest density of P. viridis have been known to persist for over 20 years (Steven Obrebski, personal communication).

The factors accounting for …

The Synecology Of Dense Assemblages Of The Deposit-Feeding Polychaete, Axiothella Rubrocincta (Maldanidae), James Robert Weinberg

University of the Pacific Theses and Dissertations

Interspecific interactions have been shown to play critical roles in determining the realized niches of species in marine rocky intertidal (ie Connell 1961, Paine 1966,, Dayton 1971) and terrestrial (i.e~ Harper 1969, Pianka 1973, Cody 1974) communities. In contrast, such interactions have not been clearly demonstrated as determinants of the distribution and abundance of marine intertidal soft-substrate organisms (however, see Levinton 1977). There are great physical differences between the rocky and mud-sandflat intertidal habitats, Some of these are wave exposure, sediment size (boulders to silts), penetrability and organic content of the substrate, frequency of log damage, and exposure to sunlight. …

The Effects Of Predation And Sediment Reworking By The Maldanid Polychaete Axiothella Rubrocincta (Johnson) On Benthic Littoral Microalgae Assemblages, Gary Scott Shusta

University of the Pacific Theses and Dissertations

The taxonomic composition of the diatom assemblages inhabiting the substrate on the mudflat, and the effects of a cohabiting deposit-feeding invertebrate on the diatom assemblage structure are the subjects of this paper. While pelagic diatoms have received considerable attention in the literature to date, comparatively little is known about the ecology and distribution of benthic diatoms are known to be cosmopolitan in their distributions (Alee, 1950). These plants have been found to be opportunistic species in that they are quick to respond to relatively small perturbations in physical conditions. It has also been demonstrated that distinct associations of diatoms exist …

Studies On The Reproduction And Larval Biology Of Polydora Giardi Mesnil (Polychaeta: Spionidae), Randy L. Day

University of the Pacific Theses and Dissertations

There are no published accounts of larval development for P. giardi, although Mesnil (1896) determined his populations to be simultaneous hermaphrodites. The present paper describes aspects of the reproductive biology and larval development of P. girardi and presents descriptions and illustrations of developing larvae and recently metamorphosed juveniles.

Biological Aspects Of Speciation In Three Sympatric Euzonus Species At Dillon Beach, California (Polychaeta: Opheliidae), Steven Rhoads Parke

University of the Pacific Theses and Dissertations

In the present study, information concerning morphology, ecology, fertilization and larval development of three sympatric species of Eusonus is presented. Morphological similarities are reviewed in part I. These similarities correspond with significant lack of variation found in larval development (part IV). Despite these similarities, as well as the ability to cross fertilize their species, the ecological and reproductive isolating mechanisms presented in part II and II provide a positive indication of the existence of three biologically distinct species. A comparative discussion reviews the efficacy of morphological criteria in differentiating the three closely related Euzonus species.

Sediment Reworking Rates And The Feeding Ecology Of Axiothella Rubrocincta (Polychaeta: Maldanidae), Jerry David Kudenov

University of the Pacific Theses and Dissertations

In the present study, the sediment reworking rates, irrigation rates, and activity patterns of Axiotheata rubrocincta have been investigated. The results are compared with studies of other deposit feeding polychaetes.

Because sediment ingestion is a feeding process, it has been necessary to examine some aspects of the feeding morphology and ecology of A. rubrocincta. Some of these findings differed from the results of Spies (MS.). The feeding biology and morphology of two additional maldanidae, Clymenella sp. and Praxillella affinis pacifica (Berkeley, 1929) have been studied. These finding are compared with earlier studies on maldanid genera and species by Pilgrim (1965b, …

The Functional Morphology And Ecology Of Chone Mollis, Dale Brian Bonar

University of the Pacific Theses and Dissertations

Chone mollis occurs in large numbers in Tomales Bay and is an ecologically important infaunal member of the bay community. As with most marine communities, very little work has been done with individual species of the community. The present study of C. mollis is a contribution towards an understanding of the community as an ecological unit.

This study investigates the structure and function of the tube; tube-building habits; burrowing and locomotion; external anatomy; feeding; and internal anatomy of the muscular, skeletal, vascular, excretory, reproductive, and alimentary systems of C. mollis.

The Functional Morphology Of Axiothella Rubrocinta (Johnson), Robert Bernard Spies

University of the Pacific Theses and Dissertations

The family Maldanidae is a group of sedentary polychaetes having a cylindrical body with elongate, but relatively few segments. The prostomium has a dorsal pair of nuchal organs and may have eye-spots ventrally; true appendages are absent. The mouth opens ventrally on the peristomium and has an extrusible sacciform proboscis. The pygidium may be plate-shaped, funnel shaped with an internal cone, or simply cone-shaped. All maldanids inhabit tubes of sand or mud, and subject to the limitations and advantages of this habjtat.

Notes On The Natural History Of The Sabellariid Polychaete Phragmatopoma Californica, Dean Ernest Griffin

University of the Pacific Theses and Dissertations

In the coves and crevices at Natural Bridges State Park, Santa Cruz, California, one can find large masses of worm tubes constructed of sand. These tube masses often cover areas of several square feet. The tubes are usually straight and packed together in large masses. The individual tubes are about one-fourth of an inch in diameter and may be up to two and one-half feet long. The worm responsible for these masses of tubes is a small polychaete, Phragmatopoma californica.

Very little work has been done on the natural history of local sabellarlids. It is therefore the purpose of this …