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Date Permissions Signed

3-8-2013

Date of Award

2013

Document Type

Masters Thesis

Degree Name

Master of Science (MS)

Department

Environmental Sciences

First Advisor

Sulkin, Stephen D.

Second Advisor

Bingham, Brian L., 1960-

Third Advisor

Donovan, Deborah Anne, 1964-

Abstract

The survival and distribution of benthic invertebrate larvae have important implications for the population dynamics of the species and, due to predator-prey interactions, can have important consequences to the communities in which they live. Nutrition and food availability are among the primary determinants of larval success. The feeding strategy of brachyuran larval crabs is a complex combination of omnivory and selection. Although ingestion of microalgae by larvae has been observed, their role in satisfying larval nutritional needs is unclear. This study examined the role ingesting phytoplankton plays in the nutrition of larval crabs by simulating conditions in which algal prey might increase survival or accelerate development. The alga, Isochrysis galbana, and zooplankters Artemia sp. nauplii and rotifer Brachionis plicatilis, were used as prey in experiments with larvae of three brachyuran crab species representing different families and hatching seasons: Lophopanopeus bellus, Metacarcinus (Cancer) magister, and Hemigrapsus nudus. Experimental conditions included exposure of larvae to algae alone immediately upon hatching, interspersed periods of algal and zooplankton prey and mixed algae-zooplankton prey. In post-hatching feeding experiments with L. bellus and M. magister, survival decreased and development was delayed as the initial period of starvation or algal feeding prior to zooplankton feeding was extended, with no differences between the unfed and algal-fed diets. Mean Point-of-No-Return (PNR) values for unfed and algal-fed treatments were not significantly different from one another and post-hoc contrasts showed no difference between the two experimental treatments, except in a few instances where stage duration of L. bellus larvae fed algae for one day was shortened by just under a half-day, and for M. magister larvae where larvae fed algae for three days had 16.7% survival while all corresponding unfed larvae died. In patchy prey experiments L. bellus survival and H. nudus survival and development rate were unaffected by exposure to algae; however, presence of algae accelerated L. bellus larval development by 5% (0.77 days). Results from mixed prey diet experiments showed no difference in L. bellus survival and development rate when algae supplemented zooplankton. Results indicate that, overall, I. galbana does not significantly contribute to larval survival or development rate. Benefits of an opportunistic feeding strategy in which widespread, seemingly inefficient feeding on algae occurs might be contingent upon particular predator-prey species interactions (i.e. a more nutrient-laden alga), or may only pay off in particular conditions (i.e. a sparse prey field).

Type

Text

Publisher

Western Washington University

OCLC Number

830879916

Digital Format

application/pdf

Genre/Form

Academic theses

Language

English

Rights

Copying of this thesis in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this thesis for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.

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