High variability in egg size and energetic content among intertidal mussels

Area of Science:

• Marine Biology
• Life-History Theory
• Reproductive Ecology

Background:

• Maternal investment is crucial in life-history theory, but variation scales (individual vs. population) are often unreported.
• Understanding variation in maternal investment is key to predicting population dynamics and evolutionary trajectories.

Purpose of the Study:

• To quantify variability in maternal investment (egg and larval traits) in Mytilus californianus.
• To determine the relative contributions of female, site, and month to this variation.
• To investigate correlations between maternal traits and offspring investment.

Main Methods:

• Examined egg volume, egg energy content, and initial larval size in Mytilus californianus.
• Collected samples from four sites near Point Conception, California, in June and September 2001.
• Analyzed effects of female, site, and month on measured offspring traits.

Main Results:

• Individual females showed substantial variation in egg volume (up to 57%) and energy content (up to 116%).
• Larval size variation was minimal compared to egg traits, with a maximum difference of 11% among females.
• No significant correlations were found between female body size and offspring traits, or between egg traits and larval size.

Conclusions:

• The primary source of variation in maternal investment for Mytilus californianus is among individual females.
• Spatial (site) and temporal (month) factors play a minor role in maternal investment variation in this system.
• Individual variation in maternal investment has significant implications for understanding population-level responses and evolution.