Ecological physiology of recovery from experimental phenology of algal food deprivation in larvae of a sea urchin (Lytechinus pictus)

Authors: Griffith, Andrew; LI, NING - University Of Southern California; MANAHAN, DONAL - University Of Southern California

Submitted to: Marine Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: The study of seasonal reproductive patterns is a central theme in the biology of marine organisms. Decades of analyses of breeding strategies of marine invertebrates led to many long-standing “Rules” (e.g., Orton; Crisp; Thorson: 1920–1950s). Currently, the world’s oceans are undergoing rapid rates of change with respect to rising temperatures and other environmental variables. The extent to which these historically formative “Rules” still apply in the modern ocean is the focus of the current study. Anthropogenic-driven ocean change is altering the phenology of animal reproduction by impacting trophic mismatch of larval phases and food availability. The present study addresses these issues in larvae of the sea urchin (Lytechinus pictus), an important species in marine ecology and developmental biology. Specifically, following experimentally-simulated phenological delays in the availability of phytoplankton, an integrated analysis of whole-organism, physiological, and biochemical responses revealed: (i) the limits of larval tolerance to algal food deprivation, (ii) mechanisms of nutritional stress resilience, and (iii) a higher energy cost of subsequent growth recovery once algal food became available. These findings highlight the constraints and limitations of the “Rules” referenced above regarding life history strategies in a changing ocean.

Technical Abstract: Studies of seasonal breeding of marine invertebrates led to many important and long-standing marine biological “Rules” (e.g., Orton; Crisp; Thorson: 1920–1950s). Currently, the world’s oceans are undergoing rapid rates of change. The extent to which these historically formative “Rules” still apply in the modern ocean is the focus of the current study. Anthropogenic-driven ocean change is altering the phenology of animal reproduction by impacting trophic mismatch of larval phases and food availability. The present study addresses these issues in larvae of the sea urchin (Lytechinus pictus), an important species in marine ecology and developmental biology. Specifically, following experimentally-simulated phenological delays in the availability of phytoplankton, an integrated analysis of whole-organism, physiological, and biochemical responses revealed: (i) the limits of larval tolerance to algal food deprivation, (ii) mechanisms of nutritional stress resilience, and (iii) a higher energy cost of subsequent growth recovery once algal food became available. Contrary to expectations, unfed larvae did not deplete egg energy stores of lipid during extended periods of food deprivation. Instead, protein was the primary biochemical reserve used to fuel the metabolic cost of delayed feeding, reduced to over 80% protein depletion in unfed larvae. When algal food become available, an analysis of protein dynamics of synthesis, and turnover, and accretion showed that delayed-feeding larvae had a faster protein accretion rate. The energy cost of this compensatory catch-up strategy was, however, 2.4-fold higher. These findings highlight the constraints and limitations of the “Rules” referenced above regarding life history strategies in a changing ocean.