Living under intertidal mussels: distribution, reproduction, and condition indices in a brooding sea star, Anasterias minuta, in Patagonia, Argentina

GIL, DAMIÁN G.; REARTES, MARÍA B.; MUTTI, CAROLINA; TOLOSANO, JAVIER A.; ZAIXSO, HÉCTOR E.

MARINE BIOLOGY

SPRINGER

Año: 2018 vol. 165

0025-3162

Anasterias minuta is an abundant brooding sea star inhabiting tidepool habitats and mussel beds of Perumytilus purpuratus in Patagonia, Argentina. This study explores the influence of mussel bed complexity and tidal height on the size distribution of A. minuta living under mussel beds, and compares the abundance, reproduction, and condition indices in contrasting intertidal microhabitats (mussel hummocks and tidepools). Distribution patterns in mussel beds were explored at four sites along the coast of Argentina (45.4°S?47.4°S) during the austral spring, 2012/2017. Microhabitat comparisons were done at Caleta Cordova Norte between May 2004 and June 2005. Abundance inside mussel beds was correlated positively with mussel bed thickness and presence of mussel hummocks, and negatively with tidal height. Within mussel beds, early juveniles (recruits) and juveniles (greatest radius R < 15 mm) were generally restricted to low-tidal heights, while adults (R ≥ 15 mm) extended to mid-tidal levels. Sea stars were more abundant and larger in tidepools than under mussel beds. Numbers of recruits and juveniles increased significantly under mussel hummocks during austral spring and summer, coinciding with the release and subsequent growth of early juveniles. Brooding and gonadal cycles were synchronized between the microhabitats; however, the brooding cycle was nearly 2 months shorter under mussel hummocks (April?August) than in tidepools (April?October). The sea stars under mussels were smaller, had a less developed body wall, and greater gonadal production, indicating that more energy was allocated to reproduction compared to sea stars of similar size from tidepools. Further studies are needed to identify the specific environmental conditions that led to the observed adaptations and to understand the underlying physiological mechanisms.