Pygmy Seahare

Overview

The Pygmy Seahare (Aplysia parvula) is a small marine gastropod mollusc belonging to the family Aplysiidae. While historically considered a circumtropical species, recent taxonomic revisions have restricted the name A. parvula primarily to populations within the tropical northwest Atlantic.

Appearance

This species is characterized by a smooth, round body and a slender head with prominent oral tentacles that resemble rabbit ears. It features wing-like flaps known as parapodia, which typically display a distinct black edge. The body color is highly variable—ranging from yellow and green to brown or maroon—often depending on the specific seaweed the individual consumes. Many specimens also exhibit clusters of white spots across their skin and possess a large, black-edged hole in the center of the mantle, which reveals a fragile, plate-like internal shell.

Biology & Behavior

Like other sea hares, the Pygmy Seahare is a hermaphrodite. During reproduction, multiple individuals often gather to mate in chains, where they simultaneously act as both male and female. Shortly after mating, they deposit convoluted egg masses. These animals are known for their sporadic appearance, sometimes occurring in high abundance at a site for several months before disappearing for years. They are capable of sequestering secondary metabolites from their algal diet, which may serve as a chemical defense against predators.

Feeding

These molluscs are specialized herbivores that primarily feed on red algae, such as Laurencia obtusa and Delisea pulchra. By consuming these specific algae, they not only acquire their characteristic coloration but also accumulate chemical compounds that make them unpalatable to potential predators. In environments where their preferred red algae are scarce, they may consume green algae, which can result in a shift toward greenish body tones.