Common Spider Conch

Overview

The Common Spider Conch (Lambis lambis) is a large, distinctive marine gastropod widely recognized for its robust shell and unique, spider-like appearance. It is a common inhabitant of shallow tropical waters across the Indo-West Pacific, where it plays an active role in benthic ecosystems as a grazer.

Distribution & habitat

This species is widespread throughout the Indo-West Pacific, ranging from East Africa and the Red Sea to maritime Southeast Asia, Japan, northern Australia, and parts of the Pacific. It typically occupies shallow, nearshore environments, including reef flats, coral-rubble bottoms, seagrass beds, and mangrove areas. It is frequently found in association with red algae.

Appearance

The shell is heavy and robust, often reaching an average length of 18 cm. Its most defining feature is a widely flared outer lip adorned with six hollow, spine-like projections known as digitations. The shell exhibits clear sexual dimorphism: males generally possess shorter, posteriorly bent digitations, while females feature longer, dorsally recurved ones. The exterior is typically cream or white with mottled brown, purplish, or black patches, while the interior is glazed in vibrant shades of pink, orange, or purple.

Biology & behavior

Spider conchs are herbivorous, feeding primarily on fine red algae. They move across the substrate using a unique, leaping locomotion powered by a muscular foot and a sharp, knife-like operculum. The species is gonochoric and reproduces via broadcast spawning, with females often laying long, coiled egg strings that are sometimes held under the shell's lip until hatching. The larvae are planktonic before settling to the seafloor to begin their juvenile stage.