Brown Sea Cucumber, Isostichopus fuscus
Brown Sea Cucumber, Isostichopus fuscus. Tidal pool collections made in the greater Los Cabos area of Baja California Sur. Lengths between 7.5 cm (3.0 inches) and 15 cm (5.9 inches).
Brown Sea Cucumber, Isostichopus fuscus. Underwater photograph taken in Zihuatanejo Bay, Guerrero, March 2018. Photograph courtesy of Ron Woheau, Zihuatanejo.
Phylogeny: The Brown Sea Cucumber, Isostichopus fuscus (Ludwig, 1875), is a member of the Stichopodidae Family of Spiky Sea Cucumbers. The Isostichopus Genus is one of ten genera in the Stichopodidae Family, and there are four species in the Isostichopus Genus. They are also known as the Giant Cortez Sea Cucumber and the Chocolate Sea Cucumber, and in Mexico as Pepino de Mar Café and Pepino de Mar Pardo. The genus name Isostichopus comes from the Greek words meaning “equal row-feet”, referring to the uniform arrangement of tube feet (pedicels). The species name fuscus comes from the Latin meaning “dark” or “dusky”, referring to the coloration.
Morphology: The Brown Sea Cucumber is a uniform brown color or mottled dark brown over a tan background. Their bodies are large with a flattened ventral surface, a square or angular cross section, and twenty mouth tentacles. Their skin is leathery and smooth to the touch. Dorsally they are covered with cone shaped projections and twenty blunt papillae arranged in rows. Brown Sea Cucumbers reach a maximum of 16.2 cm (6.5 inches) in length and between 300 grams (0.67 lbs) and 1 kg (2.2 lbs) in weight. Two cases of albinism have been discovered in this species, one found in Loreto, Baja California Sur, and another found in Bahiá de Los Angeles, Baja California.
Habitat and Distribution: Brown Sea Cucumbers resides on rocks and sand substrates and occasionally on mud. They are found from the intertidal zone to depths up to 43 m (140 feet). They are generally found in more protected areas, where water movement will not sweep their food away. Brown Sea Cucumbers are a subtropical to tropical Eastern Pacific species tha that are found in all Mexican waters of the Pacific Ocean with the exception that they are absent from the west coast of the Baja Peninsula.
Diet: The Brown Sea Cucumber is a depositional feeder that crawls along the bottom, using their sticky tentacles to collect detritus and other organic matter, such as bacteria and fungus. Some members of the family have an annual cycle of auto-eviscerating their digestive tract and gonads to remove sediment from their digestive tracts that have been accumulated from their feeding process.
Predators: The Brown Sea Cucumber is preyed upon by fish, marine mammals, and starfish. They do have the ability to auto-eviscerate their internal organs to distract potential predators. They have the ability to regrow these organs in a matter of weeks.
Reproduction: Brown Sea Cucumbers reproduce sexually via external fertilization. The larvae are free-swimming until they settle to the bottom and become benthic. This species exhibits no sexual dimorphism unless the gonads are ripe. When this occurs the male gonads are white in color and the females are orange.
Ecosystem Interactions: The Brown Sea Cucumber’s method of feeding redistributes sediment, and therefore contributes to the general ecology. They are known to host parasitic protozoa and flatworms from the genus Anoplodium. Commensal relationships with crabs or pearlfish that are found in other sea cucumber species have not been documented for this species.
Human Interactions: The Brown Sea Cucumber is currently considered to be ENDANGERED due to overfishing. They are sold commercially as Beche-de-mer and are in high demand in Asian countries. Populations are thought to have declined by as much as 60% over the last fifty years. They are now heavily regulated, but without adequate enforcement, populations have been exceedingly slow to recover. Beche-de-mer is currently available on the internet in a sun-dried format at $100 per pound. Efforts to reestablish native populations via aquaculture have had marginal results.
Synonyms: Stichopus fuscus and Stichopus badionotus