What Do Sea Cucumbers Eat?

Sea cucumbers, a fascinating and ecologically important group of marine invertebrates, have a diverse and interesting feeding behavior. These creatures, belonging to the class Holothuroidea, mostly feed on debris in the benthic zone of marine environments. However, some species, such as pelagic cucumbers and the deep-sea holothurian Rynkatropa pawsoni, have unique diets and feeding habits that set them apart from their benthic counterparts.

General Feeding Behavior of Sea Cucumbers

The majority of sea cucumbers are scavengers, consuming plankton and decaying organic matter found in the ocean. They have a highly efficient feeding mechanism that includes positioning themselves in ocean currents and using their open tentacles to catch passing food. Additionally, they sift through bottom sediments using these same tentacles, allowing them to efficiently gather nutrients from a wide range of marine environments.

Diverse Feeding Strategies

While most sea cucumbers exhibit similar feeding behaviors, some species have developed unique strategies to meet their dietary needs. Pelagic cucumbers, for instance, are known to undertake extended migrations and feed on plankton and small marine organisms. Meanwhile, the deep-sea holothurian Rynkatropa pawsoni has formed a commensal relationship with deep-sea anglerfish, benefiting from the anglerfish's own food intake.

Internal Anatomy and Digestive System

Sea cucumbers possess a complex internal anatomy that supports their nutrient intake and processing. A pharynx, located behind the mouth, is surrounded by a ring of ten calcareous plates that form the bulk of the skeletal structure in many species. These plates not only provide structural support but also attach to the muscles that retract the tentacles into the body for protection or adapt to the internal body walls, which contain the main muscles responsible for movement.

The digestive system of sea cucumbers varies among species. Many have an oesophagus and a stomach, while others directly connect their pharynx to the intestine. The intestine is typically long and coiled, looping through the body three times before terminating in a cloacal chamber or as the anus. This long and folded digestive tract allows for efficient absorption and processing of nutrients, supporting their diverse feeding habits and survival in marine environments.