Pineapple Sea Cucumber

The Pineapple Sea Cucumber (Thelenota ananas) is a truly distinctive and impressive inhabitant of the Indo-Pacific's tropical waters. Belonging to the family Stichopodidae, this macro-sized echinoderm is one of the largest sea cucumber species, immediately recognizable by its unique, rugged appearance. It plays a vital ecological role in maintaining the health of coral reef ecosystems, yet its populations are under significant threat. Listed as Endangered by the IUCN Red List, this species faces considerable pressure primarily from overexploitation for the global beche-de-mer trade.

Found across a vast range from the Red Sea and East Africa to Hawaii, Polynesia, the Maldives, and Australia, the Pineapple Sea Cucumber typically inhabits clean, sandy bottoms of lagoons, reef slopes, outer reef flats, and areas with coral rubble, often near large coral heads. Divers can encounter this fascinating creature at depths of 1–35 m, though it is commonly observed between 10–30 m. It thrives in warm tropical waters, generally preferring temperatures of 22–28°C.

As a crucial detritivore, the Pineapple Sea Cucumber slowly grazes across the seabed, ingesting sediment to feed on organic matter, detritus, algae, bacteria, and other small organisms. This feeding behavior is essential for nutrient recycling, bioturbating sediments, and even buffering seawater from localized ocean acidification, thereby contributing significantly to the overall health and productivity of coral reef environments. Its slow growth rate and relatively low reproductive output make it particularly vulnerable to overfishing, leading to drastic population declines in many areas.

Identification

• Size: The Pineapple Sea Cucumber is one of the largest sea cucumbers, reaching an impressive maximum length of up to 80 cm (31 inches) and weighing between 3 to 7 kg.
• Body Shape and Texture: Its thick, cylindrical body is highly distinctive, covered in numerous large, pointed, star-shaped papillae, often referred to as "teats." These projections are typically grouped in rows of 2 or 3, giving the sea cucumber a rough, "armoured," and unmistakable "pineapple-like" appearance. Deep skin folds further enhance this characteristic texture.
• Coloration: The body coloration can vary but is generally a warm reddish-orange, grey-brown, or brownish, often with darker patches or slightly darker teats. The ventral (underside) surface may appear brighter.
• Locomotion: It moves slowly across the seabed using numerous large tube feet located on its flat ventral side.
• Defense Mechanisms: When threatened, this species can employ remarkable defense strategies, including expelling sticky Cuvierian tubules to entangle predators or even eviscerating its internal organs, which can later regenerate.

The Pineapple Sea Cucumber, Thelenota ananas, inhabits the warm, tropical waters of the Indo-Pacific region, showcasing a broad distribution that spans from the Red Sea and East Africa across to Hawaii and Polynesia. This includes significant populations in the seas surrounding India, the Great Barrier Reef of Australia, the Maldives, East Indies, China, and southern Japan, extending southeast to various Pacific Islands such as Palau, Guam, Tonga, Tuvalu, and the Cook Islands.

Typically encountered by divers at depths ranging from 2–30 m, these fascinating echinoderms are most commonly observed between 10–30 m. While they can also be found in shallower waters, they thrive in average water temperatures of 26–27°C.

The Pineapple Sea Cucumber is a prominent resident of diverse coral reef ecosystems, playing a vital role in maintaining their health. Their preferred habitats include:

• Clean, sandy bottoms of lagoons.
• Sandy reef slopes and outer reef flats.
• Areas with large coral heads and coral rubble.
• Hard bottoms and coral patches.
• Reef slopes and passes.

As deposit feeders, they contribute significantly to nutrient recycling and sediment bioturbation, which are crucial processes for the overall health and productivity of coral reefs. Their activity also helps buffer seawater from ocean acidification on a local scale and contributes to the formation of "reef halos" around coral structures. These sea cucumbers are diurnally active, making them a captivating sight for divers exploring these vibrant underwater environments.

The Pineapple Sea Cucumber (Thelenota ananas) is a distinctive and substantial echinoderm, frequently observed by divers in the tropical Indo-Pacific, including dive sites like Sinandigan Wall. Known for its large size, reaching up to 80 cm, and its firm, "armoured" body covered in pointed, star-shaped papillae, this species plays a vital role in its marine ecosystem.

• Underwater Encounter Behavior: Divers will typically encounter the Pineapple Sea Cucumber as a slow-moving, benthic organism. Despite its seemingly sluggish nature, it possesses numerous large tube feet on its ventral side, allowing it to be quite mobile, traversing sandy bottoms and reef areas. It is primarily diurnal, meaning it is active during the day. When threatened, this sea cucumber employs a remarkable defense mechanism: it can shed sticky, white threads known as Cuvierian tubules from its posterior end to entangle and deter potential predators. These tubules are readily regenerated, a process that can take several weeks. In more extreme situations, it may even eviscerate, expelling some internal organs, which then regenerate over time. Divers may also observe commensal organisms, such as small crabs (e.g., Lissocarcinus orbicularis), shrimp (e.g., Zenopontonia rex), or worms (e.g., Gastrolepidia clavigera), living on or near the sea cucumber, often around its mouth or anus.
• Feeding Habits: The Pineapple Sea Cucumber is a classic deposit feeder, crucial for maintaining the health of its habitat. It ingests large quantities of sand and sediment, filtering out organic particles, microorganisms, and detritus for sustenance. This process helps recycle nutrients and bioturbate sediments, effectively cleaning the seafloor. Its diet specifically includes calcareous algae, such as those from the genus Halimeda. An individual can process several kilograms of sediment annually, excreting fine, clean sand.
• Social Structure: Observations indicate that Thelenota ananas individuals are typically found dispersed in low densities across their habitat. This suggests a largely solitary existence rather than forming dense aggregations.
• Notable Seasonal Patterns: While the Pineapple Sea Cucumber is not a migrant and remains in its native home range year-round, its reproductive patterns can exhibit seasonality. In subtropical regions, spawning generally occurs during the summer months, from January to March. In more consistently warm tropical waters, reproduction may occur throughout the year. Some studies suggest that spawning is concentrated in summer, peaking around late August, correlating with increased water temperatures. For instance, in the Maldives, the breeding season is noted from December to March. Divers are unlikely to observe direct spawning events, but understanding these patterns contributes to appreciating the species' life cycle. This species is often found in waters of 26–27°C and at depths typically between 5–30 m, though it can be found from 2–50 m.