Sea cucumber
Sea cucumbers comprise the class Holothuroidea within the phylum Echinodermata, consisting of elongated, flexible-bodied marine invertebrates that lack the rigid endoskeletons typical of other echinoderms like starfish and urchins, instead featuring microscopic ossicles embedded in leathery skin.[1][2] Over 1,700 extant species exist, distributed across all oceans in benthic habitats ranging from shallow intertidal zones to deep-sea floors exceeding 8,000 meters.[3][4] These animals primarily function as detritivores, ingesting seafloor sediment to extract organic matter, thereby performing bioturbation that oxygenates substrates, recycles nutrients, and mitigates organic buildup to support ecosystem health and resilience, including coral reef protection against sediment overload and disease.[5][6] Their feeding tentacles, modified tube feet arranged in a crown around the mouth, facilitate suspension or deposit feeding depending on species and environment.[7] Sea cucumbers hold substantial commercial value, particularly in Asia where dried preparations (bêche-de-mer) are consumed for purported nutritional and medicinal benefits, driving intensive fisheries that have depleted stocks in numerous regions and prompted calls for sustainable management to avert ecological collapse.[8][9] Defining traits include defensive evisceration of viscera, which they can regenerate, and diverse morphologies from worm-like forms to robust, warty bodies adapted to varied pressures and predation.[10][7]Introduction
General Description
Sea cucumbers are marine invertebrates belonging to the class Holothuroidea in the phylum Echinodermata, distinguished by their soft, elongated, cylindrical bodies that resemble cucumbers, typically covered in a leathery integument rather than the rigid ossicles or spines characteristic of other echinoderm classes such as starfish or sea urchins.[2] These bottom-dwelling animals inhabit seabeds from shallow coastal waters to deep ocean trenches, exhibiting a flexible body plan adapted for slow crawling or burrowing via tube feet arranged in rows along the ventral surface.[2] A notable defensive adaptation in many holothuroids involves the expulsion of Cuvierian tubules—branching, adhesive filaments discharged from the cloaca to ensnare predators, providing an effective, albeit sacrificial, barrier that exploits the entangling properties of mucus and coelomocytes for mechanical deterrence.[11] Complementing this, sea cucumbers possess pronounced regenerative abilities, capable of restoring lost or autotomized structures, including the aforementioned tubules, through processes involving cellular dedifferentiation and proliferation over weeks.[12] In benthic ecosystems, sea cucumbers function predominantly as detritivores and deposit feeders, processing large volumes of sediment to extract organic detritus, which drives bioturbation, enhances organic matter mineralization, and facilitates the efflux of nutrients like ammonium to support overlying algal and microbial productivity.[13] [14] This sediment reworking aerates the substrate and recycles essential elements such as nitrogen and phosphorus, underscoring their causal role in maintaining nutrient dynamics and ecosystem resilience on the ocean floor.[5]Global Distribution and Diversity
Sea cucumbers inhabit marine environments worldwide, ranging from intertidal zones in coastal areas to the deepest ocean trenches at depths up to approximately 9,000 meters.[7] In hadal zones beyond 8,900 meters, they dominate the macrofaunal biomass, comprising up to 90% of the total mass.[15] Over 1,100 extant species have been described, with estimates suggesting up to 1,800 when accounting for recent discoveries, primarily distributed across benthic habitats in tropical, temperate, and polar seas.[1] The greatest species richness occurs in the Indo-West Pacific, particularly coral reef systems of Southeast Asia, where biodiversity hotspots include Indonesia, the Philippines, and Papua New Guinea, as evidenced by fishery surveys and taxonomic inventories.[16] [17] These organisms demonstrate physiological adaptability to fluctuating environmental conditions, tolerating salinities typically between 27 and 35 parts per thousand through osmotic regulation mechanisms observed in species like Stichopus japonicus.[18] Temperature tolerances vary by species, with tropical forms thriving in warmer waters and temperate or polar species enduring cooler regimes, as supported by experimental studies on growth and survival responses.[19]Taxonomy and Phylogeny
Evolutionary Origins and Fossil Record
Sea cucumbers, classified within the class Holothuroidea, represent an early-diverging lineage within the subphylum Echinozoa of echinoderms, with molecular clock analyses estimating their divergence from other echinoderm clades around 540 million years ago during the early Cambrian period.[20] This timing aligns with the Cambrian explosion, when predation pressures intensified, favoring morphological innovations such as the reduction of pentaradial symmetry in favor of a bilateral, elongated body plan.[21] The shift to a vermiform shape enhanced burrowing efficiency in soft sediments, enabling infaunal lifestyles that minimized exposure to surface predators through streamlined propulsion via longitudinal muscles and reduced cross-sectional area for sediment displacement.[22] The fossil record of holothuroids is sparse, primarily consisting of isolated ossicles from the endoskeleton rather than complete body fossils, due to their predominantly soft-bodied construction and low mineralization.[23] Putative early holothurians appear in Cambrian deposits, such as the Burgess Shale (~505 million years ago), where Charles Walcott identified soft-bodied forms resembling modern holothuroids based on tubular structures and tentative ossicle-like elements, though subsequent re-evaluations have questioned their precise affinity, suggesting they may represent stem-group echinoderms or unrelated soft-bodied taxa.[24] More definitive body fossils emerge in the Ordovician, including articulated specimens from Middle Ordovician (~460 million years ago) strata in Wales, described as the earliest unambiguous holothurians with features like elongated bodies and simple tube feet.[25] Fossil-calibrated phylogenies and molecular data indicate that crown-group holothuroids diversified during the Paleozoic, with several lineages surviving the end-Permian mass extinction (~252 million years ago), after which ossicle-based records become more abundant.[26] The Late Ordovician yields evidence of specialized groups like synallactids, implying a pre-Ordovician evolutionary history extending into the Cambrian for stem forms, consistent with the adaptive advantages of sediment-dwelling under causal pressures from biotic interactions in expanding marine benthic ecosystems.[27] The oldest confirmed body fossil, Porosothyone from the late Silurian of Australia (~420 million years ago), exhibits primitive traits like simple tentacles and reduced ossicles, underscoring gradual refinement of the holothuroid bauplan.[28]Classification and Major Orders
The class Holothuroidea encompasses approximately 1,800 extant species of echinoderms, classified into seven orders based on integrative analyses of morphological traits and molecular data from mitochondrial and nuclear genes.[29] This framework, established through phylogenomic studies, overturned the traditional six-order system by demonstrating the paraphyly of Aspidochirotida and elevating subordinate clades to ordinal rank.[30] DNA barcoding and multigene phylogenies since 2010 have further refined family-level boundaries, particularly within Dendrochirotida, by resolving cryptic species and adjusting generic placements based on ossicle morphology and genetic divergence.[31] The orders reflect adaptive diversification in body architecture and ossicle arrays, with Apodida comprising vermiform species lacking tube feet and featuring reduced or absent ossicles, representing about 10% of holothuroid diversity.[30] Dendrochirotida includes forms with branched oral tentacles and arborescent body plans, encompassing over 500 species across 15 families, where recent phylogenomics have consolidated monophyletic groupings despite prior morphological ambiguities.[29] Elasipodida and Molpadida exhibit specialized deep-sea adaptations in tube foot arrangements and body elongation, while Persiculida and Synallactida are smaller clades distinguished by unique calcareous ring structures and gonad positions.[30] Holothuriida, formerly the core of Aspidochirotida, dominates with roughly 50% of species, characterized by peltate tentacles, respiratory trees, and deposit-feeding specializations supported by robust ossicle tables; this order includes commercially significant families like Holothuriidae and Stichopodidae.[29] These revisions underscore causal links between genetic lineages and morphological innovations, such as the evolution of sediment-processing mechanisms in Holothuriida versus suspension-capture in certain dendrochirotids, without implying normative superiority in ecological roles.[30] Family counts vary, with Holothuriida alone holding over 10 families, while Apodida has fewer but phylogenetically basal forms.[31]| Order | Approximate Species Share | Key Morphological Traits |
|---|---|---|
| Apodida | ~10% | Vermiform body, absent/reduced tube feet and ossicles[30] |
| Dendrochirotida | ~30% | Branched tentacles, dendriform habitus[29] |
| Elasipodida | ~5% | Modified tube feet for substrate interaction[30] |
| Holothuriida | ~50% | Peltate tentacles, respiratory trees, table ossicles[29] |
| Molpadida | ~3% | Elongated, burrowing forms[30] |
| Persiculida | <1% | Specific gonad and ring features[29] |
| Synallactida | ~1% | Derived from aspidochirotid stock, unique ossicles[30] |
Anatomy and Physiology
Body Plan and Endoskeleton
Sea cucumbers possess an elongated, sausage-shaped body that contrasts sharply with the rigid, plated structures of other echinoderms such as starfish and sea urchins. The body wall is composed of a thick, leathery dermis rich in collagen fibers, providing tensile strength while allowing significant flexibility for burrowing and evasion.[2][1] Unlike the continuous calcareous test of many echinoderm relatives, the endoskeleton of sea cucumbers is highly reduced, consisting of isolated microscopic ossicles—tiny, calcified spicules embedded singly or in small clusters within the dermis. These ossicles, often rod-shaped, buttons, or tables varying by species and body region, prevent complete liquefaction of the integument under tension but do not confer rigidity.[2][32] This dispersed skeletal architecture supports a hydrostatic system, where coelomic fluid acts as the incompressible core, opposed by circular and longitudinal muscle bands in the body wall for controlled contraction and elongation—enabling body lengths to shorten to one-fifth or extend beyond normal during locomotion or stress.[33][1] Morphological variations in body form occur across orders; for instance, members of Apodida exhibit slender, vermiform shapes lacking tube feet, with some deep-sea genera like Synaptula developing highly branched, dendriform extensions that enhance surface area for attachment to substrates such as sponges.[1] Anteriorly, the mouth is encircled by 8 to 30 retractable tentacles, which vary from simple digitate forms in deposit-feeders to peltate or pinnate structures in suspension-feeders, facilitating particle capture without altering the core body plan's flexibility.[34] This adaptable endoskeleton underpins exceptional regenerative capacity; experimental evisceration studies on species like Holothuria demonstrate that torn mesentery edges thicken into blastemal tissue, reforming a functional intestine within 3 to 4 weeks under ambient seawater conditions, with ossicle redeposition restoring dermal integrity concurrently.[35] Such regrowth relies on the modular spicule array, allowing rapid remodeling without structural collapse, as verified in controlled aquarium trials where full anterior viscera restoration occurred by day 21 post-injury.[36]Digestive and Respiratory Systems
The digestive system of sea cucumbers forms a continuous tubular tract from the mouth to the cloaca, facilitating deposit feeding on organic-rich sediments. The mouth is encircled by 8 to 30 tentacles—modified tube feet that are typically peltate or digitate—which collect and direct particulate matter, including detritus and microorganisms, into a short esophagus for initial ingestion.[37] The foregut, comprising the anterior intestine, processes incoming material amid a microbiota dominated by Proteobacteria, while the midgut (medial intestine) supports microbial fermentation and nutrient extraction through symbionts like Bacteroidetes.[37] The hindgut, or posterior intestine, compacts residues and expels feces via the cloaca, yielding processed material cleaner than ingested sediment due to selective microbial breakdown.[37] Respiration occurs via a pair of dendritic respiratory trees branching from the cloaca, which actively pump seawater through their thin-walled branches for diffusive oxygen uptake, compensating for low ambient levels in benthic habitats.[38] These structures, often filling much of the posterior body cavity, exhibit plasticity in function, with oxygen consumption rates increasing significantly during metabolic demands like reproduction—up to twofold in Apostichopus japonicus—and correlating positively with body mass (r=0.913, p<0.001).[38] Water influx supports not only gas exchange but also excretion, enabling survival in oxygen-poor sediments where diffusion alone would suffice minimally.[38] Evisceration serves as an antipredator defense, involving rapid expulsion of the digestive tract and respiratory trees—either anteriorly via the mouth or posteriorly—often laced with viscous, distasteful fluids to deter attackers.[39] Laboratory inductions using 0.45 M KCl injections in species like Eupentacta quinquesemita trigger autotomy at mesentery junctions within 15 minutes, followed by regeneration: anterior portions reform via mesenchymal-epithelial transitions forming tubular rudiments, fusing with posterior regrowth from the cloaca remnant in 2–3 weeks, as confirmed by histological tracking of 86 specimens.[39] This capacity underscores anatomical adaptations prioritizing escape over immediate organ integrity.[39]
Nervous, Circulatory, and Locomotive Systems
Sea cucumbers possess a decentralized nervous system lacking a centralized brain, consisting primarily of a circumoral nerve ring encircling the mouth and five radial nerve cords extending posteriorly along the body axes.[40] These nerves are hollow tubular structures divided into ectoneural (superficial, sensory-motor) and hyponeural (deeper, motor) components, with the ectoneural part featuring longitudinal strands and the hyponeural part thickened into cords.[40] This diffuse organization supports reflexive coordination, such as the rapid retraction of tube feet or body wall contraction in response to mechanical stimuli, without requiring complex central processing suited to their often sedentary or slow-moving habits.[41] The circulatory system is open and relies on coelomic fluid as the primary transport medium for nutrients, gases, and waste, directly bathing internal organs rather than being confined to vessels.[42] Unlike most echinoderms, sea cucumbers contain hemoglobin within coelomocytes suspended in this fluid, enhancing oxygen-carrying capacity in low-oxygen sediments.[43] Fluid circulation occurs via peristaltic contractions of the body wall and respiratory trees, augmented by a rudimentary hemal system of sinuses and vessels lacking a distinct heart; some species, like Stichopus moebii, exhibit ciliated epithelial linings in blood vessels to aid flow.[42] Coelomocytes also contribute to immune functions, migrating through the fluid to sites of injury or infection.[44] Locomotion in adult sea cucumbers depends on the water vascular system, which hydraulically operates thousands of tube feet (podia) arranged in three longitudinal rows for adhesion, crawling, and burrowing into sediments at slow rates typically under 10 cm per minute.[45] Tube feet extend and contract via ampullae reservoirs drawing seawater through the madreporite, enabling stepwise propulsion coordinated by radial nerves; species in flowing waters adjust podia deployment to counter currents, reducing velocity with increasing flow speed.[45] In larvae, such as the auricularia stage, movement shifts from microtubule-based ciliary bands for planktonic swimming to preparatory tube foot development during metamorphosis, reflecting ontogenetic adaptation from dispersive to benthic lifestyles.[46]Ecology and Life History
Habitats and Environmental Adaptations
Sea cucumbers (class Holothuroidea) occupy diverse benthic habitats across global oceans, ranging from intertidal zones to abyssal plains beyond 8,000 meters depth, with preferences for soft sediments like sandy mud and silt, as well as hard substrates including rocky reefs, gravel, and shell debris.[8][47] Species distribution data from trawl surveys indicate niche partitioning, where low-value species predominate in shallow waters (1–10 m) on finer sediments, while commercial holothuroids favor deeper hard substrates (20–100 m).[48] Intertidal and subtidal forms, such as those in rocky pools or seagrass beds, tolerate emersion through physiological adjustments including enhanced antioxidant defenses to mitigate oxidative stress from desiccation.[49][50] In deeper waters, holothuroids adapt to gradients of pressure and low temperatures, with abyssal species like Chiridota inhabiting mud-covered seafloors where hydrostatic pressure exceeds 800 atmospheres; their coelomic fluid provides buoyant support analogous to hydraulic systems in shallower kin.[51] Trawl-based abundance estimates from surveys in regions like the Southern California Bight reveal associations with specific invertebrate assemblages on gravelly bottoms at 100–200 m, contrasting with epifaunal clusters on reefs at shallower depths.[52] Deep-sea forms exhibit reduced metabolic rates suited to near-freezing conditions (around 2–4°C), enabling persistence in oxygen-minimum zones.[53] Physiological experiments quantify tolerances, with many species enduring salinities of 22–36 ppt (optimal 27–31.5 ppt for growth) and temperatures spanning 5–35°C depending on biogeographic origin—temperate Apostichopus japonicus thriving at 10–15°C and 28–34 ppt, while tropical Holothuria scabra shows narrower thermal limits.[54][55][56] Salinity stress beyond 40 ppt induces evisceration in sensitive taxa like Holothuria atra, underscoring substrate-mediated buffering in estuarine habitats.[57] These parameters, derived from laboratory assays and field distributions, highlight species-specific resilience without implying uniform vulnerability across clades.[19]Locomotion, Feeding, and Diet
Sea cucumbers achieve locomotion primarily through the coordinated action of tube feet arranged in three longitudinal rows along the ventral surface, which operate via hydraulic pressure from the water vascular system to grip the substrate and propel the body forward.[2] Many species supplement this with peristaltic body undulations or waves, particularly during burrowing into soft sediments, where the anterior end is anchored while the posterior contracts to advance.[58] Movement speeds vary significantly among species and are influenced by factors such as body size, substrate type, temperature, and flow velocity; for instance, Holothuria arguinensis exhibits an average daily displacement of approximately 10 meters, while smaller or reef-dwelling forms like the warty sea cucumber cover only about 15 cm per day.[59][60] Burrowing species, such as Holothuria scabra, can descend into sediment to depths of several centimeters, using tube feet to excavate and stabilize their position.[61] Feeding in most sea cucumbers occurs via a specialized oral apparatus consisting of 8 to 30 peltate or pinnate tentacles, which are extended to the seafloor to collect surface sediments laden with organic detritus, microalgae, and bacteria.[62] These tentacles sweep material into the mouth in a rhythmic motion, with particles passed to the pharynx and esophagus for initial sorting; inorganic fractions are often rejected as pseudofeces.[62] Deposit-feeding dominates, with individuals processing substantial volumes of sediment—equivalent to 75% or more of their body weight daily during active periods—to extract nutrients, as observed in species like those in the genus Holothuria.[63] Field measurements indicate ingestion rates of 10-50 grams of sediment per day for typical individuals under 100 grams body mass, contributing to bioturbation and oxygenation of benthic layers.[64] The diet consists predominantly of refractory organic matter from decaying plant and animal debris, enriched by microbial films on sediment grains, though some suspension-feeding forms, such as Cucumaria miniata, capture plankton via extended tentacles.[65] Gut microbial symbionts play a crucial role in digestion, with communities enriched for anaerobic bacteria that break down complex carbohydrates and xenobiotics, facilitating decomposition and releasing bioavailable nutrients like nitrogen and phosphorus for recycling into the ecosystem.[66][67] This symbiosis enhances digestive efficiency, as evidenced by elevated metabolic genes for organic matter processing in sea cucumber feces compared to ambient sediments.[68]Reproduction, Development, and Growth
Most species of sea cucumbers are gonochoristic, with separate sexes and a single gonad per individual, though differentiation between males and females typically requires microscopic examination of gametes due to subtle external differences.[1] Sexual reproduction predominates via broadcast spawning, in which adults synchronously release gametes into the water column for external fertilization, often triggered by environmental cues such as lunar cycles, temperature rises, or phytoplankton blooms.[69] A minority of species display simultaneous hermaphroditism or protandric sex change, enabling self-fertilization or sequential mating, but these are exceptions rather than the norm across the class Holothuroidea. Fertilized ova typically develop into planktotrophic auricularia larvae, ciliated planktonic forms that actively feed on microalgae such as diatoms and flagellates to fuel growth through the larval stages.[70] The auricularia phase transitions to non-feeding doliolaria and pentactula larvae, culminating in settlement onto suitable benthic substrates—often algae, rocks, or sediments—followed by metamorphosis into pentaradial juveniles, a process spanning 20 to 60 days post-fertilization depending on species, water temperature (optimal at 24–28°C for many tropical forms), and larval nutrition.[71] For example, in Holothuria mammata, juveniles emerge around 21 days, while in Holothuria forskali, full metamorphosis requires over 40 days.[72][71] Juvenile growth occurs benthically, with individuals transitioning to deposit or suspension feeding as they develop the adult body plan, including tube feet and respiratory trees; rates vary by habitat and food supply, but sexual maturity is generally attained in 1 to 5 years.[73] Temperate species like the giant red sea cucumber (Parastichopus californicus) may require 4 years, whereas faster-growing tropical species such as Holothuria scabra can mature in 1–2 years under aquaculture conditions with abundant organic sediments.[52][73] Viviparity or brooding, observed in roughly 30 species primarily within orders Apodida and Dendrochirotida, deviates from this pattern by retaining embryos internally or externally until they hatch as fully formed juveniles, bypassing the dispersive larval stage.[1][74] This strategy, rarer than broadcast spawning (prevalent in >95% of species), empirically correlates with low adult densities in patchy or deep-sea habitats, as internal development maximizes fertilization probability and offspring survival by shielding them from planktonic predation and dispersal losses, though it limits gene flow compared to pelagic larvae.[74][75]Behavior, Symbiosis, Predation, and Defenses
Sea cucumbers exhibit limited social behavior, typically maintaining solitary lifestyles outside of reproductive periods, though some species form temporary aggregations during spawning events synchronized by chemical cues released from males. In Holothuria arguinensis, water conditioned by spawning males attracts both sexes and induces spawning responses, demonstrating olfactory-mediated conspecific aggregation.[76] Similarly, triterpenoid saponins with disaccharide structures serve as pheromones promoting aggregation in certain holothuroids, distinct from those in non-aggregating congeners.[77] These cues facilitate mass spawning but do not indicate advanced kin discrimination, with empirical studies focusing primarily on sex- and species-specific signaling rather than familial recognition.[78] Symbiotic associations in sea cucumbers often involve commensal relationships that provide shelter to associates without apparent detriment to the host. Pearlfish (Carapidae) enter the cloaca of species like Holothuria and Stichopus, residing internally during the day to evade predators, emerging nocturnally to feed; this interaction benefits the fish via protection while sea cucumbers show no significant physiological cost in documented cases.[79] Certain shrimp and crabs also utilize sea cucumbers as mobile habitats or cleaning stations, clinging externally or associating with respiratory structures for camouflage and transport.[80] These mutualisms enhance associate survival in predator-rich reefs but remain facultative, with hosts tolerating symbionts through behavioral indifference rather than active recruitment. Predators of sea cucumbers include demersal fish, octopuses, sea stars, and predatory gastropods such as triton snails (Charonia tritonis), which target exposed individuals via drilling or engulfment.[81] In response, many species deploy mechanical and chemical defenses; holothuroids lacking rigid structures rely on autotomy of viscera or ejection of specialized Cuvierian tubules from the cloaca, which rapidly elongate into sticky, adhesive strands that entangle attackers.[82] These tubules contain holothurin, a triterpenoid saponin toxin that deters predation through cytotoxicity and repellency, biosynthesized via mevalonate pathways and stored in high concentrations.[83] Additional defenses include body wall saponins and metabolic evasion, with some species reducing activity to minimize detection. Under environmental stress such as desiccation or hypoxia in intertidal zones, aestivating species like Apostichopus japonicus enter a torpor state characterized by profound metabolic depression, reducing oxygen consumption by up to 71% over weeks to months.[84] This adaptation involves transcriptional downregulation of energy-intensive pathways, gut microbiota shifts, and atrophy of non-essential tissues, enabling survival in anoxic sediments for periods exceeding 100 days without feeding.[85] Recovery upon rehydration restores metabolic rates, underscoring the strategy's reversibility and reliance on biochemical reprogramming rather than structural modifications.[86]Human Interactions
Culinary Uses and Nutritional Value
Sea cucumbers are harvested and processed primarily for consumption in dried form, known as bêche-de-mer, which serves as a delicacy in East Asian cuisines, especially Chinese, where the rehydrated product is incorporated into soups, stews, and braised dishes for its gelatinous texture.[87][88] Traditional preparation involves eviscerating the fresh animal, boiling it to remove impurities and achieve contraction, salting if needed, and repeated sun-drying cycles until the body wall hardens into a lightweight, storable product that can expand significantly upon rehydration in water or broth prior to cooking.[88] In Japanese cuisine, dried forms are sometimes boiled in green tea or used in other preparations, reflecting regional adaptations of this ancient practice dating back over a millennium.[89] High-value species such as Holothuria scabra (sandfish) command premium prices in international markets due to their thick body walls and desirable texture post-processing, often fetching up to US$2000 per kilogram dry weight.[90] Global trade in bêche-de-mer reached a market value of approximately US$510 million in 2019, driven largely by demand from Asia, though values have fluctuated with supply constraints and species availability.[91] Nutritionally, dried sea cucumbers exhibit high protein content ranging from 41% to 63% by dry weight, derived mainly from the collagen-rich body wall, alongside low fat levels typically under 1%.[92] Mineral composition includes notable amounts of sodium as a primary component, with trace elements varying by species and processing method.[93] Mucopolysaccharides constitute a portion of the carbohydrate fraction, contributing to the product's structural qualities upon cooking.[94]| Nutrient (dry weight basis) | Approximate Range (%) | Source Notes |
|---|---|---|
| Protein | 41–63 | Predominantly collagen-based; varies by species like Parastichopus californicus.[92][95] |
| Fat | <1 | Minimal lipid content across tissues.[92] |
| Ash (minerals) | 9–12 | Includes sodium and other inorganics.[95][93] |
| Carbohydrates | 5–9 | Partly mucopolysaccharides.[95] |