Numerous studies have investigated how sessile marine prey use chemical and structural defenses to deter consumers. Much less is known regarding species that are more behaviorally complex and may integrate escape and refuging behavior with traits that deter consumers. In addition, few studies have examined prey defenses in species from non-coral reef habitats, such as soft-sediments, oyster reefs, etc., or from the deep-sea. I investigated the palatability and use of consumer deterrents in marine worms (Annelida, Hemichordata, Nemertea, Platyhelminthes) from shallow-waters and from deep-sea hydrothermal vents and hydrocarbon seeps to generalist shallow-water fishes and crabs. Of the 81 worm species surveyed, 30 (37%) were unpalatable to at least one sympatric consumer. Unpalatable species were detected in every phylum investigated, but Sabellid and Terebellid polychaetes were the taxonomic groups where unpalatable species were most frequent. Of the 30 distasteful species, eleven produced extracts that deterred feeding, while nine appeared to have structural traits that deterred consumers. The mechanism producing unpalatability for the other 12 species could not be determined. To examine palatability as a function of various ecological traits, distastefulness was examined with respect to the following: coloration, degree of exposure to epibenthic predators, mobility, the type of substrate worms were associated with (unconsolidated sediments versus more structured habitats), and latitude (high versus low). Most unpalatable worms were brightly colored, exposed to epibenthic predators, sedentary, lived on more structured habitats, and occurred in lower latitudes. In contrast, most palatable species were drab, sheltered from epibenthic predators, mobile, inhabited unconsolidated sediments, and were from higher latitudes. Of these five traits, overtness to epibenthic consumers appeared to be the trait most responsible for determining palatability for most worms. For worms with morphologically distinct body parts, predator deterrents were allocated to exposed body parts, while more sheltered body parts tended to be palatable.

Unpalatable worms that utilized predator deterrents may be less constrained by predation pressure and consequently, (1) may persist during seasons when consumer pressure is highest, (2) may be freer to exploit resources by exposing feeding appendages for long periods of time, (3) may forage on surface sediments and gain access to more recently arriving food, and (4) may forage actively for specific prey, even when their own potential consumers are active. Palatable species, on the other hand, may be more constrained by risk of predation, feeding on sub-surface sediments that may container a lower organic content, foraging only when consumers are less active, and may decrease in density when consumer pressure is high.

As with shallow-water species, most unpalatable deep-sea species (4 of 5 out of a total of ten species investigated) were sedentary, however, these sedentary species all had unpalatable body parts that were sheltered from epibenthic consumers, residing inside tough tubes or a thick shell. Distasteful body parts of these four species contained chemoautotrophic endosymbiotic bacteria, which all produced crude extracts that were deterrent to at least one consumer, suggesting that bacteria may be responsible for deterrence.