Among the most colorful shrimp found at coral reefs are 1) harlequin shrimp; 2) red banded pistol shrimp; 3) boxer shrimp; 4) sexy shrimp (anemone shrimp) and 5) cleaner shrimp. Harlequin shrimp feed mainly on starfish and to a lesser degree, sea urchins. Pistol shrimp get their name from the loud “shooting” or “popping” noise they produce with their one over-sized claw. Boxer shrimp are one of the more active species. The busily scamper around the reef foraging any organic material they can get their claws on. They are very territorial and fighter off other shrimp, even of their own kind. Sexy shrimp get their name for the way the wiggle their rear ends while cleaning their host anemone.
Cleaner shrimp pick off parasites, fungus and pests from fish. Some fish pull up to sections of reef inhabited with cleaner shrimp like cars pulling up to a car wash and wait on line for their turn to be cleaned. The shrimp even climb into the mouth's of moral eels to clean their teeth. They also provide free medical service by cleaning parasites which congregate around the fish's open wounds and drive away small predators that feed on the fishes eggs.
A number of shrimp have symbiotic relations with other marine life. Commensal shrimps live among the tube-feet on starfish's arm, grazing on dead skin cells, mucus and other detritus. Sea urchins that look like they trapped inside a small localized blizzard are in fact surrounded by hundreds of tiny shrimp in the process of laying their eggs. Some of these shrimp have kangaroo-like pouches. Shrimpfish are small fish that search for minuscule shrimp and inhale them in their tubelike mouths.
Websites and Resources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Fishbase fishbase.se ; Encyclopedia of Life eol.org ; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems
Redbanded Coral Shrimp — Cleaner Shrimp
Redbanded coral shrimp (Scientific name: Stenopus hispidus) are “cleaning shrimps.” They remove and consume parasites, injured tissue and rejected food particles from some fish and other coral reef organisms. Typically these shrimp perch near the opening of the cave or ledge in which they are living and wave their antennae to let fish know their services are available. At these cleaning stations, the shrimp to enter the mouth and gill cavities of host organisms are not eaten. Species that show up to be cleaned include include groupers, moray eels, grunts and tangs. [Source: Kristen Sanderson, Animal Diversity Web (ADW) /=]
Redbanded coral shrimp inhabit tropical waters throughout the Indo-Pacific Region from the Red Sea and southern Africa in the west and Hawaii to the east. They also live in the western Atlantic, from Bermuda and off the coast of North Carolina to the Gulf of Mexico to the northern coast of South America.
Redbanded coral shrimp are typically found at depths of two to 210 meters (6.5 to 690 feet) at an average depth of 2-4 meters (6.5 to 13 feet), usually beyond the turbulent zone. The live a variety of reef habitats including rocky ledges and crevices and coral ledges. Occasionally they are found in undercut mats of rhizomes of Thalassia or discarded man-made objects such as car tires and buckets.
Redbanded coral shrimp was one of the first species of shrimp to be imported for use in the saltwater aquarium trade. They are sometimes difficult to raise because they are very territorial and fight with other shrimp and marine organisms. There are no regular predators of redbanded coral shrimp, but they have been found in the stomachs of some groupers such honeycomb groupers.
Redbanded Coral Shrimp Characteristics, Behavior and Reproduction
Redbanded coral shrimp grows up to 6.2 centimeters (2.4 inches), Females are larger than males. These shrimp have red and white-banded body and claws, with the bands sometimes bordered in purple. They have two pairs of long, white, hair-like antennae, the first of the antennae being uniramous (undivided, consisting of a single branch). The walking legs and some parts of the body appear translucent. The third, or middle, pair of legs is enlarged and have large claws. The claws have can intentionally broken off if a shrimp feels threatened. The claw can regenerate but often results in a claw smaller than the original. Animals in the Stenopodidae family, to which these shrimp belong, have spines on their body and on the larger chelipeds. The antennae are larger than their body. [Source: Kristen Sanderson, Animal Diversity Web (ADW) /=]
Redbanded coral shrimp are sedentary (remain in the same area) territorial (defend an area within the home range). Juveniles often pair up and grow up together. Adults are usually found in pairs and remain in the same area for days, months or even years. These shrimp has never been observed to move a distance greater than half a meter from their original place unless disturbed. This is also the case with paired individuals. Depending on diet and temperature, banded coral shrimp molt every three to eight weeks [Source: Kristen Sanderson, Animal Diversity Web (ADW) /=]
Redbanded coral shrimp feed on parasites, injured tissue and undesirable food particles that they it “cleans” from cooperating coral reef species. They sense using vision, touch and chemicals usually detected with smell and communicate with touch and chemicals usually detected by smelling and employ pheromones (chemicals released into air or water that are detected by and responded to by other animals of the same species).
Redbanded coral shrimp are oviparous (young are hatched from eggs) and engage in internal reproduction in which sperm from the male parent fertilizes an egg from the female parent. They are monogamous (having one mate at a time). Males and females may pair off as juveniles and stay together for years. These shrimp breed year round. The eggs are placed on the swimmerets underneath the female’s abdomen until hatching.
Mates may go through a courtship ritual when a male is equal or larger than a female.. The female shrimp mates with her paired male immediately after molting. The eggs initially appear as a greenish mass and are placed on the swimmerets underneath the female’s abdomen. The eggs hatch 16 days later at 28̊C (82̊F), usually at night. There is pre-fertilization provisioning and pre-birth protection is provided by females. Nine larval stages have been described. Teleplanic larvae may be able to delay metamorphosis until reaching suitable habitat.
Sexy Shrimp (Squat Anemone Shrimp)
Sex shrimp (Scientific name: Thor amboinensis) are also known as squat anemone shrimp. They get their names from way they shake the rear part of their body and their relationship with sea anemones. The average lifespan of sexy shrimp is thought to be about 3.5 years in the wild, but they are known to live up to five years. [Source: Seona Choi, Animal Diversity Web (ADW) /=]
Sexy shrimp live in the Atlantic, Pacific and Indian Oceans. Specific places they have been observed include, Florida, Gulf of Mexico, Caribbean Sea, Hawaii, the western coast of Africa, French Polynesia, Mozambique, Taiwan, China, the Canary Islands, New Caledonia, and within the Red Sea. Sexy shrimp require water temperatures of 22-27°C (72-81°F) and typically found in reefs or other coastal areas very near the surface at depths of only 0.5 to 2.8 meters (1.6 to 9.2 feet) usually where there is gentle to moderate water movement although they are capable of withstanding strong currents and waves.
Sexy shrimp form symbiotic relationships with sea anemones. living very close to the anemone’s toxic tentacles. Although some populations seem to have slight preference for certain anemone species, on the whole they will form relationships with any anemone that is available and will tolerate them. In most cases only one or two shrimp live on and in a host anemone, but groups with as many as 11 to 18 individuals have been observed residing at a single anemone.
Sexy shrimp are popular in home aquaria due to their striking colors and appearance, their cute dance and relatively easy maintenance. Their numbers in the wild are believed to be stable and healthy but presumably are affected by negative impacts on their coral reef and coastal homes. They have not been evaluated for the International Union for Conservation of Nature (IUCN) Red List. They have no special status according to the Convention on the International Trade in Endangered Species (CITES).
Sexy Shrimp Physical Characteristics
Sexy shrimp are very small, ranging in length from 1.5 to 13 millimeters (0.06 to 0.51 inches). There is some sexual dimorphism (differences between males and females): Females are larger than males. Males and females have different shapes and colored or patterned differently. Males have gonopores located on their fifth pereopods, with paired testes and lateral sperm ducts. They have appendices masculinae — male organs used in copulation or spermatophore transfer — on their second pleopods. Females have gonopores on their third pereopods and paired ovaries located above their hepatopancreas. They also have white spots on their pleopods. [Source: Seona Choi, Animal Diversity Web (ADW) /=]
Base body color is drab (olive or brown), with iridescent yellow-white spots bordered by thin white and blue bands, symmetrically arranged over their bodies. They have five pairs of pereopods (thoracic appendages) and five pairs of pleopods (swimming legs). Their first pair of pleopods are enlarged into chelae, used for both intra- and interspecific interaction. Their second abdominal segment is greatly enlarged; females carry developing eggs under this segment. Sexy shrimp have a telson and uropods, which form a fanlike tail, which is glossy and light brown in color, and is used for steering while swimming. They have white eyes, located at the ends of short stalks. This species differs from others in that, when at rest, their abdomens and tails arch upward towards the head.
Sexy Shrimp communicate with vision, touch and chemicals usually detected by smelling and sense using vision, touch and chemicals usually detected with smell. They also employ pheromones (chemicals released into air or water that are detected by and responded to by other animals of the same species), which can be perceived by both sexes. Sexy shrimp select a host anemone by using visual and chemical cues. They use their first pair of chelae for intersexual communication and may make a sound to signal others or to grab a female. These shrimp sense their environments through tactile means using their antennae. They have antennular flagella, the function of which is not fully known, but which are suspected to play a role as chemoreceptors.
Sexy Shrimp Behavior
Sexy shrimp are diurnal (active during the daytime), nocturnal (active at night), motile (move around as opposed to being stationary), sedentary (remain in the same area), and social (associates with others of its species; forms social groups). Although specific home ranges have not been identified for these shrimp, individuals tend to stay within a few centimeters of their anenome host. They do not appear to defend territories. [Source: Seona Choi, Animal Diversity Web (ADW) /=]
According to Animal Diversity Web: Sexy shrimp are known to vibrate their abdomen to signal or warn others. They are capable of moving very quickly, at rates of 10-15 centimeters/s, to escape perceived threats. Sexy shrimp are usually found in pairs or in small groups on a single anemone host. There do not appear to be any complex social hierarchies at play within groups.
Sexy shrimp are carnivorous. They feed on matter trapped in mucus of their host anemone. This includes plankton, small crustaceans, such as brine shrimp and krill. When resources are scarce, the shrimp may resort to feeding on the tentacles of their hosts or maybe seaweed.
In addition to sea anemones, sexy shrimp have been found on rocks and corals, as well as other animals, including Ricordea (a kind of coral) and Crinoids. Sexy shrimp have been observed cleaning mantis shrimp, picking parasites off of their carapaces. Sexy shrimps’ vibrant colors allow them to blend in with their reef environments. If threatened outside of their anemone host, these shrimp have been observed to flip their tails backwards, propelling them back into the safety of its tentacles.
Sexy Shrimp and Sea Anemones
As we said before sexy shrimp form symbiotic relationships with sea anemones, in many cases living among the anemone’s toxic tentacles. Although some populations seem to have slight preference for certain anemone species for the most don’t seem to care. In most cases only one or two shrimp live on and in a host anemone, but groups up to a dozen and half have been observed at a single anemone.
Various fishes such as triggerfish, hawkfish, wrasses, angelfish, broadbarred firefish and harlequin bass prey on sexy shrimp. They avoid predation by relying on their hosts, who are capable of stinging and sometimes eating potential predators.
Sexy shrimp help the anemones by clean up mucus while the anemones provide protection to the shrimp. Sexy shrimp are most often found with anemones such as Entacmaea quadricolor, Macrodactyla doreensis, Stichodactyla tapetum, and Zoanthus sp. But have also been found with Actinia equina, Heteractis malu, Bartholomea annulata, Condylactis gigantea, Euphyllia sp., Lebrunia danae, Lysiosquillina lisa, Phymantus sp., Stichodactyla haddoni, Stichodactyla heliantus and Telematactis cricoides,
According to to Animal Diversity Web: When an unacclimated shrimp is introduced to an anemone, it will endure the attacks from the anemones' nematocysts. Some studies state that a shrimp acclimates to an anemone by collecting its mucus, which camouflages it from the anemone. Other studies say that a shrimp acclimates by building up chemicals that inhibit the excretions of nematocysts from anemones. It is uncertain how long it takes for a shrimp to become acclimated to a host anemone. he spatial and temporal distribution of shrimp depends upon their feeding activities and the degree of anemone expansion.
Sexy Shrimp Mating, Reproduction and Offspring
Sexy shrimp are oviparous (young are hatched from eggs), iteroparous (offspring are produced in groups) and engage in internal reproduction in which sperm from the male parent fertilizes an egg from the female parent. They are sequential hermaphrodites in which individuals change their sex at some point in their lives and typically produces eggs and sperm at different stages their lives and protandrous (the condition of hermaphrodites that have male organs and sperm before female organs and eggs). [Source: Seona Choi, Animal Diversity Web (ADW) /=]
Researchers suspect that there are no primary females but that all individuals are born male and transition into females later in life. Transitional individuals, with both male and female characteristics, have been documented in the wild. These transitional shrimp most closely resemble female. Males can change into females in relatively short periods of time — less than 23 days. In most cases it is larger males that undergo sex alteration.
Sexy shrimp engage in year-round breeding and may breed multiple times throughout the year. The number of offspring ranges from 200 to 500. The gestation period ranges from two to three.5 weeks. Females carry, clean, and oxygenate eggs under their forward tail section, on the pleopods. While bearing eggs, they hold their legs under the tail to protect them. There is no known parental involvement by males. Parental care and pre-birth protection are provided by females. Young are precocial. This means they are relatively well-developed when born. /=\
Sexy shrimp are polygynandrous (promiscuous), with both males and females having multiple partners. According to Animal Diversity Web: Sexy shrimp appear to exhibit a "pure-search" strategy for mating, in which males search continuously for females and then, with no courtship, the pair rapidly copulate. It is assumed that at this point the pair separate quickly, although reports from captive breeders indicate that males may guard females once they release eggs. It is unknown if females are passive or active regarding mate choice. During copulation, a male transfers sperm cells from his gonopores (located on his fifth pereopods) to a female's gonopores (on her third pereopods). The appendices masculinae may aid in this transfer.
Sexy Shrimp Development
Most information regarding mating and development of sexy shrimp comes from observations by aquarium enthusiasts. According to Animal Diversity Web: Eggs are light brown in color and are cared for as they develop by the female, who carries them on her pleopods and continually cleans and aerates them. Within 2-3.5 weeks after fertilization, eggs hatch, usually at night.
Larvae are tiny and slender, averaging about two millimeters in length, and are phototaxic upon hatching. They drift in ocean currents for 20-30 days as they develop, undergoing 10-12 different larval stages, with physical changes occurring in each stage. Larve molt every two to three days, most often at night.
Although larvae eventually settle on a host anemone, they do not require a chemical cue from a certain host to do so; it has been hypothesized that individuals settle first and seek out an appropriate host second. In captivity, metamorphosis and settling have been observed to occur within 26 days of hatching.
According to Tropical Fish magazine: Another joy of sexy shrimps is that they are comfortable living in groups. This is indeed advised, and they should be kept in groups of three or more. It is in this situation that their sexy epithet is earned, as they wave their backsides from side to side. At present, just about all the sexy shrimps that enter the market are wild caught. They are common and widespread, and captive breeding isn’t an economically viable proposition compared to natural sourcing, but don’t let that put you off—breeding them is apparently not a difficult proposition.
Image Sources: Wikimedia Commons, NOAA
Text Sources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.
Last Updated April 2023