Story and photos by Darelle Snyman
There are many wonderful species interactions that happen on a busy reef, but for me none are more interesting than the interactions between the hosts of cleaning stations and their often much larger clients that would normally make a meal of them. The tiniest of these industrious critters are probably the delicately designed cleaner shrimps. These barely visible little crustaceans help keep fish and other marine life healthy by freeing them of dead skin, bacteria, and pesky parasites. Their small size, however, makes them frustratingly difficult to spot, especially if you are half blind like me. Since I upgraded to a prescription mask a whole new world has literally opened up for me, and I can again seek out and enjoy the smaller reef inhabitants.
One such delightful find, hiding among the tentacles of a sun anemone (Stichodactyla helianthus), was the stunning spotted cleaner shrimp (Periclimenes yucatanicus). The poor thing is probably still recovering from my attempts to get photos of it that were not blurred. This tiny Caribbean Sea resident, which rarely exceeds one inch, is truly gorgeous, with its transparent body decorated with distinctive saddle-shaped markings and rounded off with purple spots on the head. Its delicate pincers and legs attract further attention by being boldly banded in red, purple, and white. Like many cleaner shrimps, the spotted cleaner is endowed with two pairs of long antennae — a necessity for a hungry cleaner that relies on these appendages to attract clients. By swaying its body and waving antennae around, it signals to passing fish that it is open for business. An approaching fish will typically turn a darker color to indicate its willingness to be cleaned, a wonderful truce between different species where one would normally have been the prey.
These tiny cleaners often join forces with other cleaners such as gobies and wrasses at larger cleaning stations to provide a full service clean. Spotted cleaner shrimps are known for the symbiotic associations they form with a variety of sea anemone species, but they seem to prefer sun anemones and the beautiful giant anemone (Condylactis gigantea). Because of their habit of hiding among the tentacles of sun anemones, they might be confused with the sun anemone shrimp (Periclimenes rathbunae), but once you know what each species looks like, it is unlikely that you will confuse the reddish to brown spotted sun anemone shrimp with the strikingly patterned spotted cleaner shrimp. I actually searched for these little critters while snorkeling across a seagrass bed in Bocas del Toro that was littered with sun anemones, but this time “usually associated” did not work out for me. At least I was rewarded with delights such as the spotted cleaner shrimp and our next candidate, the wispy looking Pederson’s cleaner shrimp (Ancylomenes pedersoni).
This sea anemone resident prefers to associate with the corkscrew anemone (Bartholomea annulata), and in this case “usually associated” did work out for me. The translucent bodies of these aesthetically pleasing shrimps are adorned with subtle bluish and lavender markings. Like all shrimps that associate with anemones, they acquire immunity from the anemone’s stinging cells, or nematocysts, through acclimation. In this process the shrimp gradually interacts with the anemones tentacles to diminish its capture behavior; it does not get stung because it does not trigger the stinging cells. As the shrimp roams among the tentacles, it attains additional protection by becoming covered with mucus secreted by the anemone. Observations have shown that the shrimps’ protection is probably closely related to their constant interaction with the anemone, and they lose that protection when separated from their host for an extended period of time. Pederson’s shrimps rarely venture far from the protective tentacles of their sea anemone host, where they feed on the tiny organisms and detritus that get caught in the anemone’s mucus, thereby keeping it clean and healthy. These tiny crustaceans are also prolific cleaners of fish: their tiny pincers are ideal for cleaning those delicate areas such as around the eyes and gills.
Another charming character seeks refuge among the tentacles of sea anemones: the Caribbean’s own unique version of the sexy shrimp, or Caribbean squat anemone shrimp (Thor dicaprio). This little shrimp was originally thought to be the better-known sexy shrimp, Thor amboinensis, a species whose distribution across the world’s oceans was so widespread that scientists began to question whether the species, originally described in 1888, is actually a complex of different, closely related species. As a result, the Caribbean has attained a new sexy shrimp species, whose name pays homage to the actor Leonardo DiCaprio. Although this identification involved much genetic analysis, there is one external feature that clearly sets the Dicaprio sexy shrimp apart from its widely distributed counterpart in that its antennae is striped and not solidly colored. These oddly shaped shrimps are uniquely beautiful with their reddish bodies adorned with white spots edged in blue. They enjoy a wide distribution across the Caribbean and will happily share a host with the above-mentioned cleaner shrimp species.
Not all cleaner shrimps form associations with sea anemones. Some, like banded coral shrimps (Stenopus hispidus), prefer to hide under ledges, in crevices, and inside vase sponges. There is nothing subtle about these cleaners. They stand out with their striking red-and-white banded bodies and extra-long, white antennae. Their pincers, compared to those of their anemone-dwelling counterparts, are fairly outsized, allowing them to tackle tougher cleaning jobs. Their prominent antennae allow for very visible advertising, and this is needed as they tend to advertise their cleaning services from the underside of a ledge where they often perch upside down with their bodies mostly hidden. They prefer to stay hidden during the day and use their magnificent antennae to draw a passing fish closer for a spa treatment. It is at night that they boldly venture into the open to provide cleaning services to an array of clients such as morays, tangs, grunts, and groupers.
They can become territorial and end up in fights when there are too many of them congregating in a small area. Sometimes limbs are lost during these altercations, but are grown back during their next molt.
When it comes to breeding, banded coral shrimp are unique among invertebrates as they mate for life, which in shrimp years is typically two to three years. It is therefore not uncommon to encounter these shrimps in pairs, with the male usually smaller than the female. Studies have shown that when pairs are separated they are able to recognize each other when reunited in the presence of their own kind. This ability to distinguish between individuals of one’s own species is another rare trait of invertebrates and probably relies on chemical signals. During courtship the male entices the female with a dance before transferring a sperm sack to the freshly molted female. She carries the inseminated blue-green eggs until they hatch, approximately sixteen days later. Once settled, the young will start their all-important task of keeping their fishy clients healthy while keeping themselves well fed in the process.
There are so many of these wonderful little creatures to discover, each providing an invaluable service to keep the reef residents they tend to healthy. If you have good eyesight and the patience it might be well worth your time to inspect some of these host anemones to seek out some of these tiny, industrious cleaners.
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