We aquarists have long suggested that cleaner shrimps will remove cysts from fishes infected with Cryptocaryon irritans and may also ingest other parasites (e.g., trematode flatworms). Well, it turns out that science supports our anecdotal observations. Let's take a look at the scientific evidence. The first study of interest was conducted by Williams and Williams (1998) - they documented that Pederson's anemone shrimp (Periclimenes pedersoni) feeds on the larvae of parasitic isopods. Even more exciting was a study done by Becker and Grutter (2004). They analyzed cleaner shrimp gut contents as well as conducted some aquarium studies. They found that wild cleaner shrimps in the genus Urocaridella and Ancylomenes (formerly Periclimenes) holthuisi (known commonly as Holthuis' anemone shrimp) fed on parasitic crustaceans (e.g., isopods, copepods) and monogenean flatworms (Benedenia sp.). They also demonstrated that captive A. holthuisi reduced the parasitic load (in this case flatworms) by 74 % on captive surgeonfish. In the most recent study, Militz and Hutson (2015) documented that captive -held skunk cleaner shrimp (Lysmata amboinensis) will reduce infestations of a trematode in the genus Neobenedenia in groups of lyretail anthias (Pseudanthias squamipinnis). The shrimp reduced the infection success by the trematodes by half compared to controls that were not housed with shrimp. These beneficial crustaceans were found to eat both the flatworm's eggs and the larvae.
The fire shimp (Lysmata debelius) is often seen cleaning large morays in caves and crevices. Photo by Scott W. Michael.
More on Cleaner Shrimps
Most of the reef-dwelling cleaner shrimps we see in the aquarium trade belong to the genera Ancylomenes, Leander, Lysmata and Periclimenes (some of the genus Stenopus also clean but do so less frequently). These shrimp typically occupy specific cleaning stations. In some species the cleaning station may consist of a reef crevice and caves (e.g., Lysmata debelius), while others associate with anemones (e.g., Periclimenes pedersoni). Many of these shrimp attract potential clients by whipping their antennae or antennules back and forth, by swinging their chelae or rocking their bodies from side to side. A fish will approach the cleaning station and maintain its position near the shrimp. The cleaner will “dance” as the potential host approaches and will climb on the fish when the host starts to “pose” (remains stationary and may erect the fins or flare the gill cover nearest to the shrimp). Once “onboard” the shrimp will begin picking at the body surface with its claws. Not only do these crustaceans ingest parasites and dead tissue, they also graze on the fish’s body slime and bits of fin. The shrimp will pick at the body surface, under the gill covers and in the mouth and the host seems to “enjoy” the tactile stimulation provided by strokes of the antennae. Cleaning bouts can vary in length, but may last as long as 5 minutes.
The The graceful anemone shrimp (Ancylomenes venustus) occurs in anemones and large-polyped stony corals. Photo by Scott W. Michael.
All the cleaner shrimp species do well in the home aquarium. However, the aquarist must be careful about what fish he or she keeps with them, as some predators (e.g., eels, lizardfishes, frogfishes, scorpionfishes, groupers, wrasses, triggerfishes) will eat them. The smaller, more delicate varieties are potential prey for a large number of fishes, including species that are not normally considered to be dangerous to crustaceans, like fairy wrasses and larger shrimp-gobies. If you want to keep a cleaner shrimp with a carnivorous fish, add the shrimp first and let it adjust to its new home before introducing the potential crustacean predator. During the molting process, and just after it occurs, these animals are especially susceptible to being preyed upon by fish and crustacean tankmates. It is possible to keep these invertebrates with predatory fish, in fact, it can make a fascinating display. For example, it is very engaging to watch a blood red cleaner shrimp (Lysmata debelius) cleaning the head and mouth of a large moray. There are some species of shrimp that are potential predators of your fish. For example, larger boxer shrimp (Stenopus spp.) may capture and eat smaller fishes. Aquarists be aware that many shrimp are very sensitive to sudden changes in water parameters, therefore, it is important to slowly acclimate them when transferring them from one tank to another.
© Scott W. Michael- Reef Tectonics