Feature Article: An overview of symbiotic relationships of the Caribbean, with emphasis on shrimps Periclimenes yucatanicus [Ives, 1891] and Periclimenes pedersoni [Chace, 1958] (Decapoda: Caridea: Palaemonidae), and host anemones

Symbiotic relationships are an icon of marine aquarium keeping, and no wonder – who hasn’t paused when presented with clownfish happily swimming among the tentacles of their host anemone? Symbiotic relationships are found worldwide, in every habitat, and can be described as two different organisms living together in one of four ways:[1] Commensalism is a relationship of an animal, plant, fungus, etc. living with, on, or in another, without injury to either. Mutualism is a relationship between two species of organisms in which both benefit from the association. Parasitism is a relation between organisms in which one lives as a parasite on another. Lastly, phoresis is a relationship in which a host animal provides transportation for the symbiont.[2] There are numerous symbiotic relationships to be found in the Caribbean, and a portion of these relationships will be discussed here, with emphasis placed on relationships I personally observed in the Drowned Cayes, Belize, Central America.

A window into nature that I feel illustrates how life depends on life. These species would not linger or could not live at this location if not for the scleractinian coral specie(s) in the photograph.

The commensal relationship between shrimp Pederson’s anemone shrimp (Periclimenes pedersoni) and the spotted or Yucatan anemone shrimp (Periclimenes yucatanicus) is easily observed in the wild, but seldomly (though becoming more common) in the home aquarium. I was able to personally observe both species residing commensally in host anemones in their native habitats, and would like to share information about their natural life with the marine aquarists that are so inclined. The shrimp belong to the family Palaemonidae, and are easily distinguished by their long, serrated rostrums, and small average size (to ~3.5 cm, depending on the species). Periclimenes species are found in tropical waters of the Caribbean and the Western Atlantic. (Spotte & Bubucis, 1997) Shrimp from this genus are known for their ‘cleaning’ behavior, removing and consuming parasites from fish, though I was unable to personally observe or record this behavior. (Calado, et al. 2003) Shrimp of this family are virtually always associated commensally with coral, anemones, and occasionally corallimorpharians (Williams & Williams, 1981). Coloration may vary even between members of the same species, as it can be changed to camouflage with the shrimp’s host, making members of this family sometimes difficult to identify visually. (Fenner, 2000-2007) Periclimenes species usually prefer a few select species of sea anemone to inhabit commensally. These species include the bulb-tipped anemone (Entacmaea quadricolor), The condylactys anemone (Condylactys gigantae), Bartholomea annulata, Aiptasia pallida, and Stichodactyla helianthus. The bulb-tipped and condylactys are hardy species of anemone that are commonly kept by the home aquarist. All commensal shrimp benefit their hosts by providing a nitrogen source, preventing nitrogenous limitation of the zooxanthellae in the host’s tissues. (Spotte, 1995) Anemones, in turn, provide a refuge for the shrimp, as well as a potential food source both from the host’s tentacles, and from any prey killed by the host. (Fautin, et all. 1995) Although both species potentially benefit one another, the anemone benefits much less than the shrimp, and due to the transient nature of the shrimp, may not benefit at all. Thus, the symbiosis is defined as a commensal relationship. (Spotte, 1995, Fautin, et al. 1995)

Pederson’s anemone shrimp is found off the Caribbean coast, always living commensally with a host Condylactys or Bartholomea spp. anemone, and (rarely) with Euphyllia corals (another common aquarium species). However, the shrimp does not necessarily stay with one host throughout its life; instead it appears to change hosts frequently. (Chace, 1958, Manken, 1972) Very little information is available regarding this species.

P. yucatanicus engaged in a commensal relationship with C. gigantae on the drowned cayes belize.

Condylactys anemone forcibly creating a home for itself among an unknown species of scleractinian coral on the belize barrier reef.

The Yucatan anemone shrimp has very distinctive pink abdominal markings, and is most often seen residing in Condylactys gigantae in the Caribbean. However, it has other host anemones: B. annulata, A. pallida, and Lebrunia dannae. (Williams & Williams, 1981, Spotte, 1997) P. yucatanicus is unusual in the fact that it is also known to live commensally in the corallimorpharian anemone Rhodactis sactithomae. P. yucatanicus is the only Periclimenes species know to associate with R. sactithomae. It is unlikely a corallimorpharian is able to provide the same level of protection as it lacks the nematocysts of the other anemone species, so this finding is not understood. P. yucatanicus can be sexed fairly easily when seen in pairs (a common occurrence) as the female is, on average, 5mm larger than the male. (Spotte, 1997) All members of Periclimenes are known as ‘cleaner shrimp’, and have a mutualistic relationship with many other reef inhabitants who benefit from their ‘services’. These shrimp wait outside their host and advertise their presence by waving their antennae or swimming up and down in the water column. This serves to bring animals to their location, so that the shrimp can remove and ingest dead skin cells, fungus, and parasites. Often a ‘cleaning station’ is rather apparent, with several, often large fish waiting their turn to be cleaned. Overall, information regarding this genus is scarce. Information regarding the species that Periclimenes spp. inhabits are as follows:

Entacmaea quadricolor, or the bubble-tipped anemone, is a common anemone, as it is found in shallow coastal waters from Central America to Japan. There are several color variations, ranging from a cream color to a vivid red. E. quadricolor can attain sizes of up to ~25 cm, though it is difficult to measure the exact and maximum size of an anemone. This anemone is also a common host for the Maroon Clownfish, Premnas biaculeatus. This species of anemone is commonly kept by the home aquarist, and is one of the easier species to maintain.

Neon goby perching on a cleaning station on the belize barrier reef.

Condylactys gigantae, or the Giant Caribbean Anemone, is another very common anemone, with a range extending from Cozumel to Bermuda, and any shallow coastal waters in between. C. gigantae attains a maximum size of ~30 cm, and is a common host for many species of the genus Periclimenes. This anemone species is very easy for the home aquarist to maintain, as it can adapt to a wide range of lighting and tolerates less than optimal water conditions.

Bartholomea annulata, or the Corkscrew anemone, is found from the Florida coast south to Brazil. A common host for snapping shrimp, as well as Periclimenes spp. B. annulata attains a maximum size of approximately 15 cm.

P. yucatanicus engaged in a commensal relationship with C. gigantae in the drowned cayes belize.

Aiptasia pallida is found throughout the shallows waters of the Atlantic, and members of the genus are found on reefs worldwide. A. pallida is small compared to the other host anemones for Periclimenes, attaining a maximum size of 5 cm. However, this anemone has the most potent nematocysts of any species listed, capable of quickly paralyzing fish many times larger than itself. This is considered a pest anemone species by aquarists, and should not be introduced if possible.

Stichodactyla helianthus, or the Caribbean Carpet Anemone, is a large ‘carpet’ anemone, with short tentacles and a strong sting. This species is common along the East coast of Central and South America. It is host to the banded crab (Mithrax cinctimanus) as well as Periclimenes spp. This species is sometimes available under “assorted carpet anemone” or similar, and is a fairly hardy carpet anemone.

Sponges and tunicates encrusting a mangrove root in the drowned cayes belize.

Stichodactyla spp. on a rock crevice near the belize barrier reef.

Other symbiotic relationships I observed were Elacatinus oceanops, the Neon Goby, alone and in pairs on several large pieces of brain coral. The neon gobies were often engaged in the ‘cleaning’ of other fish species. Large jacks, groupers, and angelfish were usually swimming nearby, waiting for their turn to have parasites removed by this diminutive fish. E. oceanops resides in the Western Central Atlantic, ranging from Southern Florida to Belize.[3] E. oceanops and other species of its genus are well knows for their ‘cleaner stations’ they run on prominent areas of the reef. Their services are used by many species, including fish, turtles, rays, and octopus, some of which would normally prey on gobies and similar fishes. (Johnson & Chase, 1982) I aso observed Remora remora, the common Remora, engaged in a phoresis relationship with Sparisoma viride, the Stoplight Parrotfish on multiple occasions. R. remora is found in tropical coastal waters virtually worldwide, and S. viride ranges from the east coast of Florida, and south to the Brazilian coast. I often observed multiple remoras attached to or swimming with stoplight parrotfish. Young Remoras can be beneficial to their host, as they remove and ingest parasites, and adult remoras simply participate in phoresis. Remoras commonly scavenge leftovers from their host’s meal, and may also ingest feces from the host. They are known to attach themselves to manta rays, whale sharks, turtles, swordfish, tuna, ocean sunfish, and many other large species.

There are many other symbiotic relationships occurring in the Caribbean that I did not personally observe. Amphipods of the genus Leucothoe are known to live commensally in sponges, tunicates, and bivalves worldwide. (Thomas & Klebba, 2006) These amphipods spend their entire lives inside their host, relying on the host for protection, as well as for nutrition (which is derived from the water intake of the host). Often in the case of sponges and tunicates the host will completely grow over and encase the amphipod, with no apparent adverse effects – in fact, this may be beneficial in preventing predation to the amphipod.

A very common and not always apparent mutualistic relationship is the one between zooxanthellae alga and the tissues of animals, most notably Anthazoans. These dinoflagellates species of the genus Symbiodinium inhabit the tissues of a vast majority of corals and anemone species, as well as jellyfish, clams, nudibranchs, and radiolarians. Zooxanthellae are autotrophic, and provide carbon fixation for their hosts, generating up to 90% of their hosts’ energy requirements. (Rudman, 2000. Sumich, 1996) In return, the Zooxanthellae receive shelter, protection, access to light, and a constant supply of carbon dioxide, as well as other metabolic wastes. This mutualistic symbiosis has enabled modern corals to be amazingly successful since the mid-Triassic, allowing hermatypic coral species to generate immense amount of physical reef structure from their skeletons, and creating incredibly large reef ecosystems in coastal, tropical waters worldwide. (Ezaki, 1990) These coral reefs have allowed millions of other species to evolve and flourish, and develop symbiotic relationships of their own, in a habitat that simply would not exist without this mutualistic relationship.

Symbiotic relationships are incredibly diverse, and also incredibly common. Many of the species that exist today would never have evolved without symbiotic relationships, both marine and terrestrial. Researching these relationships helps to illustrate how important life is to other life, and what an incredibly complex ecosystem Earth supports, and that ecosystem should not be taken for granted.

Special thanks to Merritt Adkins and Sarah Beggerly.

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