Marine Invertebrates of Bermuda

Red Anemone (Actinia bermudensis)

Corey Eddy
James B. Wood (Ed)

Taxonomy  Habitat  Ecology  Recent Research  Commercial Importance  Bermuda Laws  Personal Interest  References  Links 

INSERT commons and sci name

Actinia bermudensis is known as the red anemone, but may sometimes be called the maroon anemone. It is generally found in tropical waters from Brazil to Florida, and especially Bermuda (Sterrer 1986). This small blood red anemone is usually attached to the bottoms of rocks, along rock walls, or within crevices of coral reefs (Amaral et al., 2000). While there has been very little research directed specifically at A. bermudensis, a lot can be ascertained by studying anemones from within its genus. For example, while we know that it is a sessile benthic organism, we may deduce that is capable of absorbing nutrients directly through its ectoderm, and may also actively capture food with its tentacles (Van Praet 1980). On the other hand, we have direct evidence that the red anemone reproduces asexually through longitudinal fission and also may give birth to sexually produced, internally bred, live young (Walton 1918; Chia 1976). We know that related species are often aggressive species, despite their size and sessile nature (Turner et al., 2003). The evidence suggest actinians are quite capable of defending themselves with nematocyst studded acrorhagi and potentially lethal toxins (Sterrer 1986; Anderluh and Macek 2002).


Phylum: Cnidaria
  Class: Anthozoa
    Subclass: Hexacorallia
     Order: Actiniaria
       Family: Actiniidae
        Genus: Actinia
         Species: Actinia bermudensis


Actinia bermudensis is relatively common throughout the tropical Atlantic Ocean, from Brazil to Florida and Bermuda. Of the nearly 1000 identified Actiniarian species, only 17 are known from Bermuda (Sterrer 1986). A. bermudensis is usually found below boulders, under rocks, in crevices, or attached to the lower surfaces of rock walls (Amaral et al., 2000). In addition, this species of anemone generally prefers the intertidal zones of rocky shores and estuaries, but it also is frequently found in caves (Walton 1918).


Anthozoa is a broad class of marine invertebrates that includes corals and sea anemones, while the order Actiniaria more specifically describes just the anemones. Actiniaria are solitary animals that exhibit the classic cnidarian polyp body form their entire lives; never taking on the medusae shape. Species from the family Actiniidae have an adherent pedal disc, more than six pairs of mesenteries, and no acontia (Sterrer 1986).

Actinia bermudensis has a smooth body with blood red or maroon coloration (Walton 1918). The pedal disc may grow to a width of four centimeters, but the rest of the body tapers to three centimeters (Walton 1918). Overall, the red anemone generally reaches a height of five centimeters. The oral disc holds between 96 and 140 particularly short and simple tentacles, arranged in two irregular rows (Walton 1918; Sterrer 1986).

Sea anemones are sessile benthic organisms and locomotion is a rare event, typically caused by attack or a change to the animal's physical habitat. Although no observations of locomotion have been made directly on A. bermudensis, substrate detachment and pedal locomotion has been witnessed among A. equina (Ottaway 1978). These events were directly caused by predatory attack, and the anemone's responses also included tentacle retraction and column inflation. However, the red anemone does possess globular acrorhagi, with numerous nematocysts, that are also used in defense (Sterrer 1986). Other actinians, A. equina in particular, have been documented to express direct aggression towards many nearby organisms, both from the same and different species (Turner et al., 2003). In addition, this species produces lethal peptides and proteins that are likely to aid in offensive and defensive mechanisms (Anderluh and Macek 2002).

Sea anemones also exhibit a variety of mechanisms to obtain nutrients. Although there have been very few studies done directly on A. bermudensis, it has been observed that A. equina may absorb nutrients, such as dissolved glucose and amino acids, directly through its ectoderm (Van Praet 1980) In addition, the author observed other food particles and prey would be taken into the coelenteron to be extracellularly digested between the mesenteries. The most commonly preferred food of actinian species are gastropods, isopods, and small bivalves, although their diet may also include insects and algal material (Kruger and Griffiths 1996). Such a wide food variety suggests these animals should be considered non-selective omnivores, or generalist feeders. It is interesting to note that while actinians may consume gastropods, gastropods such as the nudibranch Aeolidia papillosa eat actinians as well (Edmunds et al., 1974).

Sea anemones, like many cnidarians, may form symbiotic relationships with photosynthetic dinoflagellates, called zooxanthellae. This symbiosis usually is rewarding for both organisms. Most of the time, each will receive some kind of benefit, either as food, protection, or house-cleaning. However, A. bermudensis has been observed to gain no benefit from the relationship it forms with zooxanthellae (Fulton 1921). In fact, this symbiosis has been termed parasitic because the zooxanthellae provide no photosynthate for the anemone and are often digested when other nutrient sources are lacking. It has also been suggested that light levels and photosynthesis have no effect on the vitality of actinians because they are not using their zooxanthellae for any purpose (Kruger and Griffiths 1996). Based on previous research showing organisms such as amphipods and copepods frequently inhabit actinians, it could be suggested that a similar symbiotic relationship may exist in the red anemone (Williams 1996).

Many modes of reproduction exist within the animal kingdom, but A. bermudensis primarily relies on asexual reproduction by longitudinal fission (Walton 1918; Chia 1976). However, it has also been shown that the red anemone produces sexually produced, and internally bred, live young (Chia 1976). These anemones have been seen to spawn towards the end of September and typically brood their larvae throughout the year (Jennison 1983). The author also mentioned that the number of females spawned was nearly ten times greater than the number of males. It has been seen that varying temperatures have a dramatic effect on the growth rates of some actinians (Chomsky et al., 2004). For example, A. equina grows much better at low temperatures between 15 and 20 degrees Celsius, while it actually shrinks at temperatures between 25 and 30 degrees.

Recent Research

A genetic comparison was recently employed to determine the overall divergence and isolation between Bermudian and Brazilian populations of A. bermudensis (Vianna et al., 2003). Although they concluded that it would be reasonable to raise the Brazilian anemones into a separate species, they ultimately decided the genetic divergence was within an acceptable range considering the substantial distance of isolation. Therefore, they chose to leave these anemones within the original classification.

Studies have recently been conducted to specifically prove that Actinia bermudensis reproduces asexually. (Monteiro et al., 1998).The authors sought to determine the extent of genetic similarity that existed between juveniles found within the coelenteron of their parents. They conclude that the red anemone reproduces asexually and its primary method is a type of parthenogenesis.

Commercial Importance

There has been no documented commercial interest in Actinia bermudensis so far. However, there has been considerable interest in various lethal toxins manufactured by A. equina (Anderluh and Macek 2002). In the future, it would seem logical to expect similar investigations of other actinians to determine potential pharmacological, agricultural, or medical uses.

Bermuda Laws

There are no laws in Bermuda specifically pertaining to Actinia bermudensis. However, across the Beruda platform, 29 zones have been designated as Marine Protected Areas under the Fisheries Act, 1972, Fisheries (Protected Areas) Order 2000 (Wood and Jackson 2005). Within these zones, fishing and collecting have been outlawed. These measures are all encompassing and include, of course, A. bermudensis.

Personal Interest

I chose to study the red anemone because I've always felt that anemones are a particularly interesting organism. Having spent all of my SCUBA pursuits in the northern Atlantic Ocean, I've had few opportunities to see these creatures. Anemones are especially interesting to watch as they adhere to the slightest touch of your finger. The function they serve as a microhabitat for various fish and shrimp also presents quite an image. The blood red color of Actinia bermudensis is striking as well when compared to the dreary green and cold grey I am accustomed to seeing in New England.


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Chia, F.S., 1976. Sea anemone reproduction: patterns and adaptative radiation. In: Coelenterate ecology and behavior. Plenum Press, New York, pp 27-31.

Chomsky, O., Kamenir, Y., Hyams, M., Dubinsky, Z., Chadwick-Furman, N.E., 2004. Effects of temperature on growth rate and body size in the Mediterranean Sea anemone Actinia equina. J Exp Mar Bio Ecol 313, 63-73.

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