What are Anthopleura elegantissima?
Anthopleura elegantissima are clonal intertidal anemones that can form flexible symbiotic partnerships with different single-celled algae which provide supplemental sugars to their diet, or alternatively, they can live ‘aposymbiotically’, relying wholly on prey capture for their food. They are commonly called the ‘aggregating anemone’, or ‘clonal-anemone’ because they form large clonal aggregates. Another common-name is the ‘pink-tipped anemone’, because of the pink tinge to the tips of their tentacles. As shown in the image above, they can completely cover large boulders in the intertidal zone with hundreds of individuals that are all genetic clones of each other.
“This anemone is an effective predator living in zooplankton-rich water, so one would not expect it to be as nutrient-limited, nor as dependent on algal photosynthetic productivity as its tropical symbiotic counterparts. It is also adapted to prolonged aerial exposure and greater temperature extremes; the animal feeds and its symbionts photosynthesize at temperatures approaching 5°C.” - McCloskey, Cove, and Verde (1996)
Taxonomy
The aggregating anemone was first described in scientific literature by Johann-Friedrich Brandt in 1835. Their taxonomic name, Anthopleura elegantissima (Brandt 1835), is thus tied to a latin description which can be translated:
“The body is large, pustular, red, green, blue, or brown, or even spotted with green and purple. The disc is oval, with a white striated margin and a sub-pentangular margin of half a foot in diameter. The tentacles at the base and apex are narrowed and widened white, the apex is purple, marked with a purple band in the middle. On the shores of the island of Sitka.”
Brandt was a German-Russian naturalist who was director of the Zoological Museum of St. Petersburg Academy of Sciences and described speciments from the expeditions of explorers off the Pacific Coast of North America. He may be best known for the description of birds like ‘Brandt’s cormorant’ and the spectacled eider. This original description by Brandt in 1835 suggests that the collection and description of this anemone species in Sitka1 was done in conjuction with colonial expansion and oppression.
1 In 1799 Captain Alexander Baranov, General Manager of the Shelikov-Golikov Company, establishes Sitka as a trading post as the first Russian trading charter grants the Russian-American Company sole trading rights in America for 20 years. Sitka is a strategic and important trading location and was already the indigineous homelands a large Tlingit village. Years of conflict with indigenous Koniag, Aleut, Tlingit, and colonial oppression as well as the Battles of Sitka in 1802 & 1804 predate and contextualize the timeframe in which Russian naturalists were ‘discovering’ new species in North America.
You can explore more A. elegantissima taxonomy details here, from the World Register of Marine Species (WORMS) webpage.
Puget Sound Museum of Natural History article here
NCBI taxonomy sequence resources:
https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=6110&lvl=0
Where are aggregating anemones found?
From Baja California to Southeast Alaska all along the Eastern Pacific Coast.
A. elegantissima is very tolerant to a broad range of thermal exposures. As an intertidal organism, A. elegantissima regularly experience large temperature shifts throughout the day coinciding with desiccation at low tide. They are found from Baja, California to Southeast Alaska, and in anemones hosting the brown alga Breviolum muscatinei, temperatures from 6oC to 24oC do not significantly affect their algal density, mitotic index, or total chlorophyll (a + c), but net photosynthesis and anemone respiration both increase with temperature (Verde.2002?).
Who studies them in the PNW?
E. Alan Verde
L.R. McClosky
Brian Bingham
Virginia Weiss
James Dimond
What have they found?
They may have underappreciated importance as coastal primary producers
“The sea anemone Anthopleura elegantissima (BRANDT 1835) is an important member of many rocky intertidal communities along the west coast of North America, with extensive aggregations of these clonal animals stretching from high to low intertidal zones (Dayton 1971; Sebens 1982a). Even where they co-occur with spatially dominant mussels, densities of A. elegantissima can reach 500 individuals m2 (Sebens 1982b). Hosting symbiotic green chlorophytes (Elliptochloris marina LETSCH) and brown dinophytes (Symbiodinium spp.), members of A. elegantissima contribute significantly to intertidal productivity; in Southern California, their photosynthetic contribution is on par with that of intertidal seaweeds (Fitt et al. 1982).” ((Bingham et al. 2011), p. 291)
They have a broad (5-33.6C) thermal tolerance
“Members of A. elegantissima can tolerate much higher temperatures, at least for short periods. Dayton (1971) monitored internal body temperatures of A. elegantissima in the field and found that anemones could survive body temperatures as high as 33.6°C with no apparent negative effect. Over 3 d of field study, with different levels of sunlight and wind, body temperatures of A. elegantissima in our treatments often exceeded 24°C, and reached 32°C in the most extreme cases. Although not lethal, temperatures in this range induce the production of heat shock proteins in A. elegantissima (Snyder & Rossi 2004), which may involve significant metabolic costs (Somero 2002).” ((Bingham et al. 2011), p. 296)
Bingham et al. (2011) found that aggregated anemones remain cooler than isolated individuals. They posit that the anemones in an aggregate benefit from more thermal stability due to the ‘extracorporeal’ trapped water between indivudal polyps and reduced ‘windage’.
“Seasonal surveys at our field site revealed larger aggregations of A. elegantissima in the high intertidal zone than at lower tidal elevations, but only in the summer when temperatures were highest (Fig. 5), suggesting that aggregation in high intertidal zones may be a behavioral response to desiccation and temperature stress.” ((Bingham et al. 2011), p. 298)
“In our field experiments, even in foggy emersion conditions, Anthopleura elegantissima body temperatures reached 8oC above ambient seawater. A. elegantissima body temperatures on sunny days reach values 17°C above that of ambient seawater, similar to that reported for emersed mussels (Mytilus sp.) and limpets (Patella vulgata) in temperate intertidal zones (Davies, 1970; Elvin and Gonor, 1979; Hofmann and Somero, 1995, 1996; Roberts et al., 1997; Helmuth, 1998).” (Snyder and Rossi 2004)
Snyder, Mark, and Sergio Rossi. 2004. “Stress Protein (HSP70 Family) Expression in Intertidal Benthic Organisms: The Example of Anthopleura Elegantissima (Cnidaria: Anthozoa).” Scientia Marina 68 (April).
They have warriors at their aggregate boundaries
Although aggregation has clear benefits for offsetting temperature increases, the benefits may not be shared equally by all members of the group; anemones on the edges of the clone, with their more exposed body surfaces, experienced more extreme temperatures than did individuals inside the aggregation. Individuals on the edges of clonal aggregations of A. elegantissima function as warriors, developing large acrorhagi (specialized organs filled with nematocysts) to defend the boundaries of the clone (Francis 1976). The warriors are smaller, have lower fission rates, and lack gonads, presumably because energy is diverted to defensive activities (Francis 1976).”((Bingham et al. 2011), p. 298)
Bingham, Brian L., Ileana Freytes, Meredith Emery, James Dimond, and Gisèle Muller-Parker. 2011. “Aerial Exposure and Body Temperature of the Intertidal Sea Anemone Anthopleura Elegantissima.” Invertebrate Biology 130 (4): 291–301. https://doi.org/10.1111/j.1744-7410.2011.00241.x.
They have a linear relationship between wet weight, oral disc diameter and protein content
In a paper J. L. Dimond et al. (2011), a year-long survey of Anthopleura elegantissima anemones to assess seasonality provides background information about the seasonal variation in anemone size and symbiosis.
“Anemone biomass and symbiosis—All metrics of anemone size (Table 1) indicated significant seasonal variation (protein biomass, F3,286 5 12.9, p , 0.001; wet weight, F3,287 5 3.52, p 5 0.02; oral disk diameter, F3,287 5 9.60, p , 0.001). There were no significant shore height differences in any measure (protein biomass, F2,286 5 2.36, p 5 0.09; wet weight, F2,287 5 1.97, p 5 0.14; oral disk diameter, F2,287 5 1.35, p 5 0.26) and no significant interaction effects (protein biomass, F6,286 5 0.84, p 5 0.54; wet weight, F6,287 5 0.96, p 5 0.45; oral disk diameter, F6,287 5 1.24, p 5 0.29). Wet weight was a better predictor of protein biomass than was oral disk diameter (Table 1). However, although protein biomass was significantly higher in November than in all other months, wet weight was not significantly different among July, November, and February.” - J. L. Dimond et al. (2011)
\[ Protein = 67.31e^{(0.3143wet weight)} \\ r^{2} = 0.80 \]
Animal husbandry
In the paper by McCloskey, Cove, and Verde (1996) the anemone’s were fed every other day with ~30mg of freshly hatched Artemia nauplii and maintained for 22 days with a single anemone each in its own 100mL jar, with seawater replaced every other day at 14°C ±2°C.
In the study by James L. Dimond et al. (2017), anemones were housed in 200mL glass beakers in a seawater flow-through tank as a bath, with the water level just below the top of the beakers.
Irradiance of B. muscatinei hosting Anemones
McFarland & Muller-Parker 1993 report greater photosynthetic productivity in the brown dinoflagellate (*B. muscatinei*) compared to the green chlorophyte, especially at higher irradiances. B. muscatinei
For anemones hosting B. muscatinei :
Maximum midday irradiance usually exceeded \(2,000 mu/ mol m^{-2} s^{-1}\) , where no photoinhibition was observed (Verde & McCloskey 1996)
Under experimental manipulations in the laboratory, ZX photosynthetic rates were suppressed at 2,000 lmolÆm–2Æs–1, indicative of photoinhibition (see below). Photoinhibitory phenomena are often associated with damage to the photosynthetic apparatus. If so, the ZX would likely devote more energy and resources to damage control and repair; subsequently less energy and photosynthetic products would be available to support continued algal growth. Since ZX also displayed photoinhibition at 1,400 lmolÆm–2Æs–1, yet did not show a reduction in MI, the onset of the deleterious effects of damage repair would seem to occur at intensities above 1,400 lmolÆm–2Æ s–1. In contrast, anemone metabolic rates were elevated at 2,000 lmolÆm–2Æs–1; it may simply be that the host requires more energy and organic resources to meet its elevated respiratory demands, and the ZX symbiont provides both at the expense of its own growth E. and L. (2002).
Not light saturated up to \(550 mu/ mol m^{-2} s^{-1}\) (Verde & McCloskey 1996)
B. muscatinei peaked at $800 mu/ mol m^{-2} s^{-1}$ E. and L. (2002) .
E., Verde, and McCloskey L. 2002. “A Comparative Analysis of the Photobiology of Zooxanthellae and Zoochlorellae Symbiotic with the Temperate Clonal Anemone Anthopleura Elegantissima (Brandt).” Marine Biology 141 (2): 225–39. https://doi.org/10.1007/s00227-002-0824-7.
Symbiosis
A. elegantissima gains symbionts through horizontal transmission (Lajeunesse and Trench 2000). (Trench 1987)
Normally, A. elegantissima expels symbionts from its coelenteron in a bolus of mucus and undigested material. Expulsion of symbionts should not be confused with “bleaching” phenomenon in reef corals, and may serve an ulterior purpose and undergo a different process. The anemones ‘cull’ or ‘weed’ the symbionts to maintain an optimal symbiont population density.
The optimized symbiont density is reported in the literature as 106 cells·mg-1 of host protein and 1-5·106 cells·cm-2 (McCloskey, Cove, and Verde 1996).
Sea anemones of the genus Anthopleura along northeast Pacific intertidal shores engage in a particularly unique symbiosis with two especially phylogenetically and physiologically different symbionts: the chlorophyte Elliptochloris marina (Letsch et al., 2009) and the dinoflagellate Symbiodinium muscatinei (LaJeunesse and Trench, 2000). - James L. Dimond et al. (2017)
The Symbiodinium muscatinei(Lajeunesse and Trench 2000)were reclassified as Breviolum muscatinei
Most anemones only host one symbiont, or the other. It is rare for mixed assemblages of the two ‘symbiont morphs’ to occur. In the paper by McCloskey, Cove, and Verde (1996), they found that among 91 anemones, >95% had a single symbiont type. The chlorophyte Elliptochloris marina is relatively sensitive to light and is limited to cooler, low light environments typical of the low intertidal. The dinoflagellate B. muscatinei, on the other hand, tolerates higher light and temperatures and is more commonly found in anemones in the upper intertidal zone. Aposymbiotic (non-symbiont forming) A. elegantissima anemones can be found thriving in very low light conditions, often inside rocky crevasses within the intertidal zone. Transplantation of A. elegantissima anemones with chlorophyte E. marina symbionts to warmer, higher-light environments results in shifts in the symbiont population from E. marina to B. muscatinei (James L. Dimond et al. 2017).
Anemones hosting B. muscatinei have a golden-brown color, while those that host E. marina are mossy green. Symbiont type can be verified by viewing excised tentacles under light microscopy, and commonly, no mixed-symbiont populations are observed (James L. Dimond et al. 2017).
