DRAFT: This module has unpublished changes.

The Effect of Anemones on the Distribution of Marine Life

E. Madsen

 

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Abstract                                                                           

Condylactis gigantea is a common sea anemone found in Discovery Bay, Jamaica. Compared to other species of anemone, C. gigantea is a relatively mobile anemone.  As highly tactile organisms possessing toxins readily available to deter predation, it is expected that C. gigantea will produce an observable effect on the distribution of marine life within their immediate surroundings. Anemones were located in the field and the distances from the anemone to other organisms were measured within a 0.5 meter x 0.5 meter quadrat.  Sites were analyzed as a whole, and within the context of the ‘population type’. The number, distribution and proximity of anemones within one quadrat determined population type.  Analysis showed that different population types resulted in a characteristic presence or absence of turtle grass, Thalassia testudinum, as well as quantity and placement of sea urchins. Algae was observed frequently and yielded observable trends. As a whole, these results suggest that anemones might affect the placement of invertebrates, while algae and plants may affect the location of anemones. 

 

Index Terms—Condylactis gigantea, Discovery Bay Jamaica, nematocysts, distribution

 

Introduction                                                                      

Giant sea anemones, Condylactis gigantea, is a common Carribbean sea anemone found extensively throughout Discovery Bay, Jamaica. C. gigantea is a highly tactile, comparatively mobile anemone possessing specialized stinging cells called nematocysts. Although C. gigantea utilize an ubiquitous anemone defense mechanism consisting of quickly withdrawing their tentacles when threatened, it has also been widely observed that C. gigantea react aggressively towards other marine invertebrates (Bosmans, 2006) and will use the toxins contained in their nematocysts in order to compete for space.

 

Preliminary, unofficial, observations showed that several species of sea stars would not cross over a line of anemones, despite the presence of prey on the opposite side of the anemones. The anemone’s nematocysts were believed to produce this effect. A wide variety of official studies have taken advantage of the visible reaction of anemones to direct contact. This physical reaction has lent itself well to the study of anemones and factors that influence their habitat selection.

 

Species of anemones such as A. elegantissima and M. senile have been studied for the ability to utilize intergenotypic aggression to maintain clonal borders and potentially prevent the encroachment of other neighboring anemone populations. (Ayre, 1983). The interactions of A. elegantissima between clonemates and anemones from different clones have been observed and yielded a consistent result. Typically, when two clonemates are brought into contact with each other, their tentacles will initially withdraw before extending once again. This process will repeat itself several time before it ceases. If the two anemones move closer to each other the tentacles will intertwine without any other apparent reaction. However, if two anemones from different clones are brought into contact with each other, they will then engage in aggressive behavior characterized by the acrorhagi (or marginal spherules) closest to the tentacles in contact becoming visibly white or pink, the anemone assuming a more upright posture as its tentacles extend for the last time, and swelling of the capitulum at the base of the stimulated tentacles (Francis, 1973).

 

There is also believed to be a link between habitat and personality in Condylactis gigantean. One dimension of personality has been labeled the shy-bold continuum (Bell, 2007), i.e., an individual’s reaction to the presence of a predator. Studies have shown that individuals that lived in areas of higher Thalassia density were characterized by shyer personalities (Hensley et al., 2012). The size and height of Thalassia were believed to mimic typical predation techniques. However, survival rates of certain personality types across various habitats could be influencing this result. While it is possible to draw a correlation between habitat and anemone personality, interspecific competition should be noted as well.

 

In this study, the effect of C. gigantea on marine life, and vice versa, was examined. Invertebrates were expected to be observed infrequently and at consistent distances from anemones, whereas plants and algae were expected to appear frequently and at sporadic intervals. The absence and distance of invertebrates would confirm previous studies that cite the influence of anemone toxin on invertebrates (Bosmans, 2006). The presence of Thalassia and resultant distribution of C. gigantea and Thalassia would underscore the influence of habitat and personality upon anemone distribution. The presence of algae and resulting distribution trends could also contribute to an observed trend between the presence of sessile marine life and anemone distribution.

 

Methods                                                                          

35 sites were sampled using a 0.5 meter x 0.5 meter quadrat. Quadrats were placed so that the specimen was situated in the center. The distances from the edge of the anemone to plants, algae, and invertebrates were measured.

 

Sites were randomly chosen in three general geographic areas: close to shore, within the mangroves, and in the back reef. Measurements were accurate to 5 cm. 

Fig 1. Anemone Site Locations

 

Anemone populations were divided into three different population types: tightly grouped, loosely grouped, and single anemone. Tightly grouped anemone populations were characterized by containing at least two anemones that were in direct contact with each other while loosely grouped anemone populations contained two or more anemones that were in the same quadrat, but not in contact with each other. Single anemone populations contained only one anemone. Observations were averaged across all sites, as well as within the three population groups. Due to the random selection of anemone populations, total anemones were not divided evenly into these three populations. 18 anemone sites were classified as Single Anemone, 8 were classified as Loosely Grouped, and 8 were classified as Tightly Grouped. 

 

Results                                                                            

The most prevalent organisms found near the anemones were green algae (predominately Green Feather Algae), brown algae (predominately Dictyota), and rock boring sea urchins. Only two sites contained no other visible marine life. Both of these sites contained one single anemone residing on the face of a rock.

 

A total of 84 algae groups were observed. Of these populations, 42% of the algae observed were brown algae and 58% were green algae. The majority of the brown algae (74%) observed were Dictyota, whereas 92% of the green algae observed were Green Feather Algae.

 

Sargassum appeared infrequently, but all Sargassum observed appeared within a 10 cm diameter of the anemone. Dictyota was observed throughout the area, although 88% of the Dictyota was observed within the range of 10 cm  – 20 cm. 35% of Dictyota was observed 15 cm from the anemone (fig 2).

 

Fig. 2 Presence of brown algae in relation to an anemone (all sites)


However, each anemone population group (tightly grouped, loosely grouped, and single anemone) displayed a different Dictyota trend. Loosely grouped anemone populations were characterized by appearing uniformly between 10 cm – 20 cm. Tightly grouped anemone populations appeared within the 10 cm -20 cm range as well, but displayed a different pattern (fig 3). Single anemone populations predictably maintained a similar trend described as described in fig. 2.

 

Fig. 3 Presence of Dictyota (segregated by population types)

 

Green Feather Algae was observed more frequently than all other algae. 54% of algae observed were green feather algae, in contrast to Dictyota, the second largest algae observed, which accounted for 31% of all algae observed. However, a consistent pattern of Green Feather Algae did not appear. 38% of Green Feather Algae appeared within a range of 10 cm – 15 cm of the anemone, whereas 51% of Green Feather Algae appeared within a range of 20 cm - 25 cm of the anemone. Dinosaur Foot Algae appeared sporadically and in small numbers (fig. 4).

 

Fig. 4 Presence of green algae in relation to an anemone (all sites)

 

Rock boring urchins appeared frequently and sporadically in all anemone sites. The most frequent observations of rock boring urchins occurred at the 20 cm mark. 

 

Fig. 5 Presence of rock boring urchins (all sites)


However, when anemones were divided into their populations, different patterns began to emerge. Notably, the highest frequency of observation within tightly grouped anemones differed from the pattern set by the collective data. There were an average of 2.9 ± 0.3 urchins observed in each tightly grouped population, an average of 1.5 ± 0.3 urchins observed in each loosely grouped anemone population, and 2.5 ± 0.4 urchins observed in each single anemone population.

 

Fig. 6 Presence of rock boring urchins (segregated by population types)


Thalassia was observed at only two different population sites: single anemone and tightly grouped anemone. However, trends between the two population sites were strikingly unique. Tightly grouped anemone sites were characterized by the presence of Thalassia close (within 5 cm) to the anemones. Single Anemone sites displayed a high concentration of Thalassia much farther from the anemone site (20 cm). 

 

Fig. 7 Presence of Thalassia (segregated by population types)


Discussion                                                                        

 

The presence of Thalassia could potentially support the link between habitat and personality type (Hensley et al., 2012). If the anemones were grouping together for protection, it is reasonable to conclude that loosely grouped anemones were ‘bolder’ from the lack of perceived predation, i.e. touching a blade of Thalassia, and are consequently venturing further from each other in the pursuit of habitat and nutrients. Loosely grouped anemones

 

 

 

The idea of ‘shy’ anemones congregating for protection and ‘bolder’ anemones venturing away from a community for resources is also potentially supported by the presence of rock boring sea urchins. If ‘shy’ urchins were relying on each other for protection rather than their toxins, it would be expected that more urchins would be found in a tightly grouped population. ‘Bolder’ urchins that would utilize their own defense mechanisms would predictably react more aggressively towards sea urchins, and a higher number of anemones that are loosely grouped and ‘bold’ would yield an environment with the smallest population of sea urchins.

 

 

 

While algae trends varied slightly, it is still possible to detect trends. The majority of algae observed appeared within the 15 cm – 20 cm range, suggesting that anemones tend to avoid contact with other organisms.  

 

Conclusions                                                                       

 

One variable that was not addressed was the size and tentacle color of the anemone. Studies have shown that anemone size plays a role in interspecific contact and resulting behavior (Brace, 1978). A study examining gene flow and taking place in Discovery Bay, Jamaica showed that different tentacle colors mark two distinct genetic types of C. gigantea (Stoletzki, 2005). It would also be advantageous to acquire a larger sample size of loosely grouped anemones and divide results further into how many anemones were present. 

 

References                                                                       

Ayre, D.J., Grsoberg R.K., 1995. Aggression, habituation, and clonal coexistene in the sea anemone Anthopleura elegantissima. Am. Nat. 146, 427-43.

 

Bell, A.M., Sih, A., 2007. Exposure to predation generates personality in threespined sicklebacks (Gasterosteus aculeatus). Ecol. Lett. 10, 828-834.

 

Bosmans, F., Tytgat, J.,  2006. Sea anemone venon as a source of insecticidal peptides acting on voltage-gated Na+ channels. Toxicon 49, 550-560.

 

Brace, R.C., Pavey, J., 1978. Size-dependent dominance hieracry in the anemone Actinia equina. Nature. 73, 752–753.

 

Francis, L,. 1973. Intraspecific aggression and its effect on the distribution of Anthopleura elegantissima and some related sea anemones. Biol. Bull. 144, 73-92.

 

Hensley, N.M., Cook, T.C., et al., 2012. Personality and habitat segregation in giant sea anemones (Condylactis gigantea).

 

Stoletzki, N., & Schierwater, B. (2005). Genetic and color morph differentiation in the Caribbean sea anemone Condylactis gigantean. Marine Biology. 147(3), 747-754.

 

 






DRAFT: This module has unpublished changes.