The distribution and behavior of Actinia schmidti By: Casandra Cortez, Monica Falcon, Paola Loria, & Arielle Spring Fall 2016 Abstract: The distribution and behavior of Actinia schmidti was investigated in Calvi, Corsica at the STARESO field station through field observations and lab experiments. Distribution was analyzed by recording distance from the nearest neighboring anemone and was found to be in a clumped distribution. The aggression of anemones was tested by collecting anemones found in clumps and farther away. Anemones were paired and their behavior was recorded. We found that clumped anemones do not fight with each other, while anemones found farther than 0.1 meters displayed aggressive behaviors. We assume that clumped anemones do not fight due to kinship. We hypothesized that another reason for clumped distribution could be the availability of resources. To test this, plankton samples were gathered in areas of clumped and unclumped anemones. We found that there is a higher plankton abundance in areas with clumped anemones. Due to these results, we believe that the clumping of anemones is associated to kinship and availability of resources. Introduction: Organisms in nature can be distributed in three different ways; random, uniform, or clumped. A random distribution is rare and only occurs when the environment is uniform, resources are equally available, and interactions among members of a population do not include patterns of attraction or avoidance (Smith and Smith 2001). Uniform, or regular distribution, happens when individuals are more evenly spaced than would occur by chance. This may be driven by intraspecific competition by members of a population. Clumped distribution is the most common in nature, it can result from an organism’s response to habitat differences. These differences can be daily or seasonal weather, environmental, and reproduction patterns, as well as social behaviors. The main causes in plant distribution is propagation and specific environmental requirements, while the main causes in animal distribution are resources such as food, water, and shelter (Smith and Smith 2001). Since anemones are mostly sessile animals, this rule can apply as less of a systematic function and more of a function of movement, therefore anemones were categorized as plants for this study. The theory of ideal free distribution also helps explain the geographical spacing of organisms. This states that species will distribute themselves to gain equal fitness. All else being uniform, if there is twice as many resources in an area there will be twice as many species in that area (Smith 1982). Actinia equina was previously thought to be a single species that included red beadlet anemones in the Atlantic as well as in the Mediterranean. Recently, it has been discovered that the species in the Mediterranean is not the same, and has since split off as Actinia schmidti (Monteiro et al 1997). It is unclear if the two species have completely different attributes, but some similarities may still exist (Monteiro et al 1997). Actinia equina can reproduce both sexually and asexually. The anemone creates clones through regeneration/basal laceration, brooding, and budding. Regeneration/basal laceration happens when the anemone’s pedal disk is lacerated, causing it to regenerate itself from two separate halves (Turner et al 2003). A. equina is also one of the only anemones known to brood its young, meaning that the anemone is viviparous. The juvenile anemones will crawl out of the 1 parent anemone and settle around it (Monteiro et al 1997). Budding is when new clones will develop from cell division at a particular site on the anemone and will remain attached to the mother anemone until they mature (Orr et al., 1982). These methods of reproduction are all similar in that they consist of new clonal, juvenile anemones forming and setting around the main focal genit. Since anemones are mostly sessile animals, and are only capable of small, very slow movements, it is unlikely that clones move far from the parent anemone (Shick 1991). Actinia equina has been found to be non-aggressive towards its clone mates and therefore will aggregate together in clumps. The anemone displays inter-clonal aggression and will fight with unrelated, non-clonal individuals of its own species, as well as other species of anemones (Turner et al 2003). It has been postulated that Actinia equina’s intraspecific aggression is due to maintaining territory for its clonal juveniles (Quicke & Brace, 1983; Brace & Quicke, 1985). Anemones are able to recognize their own clone mates through a highly specific cellular recognition system that allows anemones to distinguish between syngeneic and allogeneic tissue (Lubbock and Shelton 1981). During fights, A. equina uses purple fighting tentacles called acrorhagi that contain stinging nematocysts. When the anemone engages in an attack, it will extend these stinging cells, often leaving an acrorhagi peel on the opponent. This peel is a thin layer of tissue that will continue to sting even after the other anemone has retracted (Turner et al 2003). This process can take only a few minutes and is a major function of aggression. It will often result in the locomotive relocation of an unfamiliar/unrelated anemone (Ager 2008). The goal of this study is to better understand the mechanisms driving the distribution and behavior of A. schmidti. In Calvi, Corsica, France, at the STARESO field research center, we noticed an uneven, spatial distribution of Actinia schmidti. With this background information, we suspected their distribution to be clumped. Given that this was the pattern, we predicted that it was associated with kinship and resources. Our three hypotheses were: 1. The distribution of Actinia schmidti along the rocks on the coves is clumped. 2. Individuals in groups or in close proximity are related, therefore anemones found close to one another will be less aggressive than those individuals found far from one another. 3. There will be a higher abundance of plankton in areas with clumped anemones versus areas with unclumped anemones. Materials and Methods: Species description- Actinia schmidti is also known as the red beadlet anemone. This species is found on rocky shores in the north Mediterranean Sea, near the south of France (Monteiro 1997). They were observed above and below the waterline on the rock face. It is characterized by a small red stock and tentacles with a purple ring of stinging nematocysts on the outside of the central disks, called the acrorhagi. Site Description- This study was conducted during October of 2016 at Station de Recherches Sous-Marines et Océanographiques (STARESO) near Calvi, Corsica in France. Field observations were done in coves to the North and South of the harbor. This area of the Mediterranean Sea is mostly rocky bottoms, and covered in Posidonia oceanica. Actinia schmidti is typically found just below or at the water line of the intertidal zone. It attaches to bare rock face that has little to no algal cover. 2 General Approach Field Methods- Question 1: Distribution of Actinia schmidti: To test our hypothesis that Actinia schmidti have a clumped distribution, field observations were conducted. Four coves to the North and South of the STARESO harbor were chosen. We chose to observe anemones on the north facing rock within the coves to help control for light and wave/wind disturbance. Using meter tapes, each cove was measured from the tip. The smallest cove was found to be 8 meters, therefore we used this as our standardized length. Within that 8- meter section, the distance between individual anemones were recorded. The purpose of these graphs is to depict whether anemones display a clumped distribution. A variance to mean ratio test was used to determine the distribution. See Figure 1. Figure 1: Map of sites Lab Methods- Question 2: Aggression To test our kinship hypothesis, individuals found in clumps and solitary were brought into the lab where trials were conducted. We defined a clump as a group of three or more anemones 0.1 meters away or less from one another. See Figure 2. We used aggression as a proxy of relatedness. Three were taken from a single clump and one individual from a farther distance within the 8-meter section. All anemones were placed on their own rock outside of the water and given five minutes to settle. They were given 8 hours by themselves in the tank to adjust. At night, two anemones from the clump were placed next to each other in a dish as control. One 3 anemone from the clump and another found from a farther distance were placed together in a separate dish. They were left overnight, and interactions were recorded by a GoPro time lapse. The diameters of each individual were recorded and anemones were paired by similar size. Fights, as well as number of hits, were recorded from the video the next morning. We defined a successful fight as when one anemone would flash, extend, and reach with it’s acrorhagi to attack the other anemone. We counted the number of times this happened for each anemone and recorded it as a hit. Every day, new anemones from one of the 8 coves were collected and new trials ran each night. To quantify the level of aggression, we counted the ‘fights’ between anemones and categorized them binomially as ‘yes’ or ‘no’. The test we ran for this data was a chi-square test. The test we ran for the number of hits was a one-tailed t-test. Figur e 2: anemones in a clump: 0.1 meters away or less from one another. Question 3: Resource Availability Skin divers and kayakers were used to test our hypothesis on resource availability. Skin divers would locate clumped and unclumped anemones within the same four coves to the North and South of the harbor.