Anthopleura Essays - Actiniidae, Sea Anemone, Aggregating Anemone

Anthopleura Elegantissima The sea anemones that were collected for the "Clone Specific Segregation in the Sea Anemone Anthopleura elegantissima" experiment were collected by Lisbeth Francis in Pacific Grove, California (Biological Bulletin 1973, 144; 64-72). The topic of Francis's report is the particularity of the constant anemone-free areas dividing contiguous accumulations of these anemones and the connection of these areas to the dispersion and manner of these anemones. In her report Francis describes how she did her experiment and the result of each step. Francis also includes a discussion section where she discusses advantages versus disadvantages of segregated aggregations and organisms that are similar to these sea anemones. Francis first explains the materials and methods. One of the first steps in this section is collecting the anemones. Slowly sliding a spatula under the sea anemones, Francis dislodged them from the immense rocks to which they were attached. At the laboratory they were kept in glass bowls containing water from the sea and were fed periodically, exclusive of experimentation time. In case of any impairments from the collection process, the anemones were kept in these bowls for a few weeks before any of the experiments started. Only the most healthy anemones were used in the experiment. To free the anemones, Francis hit the bowl against a solid surface. To determine the sex of the anemones, they were severed and inspected for sex organs. When their sex organs are fully grown the female's are brownish-pink and they male's are yellowish-white. The anemones that contain one or more sex organs including oocytes or spermatocytes were recorded as having developed sex organs. The anemones were then placed in a drying oven for approximately 18 to 24 hours, so they could be dried to a constant weight. The anemones living in clusters isolated from other clusters were inspected to ascertain whether or not the anemones from each cluster were different. The anemones living in the same cluster, Francis noticed, had identical color patterns. There were other color patterns observed, but they always occurred when the cluster was separated by an anemone-free area. In each of the aggregations observed, Francis noticed that the sex of the anemones was the same. There were either all males living together or all females. None of the aggregations were integrated. Francis's conclusion from this is that since they "reproduce asexually by longitudinal fission" (403), each cluster is a clone and the anemone-free areas divide contiguous clones. From studying how size is related to sexual maturity in sea anemones, Francis drew another conclusion. She states that the more the anemones weigh, the more likely they are to be sexually developed. Francis's next experiment was to try to figure out if the anemones could place themselves into segregated groups. She collected anemones from two clones living beside each other and attached them to a plastic ball with a lead weight inside an aquarium. They were crammed together in five horizontal lines with four animals in each line. The anemones were arranged so that they were all mixed together heterogeneously instead of separated into their two separate groups. Three days later the anemones looked as if they were fairly attached to the ball so Francis removed the pins to let them move around so she could observe what kind of groups they formed. Thirteen days later, four of them had fallen off the ball and the other sixteen had organized themselves back into their segregated groups. They moved around some more after thirteen days, but there was not any connection between the two groups. Francis concluded from this experiment that segregation between clones can be established by the anemones themselves. The next experiment Francis conducted was to discover if the anemones would create anemone-free zones in-between clonal groups if there are no other species of animals and no waves. In this experiment the anemones were collected from two different clones but they were not side-by-side. Francis also kept them in the laboratory for an extended period of time (up to a year). A baking dish was lined with foam plastic and on one side, one clone of anemones was attached with insect pins and the other clone was attached to the other side. Microscope slides were lined up and taped together to prevent any contact between the two clones. Sea water was running into one side of the dish. The flow of the water was changed periodically because the anemones are inclined to move upstream and Francis didn't want the flow of the water to affect her experiment. The insect pins and the microscope slides were