INTRASPECIFIC AGGRESSION AND POPULATION DISTRIBUTIONS OF THE SEA ANEMONEMETRIDIUM SENILE

Abstract

Aggregations of the sea anemone Metridium senile in Monterey Harbor sometimes contained only one clone (genetically identical individuals) but often contained two or more intermingled clones. The frequent occurrence of mixed clonal aggregations was perplexing, because M. senile uses fighting ("catch") tentacles in intraspecific agonistic interactions. A photographic survey of 19 quadrats showed that mixed clonal aggregations of anemones persisted throughout the 3.5 year study. Locomotion by the anemones, low frequency of nonclonemate contact, low population density, and infrequent occurrence of fighting tentacles were eliminated as possible explanations for the persistence of mixed clonal aggregations. Laboratory studies revealed differences among clones in the frequencies of fighting tentacle inflation and of injury to nonclonemates. We believe that low expression of these aggressive traits might permit intermingling of clones. However, high expression of aggressive traits was not found consistently in clones which were not intermingled, and therefore may not cause the segregation of such clones. Apparently, the most important factor contributing to the intermingling of clones was habituation of anemones to nonclonemate contact. The decrease in fighting tentacle inflation observed during two, six-day laboratory experiments was not due to fatigue, because contact with unfamiliar nonclonemates renewed aggression. We believe that habituation to nonclonemate contact occurs in situ, and that loss of habituation must occur occasionally to account for the occurrence of fighting tentacles.

Long-term effects of competition on coral growth and sweeper tentacle development

“…1), possibly because they did not contact any competitor tissues. Thus, our corals likely did not habituate to competitor contact as observed by Purcell & Kitting (1982) for fighting sea anemones, since tissue contact was not maintained in our experiment. Damage to the F. complanata colonies continued to increase even after the elongated P. daedalea tentacles shrank (compare Figs.…”

“…3). In other species of corals and sea anemones, competitive ability is known to vary widely among individuals and to cause substantial differences in opponent survival and growth (Brace 1981, Ayre 1982, Purcell & Kitting 1982, Rinkevich & Loya 1983a, Chadwick-Furman & Rinkevich 1994. The amount of competitive damage inflicted on each coral thus appeared to influence its skeletal growth rate (Fig.…”

Sea Anemones through X-Rays: Visualization of Two Species ofDiadumene(Cnidaria, Actiniaria) Using Micro-CT

“…Absence of visibly differentiated fighting tentacles in most specimens of D. manezinha and all specimens of D. leucolena is not exceptional within Diadumenidae, as these structures have never been observed in some species (e.g., D. fransciscana and D. lighti) and when present may appear in frequencies as low as 1.7% in some populations (e.g., populations of D. lineata in England: Williams, 1975). Likewise, fighting tentacles are ephemeral during an individual's lifespan, being induced by territorial threats from non-clonemates (Williams, 1975;Purcell, 1977;Watson and Mariscal, 1983a;Östman et al, 2010a) and restricted to individuals along the border of an aggregation facing other aggregates (Purcell, 1977;Purcell and Kitting, 1982). The reversal from fighting tentacles is also possible, being correlated with isolation of individuals to areas with non-clonemates or an animal's nutritional state (Williams, 1975;.…”

Tentacle cnidae of the sea anemone <i>Metridium senile</i> (Linnaeus, 1761) (Cnidaria: Anthozoa)

“…Narrow corridors free of anemones often separate clones of different species or different clones, and individuals bearing catch-tentacles are found predominantly along these borders (Purcell, 1977b;Purcell and Kitting, 1982;Fukui, 1986). Catch-tentacles have been recorded in M. senile from the British coast (Williams, 1975) and from the Netherlands coast (Ates, 1989) and in the Californian M. farcimen (Brant, 1835) (Hand, 1956(Hand, , 1961Purcell, 1977b).…”