In this study, we found that self and non-self stimuli differentially influenced two effector systems: cnida discharge and tentacle contraction.
Stimulation of one or more receptor systems in the resident and/or the encroaching anemone might result in an activation of a wide variety of effector systems, including cnida discharge, mesenterial filament extrusion, contraction of tentacles and/or the body column, bending of the body column away from the opposing anemone, bleaching, and development and deployment of catch tentacles or acrorhagi (Purcell and Kitting, 1982; Chornesky, 1983; Kaplan, 1983; Watson and Mariscal, 1983; Buss et al., 1984, 2012; Hidaka, 1985; Sebens and Miles, 1988; Ayre and Grosberg, 1995; Rinkevich, 2012).
When properly acted upon by the supporting cells, the cnidocyte initiates the rapid eversion of its cnida, a process termed discharge.
Operationally, [S.sub.t] is measured as the adhesive force in the absence of all cnida discharge (Thorington and Hessinger, 1996, 1998).
Nematocysts, one of three types of
cnida, are intracellular capsules produced only by members of the phylum Cnidaria (e.g., jellyfish, sea anemones, corals).
In spite of many quantitative studies of cnida size (Stephenson, 1929; Chintiroglou, 1996; Chintiroglou and Simsiridou, 1997; Chintiroglou et al., 1996, 1997; Chintiroglou and Karalis, 2000; Zamponi and Acuna, 1991; Acuna and Zamponi, 1997; Williams, 1996, 1998, 2000), changes in cnida size with body size appear to have been overlooked or discounted; and no studies have been conducted on cnida scaling per se.
This variation within and among species allows strong comparative tests relating cnida scaling to species habitats and tissue functions.
In a companion study, Francis (2004) shows how scaling analysis can be used to detect evolutionary changes in cnida size and shape by comparing homologous cnida populations from different anemone tissues and species.
We demonstrate for the first time that scaling studies using data on cnida size and anemone body size can be useful for distinguishing between closely related species, even when the size ranges for homologous cnida populations are overlapping.
We have coined the term "afferent mechanisms" of cnida discharge to refer to those processes acting to or toward the undischarged cnida to regulate or initiate discharge, and to distinguish them from mechanisms acting out of or from the discharged cnida's effector functions, which we have termed "efferent mechanisms" (Thorington and Hessinger, 1996).
After 20 min we added formalin to 10% for 5 min to measure [S.sub.t] with adhesive force probes in the absence of any cnida discharge.
We define mechanisms that regulate the initiation of
cnida discharge (i.e., receptor-effector coupling) as
cnida afferent mechanisms.