ORIGINAL PAPER Regulation of spirocyst discharge in the model sea anemone, Nematostella vectensis Sherry L. Krayesky • Janna L. Mahoney • Katherine M. Kinler • Stacey Peltier • Warnesha Calais • Kate Allaire • Glen M. Watson Received: 15 October 2009 / Accepted: 25 December 2009 Ó Springer-Verlag 2010 Abstract Test probes were touched to tentacles to investigate whether discharge of spirocysts likely is regu- lated by hair bundle mechanoreceptors. Significantly more spirocysts discharge onto test probes in the presence of vibrations at 11–15 Hz as compared to 0 Hz. Adding N-acetylneuraminic acid, NANA, shifts maximal discharge of spirocysts upwards to 36–40 Hz, and possibly to 21– 25 Hz. In contrast, NANA shifts maximal discharge of basitrichous isorhiza nematocysts downwards to 1–20 Hz. Thus, discharge of cnidae (‘stinging capsules’) is differ- entially regulated according to the type of cnida. Further- more, it appears that chemodetection of N-acetylated sugars is not a prerequisite to capturing prey because, in seawater alone, maximal discharge of cnidae occurs at frequencies overlapping movements of calmly swimming prey. Nevertheless, chemodetection of N-acetylated sugars broadens the range of frequencies stimulating maximal discharge of cnidae and, therefore, likely enhances prey capture. Introduction In recent years, our understanding of prey capture in anemones has improved. While it has long been appreci- ated that prey capture involves discharge of nematocysts, we now know that ‘tunable’ hair bundle mechanoreceptors participate in regulating discharge. In the anemones, Haliplanella lineata and Nematostella vectensis, discharge of microbasic p-mastigophore and basitrichous isorhiza nematocysts, respectively, varies according to the frequency of nearby vibrations (Watson and Hessinger 1989; Watson et al. 1998; Watson and Mire 2004; Watson et al. 2009). In the presence of vibrations, discharge occurs maximally into test probes touched to tentacles at specific, key frequencies. Interestingly, upon exposure to N-acetylated sugars including NANA, key frequencies (those that elicit maxi- mal discharge) shift downward to lower frequencies over- lapping those produced by calmly swimming prey (Watson and Hessinger 1989; Watson et al. 1998, 2009; Watson and Mire 2004). N-acetylated sugars occur in glycoproteins and glycolipids where they are exposed to the extracellular fluid. Furthermore, certain secreted proteins such as mucins are extensively glycosylated. Hence, N-acetylated sugars commonly occur on the surfaces of prey organisms (or their secreted coatings) and, as such, constitute a good chemical cue to signify that a nearby object is living, was living, or is derived from a living object. The combination of N-acetylated sugars and vibrations at low frequencies confirms that a nearby object is living and swimming in the vicinity of the tentacles. Such stimuli, detected by specific receptors, sensitize the anemone to maximally discharge nematocysts in the event of contact with the prey organism. The purpose of this study was to test whether discharge of spirocysts also is regulated by hair bundle mechanore- ceptors. The spirocysts are perhaps least well understood among the types of cnida of anthozoans (corals and anemones). Spirocysts are the most abundant cnida in tentacles specialized for capturing prey (Hand 1955; Mariscal 1974; Watson and Mariscal 1983; Sebens 1998). For most anthozoans, the tentacle cnidom (complement of cnidae) consists of three types of cnida: spirocysts; Communicated by J. Purcell. S. L. Krayesky Á J. L. Mahoney Á K. M. Kinler Á S. Peltier Á W. Calais Á K. Allaire Á G. M. Watson (&) Department of Biology, University of Louisiana at Lafayette, Lafayette, LA 70504-2451, USA e-mail: gmw5722@louisiana.edu 123 Mar Biol DOI 10.1007/s00227-009-1384-x