ORIGINAL PAPER S. Blumberg á T. Haran á D. Botzer á A. J. Susswein á T. Teyke Pheromones linked to sexual behaviors excite the appetitive phase of feeding behavior of Aplysia fasciata. I. Modulation and excitation of appetitive behaviors Accepted: 28 November 1997 Abstract Pheromones presumably secreted by mating conspeci®cs ± as well as homogenates containing tissue that is homologous with the atrial gland ± increase the time that Aplysia fasciata spend feeding. This eect is caused by increasing the number of feeding episodes initiated in response to food, whereas the duration of a feeding bout remains unchanged. The increase in the number of feeding episodes is related to increases in head waving and crawling, i.e., appetitive movements that bring the animal into contact with food, as well as an increase in the responsiveness to food after it is contacted. Releasing a homogenate containing atrial gland tissue, or egg laying hormone, in the water near the animal elicited head lifting similar to that seen when animals are food aroused. The data indicate that the facilitation of Aplysia feeding caused by pheromones arises in part by an excitation of appetitive behaviors. These ®ndings suggest that neurons generating appeti- tive behaviors will be aected by pheromones. Key words Feeding á Mating á Pheromone á Atrial gland á Egg-laying hormone Abbreviations: ADH anti-diuretic hormone á BCP bag cell peptide á C-PR cerebro-pedal regulator á ELH egg laying hormone á LHD large hermaphroditic duct Introduction Pheromones released by conspeci®cs as a result of mating and egg laying facilitate a number of behaviors in Aplysia (Audesirk 1977; Botzer et al. 1991; Levy et al. 1997; Painter et al. 1989). Many of the behavioral eects of pheromones can be mimicked experimentally by placing a homogenate containing the atrial gland into the water along with an animal (Blumberg and Susswein 1998; Painter et al. 1989; Susswein and Benny 1985), suggesting that some of the pheromones may be syn- thesized and released from this tissue. The atrial gland produces a number of peptides that share sequence ho- mology with peptides that are expressed in and secreted from the neuro-secretory bag cells of the abdominal ganglion (Heller et al. 1980; Nagle et al. 1986; Rothman et al. 1986; Scheller et al. 1983). Placing peptides from the bag cells in the water along with an animal can also mimic some of the behavioral eects caused by phero- mones that are released in natural conditions (Blumberg and Susswein 1998; Levy et al. 1997). Feeding is one of the behaviors aected by sexual pheromones (Botzer et al. 1991). Food in the water initiates a food arousal state, and triggers appetitive feeding movements, such as locomotion, head lifting and head waving, by which the animals orient to and locate the food (Kupfermann 1974; Teyke et al. 1990a; Teyke et al. 1992). Contact of food to the lips initiates consummatory behaviors, such as biting and swallow- ing (Kupfermann 1974). Aplysia feeding is widely used for examining the neural control of behavior (Kup- fermann et al. 1991), and much is already known about how feeding is modi®ed by processes such as a change in motivational state (Kupfermann et al. 1991) and by learning (Chiel and Susswein 1993). In addi- tion, many neurons initiating or modulating feeding have been identi®ed (Hurwitz and Susswein 1996; Rosen et al. 1991; Susswein and Byrne 1988; Teyke et al. 1990b, 1993; Weiss et al. 1978), which makes it possible to relate the properties of the neural circuit and of identi®ed neurons to features of the natural behavior. Speci®cally, these studies have shown that the identi®ed cerebral neuron C-PR (cerebral-pedal regulator) is involved in the initiation of food arousal and of appetitive movements, in particular of head J Comp Physiol A (1998) 182: 777±783 Ó Springer-Verlag 1998 S. Blumberg á T. Haran á D. Botzer á A.J. Susswein (&) Department of Life Sciences, Bar-Ilan University, Ramat-Gan, 52 900, Israel Tel: +972-3 531 8388; Fax: +972-3 535 1824, e-mail: Avy@snnap.ls.biu.ac.il T. Teyke Institut fuÈr Zoologie (III), Johannes Gutenberg-UniversitaÈt, D-55099 Mainz, Germany