Spontaneous behavioral rhythms in the isolated CNS of insects – Presenting new model systems R. Hustert a,⇑ , A.M. Mashaly b,c,1 a Georg-August-Universität Göttingen, JFB-Institut für Zoologie und Anthropologie, Abteilung Neurobiologie, Sensomotorik, Berliner Str. 28, D-37073 Göttingen, Germany b Department of Zoology, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia c Department of Zoology, Faculty of Science, Minia University, El-Minia, Egypt article info Article history: Available online 17 May 2012 Keywords: Central pattern generators Insects Isolated ganglia Spontaneous rhythms Locusts Crickets Red palm weevils abstract Three new model systems for the study of rhythm generation in the isolated insect central nervous sys- tem are presented. Natural behavioral rhythms are produced in these cases spontaneously in the isolated CNS. They can be monitored as output of motoneurons at peripheral nerves. Recording from the neurons of the pattern generating networks during this output gives insight into neural control principles of locust respiration, of hemolymph pumping in accessory pumping organs of crickets, and of crawling movements in larvae of the weevil Rhynchophorus ferrugineus. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction The isolated CNS or even isolated ganglia of insects can produce rhythmic motor output that originates from a network of neurons called central pattern generator (CPG). When such a pattern is well correlated to a natural rhythmic behavior (Marder and Bucher, 2001) and continues without pharmacological excitation (Schön- eich and Hedwig, 2011) or genetic manipulation (Marley and Baines, 2011) it is a spontaneous and autonomous CPG. In insects, neuronal networks of autonomously active CPGs have been ana- lyzed to some extent for locust oviposition rhythms (Thompson, 1986), for frontal ganglion rhythms (Ayali, 2002) and for fictive feeding patterns of Manduca larvae (Bowdan and Wyse, 2000). For these neuronal rhythms the relation to the natural behavior were considered rather variable and therefore may be ambiguous. For their CPGs several single neuronal elements and some of their connections were identified. Generally, the CNSs of insects and other invertebrates have the advantage that their individual neu- rons have a unique function and a constant location in the CNS. In some invertebrate groups the specifically large and easy to iden- tify cell bodies of their neurons have eased intracellular studies of autonomous CPGs. That revealed the functional principles of respi- ratory pattern generation in mollusks (Syed et al., 1990), the variety of functional states of gastric mills of crustaceans (review: Selverston, 2010) and the different patterns for the control of the heartbeat in leeches (review: Wright and Calabrese, 2011). Here we present three autonomous CPGs of insects suitable as new and possibly simpler model systems for a detailed neuron by neuron study of functional principles of stable rhythm genera- tion. These robust and natural rhythms persist in isolated ganglia with low variability of their pattern for 4–5 h in isolation. We de- scribe the specific features of the spontaneous rhythmic motor out- put for: (1) A segmental abdominal ganglion (AG5) of locusts with an intrinsic CPG for its specific respiratory pattern. (2) The terminal ganglion (TG) of female crickets releasing the very stable pattern for accessory hemolymph pumping. (3) The complete isolated ven- tral nerve chord of a beetle larva releasing a stable and continuous fictive crawling pattern. 2. Materials and methods The locusts (Locusta migratoria) and crickets (Acheta domesticus) were taken from laboratory cultures of the Zoology Institute in Göttingen. The larvae of the weevil Rhynchophorus ferrugineus were obtained from a culture of the Zoology Institute of the King Saud University in Riyadh, Saudi Arabia. The weevils were reared in pieces of fresh sugar cane in the dark but many other artificial diets have also been described (Rahalaker et al., 1978; Kaakeh, 1998). That eased laboratory studies of this destructive pest for date palms and several other palm trees which in the last decades 0928-4257/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jphysparis.2012.05.001 ⇑ Corresponding author. Tel.: +49 551 395436; fax: +49 551 395427. E-mail addresses: rhuster@gwdg.de (R. Hustert), mmashely@ksu.edu.sa (A.M. Mashaly). 1 Tel.: +966 1 46 73465; fax: +966 1 467 8514. Journal of Physiology - Paris 107 (2013) 147–151 Contents lists available at SciVerse ScienceDirect Journal of Physiology - Paris journal homepage: www.elsevier.com/locate/jphysparis