PHYSIOLOGY OF THE MAXILLARY SUGAR SENSITIVE CELL IN THE RED TURNIP BEETLE, ENTOMOSCELIS-AMERICANA

The galeae of red turnip beetle larvae each have a single sensillum which is chemosensitive. One of the four chemosensitive cells in this sensillum responds to sugars, sucrose and mannose being the most effective of the sugars tested (Fig. 4). The electrophysiological threshold for the response to sucrose can be as low as 0.01 mM and the Kb for the response is approximately 1.0 mM (Figs. 1 and 2). The same cell also responds to several amino acids, alanine being the most effective (Table 2). When the characteristics of this sugar sensitive cell are compared with similar cells in adult flies, significant differences are found. The most obvious differences are related to amino acid sensitivity and the effect of PCMB on the response to sucrose (Table 1). When an attempt is made to compare data on sugar sensitive cells from most insects that have been studied, we find that many parameters cannot be compared directly either because they have not been measured or have not been measured in the same way. The comparisons that can be reasonably made indicate that we can expect to find many differences within the Insecta (Table 5). There is a need for a more systematic approach to insect chemoreceptor mechanisms in order to facilitate future comparisons. Suggestions for such an approach are made in the last section of this paper. © 1979 Springer-Verlag.