Aphid photoperiodic clocks

An overview is given of photoperiodic research performed with English and Scottish clones of the vetch aphid, Megoura vicine, and the black bean aphid, Aphis fabae, during the last decade, with emphasis on the photoperiodic photoreceptor and the clock-counter mechanisms. Photoperiodic photoreceptor. The photoperiodic photoreceptors of the vetch aphid, M. viciae, are located in the brain. Immunocy tochemical techniques have recently indicated that an anterior dorsal region of the protocerebrum possesses antigenic sites that are consistently labelled with a number of antibodies raised to invertebrate and vertebrate opsins and phototransduction proteins. Counter. In two clones of both M. viciae and A. fabae, long-night accumulation appears to be temperature compensated, whereas short-night accumulation is temperature sensitive. Clock. (1) The clocks of the English and Scottish clones of M. viciae can be modelled by a slowly damping long-night (LN) system and a rapidly damping short-night (SN) system. The LN system of the Scottish clone damps more slowly and has a shorter period than that of the English clone. The critical night length (CNL) of the English clone is highly temperature compensated, that of the Scottish clone is less so. (2) The clock;in presumptive: gynoparae of an English clone of A. fabae can be modelled by rapidly damping LN and SN systems; the SN system's damping rate being temperature dependent, but that of the LN system being temperature compensated. (3) The clocks in gynopara and male producers of the English clone of A. fabae are mimicked by rapidly damping LN systems and self-sustained SN systems, while in a Scottish clone they are assumed to consist of slowly damping LN systems and self-sustained SN systems. (4) The CNLs for gynopara and male production are temperature compensated in both the English and the Scottish clones of A. fabae. (C) 2001 Elsevier Science Ltd. All rights reserved.