j *@ - Sociedade Brasileira de Psicologia

V ISUA L SYSTEM O F TH E BEE: LAM INA M O NO PO LA R CELLS
JOHN MANUEL DE SOUZA
Universidade de Sâo Paulo
The monopolar cels (MC) of the lnmina gansionaris of the optic lobe of the
honeybee constitute the msl'n neural pathway for the relay of visual information from
the photoreceptors to the medula and must play an important role in the codification
of color and other asm cts of vkslnl processing. The importance of the MCs is evident
from the neuroanatomy of the 1st optic lobe as described by Ribi (1978 , 198 1) using
mas staining teclmiques. The bodies of these MCs are located just proximal to the
basement membrane which separates the retina from the lamina and their axons join
the receptor axon bundles to form the so-caled cartridges which projed into the
medula. n e short visual fibers (blue- and green-sensitive photoreceptors), terminate
witbin the lamina, where their ramifications probably synapse with spines of the MCs.
The three long (UV sensitive) visual fibers also have spines in the lamina but continue
across the outer chinsma to terminate in the distal layeys of the medplla together with
the lamina MCs. ,
Ribi first described six different types of lamina MCs (Ribi, 1975) but later
reduced this number to four (Ribi, 1981); a1l four types seem to be present in each
Ortridge.
Nltmerom other neural fibers, tangential, centrifugal and some inœrta sedis
cells, also run between the lamina and the medulla but their configurations su%est
secondary m odulatory or freedback functions. None of these, nor the amacrine cells,
which remain within the lamina, have yet been recorded from as far as is known.
A proper knowledge of the role of the k Cs in codi f y in gan'
d transmitiing
visual signals is thus fundamental to our understanding of functioning of the whole
visual system of the honeybee. Due, however, to their slender axons and to their
relative inaccm sibility, it has been much more difficult to record respom es from MCs
in the bmina than from cels in the retina and in other regions of the optic lobe - the
medula and the lobula. Menzel (1974) recorded with considerable difficulty from MCs
probably of one type, but was unable to mark them individually perhaps because the
very fi ne ti ps
of the electrodes, necessary to penetrate the cels without destroying
them, did not permit succesful injection of the did. Working in his laboratory for 10
weeks in . 1986 l was able to mark and record from some 20 cels (So1zm , Hertel,
Menzel, Venttlra, 1987) using electrodes puled on a Cnmpden puler; these electrodes
had very rme strongly tapered tips with m uch lower resistances than those pulled on
conventional pulers, thus facilitating die injection. Unfortunately the work, which was
14l