Sensilla are sensory structures found in flagellomeres in greater quantity in antennas and
extent in other parts of the head. The sensilla have multiple sensory modalities, are
categorized as mechanoreceptors, chemoreceptors, thermoreceptors, or hygroreceptors and are
CO2-sensitive. This study aimed to identify the types of sensilla and their distribution along
the antenna present in individuals of both sexes and castes of stingless bees Melipona
interrupta and M. seminigra. The bees were obtained in colonies from Meliponário do Grupo
de Pesquisas em Abelhas (GPA) of the Instituto Nacional de Pesquisas da Amazônia (INPA).
The antennas were removed and fixed in Zamboni solution and remained in this fixative for
24 hours; washed with saline, 0.9% NaCl, were then dehydrated in acetone solution with
increasing concentrations (50%, 70%, 90%, 95% and acetone PA) for 10 minutes each; PA
acetone three washes were done in the last material was remained in 0.5 mL of acetone to
evaporate all content. The antennas were mounted on stubs for plating with gold and
photographed in a scanning electron microscope in the Thematic Laboratory Microscopy
Optics and Electronics - LTMOE at INPA. Thirteen different types of sensillum were found in
M. interrupta and M. seminigra individuals: sensilla trichodea (ST) (trichodea type I to VI),
setae, chaeticum, basiconic, placoidea, coeloconic, ampullacea and campaniform. In both
species the sensilla trichodea type I is the most abundant found between the sexes and castes,
the sensilla STIII are exclusively found of the first segment, that in males the first antennal
segment is smaller than the females, but there is no significant differences in number of STIII
between the sexes. STII can be found the first segment to the distal segment is greater number
in female of both species. STV is exclusive of the last antennal segment in the distal segment
in both species and sexes, sensilla basicônic is exclusive to females, and the number of
workers of SB in M. interrupta and M. seminigra increases every segment near the antennal
apex. The function chemoreceptor sensillum this must be exercised by another sensilla in
males, such as the sensillum placodea, because it is present in larger amount in the male
antenna in both species. The other sensilla are distributed homogeneously by the antenna.
This work represents a breakthrough in understanding the sensory organs of M. interrupta and
M. seminigra and can serve as a basis for further work in this area with this or other insect
species, however, more complementary studies to scanning electron microscopy and
electrophysiology, electroantennography should be performed to investigate what these
sensilla functions play in the studied species.
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