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. 2022 Aug 10;12(16):2032.
doi: 10.3390/ani12162032.

Immunohistochemical Distribution of Serotonin Transporter (SERT) in the Optic Lobe of the Honeybee, Apis mellifera

Cristiano Bombardi  1 , Giulia Salamanca  1 , Claudio Tagliavia  1 , Annamaria Grandis  1 , Fanny Mille  1 , Maria Grazia De Iorio  2 , Giulietta Minozzi  2
Affiliations

Immunohistochemical Distribution of Serotonin Transporter (SERT) in the Optic Lobe of the Honeybee, Apis mellifera

Cristiano Bombardi et al. Animals (Basel). .

Abstract

Visual information is processed in the optic lobes, which consist of three retinotopic neuropils. These are the lamina, the medulla and the lobula. Biogenic amines play a crucial role in the control of insect responsiveness, and serotonin is clearly related to aggressiveness in invertebrates. Previous studies suggest that serotonin modulates aggression-related behaviours, possibly via alterations in optic lobe activity. The aim of this investigation was to immunohistochemically localize the distribution of serotonin transporter (SERT) in the optic lobe of moderate, docile and aggressive worker honeybees. SERT-immunoreactive fibres showed a wide distribution in the lamina, medulla and lobula; interestingly, the highest percentage of SERT immunoreactivity was observed across all the visual neuropils of the docile group. Although future research is needed to determine the relationship between the distribution of serotonin fibres in the honeybee brain and aggressive behaviours, our immunohistochemical study provides an anatomical basis supporting the role of serotonin in aggressive behaviour in the honeybee.

Keywords: SERT; honeybee; lamina; lobula; medulla; optic lobe; serotonin.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
General appearance of serotonin transporter (SERT) immunoreactivity in the optic lobes of the docile (A,B), moderate (C,D) and aggressive (E,F) honeybees. Note that SERT immunoreactable 100 µm. Abbreviations: La, lamina; Me, medulla; Lo, lobula.
Figure 2
Figure 2
Distribution of serotonin transporter (SERT)-immunoreactive fibres in lamina (A–C), medulla (D–F) and lobula (G–I) of docile (A,D,G), moderate (B,E,H) and aggressive (C,F,I) honeybees. In the lamina, SERT-immunoreactive fibres were located in the cell body layer (lcb). The lamina showed many SERT-immunoreactive fibres in the layer of fibres (lof). The outer medulla (om), the serpentine layer (sl) and the inner medulla (im) contained many SERT-immunoreactive fibres distributed across the different strata of the lobula. Immunoreactive fibres were also located in the outer chiasma (oc) and inner chiasma (ic). Note that, in the lamina, medulla and lobula, the immunoreactivity for the SERT decreased from docile to aggressive honeybees. Arrowheads indicate the border between lobula and inner chiasma. Scale bar: 10 µm.
Figure 3
Figure 3
Histograms showing the mean percentages of the image covered by SERT immunoreactivity ± standard deviation (SD) in the lamina, medulla and lobula and in the optic lobe as a complex for docile, moderate and aggressive honeybees.
See this image and copyright information in PMC

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