Olfactory deutocerebrum

Fig. 8.7 Comparison of the olfactory deutocerebrum in a marine vs. a terrestrial isopod (Harzsch et al., unpublished data), (a) The head of Idotea baltica (Isopoda, Valvifera) with the pair of large second antennae and the pair of smaller first antennae in-between. Inset shows higher magnification of a first antenna. Synapsin-immunoreactivity (al) and the localization of Rfamide-like immunoreactivity (a2) shows the presence of a distinct OL composed of spherical glomeruli. The tritocerebrum (TC) receives the afferents from the second antennae and the protocerebrum (PC) receives highly processed visual input, (b) The head of the desert isopod Hemilepistus reaumuri with a pair of conspicuous second antennae. The inset shows the minute first antennae. Synapsin-immunoreactivity (bl) and the localization of Rfamide-like immunoreactivity (b2) shows that an OL is not present (arrow ). Scale bars 100 pm...

When the antennae are completely ablated, the male cockroach still responds to the sex pheromone (Roth and Willis, 1952). This suggests that some pheromone-responsive cells are also located elsewhere, such as on the mouthparts. Olfactory receptor cells on the palps of P. americana project to the lobus glomeratus within the posterior region of the ventral deutocerebrum (Boeckh and Ernst, 1987). However, it is not known whether pheromone-responsive cells on the palps project to the more anterior macroglomerulus. 

The primary olfactory center of insects, the AL, is a sphere-shaped part of the deutocerebrum that receives sensory input from ORNs present on antennae and mouthparts (Figure 24.1 A). The AL consists of spheroidal neuropilar structures, glomeruli, where synaptic contacts between ORN axons and AL interneurons take place. In most insect species the AL contains 40 to 160 glomeruli arranged... 

---