Metamorphic changes in the brain of Chironomus dolichotomus (Diptera:Chironomidae)

The larval brain lacks external differentiation of the three neuromeres. The neurilemma is well developed but the perineurium has few sheath cells. The central complex is represented by well developed and elongated central and ellipsoid bodies. The corpora pedunculata are feebly developed and only two optic lobe anlagen are differentiated from the lateral projections of the larval protocerebrum. The deutocerebrum is represented by a feebly developed medullary mass whereas the tritocerebrum is not well differentiated. In adult, the ellipsoid body becomes much conspicuous and the central body fits in the anterior concavity of the former. The corpora pedunculata has well developed calyx, stalk and beta lobes. The medulla externa becomes enormously large and the lobula and lobula plate get cut off from the protocerebrum. A single optic commissure joins the medulla externa of opposite sides. The deutocerebrum lacks nodulation and deutocerebral commissure joins the two opposite lobes. The tritocerebrum remains feebly developed. In pupal period the neurilemma becomes wavy and degenerates at certain places, however, its complete degeneration is never noted. Haemocytes are not found around the neurilemma. The sheath cells become vacuolated. Ventral tubercles appear on the posterior region of the ellipsoid body.