Movement of mitochondria in the ovarian trophic cord of Dysdercus intermedius (Heteroptera) resembles nerve axonal transport

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Abstract
The motile behaviour of mitochondria in the ovarian trophic cord of the red cotton bug, Dysdercus intermedius, was observed optically using video-enhanced differential interference contrast (AVEC-DIC) microscopy. The motion of 258 video-recorded mitochondria was analysed of which 10%–30% were found to move during the observation periods. Of the moving mitochondria 76% travelled towards the oocyte with an average velocity of 3.37 μm/ min, and 24% towards the tropharium with 2.84 μm/min. The movement was found to be basically of the saltatory type I as known from nerve axons characterized by the absence of directional reversal. In some cases short periods of interrupted motion of type II, i.e. with local oscillations, were observed. Individual mitochondria often showed velocity variations during the excursions. The hemipteran trophic cords are known to contain numerous parallel microtubules. As the observed type of mitochondrial motility resembles axonal transport, a modified transport hypothesis is presented for the microtubule-based motility of organelles in the nurse strands of telotrophic insect ovarioles.