Observations on the Inner Labial Sensilla of Second-stage Larvae of Heterodera glycines.

Scanning electron microscopic (SEM) studies of tile cephalic region of members of the fainily Heteroderidae have failed to reFort inner labial sensilla of second-stage larvae, ahhough the labial sensilla of males have been observed (1,4,6,7,9,11,12,13). T h e existence and location of the labial sensilla in tile families Heteroderidae and Meloidogynidae have been discussed among hematologists conducting SEM studies o[ head morphology (1,2,6,13). Endo (3), in a recent transmission electron nticroscopic study o[ Heterode,a glycines Ichinohe larvae, illustrated inner labial receptor canals which opened into the prestoma. While conducting SEM research with second-stage larvae of H. glycines, six inner labial sensilla were observed in the prestoma. This paper reForts tile location anti appearance of these sensilla. Freshly hatched second-stage larvae were placed in a BPI watch glass containing 0.5 ml of 0.2 M phosphate buffer, pH 7.2 (PB). Larvae were then chilled to 6 C and o n e drop o[ a 4/c~ solution of 6 C glutaraldehyde buffered wittl PB was added daily for approximately 1 week until the final gluta~ o r raldehyde concentration approximated 2/o. Larvae then were rinsed at room temperature ill PB, fixed in 1 °7 osmiu2n tetroxide /O (buffered with PB), dehydrated in an 8-step ethanol series during a 3-day period, and critical point dried with CO~ using the apparatus described by McClure and Stowell (5). A SEM stub was prepared by affixing double sticky tape to tile surface, applying a 7 x 7-mm piece of silver tape on top of the sticky surface, and bordering the edges of tile tape with colloidal graphite. Stt2l~s