Histology of the LarvalNeodiprion abietis(Hymenoptera: Diprionidae) Digestive Tract

Abstract

The alimentary canal ofNeodiprion abietislarvae is a straight tube divided into foregut, midgut, and hindgut. Posterior to the mouth, the foregut is further divided into the pharynx, esophagus (crop), and proventriculus, all of which are lined with cuticle. A pair of muscular, chitin-lined pouches branch off the anterior foregut and lie lateral to the alimentary canal. Gastric caeca are located at the anterior end of the midgut, where the peritrophic membrane is formed and was observed throughout the midgut. A single layer of midgut columnar epithelial cells abuts on the basal lamina at one end with microvilli extending into the gut lumen at the other. Nidi of regenerative cells were observed between columnar epithelial cells at the basal lamina. Malpighian tubules are attached to the posterior end of the midgut. The hindgut consists of the pylorus, a muscular ileum connecting to a bulbous rectum, which then opens to the anus.

Pathology of aGammabaculovirusin Its Natural Balsam Fir Sawfly (Neodiprion abietis) Host

“…Balsam fir sawfly larvae were collected from balsam fir branches at the leading edges of the balsam fir sawfly population outbreak in the Corner Brook-Deer Lake region beginning in 1999 [18,26]. Larvae on branches were maintained in 20-kg brown paper bags at 4…”

“…Larval head capsules were measured using a calibrated micrometer mounted in the objective lense of a dissecting microscope [26,27]. Third to fifth instars were selected, at random, for NeabNPV infection because of their size and ease of handling compared with first and second instars.…”

“…Control larvae were fed single 1 µL 10% honey droplets without OBs. Larvae were individually reared on fresh, clean (5 min soak in 0.25% aqueous NaOCl followed by three 15 min rinses in tap water) balsam fir foliage [26]. Most control larvae were reared through until death or pupation to monitor for ambient levels of NeabNPV infection, whereas others were prepared for cytological examination at 48 and 96 h after feeding.…”

“…Larvae fed on NeabNPV OBs were harvested at 0.5, 1, 2, 5, 8,12,18,24,36,48,60,72,96, and 120 h after inoculation (hpi). The methods for the preparation, sectioning, and viewing of Paraplast Plus (Sherwood Medical, St. Louis, Mo, USA) and epoxy (EponAraldite, Electron Microscope Sciences, Hatfield, PA, USA) embedded larval tissues have been detailed elsewhere [26]. For in situ hybridizations, NeabNPV-infected (48-72 hpi and 96-120 hpi) and uninfected control larvae were decapitated and immediately submerged in freshly prepared 4% paraformaldehyde in phosphate-buffered saline (PBS) and were fixed for 3 h at 20…”

“…There is, however, a dearth of information on the pathology of sawfly NPVs in the literature, although they are thought to only infect the midgut epithelium of their hosts [24,25]. Recently, the histology of the larval digestive tract of healthy N. abietis has been described [26]. For these reasons and to provide a visual reference for molecular studies on Gammabaculovirus pathology, we have undertaken a study of the pathology of NeabNPV in its natural N. abietis host.…”