Esophageal gland development linked to the life cycle of Nacobbus aberrans (Nemata: Pratylenchidae).

摘要

The life cycle of Nacobbus aberrans was studied to provide a context to study esophageal gland (EG) development. This species was cultured in tomato plants under controlled conditions. The life cycle was followed under continuous, optimal environment, and with these conditions interspersed by periods of suboptimal day and night temperatures, as well as photoperiod. Results with optimal conditions agreed with previous studies, except for the earlier molting of second-(J2) stage juveniles, and the presumed obligate quiescence of J4. Suboptimal conditions tested arrested the activity of J3 and J4. Yet, differences in their development facing these conditions suggest that J4, relative to J3, is the preferential survival stage. The developmental biology of the EG of N. aberrans was studied as related to its life history. The dorsal gland (DG) and two subventral glands (SvG) of seven developmental phases in five life stages were examined with light and electron microscopy, and their secretory activity was inferred by morphology, and the abundance of organelles associated with secretory pathways. Results suggested that, in N. aberrans, the EG activity changes markedly throughout pre-parasitic and parasitic, migratory and sedentary life stages. The high secretory activity of the DG and SvG of J2 drops markedly in the presumably non-feeding J3 and J4, as well in migratory females. Feeding and secretory activity are resumed in sedentary females, in which the DG presumably participates in induction and maintenance of feeding sites, and the SvG is involved in physiological roles other than digestion. These results provided reference points to test novel approaches to assess EG activity in N. aberrans, and ultimately in other Tylenchida. Eleven developmental phases covering the whole life cycle of N. aberrans were stained, using a variety of protocols, with the Golgi complex-specific stain BodipyRTM-FL C5-ceramide, mouse anti-alpha-tubulin monoclonal antibody, and diamidinophenolindole (DAPI). As expected, BodipyRTM -FL C5-ceramide stained active EG of J2, and did not stain inactive EG of J3, J4, and migratory females. Unexpectedly, active EG of males and sedentary females were not stained, although staining of intestinal cells and (or) gonads confirmed the penetration of BodipyRTM-FL C5-ceramide in the nematode body. Mouse anti-alpha-tubulin monoclonal antibody and DAPI failed to selectively stain microtubules in active EG.