Rev 09/25/2023
Chromadorea Tylenchida Aphelenchina Aphelenchoidea Aphelenchoididae Aphelenchoidinae
Schistonchus (Cobb, 1927) Fuchs, 1937
Type species of the genus: Schistonchus caprifici (Gasperrini, 1864) Cobb, 1927
Synonyms:
Note: Davies et al., 2017 transferred most of the species described under the gaenus Schistonchus by Bajaj and Tomar (2014) to Ficophagus
Schistonchus is characterised by having the excretory pore opening in the region of, or posterior to, the metacorpus; Ficophagus by having the excretory pore opening very near the cephalic region; and Martininema by having it opening at the anterior end of the metacorpus. Several species of Schistonchus have a labial disc but there is no evidence of a labial disc in either Ficophagus or Martininema (Davies et al., 2015).
Frequently found associated with sycones (enclosed infrutescences) of Ficus spp. Probably transported by fig wasps.
Schistonchus spp. are probably transported by fig wasps. Some Ficus spp. are dependent on wasps for pollination. Thse syconium of a fig is an urn-shaped fleshy receptacle containing many simple male and female flowers; it opens to the exterior via a pore or ostiole. Wasps enter a syconium through the ostiole for egg deposition; they transfer pollen from male to female flowers and then die. A gall forms around each wasp egg and, within the gall, a male or female wasp develops. Male wasps are the first to emerge from galls, and they then fertilize the female wasps before the females emerge. Female wasps escape from the fig via the ostiole and fly to developing figs where the cycle is repeated. Many species of nematodes mature and reproduce within figs, and are transported among figs by pollinating wasps (Martin et al., 1973).
Many species of Schistonchus have been reported to grow and reproduce within the syconia of various Ficus spp.. Some Ficus spp. can host more than one species of Schistonchus (Bartholomaeus et al., 2012).
The nematodes feeding on fig epidermal cells, mature and lay eggs which develop into males and females. These adults produce a new generation of entomophilic females which mate, and penetrate the new generation of female wasps. Thus when the wasps emerge, ready to seek fresh sycones, they carry fertilised entomophilic nematodes in their haemolymph. The pre-reproductive female nematode, which is the dispersal stage of Schistonchus and related genera, use volatiles and cuticular hydrocarbons from the female pollinating wasps to select the appropriate wasp vector (Davies et al. 2015).
Bartholomaeus, F., Davies, K.A., Ye, W. and Giblin-Davis, R.M. 2012. Schistonchus (Aphelenchoididae) from Ficus benjamini in Australia, with description of S. benjamiina sp.n. Nematology 13:1005-1013.
Davies, K.A., Ye, W., Kanzaki, N., Herre, E.A., Esquivel, A. & Giblin-Davis, R.M. 2017. Two new species and three morphospecies of Ficophagus Davies & Bartholomaeus, 2015 (Nematoda: Aphelenchoididae) from Ficus subgenus Pharmacosycea (Moraceae) in Central America. Nematology19:351-374. DOI: 10.1163/15685411-00003055
Davies, K.A., F. Bartholomaeus, D.M. Li, Z.Q. Zhao, W. Ye and R.M. Giblin-Davis. 2020. Schistonchus macrophylla (Nematoda: Aphelenchoididae): an enigmatic taxon from sycones of Ficus section Malvanthera in eastern Australia, with description of a new subspecies. Nematology 22:999-1013.
Martin, G.C., Owen, A.M., Way, J.I. 1973. Nematodes, figs and wasps. J. Nematology 5:77-78.
Nickle, W.R. 1970. A Taxonomic Review of the Genera of the Aphelenchoidea (Fuchs, 1937) Thorne, 1949 (Nematoda: Tylenchida) . J. Nematology 2:375-392.