Steinernema longicaudum

Shen & Wang, 1992

DESCRIPTION

Females, first generation: Body cuticle smooth. Head truncate. Lips fused, triangular, with 6 labial papillae. Basal bulb of esophagus swollen, with vestigial valve. Nerve ring located anterior to basal bulb or arround isthmus. Excretory pore anterior to basal bulb, anterior to nerve ring in most of first generation adults and all second generation adults. Gonads didelphic, usually reflexed, but straight in some of second generation Vulva a transverse slit, near mid-body, located on a protuberence. Eggs usually develop and hatch in reproductory system. Tail rounded without projection. Tail of the second generation conoid usually with a small papillae, 1-5 um long.

 Males, first generation: Gonad monorchic, reflexed. Posterior region with 23 genital papillae. Under SEM, spicules (FIG.SEM) well curved, relatively thick compared to S. glaseri. Spicule head narrowing posteriorly to form a distinct shaft. Blade well curved bearing 2 depressions laterally which divide the blade into three lobes. Near posterior end, blade reduced in width suddenly to form a tip with flattened terminus. Velum present, terminates a distance from spicule tip. In lateral view, gubernaculum boat-shaped, curved vetrally, tapering to both ends. In ventral view, cuneus Y-shaped, not reaching posterior end of corpus. Corpus separated posteriorly. Tail rounded, without mucron. Gubemaculum variable in shape, mostly boat-shaped.

Measurements: Length=2075 micrometers (um), Width=155 um, anterior end to excretory pore=136 um, to nerve ring=133 um, esophagus length=184 um, tail=36 um, spicule length=77 um, gubernaculum=48 um, D%=74.

 Infective juveniles: With sheath around body. The interior structure not as clear as in adult. Nerve ring at isthmus. Excretory pore present. Lateral field with 6-8 incisures. Tail long, averaging 95 um long, attenuate, pointed at end with a mucron. Bacterial chamber present in intestine.

 Measurements: Length=1063 um, width=40 um, anterior end to excretory pore=81 um, to nerve ring=107 um, esophagus length=145 um, tail=95 um.

 Diagnosis: This nematode can be recognized by the long tail of infective juvenile. Other characteristics can be used:
1) First generation female without mucron on tail tip, while S. glaseri with mucron.
2) Spicules are wider, more curved than those of S. glaseri; hook-shaped spicule tip in S. glaseri not observed in this species.
3) c and E value value of infective juvenile are smaller than that of S. glaseri and without overlap between these two species.
Other diagnostic characteristics can be reconized: body length, tail length, distance between excretory pore and anterior end, distance between nerve ring and anterior end, length of esophagus, absence of caudal papillae and tail mucron, and the shape of spicules.

Reference:

     Shen, C. P., and G. H. Wang 1991. Description and studies of an entomopathogenic nematode: Steinernema longicaudum sp. nov. Proceeding of the first national academy symposium. Chinese Science and Technology Press: pp=220-231.

This document was constructed and is maintained by KHUONG B. NGUYEN
Entomology & Nematology Department
University of Florida