IDENTIFICATION OF HETERORHABDITIS SPECIES

    Presently the genus contains 8 species. Species are identified based mainly on morphometrics of the IJ, but the following key uses a combination of characteristics of both the IJ and male. After a species is identified using the key, the identity should be verified by comparing its morphometrics with the data from original descriptions or this Diagnostic characters. Ratios and abbreviations used in the following key are: E% = EP/T x 100 (EP = distance from anterior end to excretory pore; T = tail length); GS% = gubernaculum length divided by spicule length x 100; IJ = infective juvenile.

KEY TO SPECIES OF THE GENUS HETERORHABDITIS

(Key to species of Steinernema click here Species identification, Steinernema)
1- Average body length of IJ >700 um (736-800) long 

     ............................................................................      H. megidis Poinar et al., 1987

     Average body length of IJ < 700 um (528-685) long ............................................. 2
2- IJ tail short, averaging 76 um (80 m or less), E% about 147
     ...........................................................................................H. brevicaudisLiu, 1994
    IJ tail longer, averaging 80 um or more (84-119), E% = 127 or less ..................... 3

 3- IJ body length averaging > 600 um..........................................................................4
     IJ body length averaging < 600 um..........................................................................6

 4- In IJ, E% > 120, c > 7; lamina of spicule with ventral expension
     .....................................................................................H. argentinensis Stock, 1993
     In IJ, E% < 120, c < 7; lamina of spicule without ventral expension ...................... 5

 5- IJ body length averaging 654 um, E% about 96, c about 6.1; male body width
    averaging 51 m, spicule length averaging 45 um
    ..................................................................................H. marelatus Liu & Berry, 1996
    IJ body length averaging 685 um, E% about 108, c about 6.6; male body width
    averaging 41 m, spicule length averaging 51 um ..................H. zealandica (Wouts,
   1979)Poinar, 1990

 6- IJ body length averaging 528 um, E% about 94 ........................................H. indica
     Poinar et al., 1992
     IJ body length averaging 570 um, E% > 100 ......................................................... 7

 7- E% of IJ about 127; spicule averaging 47 um, lamina with ventral expansi..on
     ............................................................................H.hawaiiensis Gardner et al. 1994
     E% of IJ about 112, spicule averaging 40 um, lamina without ventral expansion
     ................................................................................. H. bacteriophora Poinar, 1975
 
 

To identify species of Steinernema and Heterorhabditis, the following should be considered:
a) IJ morphometrics usually are insufficient for species identification, and male and female characteristics must be considered.
b) IJ produced on artificial media (laboratory reared or commercial products) are shorter (rarely longer) than those produced in vivo, and usually do not meet the criteria of the original description. Males and females collected 4 or 5 days after the host dies, and IJ collected for one week after they first appear from cadavers, usually meet original species descriptions. 


Updated October, 2002
This document was constructed and is maintained by KHUONG B. NGUYEN
Entomology & Nematology Department
University of Florida