Ahmad, I.

Bilgrami, A.L.

Jairajpuri, M.S.

Horizon / Pleins textes

Notes brèves 
SOME FACTORS INFLUENCING PREDATION BY MONONCHUS A Q U A T I C U S  
Anwar -L. Eilgrami*, Irfan Ahmad* and M. Shamim  Jairajpuri** 
Few studies have been made on the predatory 
. ability of mononchs.  Nelmes  (1974)  studied the 
predatory  behaviour of Prionchulus   puncta tus  (Dujar- 
din,  1845) & Wu  Hoeppli,  1929, while t ha t  of M012012- 
chus aquaticus Coetzee, 1968 was studied by Groo- 
taert and Wyss (1979). Jairajpuri and Azmi (1978) 
observed the  predatory  potential of Mylonchu lus  
dentatus and the practicability of using mononchs 
to  control  nematodes  was assessed by Cohn and 
Mordechai (1974) and Small (1979). 
: The rate of predation  on  different species was 
determined  by  placing five Mononchus  aquat icus  with 
25 specimens of prey in cavity blocks containing 
1 % water  agar.  Five species of prey, viz.,   Chiloplacus 
symmetr icus  (Thorne,  1925)  Thorne,  1937, Cephalobus 
sp., Mesorhabdilis  sp., Prismato la imus  sp.,  and 
Aglerzchus  parvus Siddiqi,  1963  were  used  separately. 
To observe the effect of temperature on predation, 
specimens of M.  aquaticus were lrept a t  different 
temperatures ranging from 10 to 400 together with 
25  specimens of C. symmetricus in  cavity blocks 
containing 1 % water agar. Predation was recorded 
after  24  hr.  Similarly,  the effect of agar  concentration 
' was  observed  by placing five predators  with 25 
C. symmefr i cus  in 1, 2, 3, 4, 5 and 6 % water agar. 
The  number of prey killed or devoured  was  counted 
after 24 hr. 
. Activeness  (activity) was measured  in  terms of two 
parameters. In the first experiment where different 
prey were used, i t  was expressed as displacement, 
i.e., distance (mm) moved per minute while in the 
temperature and agar concentration experiments it 
was expressed as waves per minute. A swing of the 
head  to  one  side,  then  back  over  the  initial  point  to 
the  other  extreme  and  then  back  to  the  initial  point 
was  considered  as  one  wave. 
The  frequency of predation of different  nematode 
species by  M .  aquaticus was found to  Vary. Ceplza- 
lobus sp.  and Aglenclzus  parvus were  preyed  on  more 
12 
a 
g- 
p m s  
1 Displacement 
1 
aJ 
m 
CL 
- 
5 6  
Cepha- C. symrn- Mesorhab- Prism to- 
r 6 s p .  ës d& sp. L&sp. 
Prey 
Fig. 1. Effect of type of prey and prey activeness on 
predation  rate. 
than  the  others.  This differential  predation  rate  was 
inversely related to  the activeness of the prey. The 
most  active  prey, Prismafo la irnus  sp.,  was killed the 
least  while the  least  active, Cephalobus sp., was 
devoured the most (Fig. 1). The number of Cepha- 
lobus sp. killed was significantly higher ( p  < 0.05) 
than those of C. symmetr icus  or Mesorhabditis  sp. 
It was also higher  than Prisrnatolairnus sp. ( p  < 
0.01), but from Aglerlchus  papous i t  showed  no 
significant difference ( p  > 0.05). 
The  rate of predation was also found to be influ- 
enced by differences in temperature. The optimum 
temperature  appeared  to  be 250 a t  which maximum 
predation  occurred  (Fig.  2),  and  was  significantly 
reduced a t  lower or higher  temperatures ( p  < 0.01). 
The  increased  activity of prey  and  predator  increased 
the  rate of predation  while  decreased  activity  reduced 
it.  The  activeness of both  the  predator  and  the  prey 
was maximum at 250. Predation also depended on 
the concentration of the agar medium used. One or 
2 % water  agar  was  more  suitable for the  predators 
* Section of Nernatology, Department of Zoology,   Al igarh  Musl irn  Universi ty ,   Al igarh - 202002, Ind ia .  
* * Commowealth  Institute of Parasitology, 395 A Hatfield Road,  St. Albans,   Herts .  AL4 OX U ,  England.  
Revue   Nématol .  6 ( 2 )  : 325-326 (1983) 325 
A.  L. Bilgrami, I .  Ahmad h M. S. Jairajpuri 
o-o Predator  activeness 
; 15 t W P r e y  k i l l ed  p\ c--. Prey  activeness 30 
IO 15 20 25 30 35 LO 
Temp OC 
Fig. 2,. Effect of different temperatures on predation 
rate. 
and  not  much difference in  the  rate of predation  was 
observed bet#ween them (Fig. 3). Higher concentra- 
tions reduced predation significant(1y ( p  < 0.01) and 
in 6 % agar no prey was killed. In this case also 
predation appeared to be related to the activeness 
of the predat,ors and the prey as was the case for 
temperature.  Higher  agar  concentrations  reduced 
aciivity  and also predation.  Maximum  predation 
occurred in 1 % agar. 
From  the  data  presented, it is  evident tha t  M. aqua- 
tikus showed no consistent predatory pattern with 
different  prey  species  and  that  some were devoured 
more than others. Such differences could probably 
be related to the activeness of the prey, the less 
active  being  more  vulnerable  to  attack  than  the 
Fig. 3. Effect of different  agar  concentrations  on 
predation  rate. 
more  active,  and it may  be for this  reason tha t  signi- 
ficantly more Cephalobus sp. were killed than Pris- 
rnatolaimus sp.  Maertens  (1975)  using Prionchulus 
puncfatus observed an average of ten Panagrellus 
rediuiuus killed per  day while  Nelmes (1974)  using  the 
same  predator  but Aphelenchus auetzae as prey 
recorded ten kills per  hour. It seems  possible that  this 
difference could be due to differences in  prey beha- 
viour,  and  one of the  most likely  causes may  be  the 
differential prey activeness, as free-living nematodes 
possess  higher  endogenous activity (Croll, 1972). 
Besides, the  experimental  techniques  might.  have also 
caused  differences in  predation. 
Like prey activeness, predator activeness is also 
an  important  factor  governing  predation.  Those 
factors,  such  as  temperature  and  agar  concentration, 
which jnfluenced predator activity also influenced 
predation  rate. 
ACKNOWLEDGEMENTS 
We  thank  the Chairman,  Department of Zoology for 
laboratory  facilities  and  the UGC and CSIR  for 
financial  assistance  to the first and second author. 
REFERENCES 
COI-IN, E. & MORDECHAI, M. (1974). Experiments in 
suppressing citrus nematode populations by use of 
marigold  and a predacious  nematode. Nematol. 
medit., 2 : 43-53. 
CROLL, N. A. (1972). Behavioural activities of nema- 
todes. Helnzinthol. Abstr., 41 (B) : 87-105. 
GROOTAERT, P. & WYSS, U. (1979).  Ultrastructure  and 
function of the  anterior feeding apparatus  in Monon- 
chus aquaticus. Nematologica, 25 : 163-173. 
JAIRAJPURI, M. S. & AZMI, M. 1. (1978). Some studies 
on the  predatory  behaviour of Mylonchulus  den- 
tutus. Nematol. medit., 6 : 205-212. 
MAERTENS, D. (1975). Observations on the life cycle 
of Prionchulus punctatus (Cobb, 1917) (Nematoda) 
and some culture conditions. Biol. Jb. Dodonaea., 
43 : 197-218. 
NELMES, A. J. (1974).  Evaluation of the feeding 
behaviour of Prionchulus  punctatus, a  nematode 
predator. J .  anim. Ecol., 43 : 553-565. 
SMALL, R. W. (1979). The effects of predatory nema-, 
todes  on  population of plant-parasitic  nematodes  in 
pots. Nematologica, 25 : 94-103. 
Accepti pour publication le 29 juillet 1982. 
326 Revue  Nématol. 6 ( 2 )  : 325-326 (1983) 


Some factors influencing predation by Mononchus aquaticus

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