| dc.description.abstract | From December 1981 up to April 1983 ecological and biochemical
studies were carried out on the Simulium damno Sum complex sibling
spec~es in nine river-systems of Kenya, of which only six were
found suitable for ~. damno sum s.l. breeding. Ecological studies
were also conducted on 14 other Simulium species from the same
river-systems, viz. ~. hargreavesi Gibbins, ~. medusaeforme
Pomeroy, S. africanum Gibbins, S. vorax Pomeroy, S. bovis de
Meillon, S. nili Gibbins, ~. hirsutum Pomeroy, ~. sex~ens de Meillon,
S. adersi Pomeroy, S. cervicornutum Pomeroy, S. impukane de Meillon,
S. alcocki Pomeroy, ~. mcmahoni de Heillon, ~. kenyae de Meillon.
!he investigation tried to compare different ecological and
biochemical parameters such as altitude, river current velocity, pH,
turbidity, day-time water temperature, river and substrate depth,
river width or size, latitude and longitude, and biochemical
analysis us~ng isoezyme electropheresis to separate four different
forms of S. damnosum s.l. from different geographical areas
of Kenya. The study env~saged to establish an easy method of
characterizing sibling species of the above flies in Kenya.
The 10 enzyme systems used for biochemical analysis were,
Phosphoglucomutase (PGM, E.C 2.7.5.1), Hexokinase (HK, E.C. 2.7.1.1),
Phosphoglucose isomerase (PGl, E.C 5.3.1.9.), Malic dehydrogenase
(MDH, E.C. 1:1.1.37.), Malic Enzyme (ME, E.C. 1.1.1.40.), Lactic
dehydrogenase (LDH; E.C. 1.1.1.2.), 6-Phosphogluconate dehydrogenase
(6-PGDH, E.C. 1.1.1.44), Glucose-6-phosphate dehydrogenase
(G-6PDH, E.C. 1.1.1.49), Xanthine dehydro~enase (Y~H, ~.C.
1.2.1.37.), and Glutamate oxaloacetate transaminase (GOT,
E.C. 2.6.1.1;).
Based on limited ecological and cytotaxonomic studies, four
Simulium daT.nosumforms were previously reported from three widely
separated geographical areas of Kenya. These forms were designated,
"from collection labels", as 'Kibwezi', 'Kisiwani', '~:utonga'and 'Nkusi'
forms. TIlefirst was reported from the Kibwezi river-system
draining from the Chyulu Mountains, the second and third from the
foothills of Mt. Kenya and the fourth from several rivers in
western Kenya.
In the course of this study, the Kibwezi r~ver was found
devoid of any ~. damnosum s.l. in spite of repeated searches at
different points of the rive~ system and at different times and
seasons. The reason could be due to the reduced current velocity
and a slight change in the pH than what was previously reported
from this river system.
Similarly, the Mutonga r~ver was also found without S.
damnosum s.l. during the periods when collection trips were
undertaken. However, most of the ecological parameters in the
Mutonga river were quite suitable for the 'Mutonga' and 'Kisiwani'
forms based on information from Tanzanian river-systems harbouring
these forms. On the other hand, there were two river-systems,
Thiba and Nyamindi, draining from the foothills of Mt. Kenya that
were positive for S. damnosum,s .1. breeding. l.Jhetherthese two
r1ver systems are breeding grounds for the above two forms or
not requ1res further cytotaxonomic elucidation. On the basis of
PGI zymograms, there appears to be two forms of S. darnnosum s.l.
1llthe Ht. Kenya localities. One point t~ be taken into account
1S the limited number .of field trips undertaken to Mutonga river
due to logistic and financial shortcomings. Hence, one could not
boldly state that this river-system, or even the Kibwezi r1ver
for that matter, no longer supports ~. damnosum s.l.
Four river-systems 1n western Kenya, 'tala, Lusumu, Isiukhu
and Nzoia were found to be suitable breeding placescfor the above
flies. Two of these rivers, Lusumu and Nzoia, are reported for .'
the first time to be positive for ~. damnosum, s.l.
Isoenzyme characterization of the Simulium damnosum complex
sibling species from the two geographical areas, that is, the Ht.
Kenya river-system and those in western Kenya, are presented based
on 10 enzymatic loci. The two groups were easily separable uS1ng
PGH, HK, and can be separated 70% of the tine with PGI.
Using the first two enzymatic loci., PGH and HK, all the
western Kenya S. darnnosum belong to the same form while those from
o
the Mt. Kenya areas are a different form. However, PGI showed
some distinct qualitative differences 1n the western Kenya forms
1n 20% of enzymatic assays, while 50% of the Ht. Kenya forms
displayed distinct differences.
Parasitic infection rate by mermithid mematode larvae of all
larval stages of the 15 different Simulium species were identified.
It was found that S. damnosum s.l. larvae from Isiukhu and Lusumu
nvers had 17% and 13Z infection rate respectively. In bGth
rivers, only ~. damno sum s.l. larvae were infected. In Nzoia
and Yala rivers, the infection rate Has low (6% and 4% respectively)
and both S. damnosum s.l. and S. medusaeforme were infected.
Simulium damnosum s.l ..from the Thiba and Ny~niindi rivers had
veiy low infection rate of only 2% for ~ach river. The aquatic stages
of S. damnosum s.l. from the Thiba and Nyamindi rivers had
~uquatic mites attached to them, especially the pupae. ~fuile these
stages collected in the rivers of western Keriya were negative for
mites. Whether these mites are really parasites or --inadvertently
collected from the river systems flora and fauna needs further
investigation.
In a few lnstances, CDC-light traps were used at both the
Nzoia and Isiukhu rivers. A total of 116 adults of S. damnosum
s.l. from Nzoia and 3 adults from the Isiukhu river were caught
~n a 12- hour overnight collection. Two other collecting attempts
with at different periods, at the same localities gave negative
results. Light-trap collections were not tried on the Mt. Kenya
river-systems, but adults were bred from pupae corlected from
o .
these rivers and latter used for electrophoresis.
Lastly, holotype ~quatic stages (6 and 7 stages larvae)
of S. damnosum s.l. were separately collected and preserved ~n
Carnoys' solution for future cytotaxonomic studies. | en |
