Table Of ContentScandinavian Institute ofMrican Studies 1968
e s e
r e o r t
Gunnar C rlss n
Benthonic F una
in African Wa ercour es
with Speci 1R feren e
to Black Fl Po atio
Research Report No. 3
Gunnar Carlsson
BENTHONIC FAUNA IN AFRICAN
WATERCOURSES, WITH SPECIAL
REFERENCE TO BLACK-FLY
POPULATIONS.
Seandinavian e of Studies
BEN'l'HONIC FAUNA IN AFRICAN WATERCOURSES,
WITH SPECIAL REFERENCE TO BLACK-FLY POPULATIONS
By Gunnar Carlsson
INTRODUCTION
During July QYlr1 1\1.1gust 1965 and 1966 investigations were carried out
in watercourses in diff~rent ~arts of Africa, in order to test a
methodology for studying the environmental factors of importance for
the larvae of the vectors of onchccerciasis, the black-fly species
Simulium damnosum (s.L,) and So neavei (s.,L). These Simuliidae are
carriers-'o~rthe~-filarialworm OnDh-åcerca volvulus, the cause of
onchocerciasis, a disease which'is of great importance in many parts
of Afrioa and Central America, where blindness due to onohocerciasis
affliots about 30 million of the inhabitants. The field investigations
covered large rivers and small rivulets in different vegetation zones,
from tropical rain forest to semi-desert. A special technique was
used to rear parasites and to fix black-fly larvae for karyological
mappings. The investigations and conclusions are described below,
with the exception of the cytological observations.
lflATERIAL
Dv~ing 1965 data were obtained from localities A - J in West Africa
and localities K - R in East Africa were visited during 1966
Investigations, especially on black-fly larvae, were carried out in
small stres1llS and rivulets in the of the main localities"
Il
A -
2
The columns hended iJBedrockfi and 1130illl give the predominant kinds at
the investigation locality and upstre8.lll; the IICurrent velocityll
column gives the mean value of measurements at many representative
spots on the watercourse; the number given in the IILake" column shows
the distance in km to the nearest lake or large pool upstream;
+ in the liV/ater levelII column indicates a water level above the mean level
and - a water level below the mean levelon the occasion of the
investigation.
TABLE I
l.ocality Altituda, Badrock Soil 'Iidth, Invest. Current Substratum lp1'9 \'Ieter
ma.s.l. m depth, ve10city, level
m m/s
A. Barombi lake, 250 Volcanic Late- 4-8 0-0.7 0.8 Stones, o +
5kn N. KunDa, rites grass
CalOOnJon
B. Barombi lake, 210 Volcanic Lata- 5·7 0-0.5 0.4 Stones, 12 +
12 km downstream ritas (silty)
mud
C. 1'lut)jo river, 200 Granites Lata- 100-170 0..0.8 0.2 ijud, sub 30 +
21 kn ilE. I<umba rites mergoo
plants
D.Tributary toC, 150 Granitas Late- 4-10 0-0.8 o.3-J~1 Stonas, No +
5km N. i'lbat)ja ritas gravel
E. Ogun river, 100 Pnasrhatas, Late 80-100 0-0.7 0.2 t'lud$ sub- Pools +
20 km tf. Lagas, eocenic ritas, IOOI1JOO 1
Nigeria s\olamps plants
F. Shasha river, JOO Phosrnatas, late J·3 0-0.8 0.2 liud, p18nts, O +
20 km Ni/. Lagas. eocenic ritas sand
SWOO1PS around
G. Pa~71pawn rlver, 500 Granites lata- 5-12 0-0.6 0.7 Stones, 20 +
2kn S. Hohunya, diorites rites gravel,
Ghana plants
H. Seasonal stream, 350 COt)jJorne- Chamo- J-4 0-0.4 0.6 Stones, No
30 km ~E. Bamako, rates & zems rocks,
Ha11 sandstones plants
\. Seasonal stream, 330 COrYJ1orne- Chemo- 3-7 0-0.4 0.3 Iiud, stones No (+)
22 km ilE. Oamako rates & zems & (si11:';),
sandstones clay grass
J. River, 15 km 310 COt)j10100- Chemo- 7-16 0-0.7 0.7 Stones, No +
Sid. Bamako, t'lali rates zem rocks
K. Streamroar Amani, 850 Crysta11ina Late ].S-3 0.8 Stones, No +
Tanzania rocks, pre- rites gravel,
cambrian plants
Kl' SmaJl rivu1et, 850 Crysta11ine Late o.S-1.5 0-0.l 0.3 Stones, +
tributary to 1< racks, pre- rites gravel,
cambrian plants
3
LocalitJ Altituds Badrock Soil Ilidth, I!West. Current Substratum Lake Hatar
m,a.s,l. m depth, velocity, lavel
m m/s
L. l(agera river, 1,250 Cong1000- ? 20-200 0..0.5 1.1 Stones, 50 +
8I® E. Kikagati, r'ates rocks
Uganoo
N. NYamagasami, ~O Granites, Clay, 4-8 0..0.3 0.9 Stones, No ?
stream insouthern gneissas, moraina gross
Ru>KlnZori e.mphibo1itas
N. Nubuku river, 2,900 Granites, r'loraine 5·20 0..0.5 0.9 Stones, ?
eastern Ruwenzori gneisses, gravel
amphiboJites
O. telubuku river, 1,JOO Granites, CJay, 8·20 0..0.5 1.2 Stones, No ?
Fort Edward gneisses, moraina grass
amrhibolites
P. Tributary to 2,700 Granites, Moraire 4-JO 0..0.3 J.3 Stones No ?
r'lubuku gneisses,
amphibolites
U. RivuJet near 2,600 Granites, f'loraira 0.2-1 0..0.1 0.3 Stones, No ?
rlubuku graisses, grave1
amphibolites
R. Itojo river, J,2oo Granites, Sand, 2~6 0..0.3 0.7 Stones, No ?
25 I® MI. Fort gneisses, clay, gravel
Portal, Uganda amphibolites moraine
I:TETRODS
On visiting a locality, the data shown in Table 2 were obtained& For
karyological purposes, some larvae with black histoblasts were fixed
in the field in a modified Carnoy solution. Processing (cytology) was
carried out according to the standard procedure, described by Rothfels
(1956) and Basrur (1957). For detailed morphological analyses the
different characters of the larvae were prepared and put on slides.
For one snd the same specimen both the cytology and the morphology
were studied and thus direct comparisons could be made. For rearing
parasites, especially Mermithids, some 1arvae were kept alive in
tubes as long as possible, to allow the parasites to develop through
a few stages or to escape from the dying larva. The material was then
put inta a solution of 80% ethanol, l~/o glycerol and 1% methyl blue.
4
TABLE II. Physical and cnemical factors
The number given under "Pollution" shows the actual degree: 0= none,
1= insignificant, 2= noticeable, 3= heavy and 4= very heavy pollution.
-
Locallty Date Hrur Temperature pH Cl CaO Oz% Pol1ution I'leather
Air \'!ater mg/l mg/l Satur.
A1965 13/8 8-11 25.5 27.5 6.7 2.7 15 80.4 Clou:ly, 6U! cumu1us
B 13/8 14-17 28.O !I.2 6.7 3.0 20 89.5 Clou:ly, 5m cumulus
C 14/8 9-12 31.2 24.0 6.1 2.7 30 89.9 O C10lrly, 5~ cumulus
D 14/8 15-18 33.2 27.2 6.5 13 30 947 2 C10lrly, 6O'Z cumulus
E 16/8 11-14 31.2 !I.2 6.4 10 24 le.O 2 Fine, 3ql; cumulus
F 17/8 13-16 28.5 25.8 5,5 9 15 21.5 Heavy rain
G 19/8 13-15 25.7 24.2 6.2 19 20 94.3 Clou:ly, 7~ cumulus
H 22/8 11-14 28.5 33.2 5.7 3.4 28 93.4 1 Fine, thunder at adistance
I 22/8 16-18 26.4 30.1 2 Clotr!y, thunder nearby
J 23/8 9-12 24.5 26.O 7.0 20 35 86.1 2 C10lrly, 1~ nimbustratus
K1966 26/7 14-16 20.0 18.7 6.8 11 17 90..0 O C10udYl 6l1o Cumulus
1(1 26/7 14-17 20,O 18.2 6.9 O Cloudy, 6O'Z cumulus
L 30/7 1Q..13 26.O 21.2 6.9 5.9 35 91.O l Fine
N 30/7 17-19 26.O 19..5 1 C10lrly, 1~
N 31/7 15-17 17.9 9.5 6.6 O C10lrly, 1~
O 1/8 9-12 20.8 16.2 6.7 2.5 35 92.0 1 CIOlrly, 1~
p 31/7 c. 18 17.0 13.0 O Clot.rly, 1~
Q 31/7 c. 19 'IB.5 14.0 O C10lrly darkening
I
R 1/8 16-19 21+.0 22.3 7.8 3.9 101 c. 70 81ot.rly 1~
I
TABLE III. Record of field investigation.
LOCALITY: Barombi lake, outIet, 5 km N. of Kumba, Cameroon
Altitude: c. 250 m.
Bedrock: valeanie, upstre8m: volcanic.
Quaternary deposit: laterites; upstream: laterites.
T}ill STREAM: Width: 4-8 m; investigated depth: 0-0.7 m; current
velocity: mainly 0.8 m/s
Substratum: stones, submerged grass and plants. Same timber logs.
Silt on stones.
Lake: i~nediately upstream. Auxotrophy: none noticeable Same fishing.
FLORA: In the stream: very poor, same mosses only
Around the stream: tropical rain forest, very dense
5
2
FAUNA: In the stream per 1,000 cm of representative bottam
substrata:
Date o Water Ephem. Plec. Trich. Chiron. Simul. Others Total
ex;
hour level No. VIft No. wt No. wt No. Vit llJo. wt No. wt No. wt
a
13/8 + 2 5 12 20 12 7 2 5 3 125 31 402
8-11
a Including two large Odonata larvae.
2
Simuliidae: larvae and pupae present: 36 larvae from 20,000 cm •
Four S. kcnyae (4-6 stages, l with Mermitidae); 32 S. damnosum (4-6
stages, mainly 5-6, 4 with Microsporidae); 2 IIfreshll pupae.
Remarks on egg masses: none observed (cf. black flies).
Parasites: 50 pupae + 40 larvae for rearing parasites.
Karyology: 40 larvae in Carnoy solution. Salivary glands extruded.
Around the stream: c. 20 black flies at the same time around the
legs, usually not more than l m above the ground. Some bites to a
small extent. No black flies on the plants around the stream. Lots
of black flies at twilight and more intensive bites. Of 55 investigated
fem8~es of S. damnosum, all Were nulliparous, none had nematodes in
the midgut, in the thoracic nmscles or on the mouth-parts. At least
8 with Wticrosporidae in the ovaries. Seven were newly emerged. Other
insects around were Strepsiptera, Ephemeroptera, Trichoptera, and
Diptera of many kinds. Same spiders.
ORGANIC DRIFT:
Net of plankton gauze Paddle-wheel apparatus
Date Phy Zoo Det Ino T p T a 'IV 8. A a Inorg. Total
hour ml/m3
13/8 :;{ l ~d 1 l l l 4
8-10
a Mainly diatoms and Chlorophyceae. b Crustacae and Rotatoria.
c Lots of chitinous fragments. d Mainly leaves.
PI-IYSICAL AND CHEIlIIOAL FAGTORS:
-
Date Temperature pH 01 CaO O % Weather
Air Water mg/l mg/l satur.
13/8 25.5 27.5 6.7 2.7 15 80.4· Cloudy, 60% cumulus
8-11
GENERAL REMARKS: Very high water. Compared with European and North
American conditions a very poor bottom fauna (outlets usually highly
favourable localities for rheobionts and rheophilous organisms, mainly
because of a rioh and oomprehensive organio drift). Suggestions:
nulliparous females only beoause they were newly emerged; no masses
of black-fly larvae beoause of laok of suitable substrata (stones
usually with silt); the meoh8nioal effect of the high water oauses
drifting away; the organic drift of bottom-dwelling organisms low
beoause of the hour (at dawn and sunset more intensive drift is to
be expeoted); relatively few parasites, which might have been due to
low population density and olear no traces of egg development
in the ovaries whioh might mean anautogeny.
6
Generally speaking the values found are comparable with those found
in southern Seandinavia and in watereourses around the great lakes
in North America, which are not auxotrophied. The most remarkable
value in Table II is 101 for CaO at loeality R and consequently high
pH (7.S). There is no human pollution upstream, so it might have been
due to the loeal limestone bedroek around the stream. The low oxygen
saturation, 21.5%, at loeality F is erplained by the faet that the
stream runs through large swamps, where oxygen consumption is high.
ORGANIC DRIFT
The continuous drift of benthonic organisms in running water has been
studied previously (Carlsson 1962, MUller 1966). The following faets
are known about this organie drift:
l. The drift is maintained by the eolonization eyele.
2. The eauses of the drift must be sought espeeially in the mechanieal
effects of the current, but many other faetors are of importanee, e.g.
population density, intrinsie striving towards movement, oxygen
saturation, ete.
3. Nearly all benthonie animal groups present in the water investigated
are represented in the drift.
4. Extraordinarily large quantities of material, especially plankton,
make up the organie drif't below eutropbic lakes, but the amount of
material is usually surprisingly high also dowDstream of oligotrophie
lakes.
5. Lake organisms in the drift, to a small extent, are in general to
be found far do~mstre8~ of the lwre.
6. There are remarkable peaks in the amounts of drifting organisms
at dawn and sunset. For some freshwater invertebrates this is due
partly to an endogenous rhythm of loeomotor activity and partly to
the action of the light. The organic drift was collected in nets, one
with plankton gauze, the other with a special "paddle-wheel apparatus".
The former was put in the watereourse usually for one or two hours at
a spot with a known eurrent veloeity, to allow us to estimate
satisfactorj.ly the total aJ.i10unt of water whieh passed through the net,
with corrections for silting up of the net etc. The paddle-wheel
l1
apparatus" has Et net with et l Imn mesh. It gives the total amount of
the drift, ~nth the exception of microscopie organisms and silt.
7
TABLE IV. The organic drift in African watercourses.
Abbrevations.
= = = =
Phy phytoplankton, Zoo zooplankton, Det detritus, Ino inorganic
= =
compounds of the drift, Tp traces of plants, Ta traces of animals,
Wa = aquatic animals, such as black-fly imagines, spiders, etc. The
figures represent an estimation of the amount of the respective kind
= = =
of drifting organism: O none, l same few, 2 a considerable
number and 3 = masses in the drift. The predominant species are given
under the figures.
Lee. Plankton gauze Paci:lle-whool apparatu3 Species pt'esent
3
Pht Zoo Det lno Tp Ta l/a Aa Ino Total,ml/m (Dot. f3, !'Breins.. lum)
A 2 2~3 2 2 l 4 Brachionus falcatus, Tric"ocerea cfr. graci]is,
Ptygura sp.} Rotatoria sp., Synedra navicula,
&Jelloidea
B 2 2 O O 2 Cer:l1alaJella sp., SilP,ulium sp.
C 2 2 Ptygura sp." lliel10jdBa
D 2 1~2 2 2 O O 13 &JelloidGa, Lecane inopinab sympaJa, Synedra sp,
E l l 2 O l Testurhella patina, Cladothrix dichotoma, C1GStBriu~1
Sff', Area11a sp., Cyclops, AJona sp., ChirorKxnioe0,
Ephemeridue
F 2 2 l-Z 2-3 2 Z 35 Tes+l:diml1a patina, Clostcwium sp" Areella :"[}.,
Synedra sp., P'lecoptot'3, Nematoda
G O 3 1 2-3 2 Tostudir.eiia patir.a
H 3 Z Z l-Z 1-2 5 Locane bUlla, L- luna luna} L haliclysta, L
Notrmma sp" N. copaus, AlbBrtia cfr. naidis,
della cfr. gracilis, H3brotrocha sp., Rotatoria sr.,
S~irogyra ep.., Cosmarium sp." Closterium sp., ~l:J\/icu;:
n~ salOO conditions as at locality Hare to be sI", sp.., Centroro/:iis discoidea, Mona sp"
l€<pectro. Difflugia sp., Culicidae, Oligochaeta, Ephem., Chi!'"
Simulium sp,., kcella sp.•, Corixa sp.
J 2 2 Z Z l-Z 15 Euchlanis triquetra, Closterium sp., Pimularia sp,;
SyuDra SP';' Areella sp" 01igcch.J Eph., ~t.
K O 2 Z l J-Z 3 10 Oscil;:toriasp., Synedra sp.
l 2 2 Z-3 2 2 2 2 18 Closterium sp, Osci1liJtoria sp.., Fragil1aria sp.,
l
Nav;cula sp. lJitzschia sp., ftnkistraJesmus sp..,
I
Areella sp.., Syn:;dra sp.•, &Jel1oidea, l.Jc«atoda,
Simlllium sp.
H 1--2 O 2 l-Z Plecoptera, SimLl1illffi sp,
'"
N Z 1--2 2 1-2 Z O 3 35 Bdelbde3, Tf'ic:hoptera Simlllium Sj)"
ClostGrium sp.; Chir,
O Z-3 2 2 Z 2 2 Z 20 sp. Chlr,,
I
Closterium sp,
R 2 O 5 Pinnularia sp, SL,~'ire11asp" Navicu]a sp.,
Closterilim sp.., Ud811oidoo, Namatroa
The organic drift was poor or very poor, compared with European or N
American conditions This is true even considering the facts that the
investigations were carried out during the day·.time, no samples were
taken at davm or sunset, when the drift may be expected to be richest,
and that most localities visited were located far 8~ay from lakes or
pools which serve as c drift ers.
e
2
TABLE V. Macroscopic animals in the stream per 1,000 cm of
representative bottom substrata.
The number (No.) and weight (Wt) of each animal group are given. In
parentheses under "Simuliidae present" are noted the most common stages
of the larvae (l) and sexes of the pupae (p)• Figures underlined give
actual number surely parasitized immature stages; Tvi == Mermitidae,
Mi == Microsporidae.
[ph Tri Pla Chir Slfill1 Oth Tota7 Simu7iidae present
No. 1ft No. 1ft No. Itt No. Ht No. Ut No. Ht No. \,tt
A 2 5 12 260 12 7 2 5 3 125 37 4(E 32 1(4~6, 4Hi) +2P(0"+ o) S. damnoslJffii
- +
~ 4 7(4-6,] N) S. kol1/89.
B 7 15 40 9 56 201(4-6, 6Mi) +10 p(5 0"+ 50, 5['ii)
- + -
S. damnosumi 61(3-6, 1f·1\) +11 p(4 ci"+
70, 8Hi) S. 1-':'lnfae;"3 1{3-4) +75 p
+ - ----
(2 eft 13 0, 7~1i) S. unicornutum; 5p
(2 r?+ 3o)s-: a]cocki.
+
C 20 20 No larvae. t1any females of S, dalJ1!1(}')',ffi aroU:,j
O 12 23 5 40 4 32 12 5 13 22 4 47 126 31(5-6) +2P(e?'+ t0, l 111) S.
8p(3 0"+ 50, l ili f schoutfidsni,
+ -
E Nothing. f1lavy procipitation.
F If 12 2 11 14 10 3 2 2 7 25 42 19 ](3-6, rnainly 4, 2Ni) +78 p(8
100, 3Hi) S. akocki ari.J S. a1ccd<i
t - -,--- __
occldentaJa,: 'j] "1(11-6, maidy G, 3o
(2 d"+ 2O, l Ni) S. uniGorntiu:n.-
+ -
6 2 6 7 2 1 3 2 3 20 77 36 21(3-4) S, (Eusimuljum) sp.; 11(2) S,
H 5 19 19 ffi 6 2 2(15 80 2 80 2J7 268 f'lany 1arvae in 1-2 St2lpS, not det8rmin:,~1
hEre. 34 1{3-6 of which 10,5-6, 4Ni) +fl ii
(4 r?'+7o, 211i) S. m'EdusaefonMa; J7(3)
S. (Eus,)\p.,; l plC')S aicocki ie.'i,
5 15 2 9 3 2 38 35 2 24 49 85 34 ](usual]y 3stage, 8in5~6, 2Ni)t
70 P(6 flit 4o, 2Ni) S. mOOuS3eforweoi
t
2 1(3 &5) + p~o) S. a1cocki; 2'1(5& 6)
.l.
S. ruficorm. '
J 3 3 2 6 6 3 11 14 g](4-6, 1Ni) s. damn03uffi; 16 l(4~5, Hli)
S. a1cocki; 37(2).S. SJ), -
K 8 27 2 11 7 35 2 5 19 78 2 1(4 &6)S,c<''>-'';l'J1cuori (7), Abovo afar!
2
2km dOWffitream 900 l!J;roJcm . On
76 1(50 in 4-5, 26 in 2.,3,E !'ii)~,
ryasa1andicuffi,
K 3 7 3 11 16 70 3 2 25 90 21(2 &4) S..hirsutum (7); 11(" 4) S.
J
l 8 41 9 82 3 28 3 l~ 470 4 450 22Ji1;T"2 180 ](74 in5--6, 7!'Ii, 84 in !:. iii, ?2
in 1-2) +14.p (förili) s,
-
M 30 55 16 48 70 25 70 120 186 248 18 7(12 in 5~6 stagas) +]II P(4 Hi)
S. if /(4.5) S. darr"::';!)f!).
N 23 40 10 'öl 2 21 78 47 140510 6 36 259 741 9!t 7(3-6, mainly 5,~ Ni) $" ka:n':z'iL:m.
