SOME NEW SPECIES O F CYCLOPS SENSU LAT (CRUSTACEA
: COPEPODA)
123
SOME NEW SPECIES OF CYCLOPS SENSU LAT (CRUSTACEA : COPEPODA)
FROM NIGERIA. By SANYAD. ONABAMIRO, B.Sc., Ph.D., F.L.S.
lParasitology ReRearch Laboratory, University College, Ibadan, Nigeria).
(With 39 text-figures.)
INTRODUCTION.
I n a previous publication (Onabamiro, 1952) four new species of Cyclops were
reported in the c o m e of a n investigation on the ecology of Cyclops and their
relation t o the incidence of Dracunculw d i n e m i s , the guinea-worm, in South-west
Nigeria. These four species are T h e m y c l o p s iUmyhWa'8, Tropocycl~psmelhnbyi,
Ectocyclops ilariensis and H a l i c y h p s kopodien&.
By the time the investigatiorl was completed 30 species and subspecies of Cyclops
were found in all, in the region under mrvey, of which 21 are old and nine are new,
Four of these nine having been described in the paper referred to above, it is now
intended to publish the description of the remaining five. These are Mesocyc1op.r
ealina, sp. n., Mesoeyclops OQunnus, sp. n., Tropocycbps m$nis awienais, subsp. n.,
Tropcycbp8 pa8inus shagamiensie, suhsp. n. and L4frocycbpsikennus, sp. n.
M~,9ocycIopssaiinu, sp. nov. (Figs. 1-6.)
Type : Ibadan University College, index No. 5.
Female. Koradu, 24. ii. 61.
Go-types in the British Museum (Natural History).
Female :-The adult specimen measures 1.0 mm. in length. The cephalothorax
is roughly of the same length and width. The genital somite is 1.25 as long as it is
wide and is equal to the total length of the remaining abdominal somites. The
seminal receptacle is very large, and rather resembles that of Mesocyclops longiaetirs
(Thiebaud) with the anterior arms slightly recurved (fig. 2).
The furcal rami are between 2.5 and 2.8 times as long as they are wide, with the
lateral seta inserted at a point 58 per cent from t,he proximal end. There are no
hairs on the inner margin of the rami.
The fiirral setae are comparatively short ; the middle seta (No. 3) is five-elevenths
of the total length of the specimen and the innermost furcal end seta is less than twice
the length of the outermost seta. The measurements of the lengths of the outer,
lateral, middle, inner and dorsal furcal setae of a specimen which is 0.98 mm. long
are 85, 321,446, 142 and 64 p long and those of another specimen 1.05 mm. long are
93, 321, 446, 157, and 6 4 p long respectively.
The antennules are 17-johted, and extend down to the posterior margin of the
first free thoracic somite. The 16th and 17th joints both possess a hyaline membrane.
That of the 16th joint is smooth, that of the 17th joint is coarsely but evenly serrated ;
there are three shallow notches in the hyaline membrane of this joint, not one deep
notch such as is found in Me.90cyhps leuckarti (Clam). The relative lengths of the
17 joints are shown in the table below :1
bad 3
4
5
6
7
8
9
10
11
310
8
411
6
6
6
6
3
----------25
5
12
13 14
15
17
16 terminal
10
16
I
_
-
8
7
6
15
124
SASY.4 I ) . O S A R A M I H O
:
3.
FIGS.1-6.--1Ie.socycZops scdirirc, s p nor.
1. Lwt ahtloiniiral segnwnt wit11 fuwal rii,ini.
1. Genital somite and rcceptarulnin.
3. 1-nitinp lamellra of leg 4.
l h l q ~ n d3 of lcg 4.
4.
.J.
1,c.g .i.
1;.
1)istiil joiiits of aiircviiiulc of
f(wiiilt~.
125
N E W SPECIES O F CYCLOPS FROM NIGERIA
The swimming feet are 3-jointed with the spine formula 2, 3, 3, 3. There is no
seta on the basis of Leg 1. The 3rd endopod joint of Leg 4 is broad, being 2.6 times
as long as it is wide, and the terminal spines are subequal ; the inner spine is between
1-2 and 1.3 times as long as the outer spine and is slightly shorter than the joint
(15.5 : 18). The uniting lamella of Leg 4 with its pair of pointed processes is similar
to that of Mesocyclops leuchrti (Claus).
Leg 5 is thick-set ; both the basal and second joints are short and broad. The
inner spine on the second joint is shorter than the terminal seta on the joint, but
the outer seta on the basal joint is very long, and extends to the same level m the
inner spine.
Occurrence :-Specimens were found only in one place, in the brackish water a t
Korodu beach near the sea in Lagos.
The species resemble~lMesocy&ps buckarti aeqwtorialis Kiefer, in having short
fiircal rarni, pointed processes on the uniting lamella of Leg 4, three shallow notches
on the hyaline membrane of the 17th antennular joint, the ratio of the lengths of the
terminal spines of Leg 4, Endopod 3, and also that of the innermost and outermost
furcd end setae. It is different from M . leuckarti aequaturialis, however. in the
following respects :-
I. The furcal rami are not quite as short as those of aequatorialis.
11. The lateral arms of the seminal receptable are shorter.
111. The structure of Leg 5 ; (a) the two joints are short and broad ; ( b ) the
outer seta on the basal joint is longer than the inner spine on the second
joint, whereas it is shorter in aequatorialis.
IV. Habitat. This species was only found in the brackish water near the
sea where the only other Cyclops found was also a new species, Halicyclops
korodienais (Onabamiro, 1952). It has not been found in any sample of
fresh water inland and none of the species found in the latter is found in
association with it.
It appears therefore that this species is quite distinct from the others in the
subgenus MesocycEops and I am proposing for it the name aalina in consideration
of the salty nature of its habitat.
Mesocyclops ogunnw, sp. nov. (Figs. 7-12.)
Type : Ibadan University College, index No. 6.
Female : Abeokuta, 3. iii. 51. Co-types in the British Museum (Natural History).
Female :-The adult specimen is between 1.0 mm. and 1.3 mm. long, minus the
furcal end setae. The cephalothorax is nearly as wide as it is long. The genital
somite is 1.1 times as long as it is wide. The seminal receptacle (fig. 9) slightly
resembles that of Mesocyclops thermocyclopide-s Harada.
The furcal rami are between 3.1 and 3.3 times as long as they are wide and the
lateral seta is inserted at a point 60 per cent from the proximal end. The inner
margins of the rami are sparsely haired.
The innermost furcrsl end seta is three times as long as the outermost seta, and is
half the length of the middle seta (No. 3) ; the latter is approximately half of the
total length of the specimen. I n a specimen measuring 1.3 mm. the outer, lateral,
middle and inner furcal setae are 100, 393, 580 and 2861.1 long respectively and in
another measuring 1.05 mm. long the furcal setae in the same order are 89,357,535,
257 and 88 p long respectively. The dorsal setae are I00 and 88 p long respectively.
The antennules are 17-jointed, and extend down to the middle of the first free
thoracic somite. There is a smooth hyaline membrane on the 16th joint,, and a
coarsely serrated hyaline membrane on the 17th joint. I n the latter there is one
deep notch at a point about 70 per cent from the proximal end ; in this respect this
antannular joint resembles that of Mesocyclops leuckarti s. str. The 17th antennular
JOURN, LINN, S0C.-ZOOLOGY,
VOL. XWII,
10
126
SANYA D. ONABAMTRO :
8.
FIGS.7-12.-ilfesocycIops
7.
8.
9.
10.
11.
12.
ogurtnus, sp. nov.
Last abdominal segment with furcal rami.
Uniting lamella of leg 4.
Genital somite and receptaculum.
Endopod 3 of leg 4.
Leg 5.
Distal joints of antennule of female.
127
NEW SPECIES OF CYCLOPS FROM NIGERIA
joint is much shorter than the 16th ; the ratio being 15 : 20. The relative lengths
of the 17 joints are shown in the following table :1
basal 2
3
4
7
8
9
10
11
12
412
7
7
7
7
9
5 6
13 14
-------------25
6
312
8
8
7
17
15 16 terminal
-13 20
15
The swimming feet are 3-jointed with the spine formula 2, 3, 3, 3. There is
no seta on the basis of Leg 1. The endopod of Leg 4 is longer than the exopod ;
the third joint is between 2.5 and 3 times as long as it is wide ; of its two terminal
spines the inner is sometimes found to be equal to the outer spine in length and
occasionally slightly longer. The inner spine is approximately equal to the length
of the joint. The uniting lamella of Leg 4 has two short conical processes on its
free border.
Leg 5 is similar to that of Mesocyclops leuckarti s. str., except that the seta on
the basal joint is ahort.
Occurrence :--Specimens of this species were only found in stagnant pools formed
by the drying up of the River Ogun a t Abeokuta ; these pools were thickly covered
with water-lettuce and other green plants. It would appear that this species was
restricted to the dry season because as soon as the rains came and the river began to
flow from late May or June it waq no longer found and its place was taken by
Mesocyclops leuckarti s. str.
This species resembles Mesocyclops brazilianus (Kiefer) in the structure of its
furcal rami and the relative lengths of the furcal end setae but it is different from
this in the shape of the seminal receptacle and that of the uniting lamella of Leg 4.
It also resembles Mesocyclops thermocyclopoida Harada, but the latter has the
following features in which it differs from the species described here. (1) The inner
margins of the furcal rami are bald. (2) Leg 4, Endopod 3 is very slim, being 3.6
times as long as it is wide. (3) The lateral setae on Leg 4, Endopod 3 extend down
to the level of the posterior tip of the apical spines. (4) The outer terminal spine
of this joint is not shorter than the inner terminal spine.
It seems t o me, therefore, that we are here dealing with a new species quite
distinct from all the other members of the subgenus Mesocyclops, and I am proposing
for i t the name ogunnus after the River Ogun, Abeokuta, from where the specimens
were taken.
Tropocyclops conJnis awiewis, subsp. nov. (Figs. 13-18.)
Type : Ibadan University College, index No. 7.
Female : River Omi, Awa, 15.iii. 51. Co-types in the British Museum (Natural
History).
Female :-The adult specimen is 0-5 mm. in length from the tip of the cephalothorax to the tips of the furcal rami. The anterior half of the body is oval in shape ;
the length of the cephalothorax is only slightly greater than its width and is 1.5
times the length of the remaining thoracic somites. The length and width of the
genital somite are 64 and 57p long respectively while the length of the remaining
abdominal somite is 89p.
The furcal rami are twice as long as they are wide with the lateral seta inserted
a t a point two-thirds from the proximal end.
The ratio of the two long furcal end setae in this subspecies is of some importance,
from a systematic point of view, for it is the only Tropocyclops met with so far in
which the lateral seta (No. 2) is only about half the length of the middle seta (No. 3).
10*
128
SANYA D. ONABAMIRO
:
The outermost., lateral, middle, innermost and dorsal furcal setae are 21, 114,
16 and 4511 long respectively in a specimen measuring 0.5 mm. ; on the other hand,
in a slightly smaller specimen, 0.495mm. in length, the furcal setae in the same
order are 24, 114. 214, 16 and 5 3 p long respectively. From measurements taken
'4
FIGS.13-18.-Tropocydopu
15,
eonfnis awiennk, subsp. nov.
13. Female with egg-sacs, dorsal surface.
14. Last abdominal segment, with furcal rami.
15. Antsrinule of female.
16. Endopod 3 of leg 4.
17. Uniting lamella of leg 4.
18. Leg 5.
from over a score of specimens the follouing ratios are found t o be constant : Outermost seta to innermost seta, 1-3t,o 1 ; middle seta (No. 3) to lateral seta (No. 2),
p : 1 approximately ; dorsal eeta to outermost seta (No. I), 2 t o 1 approximately.
129
NEW SPECIES OF CYCLOPS FROM NIGERIA
The antennules are 12-jointed and extend down t o the posterior margin of the
last thoracic somite. I n a position of rest they are just touching the egg-sacs. The
relative lengths of the antennular joints are given in the following table :1
basal
2
3
4
5
6
7
8
9
10
11
12
terminal
20
11
5
13 10
4
17
25
27
20
23
25
The swimming feet are 3-jointed, with the spine formula 3, 4, 3, 3. There is no
seta on the basis of Leg 1. The uniting lamellae of legs 1, 2 and 3 are convex and
that of leg 4 is concave. The last joint of endopod of leg 4 is 2-3 times as long as
wide ; its inner terminal s p h e is between 2-4 and 2.6 times aa long as the outer spine
and between 2.1 and 2.3 times as long as the joint itself.
Leg 5 is as shown in fig. 17. It is very similar to that of Tropocycbp wn$nis
Kiefer .
The egg-sacs are borne dorsally, so closely that they actually touch, covering the
genital somite and the next abdominal somite.
Colour :-me body is brown with a tinge of bluish green in parts ; the antennules
are pinkish.
Occurrence :-Specimens were taken f r o 4 large pools of clear water in the shrinking
bed of River Omi-Awa, 30 miles due south from Ibadan.
These specimens,from the description given above, bear a very close resemblance
to Tropocycbp wnJnis, but the following differences are t o be noted ;(1) the relative lengths of the middle and lateral furcal end setae ; approximately
2 to 1 in these specimens, 3 to 2 in Tropocyclops confinis,
(2) the dorsal furcal seta is more than double the outermost furcal end seta in
length in the Omi-Awa specimens, but it is less than 14 times as long in Tropocycbps
mnJinis,
(3) the Omi-Awa specimens are distinctly smaller than any specimen of
T. conJinis found in Nigeria.
From the above observations it seems to me that the Omi-Awa specimens which
so far have been found in two other places in the area under investigation are a
form of Tropocy&p confinis which have become modified in their isolated habitat.
I am therefore proposing for them the subspecific name of awiensis.
Tropocyclops prwinua shqamiemis, subsp. nov. (Figs. 19-24.)
Type: Ibadan University College, index No. 8.
Female : Shagamu, 10. iv. 51. Co-types in the British Museum (Natural History),
Female :-The adult specimen is between 0.65 mm. and 0-72 mm. in length.
The cephalothorax is not much longer than it is wide, the ratio of the length to the
width being 1.2 : 1. The genital somite is narrow, the length being nearly double its
width, and approximately equal to the lengths of the remaining abdominal somites.
The furcal mmi are twice as long aa they are wide, with the lateral seta inserted
in the middle of each ramus. The two rami are fairly divergent.
The furcal end set- are short. The lengths of the outer, lateral, middle, inner
and dorsal furcal setae of a specimen measuring 0.72 mm. are 38, 143, 171, 50 and
54p long respectively. I n specimens varying from 0.64 mm. to 0-72 mm. in
length taken from places 8s widely separated rn Ilaro in the Abeokuta Province and
Ago-lwoye and Shagamu in the Ijebu Province the ratios of the furcal setae one to
another are found to be nearly the same. From these it is seen that the middle seta
(No.3) is only a little longer than the lateral seta (No. 2) and thrice the length of the
innermost seta (171 :50).
130
SANYA D. ONABAHTRO:
24
23
FIGS.19-24.-TropocycJop
pm'nw shaganiiensis, subsp. nov,
19. Female with egg-ws, d o d surface.
20. Lsst abdominal segment with furcal rami.
2 1. Antennule of female.
22. Uniting lamella of leg 4.
23. Leg 5.
24. Endopod 3 of leg 4.
The antennules are 12-jointed and extend to the posterior margin of the third
thoracic somite ; the last three joints of the antennules possess il thin hyaline
membrane. The relative lengths of the 12 joints are shown in the table below :1
basal
2
3
4
5
6
7
8
9
10
11
12
terminal
9
6
28
30
21
17
17
21
-----_______--
25
9
6
13
NBW SPECIES OF CYCLOPS FROM NIQERU
131
The swimming feet are s-jointed with the spine formula 3, 4, 4, 3. There is a
seta on the basis of leg 1 which extende to the second joint of endopod. The setae
on the first exopod joint of legs 2, 3 and 4 are much reduced in length. The third
endopod joints of legs 1, 2 and 3 have only four setae on the inner side. The last
endopod joint of leg 4 is between 3 and 3.5 times as long as wide. The inner terminal
spine of this joint is three times as long as the outer spine and between 1.6 and 1-8
as long as the joint itself.
The uniting lamellae of legs 1, 2, 3 and 4 are as in T . prasinus s. str. Leg 5
shown in fig. 71, is as in the typical form.
The egg-sacs are compact and borne on the sides of the abdomen.
Colour is light yellowish brown with a tinge of grey in the egg-saw.
Occurrence :-Found in the stagnant side pools formed by Ibu River a t Shagamu,
and in similar habitats a t Ilaro and Ijebu.
These specimens are clearly a form of Tropocyclops prasinus but are different
from the typical form in the following respects :(1) The very short middle furcal end seta which is less than four times as long
innermost furcal seta ; in T . prminus s. str. the former seta is always between
5 to 6 times as long as the latter.
ai3 the
(2) The ratio of the inner and outer spines of leg 4, endopod 3, which is 3 : 1.
I n T . prasinus s. str. this ratio is only 2.3 : 1.
The Nigerian form is different from Tropocyclops prminus f o r m guawarna (Kiefer),
Tropocyclops pasinus jerseyemis (Kiefer) and Tropocyclops praainus meridionalis
(Kiefer), both in the length of its furcal rami and in the ratio of the inner and outer
spines of leg 4, endopod 3.
The nearest to this species is Tropocyclops prasinus mexicanus Kiefer, which i t
resembles in the ratio of the inner and outer spines of leg 4, endopod 3, and also in the
shortness of the middle furcal end seta. It is different from this species, however,
in the structure of leg 5 and in the relative lengths of the dorsal and innermost
furcal setae, the former of which is shorter and the latter longer than those of
T ,praainus mexicanus.
I regard it, however, only as a subspecies of T . prasinus and I am proposing
for it the subspecific name of shccgamienais after the town of Shagamu from where
specimens were first obtained.
Afrocycbps ikennw, sp. nov. (Figs. 25-29.)
Type : Ibadan University College, index No. 9.
Female. Ikenne, 24. v . 51. Co-types in the British Museum (Natural History).
Ii'em.de :-The adult specimen is between 0.78 mm. and 0.9 mm. The cephalothorax is about a-swide as i t is long ; the fifth thoracic somite is fringed laterally
with a row of long stiff hairs. The genital somite is as wide as it is long. And the
seminal receptacle is as shown in fig. 26.
The furcal rami are on the average seven times a8 long aa they are wide with
the lateral seta inserted a t a point 82 per cent from the proximal end ; both the
outer and the inner edges are smooth. The rami are very divergent at base.
The innermost and outermost furcal end setae are of equal length in the majority
of specimens found; the innermost seta is one-third of the length of the furcal
ramus, and the middle seta (No: 3) is two-fifths of the total length of the specimen.
The outer, lateral, middle and inner furcal end setae of a specimen which is 0.945 mm.
long are 35, 214, 364 and 36 p long and those of another speaimen 0.78 mm. long are
36, 207, 357 and 32p long respectively. The dorsal seta varies between 50 and
5 6 p long.
The antennules are 12-jointed and extend only down to the level of the cephalothorax. The lateral seta on the 12th antennular joint is inserted at. a point 75 per
132
,
SAKYA I). OSABAMIRO:
cent from the proximal end. The relative lengths of'the 12 joints are shown in the
table below :1
hssl
2
3
4
5
6
i
8
9
10
15
4
3
7
5
2
6 1 2
9
1012
11
12
terminal
FIGS.25--29.-Aftoeyclops e'kkenaus, sp. nov.
26. Last abdominal segment with furcal rami.
26. Genital somite of female showing receptacululn and leg 5 .
27. Endopod 3 of leg 4.
28. Antennule of female.
29. First and semnd abdominal segment8 of male.
-
14
NEW SPECIES OF CYCLOPS FROM NIGERIA
133
The swimming feet are 3-jointed with the spine formula 2, 3, 3, 3. There is a
seta on the basis of leg 1 ; this seta extends to the level of the posterior margin of
the third endopod joint. The third endopod joint of leg 4 is between 2 and 2.3
times as long as it is wide ; its inner terminal spine, curved i n w a d , varies between
1.33 and 1.5 times as long as the outer spine and between 1.25 and 1.39 times as
long as the joint itself. Leg 5 is a flat triangular plate as long as it is wide. It
bears an inner spine and an outer seta both inserted at points in the middle of the
plate, and an apical seta. The inner spine is slightly longer than the apical seta,
which is 1.6 times &B long as the outer seta.
The egg-saw are long ; they extend down to the posterior margin of the furcal
rami .
C o h r :-The colour of the body is brown and that of the egg-sacs is light green.
Remarks.-F. Kiefer, 1939, reviews the subgenus Afrocycbp as a whole and
described species found in East and South Africa. Kiefer's list comprises Afrocyclops
gibsoni (Brady), A . doryphorus (Kiefer),,4. lanceolatw (Kiefer),A . curticornis (Kiefer),
A . alter (Kiefer), A . p p i n q u u s (Kiefer) and A . nubicus (Chappius).
Of these the Nigerian species is nearest only to Afrocyclops gibsoni (Brady) with
which it waa found in common in the same brooks. It wm first thought to be
another variety of Afr. gibsoni, but the following differences were found :1. The inner spine of Leg 5 is slightly longer than the apical seta in this new
species, whereas it is smaller than the apical seta in Afr. gibsoni.
2. The inner terminal spine of Leg 4, End. 3 is 1.4 times as long as the joint in
this new species whereas, it is equal in length to the joint in Afr. gibsoni.
3. The relatively greater length of the middle seta (No. 3) in this new species.
4. The shape of the seminal receptacle.
5. The colour, which is brown, while specimens of Afr. gibsoni found in close
association with it in the same brooks and found alone elsewhere were all yellowish
green in colour.
It seems from the above considerations that we are dealing with a new species
for which I am proposing the name ikennus, after the town Ikenne, Ijebu-Remo,
where the specimens were b t obtained.
ACKNOWLEDGMENTS.
The writer is indebted to the Colonial Medical Research Committee for a grant
to the Para&ology Research Laboratory, University College, Ibadan, which enabled
the work to be carried out, to Professor R. M. Gordon of the Liverpool School of
Tropical Medicine for the use of some instruments, to Dr J. P. Harding of the
Crustacea Department, Natural History Museum, London for some valuable
suggestions and to the junior members of the research team for their loyal cooperation.
REFERENCES.
CORER,R. E. 1943. Memcyclopa e d m (6. A. Forbes), M . Zeeaokarti (Claw) and Related Species
in America. J . / l k h Midciaell SOi. Soc., S% (Z), 181-198.
HARADA,
I. 1931. Studien uber die Susswassekfauna Formosea, IV. A m t . zool. jap., 13,
149-167.
KJEWER,
F. 1929 a. Das Tierrekh. Cyclopoide ; Gnathostomats 11.
1929 b. Artengmppen der Susswasser Cyclopiden. 2. &a. Zool., 133 4-17.
1931. Die Untergettung Tropocydopa der Gattung Eucydops. 2. wka. Zool., 138,
487614.
1938. Ruderfuiwkrebse (Crust. Cop) aux Mexiko. Zool. Anz., laa, 274-280.
1939. Mission Scientifique de L'Omo ; Crustacea 4. Copepoda. Mem. Mua. Hiat. ~ l
Pa&, 9, 319-323, 333-378.
LINDBERQ,
K. 1939. Etude de Representants Indiens du Souagenre Tro p y c l o p s. Crustaces
Copepodes Cyclopoides. Rec. I d . Mua. Calcutta, 41, 1-16.
1942. Cyclopoides (Cmtaoes Copepoides) de L'Inde. Rec, Indian Mus., 44, 73-84.
O N A B ~ ~ 6.
~ OD.
, 1962. Four New Species of Cyclops Sensu Lat. (Crustaoea : Copepoda)
from Nigena. Proc. Zool. Soo. Lond., 122 ( l ) , 263-266.
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