Zairian population of Pisidium viridarium KUIPER, 1956 (Bivalvia

POLSKA
MUZEUM
I
A N N A L E S
Tom 44
AKADEMIA
INSTYTUT
NAUK
ZOOLOGII
Z O O L O G I C I
W arszawa, 15 II 1993
Nr 5
A n d r z e j P ie c h o c k i
Zairian population o f P isid iu m virid a riu m K u i p e r , 1956 (Bivalvicu Heterod o n ta : S p h aeriidae)
[With 9 figures in th e text]
A b stract. In th e p re se n t p a p e r a d escrip tio n of a Z airian p o p u latio n of th e pill-clam P isidium
viridarium K u i p . is m ade. The sh ell m orphology, ex tern al an ato m y , biology of rep ro d u c tio n a n d
ecology o f m entioned species are stu d ied .
INTRODUCTION
Pisidium uiridadum was described by KUIPER (1956) on the b asis of specim ens
collected by B. V e r d c o u r t in the Kenyan K arura River. Later on the localities of
th is species were recorded in S outhern Rhodesia (the Republic of Zimbabwe),
Ethiopia, Uganda, Rwanda, Zaire, the Republic of South Africa, B asutoland
(Lesotho) and M adagascar (K u i p e r , 1964, 1966, B r o w n 1967). This indicates
th a t P. viridarium is one of the m ost widely distributed Pisidium-species in
tropical Africa.
D espite the fact th a t this pill-clam is so common it is relatively little investi­
gated. J . G. J . K u i p e r ’s stu d ies cited above give valuable d ata on the shell
stru c tu re and geographical distribution of P. viridarium b u t little is till know n of
its ecology and nothing at all of its anatom y and biology.
A new site of P. viridarium was detected in so u th ern Zaire, w ithin the S haba
province. It is located close to the village Kiungu, n ear the road leading from
L ubum bashi (Elisabethville) to Kasenga, about 40 km n o rth east of Lubum bashi.
P. viridarium occurred in the small Luam isam ba River, a trib u tary of the
Luiswishi River, which belongs to the catchm ent area of the Luapula River.
The ab u n d an t sam ples of P. uiridariumwert collected in bogs constituting the
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A. Piechocki
56
w idespread headw aters of the Luam isam ba River and in the u p stream section
of th e river on 11th Aug. and 9th Sept. 1988. The section investigated w as about
100 m long, 2-4 m wide and 0.10-0.50 m deep. The bottom w as covered with a
th ick layer of fine clay sedim ents, causing a strong turbidity of the slow flowing
w ater. The boggy headw aters covered an area of about 1 km 2, which w as very
extrem ely slimy and well w ater-saturated.
Sam ples were taken using a h and-net of 0.5 x 0.5 mm m esh size. The bottom
sedim ent was then w ashed on a screen of the sam e m esh. The clam s inhabiting
th e river and the spring-swam p produced a dense population th a t enabled to
collect up to hundred s of specim ens by a single haul of a net.
I owe my sin c e re st th a n k s to Mrs. Ewa Z a j ą c z k o w s k a - M a t u s ia k , M. S c ., for th e original d raw in g s
o f th e P. viridarium. I a m g rateful to Mr. Ł. G ł o w a c k i , M .S c ., D ep artm e n t of Ecology an d V erteb rate
Zoology of the Łódź University, for p rep arin g th e E nglish tran sla tio n . I w ish to ex p ress my h e art-fe lt
th a n k s to Dr. J . G . J . K u i p e r , Paris, for verification of my d eterm in atio n o f P. viiidaiium .
RESULTS
1 mm
Fig. 1. L ateral view o f P. viridarium.
The shells of P. viridarium from the Luam isam ba River are oval in outline with
um bones displaced som ew hat posterad (fig. 1). As in m ost pisidies, the um bones
are distinctly m arked in the largest individuals. The shells are w hitish, thin-w al­
led an d delicately striated (especially in their lower parts). Their characteristic
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Z aire an po p u latio n of P isidium viridarium
57
feature is the presence of very num erous, densely located canaliculi perforating
th e shell and visible on th e surface in the form of pores (fig. 2). D im ensions of
th e largest shell are: 4.5 m m in length, 3.8 m m in height, an d 2.7 m m in b read th
(convexity). The shells are relatively little convex. M easurem ents of a series of
153 individuals chosen at random proves th a t the convexity increases propo­
rtionally to the shell size (fig. 3).
U .U
,
I ,-V -
/,
4..
■■ v'. ■
• *-S.*
1 *, --1--f1
u • vrv
v V .r
Fig. 2. P. v irid a riu m - p a tte rn of sh ell-m icro scu lp tu re.
E
E
2
-
• ••• •
1
-
:.
• • :
1
2
3
mm
le n g h t
Fig. 3. C orrelation betw een length a n d b re a d th of th e sh e lls o f P. viridarium
from the L u am isam b a River.
8 — Annales Zoologici
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58
A. Piechocki
The hinge-plate is relatively thin. The m ost characteristic feature is the
occurrence of a callosity at the inner end of the lateral tooth PHI (fig. 4). This
callosity develops at various extent, b u t in m o st values is easily noticeably (fig. 5).
Fig. 4. Interior of shell o f P. viridarium. A bbreviations: AI-AII1 - a n te rio r lateral teeth.
C 2 - C 3 - card in al teeth, Lg - ligam ent-pit, P1-PII1 - p o sterio r lateral teeth;
arro w show s a callosity on rig h t valve.
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Z airean p o p u latio n of P isidium viridarium
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The cardinal tooth C3 is straight or little bent, situ ated parallel to the
hinge-plate and forked in its posterior part; C2 is relatively short, straig h t or
slightly bent; C4 is located above C2 and som ew hat displaced posterad; C2 and
C4 are of about the sam e length or C4 is a bit longer. The ligam ent-pit is relatively
long and narrow . Lateral teeth well m arked b u t not very large. In th e right valve
AIII and AI are more pronounced th a n PHI and PI. The left valve an terio r tooth
All is b etter developed th a n the posterior one - PII (figs 4 and 5).
B
C
D
Fig. 5. Hinge p lates of Pisidiuni viridarium from th e L u am isam b a River.
At gaping valves an exhalant siphon and branchial opening are well visible
in the posterior p art of the anim al (fig. 6). They are close to each other b u t
distinctly separated. Pre-siphonal su tu re, i.e. the distance between th e m antle
slit and branchial opening, is relatively short.
The inner gills are large, triangular, w hereas the outer are m uch sm aller b u t
well developed and always visible. Digestive diverticula are located close to
um bones and to the upper edge of the anterior gill (fig. 7). The anterior and
posterior adductor m uscles are situ ated at the sam e height; the an terio r one is
larger and more elongated (fig. 4).
In A ugust 1988 the P. viridarium population of the Luam isam ba River
consisted m ostly of mid-sized individuals of two size classes: 2.6 -3 .0 m m and
3 .1 -3 .5 mm. The individuals of these two classes constituted together 58.1% of
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A. Piechocki
60
th e pill-clam s collected. The rem aining size classes were represented by a m uch
lower n u m b er of individuals (fig. 8). In Septem ber th e com position of the
population was very similar: individuals 2.6-3.5 m m in shell length dom inated
constituting 66.1% of all pill-clams. Sm aller and larger individuals were less
a b u n d a n t (fig. 8).
S
BD
P-SS
F
MTL
Fig. 6. a n d 7. P. viridariiim. 6 - P osterior view; abbrev iatio n s: BD - b ra n c h ia l opening, F - foot,
MTL - m antle, P-SS - p re-sip h o n al s u tu re . S - sip h o n .7 - anatom y; ab b rev iatio n s: AAM - a n te rio r
a d d u c to r m uscle, DDV - digestive diverticulae, F - foot. GND - gonad, HV - h e a rt ventricle, 1GL in n e r gill, MTL - m antle, OGL - o u te r gill, PAM - p o sterio r a d d u c to r m uscle, RC - rectu m .
u
c
(L)
179J
5 .0 -
Specimens
Specimens
4.0
3.0
2 .01.0 -
, ftAug.1988.
9. Sept.1988.
Fig. 8. L ength-frequency d is trib u tio n of P. uiiidarium in the L u a m isa m b a River.
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Z airean p o p u latio n o f Pisidium viridarium
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In the sam ple collected in A ugust 14 gravid specim ens (7.8%) were recorded
w ith larvae in the gills (fig. 9). Gravid anim als had shells 2.8 -3 .9 m m long. Larvae
n u m b er ranged from 2 to 17, averaging 7. Larval individuals h ad 0 .6-1.2 m m
long shells. It w as determ ined th a t 0.8 m m long em bryos were still em bedded
in the brood-pouches (m arsupies), while 0.9 m m and longer ones were already
extra-m arsupial. The largest extra-m arsupial larvae were 1.2 m m length x 0.8
m m in height x 0.4 mm in breadth.
, 1mm
,
Fig. 9. G ravid sp ecim en o f P. viridarium from th e L u am isam b a River; EMB - em bryo.
Presence of em bryos in gills was also noticed in specim ens sam pled in
Septem ber. 6 specim ens o u t of 207 (2.9%) were gravid. The length of larvae
ranged from 0.5 to 1 .1 mm. These larvae were detected in p aren tal individuals
2 .6 -3 .5 m m in length. Larvae n um ber ranged from 5 to 9.
The age distribution of P. viridarium presented in histogram s (fig. 8) shows
th a t juvenile individuals (1.0-2.0 m m in shell length) constituted an im portant
p a rt during the dry season (August, September). This testifies th a t in th a t period
ex tra-m arsupial larvae are b o m by p arental individuals.
DISCUSSION
The p resen t investigations proves th a t P. viridarium is one of the m ost
com m on and w idespread Pisidium-species of tropical Africa. In agreem ent with
form er K u ip e r ’s ( 1 9 6 4 , 1 9 6 6 ) observations P. viridarium prefers boggy h ab itats
a n d slowly flowing river sections. In environm ents of this type the pill-clam
reach es high abundance.
A callosity of the anterior p art of the posterior lateral tooth - PHI is the
c h a ra c te r th a t allows m ost certain distinguishing between P. viridarium and
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A. Piechocki
oth er African Pisidium-species. In pill-clams from the L uam isam ba River th is
feature is as strongly developed as in the specim ens from Zimbabwe (K u i p e r ,
1964; fig. 10) and Ethiopia (K u i p e r , 1966; pi. VIII, fig. 4). It w as decisively
stronger th a n in P. viridariiunfrom the Zairian River L ubum bashi (K u i p e r , 1966;
pi. VIII, fig. 5).
The size of the largest extra-m arsupial em biyos (1.1-1.2 mm) and the length
of sm allest free-living individuals (1.1-1.2 mm) proves th a t young P. viridariam
are bom with sizes sim ilar to those of other Pisidium-species (M e i e r - B r o o k
1977). However, it seem s th a t P. viridarium embryos stay a bit longer in
brood-pouches. In P. viridarium larvae 0.8 m m in length were observed in th e
brood sacs, while according to M e i e r - B r o o k (1977) the em bryos of other
Pisidium free them selves from the sacs and drop to gill-cham ber at 0.7 mm.
The analyzed m aterial do not allow to reconstruct the whole life cycle of P.
viridarium The composition of the A ugust and Septem ber populations suggest
however, th a t P. viridarium reproduces continuously over the y ear (fig. 8). The
reproduction is probably m ost intensive in the late rainy season (March-April),
w hen anim als w hich had reached 2 .6-3.5 m m in length by A ugust were m ost
likely bom . With the advance of the dry season (May-September) environm ental
conditions w orsen in w ater-bodies and the abundance of released brood decli­
n es, b u t reproduction continues. This is proved by the occurrence of free-living
clam s 1.1-1.5 m m in length as well as the presence of extra-m arsupial larvae
in p arental individuals. It seem s th a t P. viridarium represents the co n tin u o u s
interparity type of reproduction, i.e. it h a s the ability to fertilize and breed
th roughout the whole year and its successive generations are not clearly
separated (H e a r d , 1965, M e i e r - B r o o k , 1970). A sim ilar life-cycle w as described
by M e i e r - B r o o k (1970) in the Brazilian species P .forense M.-B.
REFERENCES
D. S. 1967. A review of the fresh w ater Mollusca of N atal an d th eir d istrib u tio n . A nn. N atal
M us., P ieterm aritzburg . 18 (3): 4 7 7 -4 9 4 .
H e a r d W. H. 1965. C pm parativ e life h isto ries of N orth A m erican pill clam s (Sphaeriidae: Pisidium).
M alacologia, A nn Arbor. 2 (3): 3 8 1 -4 1 1 .
K u i p e r J . G. J . 1956. Pisidium viridaiium, eine n eu e Art a u s O st-Afrika. Arch. Moll., F ra n k fu rt a. M.,
8 5 (1-3): 6 1 -6 3 .
K u i p e r J . G. J . 1964. C o n trib u tio n to th e know ledge o f th e S o u th African species of th e g e n u s P isidium
(Lamellibranchiata). Ann. S. Air. M us., C ape Town. 4 8 (3): 7 7 -9 5 .
K u i p e r J .G .J . Les esp ces africain es du genre P isidium leu r synonym ie et leu r d istrib u tio n (Mollusca,
L am ellibranchiata Sphaeriidae). A nnls Mus. r. Afr. cent. (Sc. Zool.), T ervuren, 151: 1-78, 15 pi.
M e i e r - B r o o k C . 1970. U n tersu c h u n g e n z u r Biologie einiger Pisidium -Arten (M ollusca Eulam ellibranc h ia ta Sphaeriidae). Arch. Hydrobiol., S uppl., S tu ttg a rt, 3 8 (1- 2): 73 -1 5 0 .
M e i e r - B r o o k C . 1 9 7 7 . In tra m a rsu p ia l su p p re ssio n o f fetal d evelopm ent in sp h a eriid clam s. M alac.
Rev., M ichigan, 10: 5 5 -5 8 .
B
row n
Z akład Zoologii Bezkręgowców i Hydrobiologii
U niw ersytet
ul. S. B an a c h a 1 2 /1 6 . 90-237 Lódż, Poland.
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Z airean p o p u latio n o f P isidium viridarium
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STRESZCZENIE
[Tytuł: Z airska populacja Pisidium viridariumK\J\PER, 1956 (Biualuia: Heterodonta: Sphaeriidad]
Nowe stanow isko afrykańskiej groszkówki - P. viridarium - wykrył au to r n a
obrzarze źródłowym rzeki L uam isam ba (dorzecze Luapuli) w prowincji Shaba.
Analizowano budowę m uszli, morfologię miękkich części ciała oraz ekologię i
biologię rozrodu tego małża. Cechami charakterystycznym i m uszli są bardzo
liczne drobne kanaliki (pory) (rys. 2) oraz obecność modzelowatego zgrubienia
n a listwie zam ka - w sąsiedztwie zęba PIII (rys. 4).
P. viridarium rozm naża się prawdopodobnie w ciągu całego roku, a najw iększa
intensyw ność rozrodu przypada n a koniec okresu deszczowego (marzec-kwicień). Liczba embrionów produkow anych przez jednego osobnika rodzicielskiego
w ynosiła 2-17, średnio 7. Długość m uszli nowo narodzonych małży: 1,1-1,2 mm.
R ed ak to r pracy - prof, d r A. Riedel
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