Evaluation of density and biomass of a bivalve population (Diplodon delodontus expansus) (Küster, 1856) in a small tropical reservoir

Raoul HENRY (1) and Claudete Aparecida SIMAO (1)

Density and biomass of D. delodontus expansus (ICÜSTER, 1856) (, ) were estimafed in the Reservoir of fhe Rio Pardo (Botucatu, Sao Paulo, Brazil), in December, 1982. The average population densi$ of the bivalves in the reservoir was 36.62 specimens.m-2, ut 98 sampling stations. Tofal density in the reservoir was esfimated ut 5.8 million individuals. Average biomass tuas 347.27 gm-2 (alcohol ureight) ; 225.00 g.m-2 (shells dry ureighf) and 10.92 g.m-2 (bodies dry weight). Total biomass in the reservoir ruas estimated ut 55.0 tons (alcohol rveight), 35.6 tons (shells dry weight) and 1.7 tons (bodies dry weight). The granulomeIric analysis of fhe sediment showed that silt presented greater correlaiion with biomass and density (r = 0.16), ihough unsignificant. The other fractions of sediment (Sand and clay) showed lorver correlation coeficienfs with density and biomass of the bivalves. The granulometric composition of the sediment ulas not related wibh density ancl biomass of the . A revision of other ecological factors showed Chat fhere are no limiting facfors on the distribution and abundance of bivalves in fhe reservoir. This explains probably the high values of density and biomass.

KEY WORDS : Density - Biomass - Bivalve - Tropical reservoir - Brazil.

RÉSUMÉ

ÊVALUATION DE ~4 DENSITÉ ET DE LA BIOMASSE DU PEUPLEMENT DE BIVALVES (Diplodon delodontus expansus) (ICÜSTER, 1856) DANS UN PETIT RÉSERVOIR TROPICAL

La densité et la biomasse de D. delodontus expansus (ICÜSTER, 1856) (Mollusca, Bivalvia) onf ét& estimées dans le réservoir du Rio Pardo (Botucatu, Sao Paulo, Brésil) en décembre 1982. La densité moyenne du peuplement de bivalves a Eté estimée à 36,62 individusm:2 pour les 98 stations de pr~lèvemenf, el le stock total dans le réservoir à 5,8 millions d’individus. La biomasse moyenne était de 347,27 g.m-2 (poids alcoolique); 225,00 g.m-2 (poids sec des coquilles) et 10,92 g.m-2 (poids sec du corps). La biomasse totale dans le réservoir a été estimée à 55,O tonnes (poids alcoolique), 35,6 tonnes (poids sec des coquilles) et 1,7 tonnes (poids sec des corps). L’analyse granulo- métrique du sédiment a rèvèlè que le limon a une plus grande corrélation avec la densité et la biomasse des animaux en relation aux fractions du sédiment, mais n’est pas significaiive (r = 0,16). Les autres fractions du sédiment (sable et argile) ont d es corrèlations plus basses avec la densité ei la biomasse des bivalves. La composition granulo- métrique du sédiment n’a pas de relation évidente auec la densité et la biomasse des animaux. Une révision des autres facteurs écologiques a pu montrer qu’il n’existe aucun facteur limitant la distribution et l’abondance des bivalves dans le réservoir. Cela est probablement l’explicalion des grandes valeurs de densifé et biomasse obfenues.

MOTS-CLÉS : Densitk - Biomasse - Bivalve - Réservoir tropical - Brésil.

(1) Deparlamento de Zooloyia, IBBMA, C.P. 502, Universidade Estadual Paulista, 18600 Botucafu, Sao-Paulo, BraziZ.

Rev. Hydrobiol. hop. Ii’ (4): 309-318 (1934). 310 R. HENRY AND C. A. SIMÂO

1. INTRODUCTION (HENRY ef al., 1978), ecology of Escherichia coli and coliforms (HENRY & LOPES, 1978), fish and some In t.ropical regions, the benthic fauna has been aspects of the biology of Hoplias malabaricus studied less profoundly that zooplankton or phyto- (PELLEGRINI-CARAMASCHI, 1979; PELLEGRINI-CARA- plankton. Thc works conducted in Africa, in Lake MASCHI eb dl., 1982). Chad (DEJOUX ef al., 1969; LÉVÊQUE, 1971, 1972; As a result of this studies, the Reservoir of t,he LÉ~ÊQ~E et ul., 1983), in Lake Chilwa (RICLACHLAN Rio Pardo show ecological characteristics wbich are & RIÇLACHLAN, 1969), in Lake George (BURGIS more similar to those of rivers than of lacustrine et al., 1969) and Lake Kariba (MCLACHLAN & systems (HENRY & SOUSA, 1984). MCLACHLAN, 1971) showed that the benthic biomass in December 1982, as a consequence of heavy was not low and had a very important role in the rains, the dam broke and the Reservoir was emptied. productivity of the ecosystem. Particularly in Lake The water inflow of the Rio Pardo was t.hen lrept in Chad and probably in Lake Chilwa, the benthic it,s older riverbed (Fig. 2). A fairly high density of mollusks are very ahundant and constitute the the bivalve D. delodonins e~pnnsus was observed on major part of the benthic biomass. exondated zones and we took this opportunity t,o In Brazil, tbe investigations on the benthic fauna study dist,ribution and biomass of that species in t.he in reservoirs are yet scarce and concern mainly the Reservoir. study on densit,y and spatial distribution of the Chironomidae (STRIXINO & STRIXINO, 1980, 1982) and Olig0chaet.a (CO, 1979j. Some ohservations 3. METHODOLOGY were also conduct.ed on a bivalve mollusk (Diplodon Geck-earlus) in the littoral zone of Lake Juturnaiba Sampling Methods (ALVARENGA et ul., 1979). The rupture of the dam of Rio Pardo in December The bivalves were manually collected two days 1982 appeared to be an opportunity to carry out the aft,er drainage of the Reservoir at 28 samplings sit,es first evaluation of biomass of Diplodon delodontus (Fig. 2). On each site, an area of 1 rn” was investigated espansus (RIollusca, Bivalvia) in a brazilian reservoir. down to a depth of 10 cm in o

Rev. Hydrobiol. trop. lî’ (4): 309-316 (1984). DENSITY AND BIOMASS OF D. DELODONTUS EXPANSUS IN A SMALL TROPICAL RESERVOIR 311

FI~. 1. - Situation of the Reservoir of the Rio Pardo (Botucatu) in the State of Sao Paulo and in Brazil

Relationships Between Size and Individual Weight 4 RESULTS 4.1. Probable effects of ecological factors on the Length of bivalves were measured using a pachy- distribution and abundance of bivalves meter. For eleven size classes, alcohol weight, shell dry weight and body dry weight were estimated. For RELATIONSHIP BETWEEN GRANULOAIETRY AND dry weights, bodies and shells were dried in oven at DENSITY OF MOLLUSKS 60 OC, for 48 hours. Considering t,hat the nature of bottom may have The relationships between size and weight were an effect on the benthic distribution and abundance, used for biomass estimates of samples: the granulometric study was carried out in the - alcohol weight = - 12.13+4.14 length (r = 0.936) majority of sampling stations (Fig. 2). Half of the - dry shell weight = - 8.21+2.75 length (r = 0.923) sediment samples were classified as silt loam and - dry body weight = - 0.38+0.13 length (P = 0.885) clay (Fig. 3). The contribution of sand in the granulo-

Rev. Hydrobiol. trop. 17 (4): 309-318 (1984). 312 R. HENRY AND ‘2. A. SIMÀO

distribution of bivalves (HENRY Ji. SIMAO, 1984). in fa& previous st.udies (HENRY, 1981; I-IENRY & CURI, 1981a) showed that t.he water is well oxygenated near the bottom during the year and t,herefore, the mollusks cari live in a11the regions of the Reservoir. The conductiviiy of water is low (< 25 $.c.m-l) CHENRY, 1981) and, therefore, don’t affect the distribution of mollusks. The Reservoir of Rio Pardo had a mean retention time of 6.3 days during the year (variation amplitude 3.4 t.o 12 days) and the ecological charact.eristics are more similar to those of rivers than of lacustrine systems (HENRY & SOUSA, 1984). The water flow, measured in the Rio Pardo and COrrego Agua da Madalena (other t.ributary of the Reservoir) was in both the lotit systems higher than 0.3 m.s-l during the year (HENRY 8r SOUSA, 1984). These hydrological characteristics allow a cont,inuous renewal of a water in the Reservoir and therefore affect positively on the distribution of bivalves in the environment.

4.2. Abundance and biomass of mollusks The Figure 4 shows the length of a11the specimens FIG. 2. - Sampling sites of the organisms and sedirnent in the Reserwir of the Rio Pardo (Bot.ucatu, SF’) (n = 913) collected two days after drainage of Reservoir. The majority of bivalves was found in the length classes 5.10 to 5.65 cm (n = 323). No small specimens (1.80 rm) were collected in the Reservoir metric composition of bottom of the reservoir was during our study. The mean weights for eaçh length reduced to approximately 10 o/. of the samples. The classes are given in Table II. Density is lower than result of suspended particles sedimentation, from the 30 ind.m-3 for half of the sampling sites (Fig. 5), but flowing waters, is the cause of low amount of sand cari reach much higher values in a few ones. in a11the samples. On an average for the 98 stations, density and The estimate of correlation coefficients between biomass are rather high (Tab. III). If we consider the main fractions of sediment and densit*y of such values as means for the Reservoirs, and bivalves shows no significant. relation between the assuming an area of 15.82 ha, the mollusk stock is sediment granulometric composition and abundance t,herefore 5.79 x 10G individuals, and the biomass of mollusks (Tabl. 1). Therefore, Diplodorz delodontzzs 55 t.ons alcohol weight,, 35.6 t,ons dry shells, 1.7 tons expansus appear to have no striking preference for dry organic matter. a sediment type in the Reservoir of Rio Pardo, at least between the different. types of sediment from the samples of the environment. 5. DISCUSSION

According to ALVARENGA & RICCI (I%l), Unio- OT~ER FACTORS nidea are more frequently observed in muddy The water content and the pH of sediment were bottom. However, they c.an also be found in sandy also studied and correlated wit,h the benLhic fauna bottom. For MANSUR (1972, 1973), Castalia undosa in the Reservoir. The pH of sediment was clearly martensi (Bivalvia, ) give preference to acid (variation amplitude 3.8 to 6.0) and the sediment habit,ats located near rushes in soils consisting mainly presented a water loss of 2.64 t,o 37.78 yo after of fine Sand, and Diplodon species are mainly observed drying the samples in oven (105 OC, 24 hours). in fine sand areas. D. charrzzunus and D. pilsbryi The estimate of correlation coefficients between prefer bottom consisting of coarse sand and current these characteristics and the density of bivalves water and muddy bottoms with calm waters showed no significant relation between the abundance (MANSUR & ANFLOR, 1981). VEITENHEIMER & of mollusks and pH and wat,er content. MSNSUR (1978) pointed out that Mycetopoda legzzmen The low depth of the Reservoir (average depth: is mainly found in compact fine sand areas. 2.5 m) appears not to be a limiting factor on the Anodontites trapezezzs, A. frapezialis and Diplodon

Reu. Hydrobiol. trop. 17 (4): 309-318 (1984). DENSITY AND RIOMASS OF D. DELODONTUS EXPANSUS IN A SMALL TROPICAL RESERVOIR 313

- % SAND

FIG. 3. - Dispersion of the sediment samplcs in the Reservoir of the Rio Pardo (Elotucatu, SP) in relation to the total Sand, day and silt, fractions (SO). (T&urc classes: 1. Clayey clay; II. Clay; III. Silt clay; IV. Sandy clay; V. Clay lonm; VI. Silty clay loam; VII. Sandy clay loam; VIII. Silt; IX. Silt loam; X. Loam; XI, Sandy loam; XII. Loamy Sand; XIII. Sand)

TABLE 1

Correlation coefticients hetween the granulomet.ric fractions (V~S = very coarso Sand; Cs = coarse Sand; MS = medium Sand; FS = fine Sand; \‘fs = very fine Sand; silt and clay) and biomass (Aw = alcohol weight; Dw = dry weight) and density of Diplodon delodonfus ezpnnsus

VCS 1.000 0.330 0.439 0.358 0.044 -0.239 -0.106 -0.182 -0.180 -0.185

CS 1.000 0.596 0.124 0.089 -0,087 -0.280 -0.113 -0.111 -0.103

MS 1.000 0.757 0.472 -0.340 -0.348 -0.046 -0.044 -0.030

FS 1.000 0.639 -0.394 -0.348 -0.074 -0.072 -0.053

Vfs 1.000 -0.374 -0.223 -0.132 -0.129 -0.135

Silt 1.000 -0.650 0.159 0.161 0.154

Clay 1.000 -0.006 -0.009 -0.017

AW 1.000 0.999" 0.981* Dw 1.000 0.980*

Density 1.000

‘p c 0.05

Reu. Hydrobiol. trop. 17 (1): 309-318 (1984). 314 R. HENRY AND C. A. SIMÂO

length(cm)

Fig. 4. - Distribution of the Diplodon delodontus eq~cpansus specimcns in function of length

TABLE II

Means (x) and standard deviations (s) of lenght and biomass (alcohol and dry weights of the shell and body) of Diplodon delodontus expunsus

ALCOHOL WEIGHT SHELL DRY WEIGHT BODY DRY WEIGHT SIZE CLASSES (9) (9) (9) (cm) ff S x. S x S

1.80 - 2.35 0.670 0.138 0.420 0.066 0.023 0.006 2.35 - 2.90 1.230 0.237 0.785 0.101 0.040 0.014 2.90 - 3.45 1.934 0.512 1.222 0.303 0.062 0.017 3.45 - 4.00 2.998 0.710 1.889 0.531 0.089 0.027 4.00 - 4.55 4.687 0.789 3.026 1.026 0.161 0.023 4.55 - 5.10 6.558 1.312 4.409 0.746 0.235 0.058 5.10 - 5.65 9.252 1.526 5.794 1.172 0.274 0.060 5.65 - 6.20 11.544 1.824 7.243 1.071 0.347 0.076 6.20 - 6.75 15.746 1.772 10.453 1.619 0.475 0.110 6.75 - 7.30 19.237 2.567 12.874 1.816 0.662 0.188 7.30 - 7.05 22.046 2.789 14.886 1.836 0.690 0.085

~O~UI&S gratus are found in a muddy or a muddy- In Lake Chad, the nature of sediment has a sandbottom (HEBLING,~~~~;HEBLING&PENTEADO, significant intluence on distribut,ion and density of 1974). LEWANDOWSKI & STANCZYKOWSKA (1975) the benthic fauna (DEJOUX et al., 1971). comparing the density of Unio tumidus at three ‘In the Reservoir of the Rio Pardo, the results of stations with different granulometric characteristics, granulometric analysis showed that silt was the found a higher number of individuals in areas most frequent fraction observed. Althought the consisting of sandy bottoms covered with a fine layer correlation-coefficients obtained between silt and of silt and a considerable amount of decayed vegetal density and silt and biomass were the higher matter whereas the distribution of Anodonta pisci- correlat8ions, they were not Sign&ant. Therefore, nalis was approximately identical at the three this granulometric fraction was not directly related stations. HARMAN (1972) studied the distribution of to biomass and density of the species. Acc.ording to mollusks in the State of New York (USA) and found HEBLING & PENTEADO (1974), water content is very four different associat.ions according to the nature important for the vertical distribution of bivalves of the bottom. in the sediment. They reported that Diplodon

Rev. Hydrobiol. trop. 17 (4): 309-315 (1984). DENSITY AND BIOMASS OF D. DELODONTUS EXPANSUS IN A SMALL TROPICAL RESERVOIR 315

5-r

10 20 30 40 50 60 70 80 90 100 110 120 130 MO ISO 160 -2 number of individuals m

FIG. 5. - Sampling frequence in function of population density (specimens.m-*), for the 98 sampling stations in the Reservoir of Rio Pardo

TABLE III density of D. delodonfus expamus. The apparent absence of limiting fac,tors explains t.he hi& density Means (z?) and standard deviations (s) of biomass (g.m-e) and density (individuals.mF2) of ~iplodon delodontus erpansus in 98 of bivalves in the Reservoir. sampling stations Density and biomass of D. delodonfus expansus in the Reservoir of the Rio Pardo were high when STATISTICS compared to the data on the other species in the VARIABLE x s temperate and tropical lakes (Tab. IV). Comparison of these data in temperate (Lake Mikolajskie, Alcohol weight 341.27 293.97 Poland) and tropical (Reservoir of the Rio Pardo, Shell dry weight 225.00 191.07 Rrazil) regions showed that t.he population density Body dry weight 10.92 9.30 of Unionidae (3 species) in Lake Mikolajskie was 0.6 specimens.m-2, ext,remely low when compared to Dens i ty 36.62 32.31 the Reservoir of the Rio Pardo (36.62 specimens.n?). The same was observed for biomass. In Amazonian Lakes, the percentage composition of Bivalviti (Pisidium sterkanium) to benthic biomass ranges rofundrrs grntus OCC~IS in substrata with high contents of silt and c.lay and water content. In the from 0 to 22 y0 in seven lekes and the absence of mollusks and other groups (Hirudinea, Oligochaeta, Reservoir of the Rio Pardo, the majority of sediment consisted of silt, but water content appear to bave Chironomidae and Ephemeroptera) in some lakes, no effect on the abundance of bivalves. was due to low oxygen content, chemical factors Depth had no limiting effect on the occurrence of and to water level fluctuaGons during the year (FITTKAU et al., 1975). bivalves in the Reservoir of the Rio Pardo (HENRY & SIMAO, 1984). Others chemical parameters (dis- The results in t,he Reservoir of Rio Pardo are the solved oxygen, conductivity) had no direct effect on first step to better knowledge of benthic fauna of

Rev. Hydrobiol. irop. 17 (4): 309-318 (1984). 316 R. HENRY AND C. A. SIMhCl

TABLE IV

Comparison of densit.y and biomass of aquatic, shells in t.emperûte and tropical environments

BIOMASS ALCOHOL SHELL DRY BODY DRY LAKES OR SPECIES DENSITY REFERENCES RESERVOIRS (ind.m-2) \VE1 GHT WEIGHT WEIGHT (g.m-2) (g.m-2) (g.m-2)

Anodonta piscinalis Anodonta cygnea Lewandowski & Mikolajskie 0.60 10.965 2.632 0.184 Stanczykowska (littoral zone) (1975)

Alvarenga et Juturnaiha Diplodon hesckeanus 12.48 al. (1977) Corhicula africana 42.43 Caelatura aegyptlana 4.37 Lévêque (1972) Chad (1968) Pisidium pirothi 7.86 Byssanodonta parasite 10.13 Corbicula africana 43.42 10.091 - - Chad (1970) PisidiumCaelatura pirothiaegyptiana 6.703.54 10.5270.018 - Lévêque (1972) Byssansonta parasitica 3.61 0.027 - Reservoir Diplodon delodontus Rio Pardo expansus 36.62 347.27 225.00 10.92 This work

brazilian reservoirs and t.o their role in the &XNOWLEDGEXENTS funçtionning of these reservoirs. The bivalves are fllterers and cari c0ntribut.e for a decrease of We are grateful to Dr. C. LÉVBQUE for his encouragement suspended particles in the water column. A previous and suggestions at the start of our study and for the comments on the manuswipt; to CNPq (Proc. 40.31X2/83) and IBBiMA/ study (HENRY & CURI, 1983) showed that the FAPESP for their financial support; to Dr. L. C. F. ALVARENGA suspended matter is, in water surface, smaller in for identification of the bivalve; to Dra. M. C. D. MANSUR for lower than in Upper reservoir. D. delodontus expansrrs confirmation of the ident.ification of the and for the is surely an important component for decreasing of suggest.ions; to Dr. P. FL CURI for the statistical assistance; the suspended parlicles through filtration, beyond to Dra. V. A. CARVALHO for facilitating the granulometric of seston sedimentation. The filtration rate cari vary analyses by putting at our disposa1 laboratory equipment; to from 0.3 I.h-1 for Unionidae in Lake Mikolajskie, N.CARNEIRO,E.M.PELLEGRINI-CARAIIIASCHI, U.CARAMAsCUI, Poland (LEWANDOWSKI & STANCZYKOWSKA, 1975) to J. M. PAVAN and S. V. Basse, for their contribution to field 3.6 l.h-l for Unio pictorum (ELLIS, 1978). If these researcb; to Mrs. G. HENRY for the english version of the filtration rates are applied for D. delodontus expansua manuscript, and to N. A. Basse for typing the manuscript and drawing thc figures. Miss C. A. S. received flnancial and considering the population density in the support, from the FUNDAP. Specimens were given to the Reservoir of the Rio Pardo, a11 the volume of National Museum of Rio de Janeiro (Brazil) and the Museum Reservoir (406,411 m3) could be filtered in approxi- of Natural Sciences of the Zoobotanic Institute of Rio Grande mately 10 days to less than one day, respect.ively. do Su1 (Brazil) (deposit.ed in the Malacology Section under These considerat#ions show t.hat a study of aquatic number 5218). ecosystem should take into account the benthic fauna for a better understanding of their structure, ïkfanuscrit rqu au Seroice des Edifions de I’ORSTOM le dynamics and productivity. 6 septembre 1.984

Reo. H!ydrohiol. trop. 17 (4): 308-318 (1934). DENSITY AND BIOMASS OF D. DELODONTUS EXPANSUS IN A SMALL TROPICAL RESERVOIR 317

REFERENCES

ALVARENC;A (L. C. de F.) and RICCI (C. N.), 1981. - Bivalvia, HARMAN (W. N.), 1972. - Benthic suhstrates: t,heir effect on in: Aquat.ic biota of tropical Sout.h America Part.. fresh-water mollusca. Ecoloyy, 53 : 2.71-277. 2: Anarthropoda (Eds. Hurlbert, S. H.; Rodrigucs, G.). HEBLING (N. J.) and PENTEADO (A. M. G.), 1974. - Anatomia San Diego State Universit.y. San Diego. California : 208-217. funcional de Diplodon rotundns gratus Wagner, 1827 (Mollusca, Bivalvia). Reo. Brasil. Biol., 34 : 67-80. ALVARENGA (L. C. de F.), COELHO (A. C. dos S.), RICGI (c.. N.), GOMES (L.A.L.) and BIRROS (1%. M.), 1979. - a. Rcsul- HEBLING (N. .J.), 1976. - The functional morphology of tados preliminares dos trabalhos ecologicos realizados na Anodonfifes frapazius (Spix) and Anodontifes frapesialis Represa de Juturnaiba, Municfpio de Araruama, (Lamarck) (Bivalvia: Mycetopodidae). Bolm. 2001. Estado do Rio de Janeiro, criadouro natural dos Univ. S. Paulo, 1 : 265-297. bivalves Diplodon bssckeanus (DUNKER, 1849) (Uniono- HENRY (R.), 1981. - Estudos ecologicos na Represa do Rio idea, Hyriidae) e Anodontites frapesialis (LAMARCK, Pardo (Botucatu, SP, Brasil). 1. 0 ambiente e varia@es 1819) (Muteloidea; Mycetopodidae). Anais do TM diurnas de alguns fatores ambientais. Reo. Bras. Biol., E71conlr0 de ïtfalacologisfas Brasileiros, ~Ilossord, RN, 41 : 153-161. de 14 a 17 de julho de 1977. Funda@io Zoobotânica do Rio Grande do SUI, Porto Alegre : 73-89. HENRY (R.) and CURI (P. R.), 1981a. - Influências de BURGIS (M. J.), DARLINGTON (J. P. E. C.), DUNN (J. G.), parâmetros climatologicos sobre alguns fatores fisico- GANF (G. G.), GWAH~BA (J. J.) and MCGOWAN (L. ni.), quimicos da Qua na Represa do Rio Pardo (Botwatu, 1973. - Biomass and distribution of organisms in SP). Reu. Bras. Biol., 41 : 299-306. Lake George, Uganda. Proc. r. Soc. London B., 184 : HENRY (R.) and CURI (P. R.), 1981b. Anhlise de parêmetros 271-29s. hidrolbgicos da Represa do Rio Pardo (Bot.ucat.u, SP). CO (L. C.), 1979. - Distribuiçfio de Oligochasta na Represa Heu. Bras. Biol., 41 : 321-326. do Lobo (Est.ado de Sao Paulo, Brasil). Tese de Mestrado, HENRI; (R.) and CURI (P. R.), 1983. - Estudos ecol0gicos Universidade Federal de Sao Carlos, 169 p. na Represa do Rio Pardo (BOtUCCLtLl, SP, Brasil). II. CURIAL (0.) and LANGE (R. R.), 1974a. - Hermafrodistismo Distribuiçao horizontal e varia@0 anual do material em Diplodon delodontus expansus. Arq. Biol. Tecnol., em suspensao. Reo. Bras. Biol., 43 : 31 l-316. 17 : 109-110. HENRY (R.) and LOPES (C. A. de M.). 1978. - Estudos ecol& CURIAL (0.) and LANGE (R. R.), 1974b. - Observaçoes sobre gicos na Represa do Rio Pardo (Botucatu, SP, Brasil). a propor@o de sexes em Diplodon delodontus ezpansus. III. « Standing-stock 3, varia@0 arma1 e distribuiçao Arq. Biol. Tecnol., 17 : II I-112. vert.ical de hart.@rias çoliformes e Escherichia coli. 0 Bioldgico, 44 : 183-188.. CURIAL (0.) and LANGE (R. R.), 1975. - Varia@es hist.olQicas sazonais das g«nadas do Diplodon delodontus e.cpansus HENRY (R.) and SrnrAo (C. A.), 1984. - Spatial distribution (Küster) (Mollusca, Unionidae). Arq. Bool. Tecnol., of a bivalve populat.ion (Diplodon delodontzzs expansus) 18 : 65-67. (Küster, 1856) in a small tropical rescrvoir (submited for puhlicntion). DARLIWGTON (J. P. E. C.), 1977. - Temporal and spatial variation in the bent.hic invertebrate fauna of Lake HENRY (R.) and SOUS.~ (A. P.), 1984. - Represa do Rio Pardo George, ZJganda. J. ZOO~., 181 : 95-111. (Botxcatu, SP). Rio o Lago? (submitcd for publica- DEJO.CTX (C.), LAUZANNE (L.) and LÉ~ÊQuE (C.), 1971. - tion). Nature des fonds et repartit.ion des organismes ben- HENRY (R.), CARAMASCHI (E. M. P.) and TUNDISI (J. G.), thiqurs dans la region de Bol (Archipel Est du lac 1978. - Preliminary results of a survey of a ecological Chad). Cah. ORSTO& sdr. Hydrobiol., vol. V, nos 3-4 : factors in a shallow tropical reservoir. Rev. Bras. 213-223. Biol., 38 : 171-175. FITTKAU (E. J.), IRMLER (U.), JUNR (W. J.), REISS (F.) and JIM (J.), 1970. - Contribuicai, ÜO estudo de uma Hyln da ScHhfIDT (G. W.), 1975. - Productivity, biOmaSS rrgiao de Bot.ucatu (Amphibia, Anura). Tese de Mestra- and population dynamics in Amazonian water bodies. do. Universidade de Sjo Paulo, 150 p. In: GOLLEY (F. B.) and MEUINA (E.) (Eds.). - Tropi- cal Ecological Systems - Trends in terrestrial and KENITIRO (S.), 1973. - Tntrodu<;ao à Sedimentologia, aquatic research : 289-311. EDUSP, Sao Paulo, 371 p,

Reo. Hydrobiol. trop. 17 (4): 309-318 (19831. 318 R. HENRY AND C. A. SIWÂO

KIMER & ALE~ANDER, 1949. - Methods of making mechanical MCLACHLAN (A. J.) and MCLACHLAN (S. M.), 1971. - Benthic analysis of soils. Soil Sci., 68 : 15-26. fauna and sedimrnts in the newly creat.ed Lake Kariba (Central Africa). Ecology, 52 : 800-809. I.EVÈQOE (<:.j, 1971. - Équation de Von Bertalanffy et. croissance des mollusques brnthiques du lac Tchad. MOLFI (A.) and ÇVRI~L CO.), 1977. - Observa@?s sobre a Cuh. ORSTOM, sér. Hydrobinl., vol. V, nos 3-4 : 263-283. histoquimica de polissacarideos em $%ndulas da r?-;iao podal de Diplodon delodontus espansus (Küst.er) LEvAQue ((:.r, 1972. - Mollusques benthiques du Lac Tchad : (Molluxa, Unionidae). Arq. Biol. Technol., 20 : 27-30. r!cologie Ptudr des pruplrments et estimation des biomasses. Ccrh. ORSTOM, Cr. Hydrobiol., vol. 1.1, Pa~ourz (J. .J.), 1973. - Thp spc%ies complex of Diplodon II” 1 : 3-45. delodontus (Lamarck) (Unionacea-Hyriidae). iWalaco- logis, 14 : 217-270. L.&Y%QIIE fC.1, DE.JOVX (Ci.) and LAUZ~ZNNI~. (L.), 1983. - 8. The bent.hic fauna: ocology, biomass and communities. PELL~~,RINI-(:.~R~~~A~(:HI (E. &I.), 1979. - Rcproducao o Tn: CARMOI.IZE (J.-P.) ef ul. (eds.j. Lake Chad. DR. alimentaggo de Hoplias malabaricus (Bloch, 1794) na \V. .Junk Publishers. The Hague : 233-272. Represa do Rio Pardo (Botucatu, SP). Tese de Mestrado, Universidade Federal de Sao Carlos. 144 p. LWOS (R. C. da! and SANTOS (R. D. dos), 1976. - Manual de mbtodo de trabalho dc campo. Socieldde Brasileira PELLEGRIM-C.~RAWASCHI (E. M.), GODINHO (I-I. M.) and de Ciência do Solo, 36 p. FORESTI (F.1, 1982. - Reprodu@o de HopZias mala- buricus (Bloch, 17941 (Telaostei, Erylhrinidae) na L~WANDO~WI (K.i and S~~AXCZYIWWSKA (A.), 1975. - The Represa do Rio Pardo (Botucatu, SP). 1. Histologia occurrence and role of Bivalves of the family Unionidae e rscala de maturaçao do ovario. Reu. Bras. Biol., in Mikolajskie Lake. Ekol. Pol., 23 : 317-334. 42 : 635-640.

MANSUR (M. C. D.), 1972. - Morfologia do sistema digestive STRIXINO (G.) and STRIXINO (S. T.), 19SO. - Macroinverte- dr Custalia nndosa martensi (Ihering, 1891) (Bivalvia, brados do fundo da Represa do Lobo (Estado de Sjo Hyriidae), Iheringia, sér. ZOO~., 41 : 21-34. Paulo, Brasil). 1. Distribuiçao e abundancia de Chiro- nomidae e Chaoboridae (Diptera). Tropical Ecoloyy, M,wsrm (M. (;. D.r. 1973. - Morfologia do sistema digestive 21 : 16-23. (las espécies do gênero Diplodon SPIN, 1827, do Rio Guaiba, Rio Grande do Su1 (Unionacea-Hyriidaei. STRIXINO (G.j and STRIXINO (S. T.), 1982. - Macrobentos da Iheringia, sr’r. Zool., 42 : 75-W. Represa do Monjolinho (Go Carlos, SP). Rev. Bras. Biol., 42 : 165-170. MANSUR (M. C. D.i and ANFLOR (L. M.I, 1981. - Diferencas morfol@icas entre DipZodon charrunnus Orbigny, United Skates Department of Agriculture, 1951. - Soi1 1835 r D. pilsbryi, Marshall, 1928 (Bivalvia, IIyriidae). Survey Manual, Handbook 110 8, Soi1 Survey Staff, Iheringiu, sér. Zoo[., 60 : 101-116. Soi1 Conservation Service, Washington, D. C., U.S.A.

W~LA~FILAN :A. J.) and MCLACHLAN (S. M.), 1969. - The VEITENHEIMER (1. L.) and &kNSUR (M. c. D.), 19%. - bottom fauna and sediments in a drying phase of a Morfologia, histologia e ecoloyia de Mycetopoda Zegumen saline i\frican lake (L. Chilwa, Malawi). Hydrobiologia, (Martens, 1808) (Bivalvia, Mucetopodidae). Iheringia, 3-l : ‘401-403. sér. ZooZ., 6’5 : 33-71.

KW. Hytlrobiol. trop. li (4): 309-318 (1984).