ON THE IONIC REGULATION IN SOME FISHES FROM THE COCO RIVERESTUARIES IN FORTALEZA (CEARA STATE. BRAZIL)*.

MARIA IVONE MOTA ALVES**

ABSTRACT kidney were made to find out arelationship between the structure ofthi~ organs and the osmoregulatoryresponse from the fishes studied.

The values of salt content in theblood suggest a behaviour of osmocon-formist for ali the studied species.

The hystological analysis of the skin,gills and kidneys has not identified verysgnificant differences between thespecies, but the presence of a number ofmucus-secretory cells in Gobionnell!soceanicus has been observed. It is alsonoteworthy the larger size of Malpighi'sglomeruli in the kidneys of Elops saurus.

Teleost fishes, both stenohaline andeuryhaline, keep a ionic concentration ofits plasma' at a higher levei in the seathan in freshwater. In general, regulationof hidromineral balance is not rigid, butrather it varies with changes that allowsurvival (HOLMES & DONALDSON8,JOHNSON9 ).

Little information is avaiable on theosmoregulatory response of teleost livingpermanently in hiposmotic brackishwater, to environmental salinity stress.In the present paper 500 fish of Elopssaurus, Anchova clupeoides, Bagremarinus, Oligoplites palometa, Eugerresbrasilianus, Micropogonias fournieri,Mugil curema and Gobionnelus ocea-nicus were exposed to lower and h ighersalinities than usual, and measurementswere then made of plasma concentrationof CI-, Na+, K+, Mg +2 and Ca+2.Histological analysis of the skin, gills and

RESUMO

Peixes teleósteos, tanto estenohalinoscomo eurihalinos mantêm uma concentraçãoiônica de seu plasma num nível mais elevado nomar do que na água doce, Geralmente, a regula-ção do balanço hidromineral não é rígida, masvaria com as mudanças que permitem suasobrevivência (HOLMES & DONALDSON8,JOHNSON9), '

Existem poucas informações sobre aresposta osmorregulatória de teleósteos quevivem permanentemente em águas estuarinashiposmótica em condições de "stress", Nopresente trabalho 500 peixes pertencentes asespécies Elops saurus, Anchova clupeoides,

* Paper presented at the "International Symposiumon utilization of Coastal Ecosystems: Planning,Pollution and Productivity" held- on November

21-27,1982.* * Professor of the F ishery E ngineering Department -

Federal University of Ceará. P. O. Box 3038 -

Fortaleza, Ceará, Brazil. 60.000

97r;,;n Aornn Pnrtal,,7a 1(, (1): oáQ. 97-104 Junho. 1985

- . -, ~brasilianus, Micropogonias fournieri, Mugilcurema e Gobionnelus oceanicus foram expos-tos a altas e baixas salinidades do que a usuale medidos a concentração de CI-, Na+, K+,Mg+2 e Ca+2 do seu plasma. Análise histoló-gica da pele, brânquias e rim também foi feitana tentativa de correlacionar estas estruturascom a resposta osmorregulatória dos peixesestudados.

Os valroes do conteúdo de sal do sanguesugere um comportamento osmoconformistapara todas as espécies estudadas.

A análise histológica efetuada não apresen-tou diferença significativa entre as espécies, masfoi observada a presença de numerosas célulassecretoras de muco em Gobionnelus oceanicus.Também é digno de nota o maior tamanho dosglomérulos de Malpighi no rim de Elps saurus.

Key-Words: lonic regulation, teleost fishes,osmoregulatory response.

__00__"" 00 00' ...~ ~.~~- ... ~..

salinity levels (POTTS & PARRy12).However, a certain degree of tolerance totolerance to internal changes is arequirement of some anadromous andcatadromous fishes when they migratebetween the sea and the freshwater.Those species are capable of osmoregula-tion, to some extent in both environ-ments and they do not stay isosmotic fora great length of time.

A few species require a gradualadaptation so as to change their osmoticcondition, but others are able to undergovery rapid metabolic adjus1;ment.

Teleost fishes, both stonohaline andeuryhaline, keep a ionic concentrationof its plasma at a higher levei in the seathan is freshwater. In general, regulationof the hidromineral balance is not rigid,but rather it varies with changes thatallow survival (HOLMES & DONALD-SON8; JOHNSON9).

The present paper aims at determi-ning, by means of laboratory studies, thetolerance shown by estuarine fishes atdifferent level~ of salinity, as a way toarriving at their mechanisms of ionicregulation.

INTROOUCTION

Estuarine waters, as a rule, do nothave a typical fauna, but rather a groupof marine, estuarine and freswaterspecies (OLIVEI RA1O).

CAMERON & PRITCHARO4 andPRITCHARO13 define an estuary as abody of coastal, semienclosed water,that connect with the sea and withinwhich the sea is gradually diluted by the MATERIAL ANO METHOOSfreshwater derived from earth drainage. The study material is comprised of

The number of marine species that 500 specimens belonging to the speciesenter inland water outweighs that of E/ops saurus, Anchovia c/upeoides, Bagrefreshwater species (GUNTHER6,7). The marinus, O/igop/ites pa/ometa, Eugerresmain factor to contrai entry of brasi/ianus, Micropogonias fournieri,brackish water fish is the revel of water Mugi/ curema, Gobionne/us oceanicus,salinity. On the other hand, many for which data on length are set out ineurihaline fishes keep the same salt Table 1.

TABLE 1

Statistics of length (mm) of the specímens used in the study of ionic regulatíon of estuarine físhes,throuQh salínitv varíatíons. ín normal temperaturf! conditíons (28°C)

CV{%)

3.405.207.027.653.602.184.321.45

98 Ciên. Agron.. Fortaleza. 16 (I): Pá2. 97-104 J unh()- I QR~

At sampling time the 02 content andtemperature were estimated by meansof an Oxygen Meter, Model 51 -AYSI, while the pH value wasestimatedby a meter pH FANEM-OR ION,'Model301 (Table 2). '

had fragments of the skin, gills andkidneys taken, and fixed at 10%formalin for microtomic cuts of 5 micraof the pieces embedded in paraphin,by the usual method via xylol. Forcolorations, hematoxilin of Delafieldand eosine at 1% have been used.

TABLE 2

Characteristics of the water in the estuarine region ofCoc6 River, in the period July/1980 - June/1981

RESUL TS AND DISCUSSION

The specimens caught with atrawlnet were placed in containers withwater from the sampling site, previouslyfiltered, and left for acclimation inlaboratory, for a while. As food supplyoats was used in a 4 pen cent proportionof the live weight.

In testing tolerance to salinity, seaand freshwater, were - mixed at thefollowing proportions: 0- 20 - 30 - 40- 50 - 60 - 70 - 8"0 - 90 - 100%.Salinity was measured by the Knudsenmethod with the modifications intro-duced by- SWI NG LE '4. Water tempe-rature in .all experimental phases variedfrom 27 to 29°C.

The salt content in the blood forspecies submitted to the tolerance testwas estimated from a blood sampletaken from the cardiac region just beforethe line which links the insertion of thepectoral fins, as recommended byAMLACHER'.

As an average, 0.2 ml of blood havebeen collected, submitted to centrifu-gation, the plasma being used for theestimates according to the method ofspectrophotometry. The values of Na+,K+, CI-, Mg+2 and Ca+2 were calculatedafter dilution of the plasma in destilledwater, in a proportion of 1: 500, inmEg/1 units.

For histological studies, randomlychosen specimens of the different species

- Junho,191Ciên. Agron., Fortaleza, 16 (I): pág. 97-104

The variability of environmentalconditions ensures the appearance ofspecies ~ighly sensitive to this factor aswell as others which adapt themselveseasily to a certain range of values.

One of the most important factorsbrought to bear on fish behaviour isresistence to the water salinity in theirrespective habitats.

Testing of tolerance to salinity inElops saurus, Anchova clupeoides,Bagre marinus, Oligoplites palometa,Eugerres brasilianus, Micropogoniasfournieri, Mugil curema and Gobionnelusoceanicus, at different levels, show thatamong the studied species Elops saurus,Eugerres brasilianus and Micropogoniasfournieri are less able to support changesin salinity than ,the other species(Table 3).

After the experimental tests, thequantities of salt underwent changes inali species, as shown by the t - testedstatistical differences between means(Table 4).

Some species require a gradualadptation in arder to change theirosmotic condition, but other are capableof a very quick metabolic adjustment.The present data seem to characterizeperfectly the condition of osmoconfor- mist in the studies species.

According to BLACK2, it seemsthatthe likelihood of stenohaline fishsurviving in water higher salt concentra-tions may depend on the histology andsurface areas of the gills, 02 intake, tole-rance of the tissues to salts and contraiof permeability. This contrai, on itsturn, may be the result of the neurose-cretory action or the hormonal reaction

~5 99

le study of ionic regulation of estuarinetests of saline shock (30 days period)

Seawater proportion (%)

Species 80 90o 10 20 30 40 50 60 70 100

100100100100

100100

50

-

1002010

10040

100100

-80

100

10050

-10020

100

100100

Elops saurusAnchovia clupeoidesBagre marinus

Oligoplites palometaEugerres brasilianusMicropogonias fournieriMugil curemaGobionnelus oceanicus

TABLE 4Data of t - tested statistical differences between means, after the experimental tests.

-

Mg2+

-Ca2+

-Na+

-K+ CI-Species

Elops saurusAnchova clupeoídesBagre marínus

Oligoplítes palometaEugerres brasílíanusMícropogonías fourníeriMugil curemaGobíonnelus oceanícus

basic layers: on other one, the epidermisand an inner one, the dermis, also knownas "corium". These layers differ fromone another according to position,origin, structure, character and function.

to the new environment, as well as of adirect effect on cellular surfaces.

From the behaviour of the fishspecies and through histological analysessigns were sought of changes in the skin,gills and kidneys which could be relatedto this condition of osmoconformist ofthe species. A description of theanalysed structures is given below,separately, pointing out that it appl ies toali species, but with emphasis onobserved differences in some cases.

In the considered species, theepidermis at the intermediate region ofthe body, by dorsal fin, is comprisedof eight to ten layers. In Gobionnelusoceanicus, at the insertion point of thefin, it is comprised of five layers.

The epitelial cells are bound by aviscous intercellular elemento The germi-native stratum is composed of colunarcells and there from new cells arederived. Reproduction in this layeroccurs by mitotic division. The new cellsubstitutes the one from which itoriginated, while pushing it upward asfar as the surface, where it takes theplace of another cell that beco me uselessfrom wearing or damage.

1 - Skin

The skin, with its auxiliary structu-res, stands for an externa I wrapper of thefish's body, through which most of thecontacts with the externa I medium aremade, It carries out many importantfunctions in fish that are, essentially. ofa protective nature (OOSTEN" ).

As in the other fishes, the skin of thespecies here studied is made up of two

100 C"iên. Agron.. Fortaleza. 16 (I): pág. 97-104 Junho. 1985

According to OOSTEN1l , experimentshave shown direct losses to occurthrough damaged skin of freshwater fish,a large loss of water and a salts diffusionin damageçj marine species.

Among the studied species, the oneswith higher resistance to salinityfluctuations are exactly those whichhold a skin with thick epidermis, andmucus cells in larger quantities.

2 - Gills

The gills consist of a row of folds,the branchial filaments, placed at adorso-lateral position, from radial toventral-lateral of the tips of thepharingean clefts. Those filaments aresettled in two vertical semi-gills anteriorand posterior to the opening and eachsemi-gill is supported in the foregoingand hinder sept, respectively.

The branchial filaments support oneach side a series of transversalstructures, the secondary lamellae,responsible for the respiration, andconsist of central tissue with a singlelayerofauxiliarycells(FIG.1).

The lamellae on the adjacent sides oftwo adjacent filaments hold a serie ofminute grooves, through which waterflows in a perpendicular direction tothe three ends of the filament. Thisway, water f~ows straight from thepharingean cavity into the epibranchialspace through several minute holes intro-duced by the intermediate lamellae.

Another anatomic feature thatcontributes largely to the gill's efficiencyis the behaviour of blood supply. Thedisposition of the efferent and afferentblood vessels is such that blood flowsthrough the branchial lamellae in theopposite direction to that of water'sflow. This counter-current systementrances a wider exchange of respira-tory gases and other substances.

The branchial filaments are dressedup by a single cavernous epitelium,containing a layer of conective tissueinto which the afferent an efferent

101

cell undergoes a chemical change andgradually takes on a scal or flat aspectoOn the surface it finally dies and iseliminated. This scaling off is acontinous process and thus the wholeof the epidermis stays alive, save for thesuperficial layer of the cells that havealready run their courses and arereplaced continuosly.

Nutrition for growth and repro-duction of the basal cells is obtainedby the vascular underlying system ofthe dermis.

The dermis originates from theembrionic mesenquima of mesodermalorigin (OOSTEN11). In this studiedspecies, no noteworthy detailed specificstructures have been put to evidence, butrather a fiberelastic conective tissueshowing in ali of then with relativelyfew cells. The upper layer, very fine,comprises the vascular or spongystratum, the lower layer is trick anddense standing for the compact stratum.

In the skin of Gobionnelus oceanicusthere are severa I mucus-secretive cells,which carry out a lubrication function.They derive from the basal layer of theepidermis, in great numbers, andsecrete a large quantity of mucus, ofwhich it was not possible to determinethe specific composition. However,OOSTEN11 reports that in species thatproduce mucus this would interfere inthe process of osmosis. This same authoralso emphasizes the role of the mucus inthe protection against infestation byfungi, and coagulation power of blood,in addition to the precipitation action asa result of neutralization of negativeelectric changes in coloidal suspensionby means of ionization of an acidanother agent which liberates positivelons.

The other estuarine species holdfew mucus-secretive cells, scattered inthe epidermis.

The skin of teleost fishes is, as rule,permeable to water, but to varyingdegrees it has little or no permeabilityto organic substances or ions. Permeabi-

Ciên. Agron., Fortaleza, 16 (I): pág. 97-104 - Junho, 1985

Figure 1 - BrM1Chil' filM18ntl and MCOndlry II~I'.. of Mugi' cu,.~. They Ire dr~ up by I

single cavernous epitelium.

3 - Kidney

Nash (1931); Romer & Groove(1935) and Smith (1930), according toreport by WORSMANN et alii15 ,havepointed out the presence or absence ofglomeruli in the habitat, dis.cussing thevarious factors involved in the absorp-tion, excretion and osmoregulation inmarine and freshwater fishes.

GERARO5 reports a renal differen-tiation of some teleost species, especiallyin the breeding season. Such differencehas not been observed in the studiedspecies, but it must be said that thesampled individuais were not in repro-ductive activity.

With reference to the glomeruli ofMalpighi the mesonephros of teleostsmay be glomerular, glomeruless orfunctionally glomeruless. In freshwaterfishes those structures are welldeveloped, to a variable extent, andfractional or full counts of a number ofglomeruli have been used as a parametersfor fish grouping (WORSMANN etalii 15).

arteriolae enter, the some h01ding fornervous sheaves.

The filaments are supported by acavernous tissue wich stretches in thebase and penetrate in each one by meansof rather broad extension. This tissue ismade out functionally of branchialcartilagenous columns which hardenthe filaments.

- .Keys & Wilmar (1932, 41), Liu

(1942) and Copeland (1948), reportedby BERTIN2 have identified in the baseof the branchial lamellae and in its twofaces, bulky epitelial cells acidophilousand a large nucleus, comparable to thoseof HCI of mammal's stomach. Theexistence. of those cells would probablybe related to a great osmoregulatorypower and would have as function tosecrete sodium and potassium chloridesand to oppose to the animal's dismine-ralization on its way through water ofdifferent salinities.

No cells with such characteristicshave been found in the branchialfilaments of any of studied species.

102 Ciên. Agmn.. Fortaleza. 16 (I): pág. 97-104 - Junho. 1985

--Figure 2 - A transvertal cut of the kidney of ElopsMurus. emph.lzing. glom8fUlUI of

Malpighi and proximal tubules.

brasilianus, Oligoplites palometa andMicropogonias fournieri are less abre tosuport changes in salinity than the otherspecies.

The values of salt content in theblood suggest a behaviour of osmocon-formist for ali the studied species.

The hystological analysis of the skin,gills and kidney has not identified verysignificant difference between thespecies, but the presence of a numberof mucus-secretory cells in Gobionnelusoceanicus has been observed. It is alsonoteworthy the larger size of Malpighi'sglomeruli in the kidney of Elops saurus.

Ali species here considered presenta small glomerulus of Malpighi, withrenal parenquima comprised of tubules,most of them proximal with have anample light with a spheric and centralnucleus.

A transversal cut of the kidney ofE/ops saurus is show in Figure 2enphasizing a glomerulus of Malpighiand proximal tubules tranversallyobserved. This species was the onewith the most developed glomeruli.

The existence of well depelopedMalpighi's glomeruli is probably relatedto the tolerance shown by the species tovariation in the environment's salinities.

AcknowledgementsGENERAL CONCLUSION

Many thanks are due to Mrs. AídaMaria Eskinazi de Oliveira from. theBiology Department of the FederalUniversity of Ceará, for identifying thespecies herein studied.

LITERATURE CITED

1. AMLACHER, E. 1964. Manual de enfermi-

From the study of the species'sbehaviour to the saline shock, it hasbeen shown that Anchova clupeoides,Bagre marinus, Mugil curema andGobionnelus oceanicus tolerate largevariations of salinity, ranging fromfreshwater (0,4%0) to sea water35,7° /00). Elops saurus, Eugerres

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--. . .Hoar & O. S. Randall (Ed.). AcademicPress, New York.

9. JOHNSON, O. 1973. Endocrine contrai ofhidr.omineral balance in teleosts. Am.Zoo/., 13: 799-818.

10. OLIVEIRA, A. M. E. 1972. Peixes estua-rinos do Nordeste Oriental Brasileiro.Arq. Ciên. Mar, Fortaleza, 12 (1):35-41.

11. OOSTEN, J. V. 1957. The skin and scales./n: The Physi%gy of Fishes, pp. 207-244, 10 figs. Brown, M. E. (Ed.)

12. POTTS, W. T. & G. PARRY. 1964. Theenergetics of osmotic regulation inbrackish and freshwater animais. J.exp. 8io/., Amsterdan, 31: 618-630.

13. PRITCHARO, O. V. 1967. What is anestuary: physical viewpoint. Pub/. Am.Ass. Advmt. Sci., Washington (83):3-5.

15. WORSMANN, T. V.; A. G. FERRI & S.R. BARCELOS. 1971. Estruturamorfológica do rim de peixes de águadoce. Rev. 8ras. 8io/., Rio de Janeiro,31 (3): 283-289, 8 figs.

14. SWINGLE, H. S. 1969. Methods of ana/ysisfor waters, organic mater and pondbotton sci/s used ín FísheríesResearch. Auburn University, 106 pp.,Auburn.

-2. BERTIN, L. 1958. Organes de Ia respira-

tion aquatique. In: Grassé, P. (Ed.).Traité de Zoologie, Anatomia,Systematique, Biologie, Tome XIII;Fasci Guie 11, pp. 1303-1341,28 figs.,Masson & Cie., Paris.

3. BLACK, V. S. 1957. Excretion andOsmoregulation. In: The Physiology ofFishes. I: pp. 163-205, Brown M. E.(Ed.), Academic Press Inc., New York.

4. CAMERON, W. N. & D. Y. PRITCHARD.1963. Estuaries, pp. 306-324, In:Hill, M. M. (Ed.), The Sea, vai. 2.Interscience, New York.

5. G~RARD, P. 1958. Appareil Excreteur.ln:Grassé, P. (Ed.), Traité de Zoologie,Anotomic, Systematique, Biologie,Tome XIII, Fascicule 11, pp. 1545-1564, 21 figs., Masson & Cie. Paris.

6. GUNTHER, G. 1942. A List of the Fishesof the Mainland of North and MiddleAmerica Recorded from bothfreshwater and Sea Water. Amer. Midl.Nat., Notre Dame, 28 (2): 305-326.

7. GUNTHER, G. 1956. A Revised List ofEuryalin Fishes of North and Midd!eAmerica. Amer. Midl. Nat., NotreDame, 65 (2) : 345-354.

8. HOLMES, W. N. & E. M. DONALDSON.1969. The body compartments and

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