Camp. Biodwm Pky.Cof. Vol. ItHA, No. 4, pp. 873475, 1991 Printed in Great Britain

#~%29~~ S3.00 + 0.00 Q 199 I Pergamon Press plc

PHYSICAL CHARACTERISTICS OF THE BLOOD PLASMA OF LABEQ ~~~~~ AND LABEU ROSAE

(PISCES: CYPRTNIDAE)

B. C. S. VILJOEN* and 3. H. J. VAN VURE~~ Research Unit for Aquatic and Terrestrial Ecosystems, Rand Afrikaans University, PO Box 524, ~ohan~~sb~rg, 2oo0, Republic of South Africa, Fax: (01 I) 489-241 I

{Received ZI March 1991)

Abstract-l. The physical compasition of blood plasma of Labeo ruddi and Lnbeo rosae males were determined during the breeding and post breeding phases.

2. The mean values for most blood electrolytes, pH and osmolality of the two species showed the same variation as was found for other cyprinids.

3, The abitity to handle stress may be refSected in the presence of certain electrolytes in the blood and efforts are made to relate differences in the concentration of these parameters to interspecies differences between L. ruddi and L. rosae.

INTRODUCTION

The genus L&w occurs ~~i~~~~ous~y in Africa and has been the subject of many studies. Information is, for example, available on embryology and larval development (Fryer and Whitehead, 1959), growth (Blake and Blake, 1978), and reproduction (Gaigher, 1984). In this respect ginogenesis was studied by John et a!. (1984). Feeding of La& nilotirtis was studied by Moghraby and Rahman (1984). Except for L. cupertsis and L. clmbratus {Hattingh, 1972, 1974, 1976a,b; Van Vuren, 1978, 1980, 1986), which are indigenous to the riversystems of cooler regions of the country, no published information on the haema- tology of other members of the genus is available. It was therefore decided to collect data in this regard in order to determine differences in concentration be- tween particular electrolytes namely sodium, potass- ium, calcium and chloride and physical parameters (osmolality and pH) during the breeding and post breeding phases of L. ruddi and L. rosae males and to relate it to possible stress reactions in these fish.

MATERIALS AND METHODS

Male specimens were collected in the northern part of South Africa during their breeding and post breeding phases in Glen Alpine Dam (23” 20’S, 28” 40’E). Gill nets were employed and specimens were handled with care since this sampling technique has the potential to induce stress (Oikari and Sovio, 1975; Hattingh, 1976a). Blood was collected by cardiac puncture from males of both species with as fittle delay as possible after capture, centrifuged and the supernatant frozen. Blood samples were later thawed in the laboratory in a waterbath at 25°C after which it was volumetrically divided according to the amounts required for each analysing procedure. A Wescor 5100 vapour pressure osmometer as well as a Osmomat 030 Cryoscopic osmometer were used for osmotality det~~~nations. A BMS 3 acid-base analyser (Radiometer, Copenhagen) was used for pH. A Corning 925 chloride analyser and Corning 940 calcium analyser were employed for the determinations

*To whom all correspondence should be addressed.

of chloride and calcium levels, while a FLM 3 flame photometer (Radiometer, Copenhagen) was used to establish sodium and potassium ~n~ntrations. Student’s r-test was used to determine statistical differences, which were considered significant when P < 0.05.

RESULTS

The results are presented in Table I. In the case of L. t-u&i the only statistically sibilant difference between values collected during and after breeding is the concentration of chloride (P < 0.001). In the case of L. rosae the pH (P < 0.025) and concentration of sodium (P < 0.05) and chloride (P < 0.001) differed statistically significantly between the breeding and post breeding phases.

The potassium con~ntration and pH in the blood plasma of the species investigated differed significantly during the breeding phase (P < 0.05; P < 0.025). No significant differences in these values in plasma collected after the breeding season could be shown to exist. Osmolahty and the pH values were constant in both species, but the latter was slightly higher in t. ruddi. Mean potassium values of both species increased slightly during post breeding and the highest value was found in L. ruddi. A marked fluctuation occurred during this stage. In L. rosae the potassium concentration fluctuated little during the breeding season but more thereafter. The mean potassium value in L. ruddi increased slightly during the post breeding phase, but was very constant in L. rosae while the mean calcium values were generally higher in this species compared to L. ruddi.

DISCUSSION

The nature of the blood plasma and ionic balance in fish is in general, determined by factors like water temperature, maturity, collecting method and stress (Lane, 1979; Smeda and Houston, 1979). It was established for L. caper&s that the pH decreasek dur- ing stress (Coetzee and Hattingh, 1976) and a similar

873

874 B. C. S. VILJOEN and J. H. J. VAN VUREN

Table 1. Physical composition of in the blood plasma of L. ruddi L. and L. ~osae L. during the breeding and post breeding stages. (* = P < 0.001; tP < 0.025: v < 0.05)

Variable

Osmol (mOsm/kg) PH Na (mmol/l) K (mmol/l) Ca (mmol/l) Cl* (nmol/l)

N

IO

IO

IO

10

IO

9

L. ruddi (breeding) L. ruddi (post breeding) VA X SD SE N VA X SD SE

269-333 288.8 20. I 6.4 8 269-333 292 21.3 7.5 6.3-8.5 1.4 0.6 0.2 10 6.3-8.5 7.2 0.7 0.2 122-196 140.9 26.0 8.2 10 122-132 163.3 60.4 19.1 4.9-15.9 8.5 3.9 1.2 10 4.9-19.7 II.0 4.9 1.6 7.8-13.8 9.9 1.8 0.6 10 7.8-14.8 10.3 2.4 0.7 51-89 70.4 10.6 3.5 8 95-207 141.4 33.6 11.9

L. IZWZ (breeding) L. rosae (post breeding)

Osmol (mOsm/kg) IO 288-325 303.6 13.0 4.1 IO 289-325 302 Il.8 3.1 PHt IO 6.1-7.5 7.0 0.45 0.1 IO 6.lL7.1 7.0 0.45 0.14 Naf (mmol/l) IO 128-146 134.7 5.4 1.7 IO 132-200 145.5 24.0 1.6 K (mmol/l) IO 7.5-17.4 Il.0 2.9 0.9 10 7.5-17.4 10.8 2.9 0.9 Ca (mmol/l) IO 8.3-16.1 12.3 2.5 0.8 IO 8.3-16.9 12.4 2.5 0.8 Cl* (mmol/l) IO 46100 78.4 18.0 5.7 9 82-210 131.6 34.7 Il.6

Osmol = osmolality; VA = variation; SD = standard deviation; SE = standard error (pH values are presented as instrument averages).

observation was made for other species (Oikari and bodies of Stannius in the pericardial region. If this tissue is removed, the blood calcium concentration increases as was shown in eels. It would seem as if hippocalcein is formed by the bodies of Stannius, which results in a decrease of blood calcium levels (Goldstein, 1977).

Soivio, 1975). The species studied &ring this investi- gation were collected simultaneously under similar circumstances. Interesting conclusions regarding inter- species differences may thus be made regarding their ability to handle stress. A change in the blood sodium concentration of L. capensis from 50.57 f 2.93 mEq/l to 52.19 f 2.33 mEq/l occurred after fish that were transported, were kept in water with a sodium con- centration of 0.7%. These fish showed a higher survival rate than fish that were not kept in saline water (Coetzee and Hattingh, 1976). A constant level of Na+ in the blood is indicative of a stable ionic balance in the body fluid. It minimises haemolysis, a very important factor for survival under stress con- ditions. It may therefore be concluded that sodium presence at a concentration of at least 0.7% (in the case of L. capensis) may be beneficial in counteracting osmotic disturbances caused by stress. Another factor is the concentration of potassium which may be indicative of stress. The high potassium concen- tration when the pH ranges from 6.1 to 6.3 shows that it can serve as a parameter for stress, as was shown for Onchorhynchus mykiss (Soivio et al., 1977; Railo et al., 1985). Sodium and potassium thus play an important role in maintaining osmotic balance in blood, while no proof could be found that chloride can be used as a stress indicator in this respect (Coetzee and Hattingh, 1976). The role of calcium as an indicator of stress in fish is unclear, but blood calcium values are maintained by vitamin D and the

It is generally accepted that fish are more active during the breeding season than at other times and may then be more susceptible to stress. If the vari- ation in the studied parameters during and after the breeding phase is taken into account and judged as being indicative of the ability of a particular species to tolerate stress, L. ruddi is better adapted to stress situations than L. rosae. More research should be done before final conclusions can be made.

It is difficult to explain the significant differences in blood calcium and chloride concentration in the blood plasma. When values obtained for different blood parameters of different members of the Teleostei by employing the same sampling techniques (direct cardiac puncture) are compared it is clear that con- centrations of most of the variables listed are within the same range (Table 2).

When this information is carefully evaluated, it is evident that the blood plasma levels of calcium in those species investigated, fluctuate within a wide range. Furthermore it suggests that all these fish have specific needs for these ions in the maintenance of the osmotic equilibrium. This leads to the conclusion that it is not feasible to determine standard values for the teleosts as a group, but for each individual species

Table 2. Comparison of osmolality, pH, sodium, potassium, calcium and chloride concentrations in the blood plasma of certain teleosts

Osmol Na K Ca Cl Species (mosmikg) PH (mmol/l) (mmol/l) (mmol/l) (mmol/l)

Xfonfinalis 307 152 2.0 124 Esox lucium - 135 3.4 2.6 126 Myoxocephalus quodricornis - 170 3.5 2.9 - Zoarches viviparus - 168 4.0 2.7 0. keta 324 - I51 1.6 4.6 II8 S. salar 232 8.3 237 86.0 5.2 0. mykiss 7.6 139 2.5 - 124 S. fontinalis 377 - 152 2.0 - 124 C. gariepinus 223 7.3 137.5 3.3 10.7 95 L. ruddi’ 288 7.4 140.9 8.5 9.9 70 L. rosae’ 303 7.0 134.7 II.0 12.3 78

*Mean values during breeding (present investigation). pH values are depicted as instrument averages.

Blood plasm .a of Labeo 875

John G., Reddy P. V. G. K. and Gupta A. S. D. (1984) Artificial gynogenesis in two major carps, Lubeo rohita (Ham.) and Catla Carla (Ham.). Aquaculture 42, 161-168.

Marshall W. S. (1986) Sperm duct epithelium of brook trout: Na+ transport and seminal plasma composition. Can. J. 2001. 64, 1827-1830.

McCormick S. D. and Naiman R. J. (1984) Osmoregulation in the brook trout, Salvelinus fontinalis I. Diel, photoperiod and growth related physiological changes in freshwater. Comp. Biochem. Physiol. 19A, 7-16.

Moghraby A. I. and Rahman A. A. (1984) Food and feeding

only. Fish are also very closely associated with their environment and may thus show marked haemato- logical variation depending on the locality and the characteristics of their medium (Blaxhall, 1972; Van Vuren and Hattingh, 1978).

The species, locality and sampling technique should therefore always be considered when conclusions are drawn from values obtained for haematological variables.

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