Author Institution: Chesapeake Biological Laboratory, Solomons, Marylan

Kendall, Arthur

Schwartz, Frank J.

The Ohio Journal of Science

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SALINITY TOLERANCES OF TWO MARYLANDCRAYFISHES12ARTHUR KENDALL3 AND FRANK J. SCHWARTZChesapeake Biological Laboratory, Solomons, MarylandThe recent population expansion and the ecological tolerances of the intro-duced crayfish, Orconectes virilis (Hagen), within the Patapsco River watershed ofMaryland have been demonstrated by Schwartz, Rubelmann, and Allison (1963).We wish to determine the salinity tolerances of this species prior to its possibleexpansion into other watersheds of the state and to compare them with a typicalfreshwater form, Cambarus b. bartonii (Fabricius), which is not known to haveinhabited saline waters.Few data are available on the tolerance of the euryhalinity of freshwatercrayfishes. Herrmann (1931) found Astacus astacus ( = Potamobius astacus) wouldsurvive for three months in 50 per cent seawater while Bogucki (1934) found thatthe same species, which he designated Astacus fluviatilis, would tolerate 66 percent sea water for one month. Clemens and Jones (1954) found an Oklahomacrayfish (species unknown, personal communication August 15, 1963) tolerant ofoil well brine solutions which were diluted to 8.7 per cent by volume of the originalbrine. Three species, Rhithropanopeus, Callinectes, and Platychirograpsus, ofNorth American marine or fresh water crabs have been known to invade or inhabitfreshwaters (Chace et al., 1959). Most observations, however, have dealt withtissue osmoregulation, ion concentration, osmotic receptor sites, influences ofmolt cycle, etc. (Krogh, 1939; Prosser, 1950; and Waterman, 1960, 1961).Schleiper (1935) stated that no freshwater invertebrate could maintain a normalconcentration of its internal medium when placed in seawater. Presson (1957)noted that temperature had no effect on the ionic concentration of the blood ofO. virilis when it was placed in solutions containing calcium and potassium ions;the blood concentrations of sodium were different at various temperatures. Gross(1957) found that Procambarus clarkii (= Cambarus clarkii) had the least permeableexoskeleton among various marine and aquatic decapods and reasoned that thispermitted the species to regulate to osmotic stress.METHODSOrconectes virilis specimens were seined from above a dam on the 100-ft wideand 3-ft deep Patapsco River in the Patapsco State Park, 1.5 mile W. of U. S. Rt.1 near Relay, Maryland. The river water was fresh, non-tidal, and heavily pol-luted by industrial and domestic waste (Schwartz, Rubelmann, and Allison, 1963).The exoskeleton and appendages of many of the 80- to 110-mm long specimenswere overcoated with a filamentous-hairy growth (Epistylis?) (fig. 1). The speci-mens were placed in a styrene ice chest containing ice and river water and trans-ported 90 miles to the Chespeake Biological Laboratory at Solomons by car.Cambarus b. bartonii were similarly collected from the Casselman River nearU. S. Rt. 40, Garrett County, Maryland. The habitat, in contrast to the slow,silt-and sewage-ladened Patapsco River, was a rapidly flowing, shallow, rocky,mountain stream. A similar double-trayed ice chest permitted safe conduct ofthe crayfish during the seven-hour trip to the laboratory.Contribution No. 266, Natural Resources Institute of the University of Maryland,Solomons, Maryland.2Manuscript received October 5, 1963.3Present address: Department of Oceanography, University of Washington, Seattle,Washington.THE OHIO JOURNAL OF SCIENCE 64(6): 403, November, 1964.404 ARTHUR KENDALL AND FRANK J. SCHWARTZ Vol. 64FIGURE 1. Typical specimen of 0. virilis collected in June and August, 1962, in the PatapscoRiver, Maryland.No. 6 CRAYFISH SALINITY TOLERANCES 405Experimentally, four lots (lOcfcf, 109 9) of each species were placed inseparate aquaria. Running fresh well water and approximately 6 ppt (parts perthousand), 14 ppt, and 27 to 33 ppt saline waters were the test media (table 1).TABLE 1Longevity of two species of crayfishes subjected to varying salinities and temperaturesExpt. ITotal days survived by any orall specimensSalinityMeanRangeTemperature (C)MeanRangeExpt. IITotal days survived by any orall specimensSalinityMeanRangeTemperature (C)MeanRangeFresh13+0.80.4-1.721.319.7-23.031 +1.20.7-1.622.719.9-25.16 ppt 14 pptOrconectes virilis9 126.13.4-9.722.420.4-24.031 +5.81.6-8.923.219.4-24.813.112.8-13.724.021.9-25.42315.214.4-15.824.119.0-26.330 ppt1027.426.9-28.22.220.7-23.533.032.7-33.24.523.4-25.5539Expt. ITotal days survived by any orall specimensSalinityMeanRangeTemperature (C)MeanRangeExpt. IITotal days survived by any orall specimensSalinityMeanRangeTemperature (C)MeanRange11 +1.40.8-1.7Cambarus b. bartonii11 55.23.4-9.413.6 27.512.8-14.2 26.7-28.421.9 22.9 24.9 24.919.9-25.1 22.1-24.8 22.8-25.9 22.3-26.331+ 10 271.2 5.9 15.4 33.60.7-1.6 2.1-8.9 14.5-15.8 33.0-34.022.8 23.5 24.0 24.719.9-25.1 22.1-25.0 19.0-26.1 22.4-25.9The 6 ppt solution was obtained by mixing nearly equal amounts of fresh wellwater with that of the Patuxent River (14 ppt). The 14 ppt test solution wassimply Patuxent River water which was pumped into the aquarium. A closedrecirculating system of water from the Atlantic Ocean was maintained near 27or 33 ppt. Plexiglass dividers separated the species within each aquarium. Holes406 ARTHUR KENDALL AND FRANK J. SCHWARTZ Vol. 64drilled in the plexiglass permitted the water to flow freely between the two halves.Twelve or 24-hour observations consisted of noting the number of animalsalive in each lot, the water temperature, and the salinity (determined by a hydro-meter). Each experiment was run until all but the controls succumbed or untilan individual or a particular species tolerated a given salinity for some prolongedperiod of time without further deaths. The LD5o's for each species were determinedby simply noting (fig. 2 and 3) the elapsed time interval when 50 per cent of thetest animals had succumbed.RESULTS AND DISCUSSIONOrconectes virilisIdentical salinity tolerance tests begun July 2 and August 13, 1962, revealedthat O. virilis, when temporarily subjected to saline waters, as during a tidalflush, could tolerate salinities up to 33 ppt. However, if the influences wereprolonged (fig. 2), one-half of the population so subjected would have died withinORCONECTES VIRILIS96 144 192 240 288 336 384 432 480 S28 576 624FIGURE 2. Survival tolerances of O. virilis subjected to salinities of approximately 0, 6, 14and 27 to 33 ppt.96 hours. Specimens of O. virilis, regardless of sex, tolerated salinities of approxi-mately 0, 6, 14, and 30 ppt for a maximum of 288, 216, 288, and 240 hours, duringthe first test, while survival periods of 696, 696, 528, and 120 hours were notedduring the second test (fig. 2). Water temperatures, throughout the experiment,approximated that of the ambient temperature of the laboratory room (table 1)and were insignificant as death causal agents. A test of the survival-salinitydata substantiated that no statistical differences existed in the rates of mortality,except in experiment 2, when the 33 ppt salinity was a serious delimiting factorkilling 17 of the 20 test individuals in 48 hours and the remainder in 120 hours(fig. 2). The removal, statistically (Snedecor, 1950) of the effects of the 33 pptsalinity on the remaining data indicated comparable mortality patterns amongthe specimens subjected to 0 to 14 ppt salinities (F = 1.03). The regressions ofNo. 6 CRAYFISH SALINITY TOLERANCES 407salinity and survival were best shown by the formulae Y = 1.437-0.189X (Experi-ment 1) and Y=l.641-0.347X (Experiment 2).Higher salinities seemed to increase the incidence of molting. Likewise, thosespecimens, regardless of species, that molted seemed to die sooner than those thatdid not shed. Molted specimens were found to have greatly deformed chelae,antennae, antennules, and other appendages.Cambarus b. bartoniiTwo similar experiments, begun July 11 and August 16, 1962, employing aseemingly fresh water specific species, C. b. bartonii, produced several startling re-sults. Individuals of the C. b. bartonii population collected from a clear mountainstream with no previous saline history were able to withstand salinities of 0, 5.2,13.6, and 27.5 ppt for 240, 252, 108, and 192 hours (fig. 3), respectively. Again,one-half of the test population died within 72 to 96 hours (fig. 3). Repeating theexperiment with 0, 5, 9, 15.4, and 33.6 ppt salinities, overall survival periods were0 48 96 144 192 240 288 336 384 432 480 528 576 '624TIME IN HOURSFIGURE 3. Survival tolerances of C. b. bartonii subjected to approximately 0, 6, 14, and 27 to33 ppt salinities.624, 612, 228, and 120 hours, with one-half the test specimens dying within 96hours. Both sets of data were comparable statistically (table 2). Salinities of6 to 15 ppt were readily tolerated for a period of 27 days, while higher concentra-tions were detrimental. These salinity-survival relationships (fig. 2) were bestexpressed by the regression formulas Y = l.314-0.073X for Experiment 1 andY = 1.473-0.191X for Experiment 2.These data were interesting, as they suggested new fields for exploration.The ability of both 0. virilis and C. b. bartonii to withstand varying degrees ofsalinity might permit migrations or dispersals of these and other species (Meredithand Schwartz, 1960) across salinity barriers. It has been shown that one-halfof the test population could survive high saline conditions for at least four days.This would permit a species to transgress a salinity barrier and travel into adjacentwatersheds. Perhaps disjunct populations of seemingly fresh water species ofcrayfishes are a result of migrations across salinity barriers. Increased down-408 ARTHUR KENDALL AND FRANK J. SCHWARTZ Vol. 64stream salinities might further isolate the populations or hold them in check.Although we know little of the rate or extent of crayfish movements in fresh-waters as we do for marine Portunids (Cargo, 1958) or Homarids (Templeman,1935; Wilder, 1963), observations suggest that they often undertake sizeablemigrations (Black, 1963). Experiments should be conducted to see what otherspecies tolerate saline waters. Conclusions concerning disjunct crayfish ZOO-TABLE 2Analysis of covariance and test of significance of the effects of various salinities on thesurvival of two species of crayfishes10. virilisExpt. I0. virilisExpt. IIC. bartoniiExpt. IC. bartoniiExpt. IISource ofvariationTotalsalinitywithin lots (error)d.f.46343Sum of squares and productsSX21.90931.8821.0272Sxy-0.3613-0.3578-0.0035For test of significance of adjusted meansTotalsalinitywithin lots (error)883852.759442.656090.10335-0.95826-0.964290.00603For test of significance of adjusted meansTotalsalinitywithin lots (error)383351.560391.543530.01686-0.11338-0.07494-0.03844For test of significance of adjusted meansTotalsalinitywithin lots (error)703672.69962.65430.0453-0.5146-0.62350.1089For test of significance of adjusted meansSy*0.98830.12770.86062.126221,493240.632981.057060.034981.022081.15470.21920.9355Errors of estimateSum ofsquares0.92000.85700.06301.793450.623601.160851.048820.934300.114520.69860.67290.0257d.f.45423878433734369663Meansquare0.02040.02100.007530.386950.027480.038170.01010.0085F = 1.0294F = 51.39**F = 1.389F=0.84JData in logs and coded by adding 10 throughout for ease of analysis.geographies as either the result of extripated populations, gradient, ecologicalchanges or interspecific competition (Penn and Fitzpatrick, 1963) should be re-viewed or cautioned. Likewise, in the light of the above, the role of the salinewater areas of the central and southwestern United States should be investigatedas dispersal agents or barriers to crayfish populations.Thanks are due Mr. R. Reppert, National Resources Institute, La Vale, Mary-land, for collecting the C. b. bartonii specimens used in the study; Mr. G. Gerberg,Interamerican University, Mayaguez, Puerto Rico, for assistance in the field;Dr. Jess Muncy for comments regarding the statistical methods; and Dr. H.Hobbs, Head Curator, Department of Zoology, U. S. National Museum, andMr. P. Robinson, Physiology Branch, U. S. Army Chemical Center, Edgewood,Maryland, for a review of the manuscript.LITERATURE CITEDBlack, J. B. 1963. Observations on the home range of stream-dwelling crawfishes. Ecology44(3): 592-595.Bogucki, M. 1934. Recherches sur la regulation de la composition minerale du sang chezl'ecrevisse (Astacus fluviatilis, L.). Arch. Intern. Physiol. 38: 172-179.Cargo, D. G. 1958. The migration of adult female blue crabs, Callinectes sapidus Rathbun, inChincoteague Bay and adjacent waters. J. Mar. Res. 16(3): 180-191.Chace, F. A., Jr., J. E. Mackin, L. Hubricht, A. H. Banner, and H. H. Hobbs, Jr. 1959.Malacostraca. In Freshwater Biology, Ward & Whipple, J. Wiley & Sons. N. Y. Chap.31:869-901.Clemens, H. P. and W. H. Jones. 1954. Toxicity of brine water fiom oil wells. Trans. Am.Fish. Soc. 84: 97-109.Gross, W. J. 1957. An analysis of resonse to osmotic stress in selected decapod Crustacea.Biol. Bull. 112(1): 43-62.Herrmann, F. 1931. Uber den Wasserhaushalt des Flusskrebses (Potamobius astacus Leach).Z. vergl. Physiol. 14: 479-524.No. 6 CRAYFISH SALINITY TOLERANCES 409Krogh, H. 1939. Osmotic regulation in aquatic animals. Cambridge Univ. Press, London.242 p.Meredith, W. E. and F. J. Schwartz. 1960. Maryland Crayfishes. Md. Dept. Res. & Educ.Solomons, Md. Educ. Ser. 60. 32 p.Penn, G. H. and J. F. Fitzpatrick, Jr. 1963. Interpsecific competition between two sympatricspecies of dwarf crawfishes. Ecology 44(4): 793-797.Presson, A. V. 1957. A study of the relationship between the inorganic content of the blood ofcrayfish and their environment. Purdue Univ. Lafayette, Ind. Dis. Abstr. 17(9): 2098.Prosser, C. L. 1950. Comparative animal physiology. W. B. Saunders Co. Phila. 888 p.Schlieper, C. 1935. Neure ergebnisse und probleme aus dem gebeit der osmoregulation was-serlebender Tiere. Biol. Rev. Cambridge. Philos. Soc. 10(3): 334-360.Schwartz, F. J., R. Rubelmann, and J. Allison. 1963. Ecological population expansion of theintroduced crayfish, Orconectes virilis. Ohio J. Sci. 63(6): 266-273.Snedecor, G. W. 1950. Statistical Methods. Iowa St. Coll. Press., Ames, Iowa. 4th ed. 4thprint. 385 p.Templeman, W. 1935. Lobster tagging in the Gulf of St. Lawrence. J. Fish. Res. Bd. Can.1(4): 269-278.Waterman, T. H. (Ed.) 1960, 1961. The physiology of Crustacea. Academic Press, N. Y.Vol. 1. 670 p.; Vol. II. 681 p.Wilder, D. G. 1963. Movements, growth and survival of marked and tagged lobsters liberatedin Egmont Bay, Prince Edward Island. J. Fish. Res. Bd. Can. 20(2): 305-318.

Salinity Tolerances of Two Maryland Crayfishes

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Salinity Tolerances of Two Maryland Crayfishes

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