Salinity tolerance of mud shrimp Solenocera crassicornis investigated at different salinities ranging

from 15‰ to 55‰ showed that shrimps in the salinity range 30‰ - 42‰ survived but those in lower and

higher salinities died soon after the transfer. Ionic concentration in the hemolymph and free amino acids

in the body muscle in response to different salinity ranges showed hypo-regulation initially but later

became hyposmotic to the medium and died eventually when the salinity decreased. The abundance of

shrimp showed inverse relationship with rainfall and consequent lowering of salinity in the inshore

waters. The study showed that S. crassicornis can regulate osmotic and ionic concentrations of body

fluids efficiently in the salinity range of 30 - 42‰ but unlike euryhaline penaeid shrimps it is a poor

regulator at lower salinities and therefore it migrates offshore during monsoon months

Damle, R S

Deshmukh, V D

CMFRI Digital Repository

230Journal of the Marine Biological Association of India (2011)R. S. Damle and V. D. DeshmukhJ. Mar. Biol. Ass. India, 53 (2) :  230 - 236, July - December 2011doi: 10.6024/jmbai.2011.53.2.01594-12IntroductionIn marine environment, salinity plays crucialrole in osmoregulation and seems to have profoundimpact on the general pattern of distribution ofanimals. The abundance of penaeid prawns haslong been related to distribution of salinity in thesea (Williams, 1955; Gunter et al., 1964). Thedynamic physico-chemical processes in coastalwaters and estuaries in particular, bring aboutfrequent changes in pH and salinity due to whichprawns face duel problem of dilution of internalbody fluids at low salinity (hyposmosis) and lossof water at higher salinity (hyperosmosis). Thesalinity tolerance and distribution of prawnsdepend on ability to regulate ionic concentrationin their body fluids which can be determined bycomparing the concentration of the hemolymph tothat of the ambient sea water over a range ofsalinities. Besides ionic concentration in thehemolymph, intracellular free amino acids arereported to play an important role in osmoticregulation (Sameshima and Shimamura, 1980) andmaintaining the hydrogen ion concentration (Gilesand Schoffenils, 1969).Salinity tolerance and fishery of mud shrimp Solenocera crassicornis(H. Milne Edwards) in the coastal waters of MumbaiR. S. Damle and *V. D. DeshmukhMumbai Research Centre of C.M.F.R. Institute. *E-mail: vindeshmukh@rediffmail.comAbstractSalinity tolerance of mud shrimp Solenocera crassicornis investigated at different salinities rangingfrom 15‰ to 55‰ showed that shrimps in the salinity range 30‰ - 42‰ survived but those in lower andhigher salinities died soon after the transfer. Ionic concentration in the hemolymph and free amino acidsin the body muscle in response to different salinity ranges showed hypo-regulation initially but laterbecame hyposmotic to the medium and died eventually when the salinity decreased. The abundance ofshrimp showed inverse relationship with rainfall and consequent lowering of salinity in the inshorewaters. The study showed that S. crassicornis can regulate osmotic and ionic concentrations of bodyfluids efficiently in the salinity range of 30 - 42‰ but unlike euryhaline penaeid shrimps it is a poorregulator at lower salinities and therefore it migrates offshore during monsoon months.Keywords: Solenocera crassicornis, salinity tolerance, osmotic regulation, fishery abundance,monsoon migrationThe marine prawn, Solenocera crassicornis(H. Milne Edwards) with annual landings of 25,000-30,000 t along the northern coast of Maharashtraand Gujarat, is an important constituent of penaeidprawn fishery (Sukumaran, 1978; Deshmukh,2007). This prawn has long been believed toemigrate to deeper offshore waters en mass duringsouthwest monsoon season owing to lowering ofsalinity in the coastal inshore and nearshore waters(Kunju, 1967). Therefore, in the present studysalinity tolerance and osmoregulatory capabilityunder laboratory conditions of S. crassicornis wereinvestigated to relate its fishery in the coastal watersand ascertain the cause of migration duringmonsoon months.Material and MethodsThe fishery data for S. crassicornis was collectedfrom bag nets operated in inshore and nearshorewaters from New Ferry Wharf (NFW) and SassoonDocks landing centres respectively during the year2000. For offshore fishery data, species-wise shrimptrawler landings maintained by Fishery ResourcesAssessment Division of CMFRI was used for the231Journal of the Marine Biological Association of India (2011)Salinity tolerance and fishery of mud shrimp Solenocera crassicornissame year. The catch, effort, catch rate and percentageof S. crassicornis in total penaeid shrimps werecollected once a week and estimated monthly,considering the number of fishing days and the boatslanded.For salinity tolerance and osmoregulatorystudies, live specimens of S. crassicornis werecollected from bag net fishing grounds near Mumbaiharbour mouth and transported to the laboratory inwell aerated containers. The animals were maintainedin 100% seawater (35 ± 1‰) at 28° ± 2° C for aweek in large glass aquaria of 500 l capacity andfed with clam meat and fresh paste shrimp Acetesindicus. The experimental salinities, ranging from15‰ to 55‰ were adjusted by adding requiredquantity of tap water and raw common salt collectedfrom the salt pans. Seawater was changed daily,aerated constantly and uneaten food was removed.Healthy prawns in intermoult stage ranging from41 to 80 mm in total length were selected for theexperiment.For the salinity tolerance experiments, 20prawns were directly transferred from the stocktank to 100 l capacity aquaria each with seawatersalinity from 15‰ to 55‰ at 5‰ interval initially.Later on for more precision, 18‰, 42‰ and 52‰salinities were also tested. The response andsurvival of the prawns in the aquaria wasmonitored for at least 48 hours from the time oftransfer. Judging from the results of the ‘directtransfer’, the prawns were gradually acclimatedto 22‰ and 48‰ salinity at the rate of 5‰ every24 hours. The prawns were held at the desiredsalinity for 24 hours before they were sacrificedfor extraction of hemolymph for electrolytes andfree amino acid analysis. Prawns were used forhemolymph extraction only after 3 hours at 22‰and 48‰ salinities as their survival period wasvery short. Hemolymph was taken by inserting amicro capillary tube into pericardial cavitybetween cephalothorax and the first abdominalsegment. The hemolymph was centrifuged and 100µl of clear supernatant was used to determineosmolality and concentrations of Na+, K+ and Cl-.The osmolality was estimated by freezing pointosmometer (Osmatte A, model 5002) while Na+,K+ and Cl- concentrations were estimated by flamephotometer (Systronics, Model 121) after dilutingthe hemolymph 500, 200 and 1000 timesrespectively.Monthwise rainfall data were collected fromColaba observatory (Indian MeteorologicalOrganization) situated at the southernmost tip ofMumbai island city very close to the sea. The salinityof seawater was recorded monthly by the FisheryEnvironment Management Division of CMFRI atApollo Bundar near Gateway of India which islocated between NFW in the north and SassoonDocks in the south by the eastern coast of Mumbaiisland alongside the harbour.ResultsSurvival: Direct transfer of prawns to 15‰,18‰, 20‰, 52‰ and 55‰ salinities resulted intotal mortality of prawns within 5 minutes. In 25‰salinity, nearly 40% mortality of prawns occurredwithin 6 hours and 80% mortality within 5 hours.In 45‰ salinity, 50% prawns died after 9 hoursand 70% after 28 hours and those at 22‰ and 48‰salinities showed total mortality afterapproximately 5 hours after the transfer. Theprawns in 30‰, 35‰, 40‰ and 42‰ salinitiessurvived through the experimental period of 48hours (Table 1).Osmolality: The osmolality and electrolytecontents of the hemolymph and seawater at 30‰,35‰, 40‰ and 42‰ salinities in which the prawnssurvived indefinitely (30-42‰) is given in Table 2.The osmolality of the seawater medium from 30‰to 42‰ salinity ranged between 642 and 1,480mOsm/kg and electrolyte contents 365-710 meq/l forNa+, 5.4-9.4 meq/l for K+ and 475-1015 meq/l forCl-. It was noted that the hemolymph osmolalityshowed a significant decline (p<0.001) as the salinityincreased to 45‰ (Fig. 1).Electrolytes: Na+: At 30‰ and 35‰ salinity,hemolymph remained slightly hypertonic withrespect to Na+ and declined significantly with furtherdecrease in salinity. The Na+ concentration inhemolymph showed significant increase (p<0.01) at40‰ salinity but declined significantly with further232Journal of the Marine Biological Association of India (2011)R. S. Damle and V. D. Deshmukhincrease in salinity. The hemolymph remainedhypoionic at higher salinities (Fig. 1).K+: The hemolymph was slightly hyperionic at35‰ salinity, but became hypoionic with furtherdecline in salinity. Although concentration of K+ inhemolymph declined marginally at 30‰ salinity, itreduced significantly (p<0.001) further when thesalinity was reduced to 22‰. At higher salinities thehypoionic regulation was evident. Although,significant decline (p<0.001) at 40‰ was observed,an increase in concentration was noted at 45‰(p<0.02) and 48(p<0.005).Cl-: The hemolymph was hypoionic to allexperimental salinities with respect to K+ but anoteworthy increase (p<0.001) with the increase insalinity and a significant decrease (p<0.001) wasdiscernible when salinity was decreased (Fig. 1).Free amino acids: Total free amino acid contentin the abdominal muscles at 35‰ salinity was 446.6µmole/g wet weight but declined to 49.8 µmole/g at22‰ with decreasing salinity and with rising salinityof the medium, it increased to 929 µmole/g at 48‰(Fig. 1).Fishery: The bag netters operating in inshorewaters of Mumbai harbour landed an estimated catchof 3.6 t of S. crassicornis at NFW landing centre atthe catch rate of 1.76 kg/boat trip in the year 2000that contributed 14.5% to the total penaeid prawnlandings by the gear. The species was landed in mostof the months except in July; the abundance ofprawns indicated by the catch rates peaked in pre-monsoon months from January to May but the ratewas meager in post-monsoon months fromSeptember to December. During monsoon from Juneto August, the catch was negligible and no catch wasTable 1. Survival of S. crassicornis after direct transfer to different salinity concentrationsSurvival time in minutes at tested salinitiesSalinity 15‰ 18‰ 20‰ 22‰ 25‰ 30‰ 35‰ 40‰ 42‰ 45‰ 48‰ 50‰ 55‰% mortality10 - - - 5 30 IS IS IS IS 120 45 - -20 - - - 18 120 IS IS IS IS 250 72 - -30 - - - 60 270 IS IS IS IS 348 90 - -40 - - - 90 300 IS IS IS IS 450 108 - -50 - - - 108 480 IS IS IS IS 540 120 - -60 - - - 120 630 IS IS IS IS 1200 210 - -70 - - - 180 780 IS IS IS IS 1680 246 - -80 - - - 240 900 IS IS IS IS IS 264 - -90 - - - 270 IS IS IS IS IS IS 285 - -100 5 5 5 300 IS IS IS IS IS IS 300 5 5IS: Survival until end of the experimentTable 2. Osmolality and ionic concentration in seawater and hemolymph of S. crassicornis at different salinitiesSalinity Seawater Hemolymph‰ Osmolality Na+ Cl– K+ Osmolality Na+ Cl– K+mOsm/kg meq/l meq/l meq/l mOsm/kg meq/l meq/l meq/l48 1480±4.5 710±1.2 1015±4.3 9.4±0.04 1074±2.3** 465±1.73** 950±5.77*** 7.7±0.05***45 1352±3.1 605±2.5 960±5.7 8.8±0.1 1238±5.77*** 505±4.04n.s. 875±6.92*** 7.4±0.23***40 1229±1.6 560±2.3 842±8.4 8.6±0.1 1185±1.73n.s. 540±2.88** 700±10.39* 7±0.11n.s.35 1156±12.2 510±3.5 727±7.3 8.5±0.04 1156±11.36 512±4.58 625±8.08 8.5±0.0530 995±8.2 475±4.2 600±3.5 7.6±0.1 1020±7.21** 490±5.29n.s. 545±2.51** 8.1±0.11***25 847±4.8 420±6.2 560±10.8 6.8±0.1 693±5.56*** 400±6.8*** 410±14.36*** 5.9±0.15***22 642±6.7 365±2.8 475±7.2 5.4±0.04 459±8.02*** 185±3.6*** 328±5.68*** 4.1±0.05****p<0.05, **p<0.01, ***p<0.001, n.s. not significant233Journal of the Marine Biological Association of India (2011)Salinity tolerance and fishery of mud shrimp Solenocera crassicornisFig. 1. Osmolality and ionic concentrations in seawater (----) and hemolymph (- - -) and total free amino acids inhepatopancreas and muscles234Journal of the Marine Biological Association of India (2011)R. S. Damle and V. D. Deshmukhnoticed in July which coincided with peak rainfallrecorded in Mumbai.At Sassoon Docks, bag nets are operated inrelatively open sea at the mouth of the harbour noticein July which coincided with peak rain fall recordedin Mumbai (Fig. 2). These boats landed an estimated9.1 t of the species contributing 7.1% to the totalpenaeid prawn landings at the catch rate of 1.27 kg/boat trip. The catch rate peaked from January toMarch and in May and October. The catch as well asthe catch rate of S. crassicornis was poor in June,August, September, November and December andno catch was recorded in July 2000.At NFW shrimp trawlers operating from 30 to90 m depth in the open sea landed 1,866 t S.crassicornis contributing 16.2% to the total penaeidprawn catch. The species occurred in the catchthroughout the year and the catch rate increased inpre-monsoon from January and peaked in April. Inmonsoon months also the catch rate was notablethough it was less in August (0.70 kg/h) butcomparable to that in January (0.73 kg/h).Rainfall and salinity: The Colaba observatoryrecorded 2,445 mm of annual rainfall in the year2000. The month-wise rainfall increased from May(188 mm) and continued till September (122 mm)with peak at 1,130 mm in July.Monthwise salinity of seawater ranged between12.8‰ in July and 35.8‰ in February in the year2000. Throughout the monsoon season, salinity alongthe inshore and nearshore waters fluctuated,Fig. 2. Monthly catch rates of S. crassicornis in trawlersand in 'dol' nets at NFW and S. Docks during2000Fig. 3. Monthly rainfall and salinity of seawater in Mumbairecording 28.6‰ in June, 12.8‰ in July, 25.1‰ inAugust and 28.6‰ in September but regaining to35.9‰ in October (Fig. 3).DiscussionA number of penaeid prawns can withstand awide range of salinities and they have been shownto be strong osmoregulators, conforming to theireuryhaline nature. While Metapenaeus monocerosremains hyposmotic to seawater (Panikkar andViswanath, 1948), Penaeus aztecus, P. duorarum andP. setiferus are reported to be hyposmotic at highersalinities (>40‰) and hyperosmotic at lowersalinities (<30‰) (Castille and Lawrence, 1981).However, the present study shows that S. crassicornishas unique pattern of osmotic and ionic regulation.While its hemolymph remains hyposmotic to themedium at higher salinities (35‰), it is marginallyhyperosmotic at 30‰ and then becomes hyposmoticwhen the salinity is further reduced, and dieseventually at 22‰. The ionic regulation with Na+and K+ shows almost similar pattern. The prawnseems to be isoionic with respect to Na+ when salinityis increased but the concentration of Na+ inhemolymph decreases further as it can not regulateit and dies eventually. The concentration of K+ showsa sudden drop initially when the salinity is increasedbut it increases further and remains hypotonic to themedium. Hyporegulation of chloride concentrationis evident at all the experimental salinities.In crustaceans, the role of large free amino acidspool in osmoregulation has been well documented235Journal of the Marine Biological Association of India (2011)Salinity tolerance and fishery of mud shrimp Solenocera crassicornis(Awapara, 1962; Giles and Schoffenils, 1969;Sameshima and Shimumura, 1980). In case of S.crassicornis it was seen that there is decrease in theconcentration of free amino acids when salinity ofthe medium is lowered and the concentration isenhanced when salinity is increased. Sameshima andShimumura (1980) reported that in Penaeusjaponicus when the salinity of ambient seawater waslowered the shrimp was obliged to decrease itsconcentration sharply and change the compositionof free amino acids. The release of large quantitiesof free amino acids in hyposmotic medium wasregarded as a significant mechanism for reducingintracellular osmolality and an increase inconcentration in the hemolymph has been attributedto enhanced synthesis of non- essential amino acids,together with decreased diffusional loss from thenerve fibres in crustaceans (Giles and Schoffenils,1969). It was further pointed out that nonessentialamino acids such as glycine, proline, alanine andarginine were the osmoregulatory factors. In thepresent case, increase in free amino acids at highersalinities and decrease at lower salinity in thehemolymph indicate their primary function asintracellular osmoregulators in S. crassicornis.Besides, they have a role in maintaining the pH thatregulates various enzymatic processes concernedwith osmoregulation (Huang et al., 2001).The present study shows that S. crassicornis canregulate osmotic and ionic concentrations of its bodyfluids efficiently in the salinity range of 30-42‰ butunlike other euryhaline penaeid prawns it is a poorregulator at lower salinities. Similarly, the adults ofbrown shrimp P. aztecus are better osmoregulatorsat higher salinities than in the lower ranges(McFarland and Lee, 1963).Kunju (1967) and Sukumaran (1978) did notnotice S. crassicornis in bag net catches during June-October and therefore opined that possibly it migrates en mass to offshore waters due to lowering ofseawater salinity in monsoon months. It is evidentin the present investigation that S. crassicornis occursin offshore catch almost throughout the year whereinfluence of rain and land run off is minimal. This isdue to the fact that saline water being heavier remainsat the bottom, while freshwater lies at the top instratified manner in offshore region where the prawnsremain buried in the mud. However, in inshore andnearshore waters due to mixing by the tidal forcesthe influence of rainfall and consequent lowering ofsalinity is pronounced. As the species is a poorosmoregulator at lower salinities, it disappears fromthe bag nets in June and totally vanishes in July whensalinity of the inshore water drops below 20-25‰.However, the species reappears in the fisherygradually from August onwards when salinity ofinshore water rises up and returns to normal byOctober. Therefore, almost total absence of S.crassicornis in bag net catches concurrent withlowering of salinity during monsoon stronglysupports the possibility of monsoon migration of thespecies en mass to higher saline offshore waters.AcknowledgementsThe authors are grateful to the Director, Instituteof Science, Mumbai for laboratory facilities, theDirector, C.M.F.R.I. Cochin, for the fisheryenvironment data and the Regional MeteorologicalCentre RS/RW Observatory, Vile Parle, Mumbai forproviding the rainfall data.ReferencesAwapara, J. 1962. Amino acids in invertebrates. Acomparative study of their distribution. In: T. J. Holden(Ed.) Amino Acid Pools. Elsevier PublicationAmesterdams, Netherlands, p. 158-175.Castille, F. L. and A. L. Lawrence. 1981. The effect ofsalinity on the osmotic sodium and chlorideconcentrations in the hemolymph of euryhalineshrimps of the genus Penaeus. Comp. Biochem.Physiol., 68: 75-80.Deshmukh, V. D. 2007. Reproductive dynamics of penaeidprawns. A. P. Cess Fund Report (I.C.A.R.) New Delhi,111 pp.Giles, R. and E. Schoffenils. 1969. Isosmotic regulationin isolated surviving nerve of Eriocheir sinensis MilneEdwards. Comp. Biochem. Physiol., 31: 927-939.Gunter, G., J. Y. Christmas and R. Kellebrew. 1964. Somerelations of salinity to population distribution of motileestuarine organisms with special reference to penaeidshrimps. Ecology, 45: 181-185.Huang, T., W. Yang, A. Okuma and M. N. Wilder. 2001.Changes in free amino acids in the hemolymph of giant236Journal of the Marine Biological Association of India (2011)R. S. Damle and V. D. Deshmukhfreshwater prawn Macrobrachium rosenbergii exposedto varying salinities: relationship to osmoregulatoryability. Comp. Biochem. Physiol., A 128: 317-326.Kunju, M. M. 1967. Some aspects of biology of Solenoceraindica Natraj. Proc. World Scientific Conference onthe Biology and Culture of Shrimps. FAO BSCP/67/E/20, p. 1-19.Panikkar, N. K. and R. Viswanath. 1948. Active regulationof chloride in Metapenaeus monoceros Fabricius.Nature, 161: 137-138.Sameshima, M. and F. Shimamura. 1980. Amino acids inprawn Penaeus japonicus as osmoregulation factors.Mem. Fac. Fish Kagoshima University. 29: 293-299.Sukumaran, K. K. 1978. Studies on the fishery and biologyof Solenocera crassicornis (H. Milne Edwards) fromBombay waters. J. Mar. Biol. Ass. India, 20(1 & 2):32-39.Williams, A. B. 1955. The influence of temperature onosmotic regulation in two species of estuarine shrimps.Biol. Bull., 125: 188-196.Received : 03/11/2009Accepted : 20/09/2011Published : 15/12/2011

Salinity tolerance and fishery of mud shrimp Solenocera crassicornis (H. Milne Edwards) in the coastal waters of Mumbai

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Salinity tolerance and fishery of mud shrimp Solenocera crassicornis (H. Milne Edwards) in the coastal waters of Mumbai

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