This is the largest genus of the family Palaemonidae Rafinesque, superfamily Palae-monoidea Rafinesque, ; infra-order Caridea Dana, ; order Decapoda Latreille, ; sub-order Pleocye-mata Burkenroad, , and about species have been described so far C. De Grave, pers. Almost all of them live in freshwater, at least for part of their life. The genus is circumtropical and native to all continents, except Europe and Antarctica. Until recently, most commercial culture had been based on Macrobrachium rosenbergii De Man, , the species with which most of the present volume is concerned.

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Republic of Singapore Abstract Only one species of fresh-water prawn, Cryphiops Macrobrachium rosenbergii de Man , is at present exploited on any considerable scale in Malaysia. A species of potential value is Cryphiops Macrobrachium lanchesteri de Man , despite its relatively small size.

Favourable features include: the large numbers in which it may occur; its ability to reproduce in standing fresh waters; its pronounced eurytopy; and its apparently vegetarian habits.

Given suitable environmental conditions, it would be a suitable species for pond culture. Their abundance, their role in the ecology of fresh-water habitats and their high protein content give them considerable potential importance. Lanchester reported a few species of prawns collected by the Skeat expedition. He also collected several species at Singapore in but made no report on these.

They have been examined by Johnson a together with specimens collected by Flower. Roux ; deals with two species of fresh-water prawns.

In recent years the author has been carrying out a program of taxonomical and distributional studies. The results have been published in a series of papers Johnson, a, b, , a, b, The relation between distribution of several species and various physical and chemical factors is discussed by Johnson b.

Two recent papers Johnson and Johnson in press attempt to assess their potential value as food organisms. The only Malaysian species which is at present exploited on any considerable scale is the udang galah, Cryphiops Macrobrachium rosenbergii de Man. This species, the largest of the oriental fresh-water prawns, is popular in Malaysia, though not in Singapore, and available supplies are scarcely sufficient to meet the demand. The Malaysian Fisheries Department instituted a program of research, which is chiefly concerned with developmental requirements and other problems involved in large-scale culture of this prawn Ling, ; Ling and Merican, The larvae can now be reared on a large scale in low salinity water and the young prawns used for stocking isolated fresh-water ponds.

The carnivorous and cannibalistic tendencies of this species, however, limit its usefulness for pond culture.

One justification, though by no means the only one, for pursuing general research on Malaysian fresh-water prawns, is the possibility that one or more hitherto unexploited or under-exploited species may prove to possess potential economic value. The present paper is an attempt to summarize some of this research carried out with limited facilities, as a part-time study. It does not purport to be a final report, but is intended rather as a pointer to possible further research.

Johnson in press has given detailed comments on these. Caridina gracilirostris de Man is specifically indicated as being cultured in area , whereas it is not exploited at all. Of the species which they list, the only one that is currently exploited in Malaya on any noteworthy scale is Cryphiops Macrobrachium rosenbergii. Atya spinipes Newport is the object of a very small-scale subsistence fishery in a few areas. It is possible that the small atyid prawns, such as Caridina gracilirostris, C.

The more typically fresh-water species of this genus are distinctly local in Malaysia and sporadic in occurrence. In combination with their small size these distributional features suggest that they are not the most suitable species for exploitation in Malaysia, though pond culture of C. The two commonest prawns of the tree country of southern Malaya are Cryphiops Macrobrachium geron Holthuis and C.

Both may be abundant in forest streams and rivers; both have excellent flavour. But the waters of their natural habitats tend to be unproductive so it is unlikely that either will ever be exploited on a large scale.

Of the remaining species only two, C. The former is more likely to prove important. Though it is somewhat the smaller it is more widespread, often more abundant where it occurs, and more commonly found in ponds and ditches. A good swimmer, it is less strictly a bottom dweller than are many palaemonids.

It has a light and somewhat compressed build and a relatively large abdomen and lives in fresh waters throughout its life cycle. The species appears to be indigenous to the swamps and ricelands of southeast Asia from where it appears to have penetrated south along the Malay peninsula. It has reached Singapore, probably through human agency, but has not yet been recorded in Indonesian waters. Johnson mapped the Malaysian distribution of this species, but a number of new records have subsequently been added.

It is now known to occur in the ricelands of central Trengannu and near Kuala Sedili Besar in eastern Johore. It probably occurs generally in riceland areas, and in the numerous fish ponds, slow rivers, streams, canals, many ditches, and in inundated disused mines. Wild caught specimens seldom exceed 50 mm but the author obtained larger specimens from the research ponds of the Tropical Fish Culture Research Station at Batu Berendam, Malacca.

The largest, a male, had an overall length of 62 mm. The large-sized males differ somewhat from the smaller individuals previously described and will necessitate a redescription of the species. In these ponds the pH, calcium content, and phosphate content of the water tend to be higher than in many natural habitats, and there is an abundant supply of digestible algae; but even where these conditions prevail in natural habitats such large individuals have not been obtained.

A probable contributory factor is the rarity of efficient predatory fish which are excluded and eliminated in the ponds. It is quite likely that in uncontrolled habitats prawns do not survive long enough to attain the maximum size. Zoeae and post-larvae can sometimes be obtained from isolated pond habitats, and populations in such habitats appear to maintain themselves. It thus seems clear that breeding as well as growth may occur in stagnant water. Nonetheless populations can become established in streams with a moderate water flow if other conditions are favourable.

The maximum flow which the author has recorded for such a habitat was 0. The full range of temperatures from which the species has been collected is Presumably it occurs at somewhat lower winter temperatures of countries to the north of Malaysia.

It would be interesting to know the high temperature tolerance of the species in these countries since Malaysian specimens appear to be killed by slightly higher temperatures. The upper safety margin is thus very small with the species flourishing in habitats in which the highest temperatures are only slightly below the lethal. Nothing is known of lower temperature limits, but since the species occurs in more seasonal climates than in Malaysia it is unlikely that any such limitation by low temperature will be operative in the Malaysian area.

About All readings were taken during daylight at least 3 h after sunrise. The present observations indicate that C. It is the only species which has been collected from a habitat with less than 10 percent oxygen saturation. It should be noted, however, that it has never been collected from any habitat with oxygen so low as to be undetectable by the ordinary Winkler method.

Low oxygen content might be operative in some habitats but the species is absent even where the oxygen content is apparently high. Intolerance to high concentrations of ammonia is another possible limiting factor. No records from habitats with ammonia concentrations greater than 4 ppm are available. Though there is no precise information it is probable that this species is more tolerant to tin mine pollution than are most species, as evidenced by its common occurrence in mine pools and pools in tin tailings.

However, in the absence of experimental evidence one cannot rule out the possibility that it is euryhaline, being excluded from more saline waters by biotic factors. Whatever the reason, this inability to penetrate high salinity waters is important in restricting its natural distribution, and has probably prevented it from spreading to Indonesia. Though it is present on Penang and Singapore islands, it has not been found on other small islands in the area. It has been stated earlier that all developmental stages of this prawn can thrive in fully fresh-water habitats.

It occurs in a reservoir near Malacca where the salinity Hutchinson, is only 5. Tolerance to chloride ion concentration is related to the general problem of salinity tolerance.

In the ionically well balanced waters of the Sembawang hot springs the chloride ion concentration was 9. The species can survive in ionically well balanced waters when the chloride ion is as little as 0. The recorded limits for sodium concentration cover much the same range as those for chloride but with both lower and upper limits slightly higher, from 0.

The ability of this and other Malaysian fresh-water prawns to survive in waters which are very poor in chloride and sodium is especially noteworthy.

It is most frequently found in waters with pH between 6. Johnson b gives 7. The rarity of such records merely reflects the rarity of freshwaters with pH exceeding 7. The records for alkalinity give a similar picture to those for pH, the mean value of 46 records being 0.

There are few records from localities with alkalinity below 0. Thus though C. It does, however, occur in habitats with alkalinities up to 2.

It is absent in waters in which there is a considerable absolute anion excess. Chloride ion concentration has already been considered under section 3. The limited records for sulphate ion concentrations are mostly from waters which are poor in sulphate with concentrations ranging from about 0. The exception was at the Sembawang hot springs where the sulphate concentration is as high as 1.

Thus C. Its absence from acid sulphate waters may well be due to the marked anion excess and consequent low pH of these waters. The ability to survive in habitats where there are only traces of sulphate ion is especially noteworthy in view of the widespread occurrence of such waters in many tropical areas. Almost all southern Malayan waters are poor in calcium Johnson, a.

The author has recorded C. It is fairly certain that there are localities in northern and central Malaya in which C. According to the classification of Ohle as modified by Williams all these habitats are poor in calcium.

However it is as well to note that many C. Thus in Lake Chenderoh in Perak, snails and bivalves are very abundant, yet, according to the analysis kindly provided by J. The capacity of this prawn and such other species as C. Concentrations of magnesium appear to be parallel to those of calcium, but the species has not been found in habitats devoid of magnesium.

It is also absent from the magnesium rich gelam-type waters of the Malacca area, with pronounced anion excess and very low pH. Sodium contents of the habitats have already been discussed in section 3.


Macrobrachium lanchesteri



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