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1 The University of Notre Dame Life History and Ecology of the Freshwater Caridean Shrimp, Palaemonetes paludosus (Gibbes) Author(s): J. Thomas Beck and Bruce C. Cowell Source: American Midland Naturalist, Vol. 96, No. 1 (Jul., 1976), pp Published by: The University of Notre Dame Stable URL: Accessed: 30/05/ :53 Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available at. JSTOR's Terms and Conditions of Use provides, in part, that unless you have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and you may use content in the JSTOR archive only for your personal, non-commercial use. Please contact the publisher regarding any further use of this work. Publisher contact information may be obtained at. Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printed page of such transmission. JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. The University of Notre Dame is collaborating with JSTOR to digitize, preserve and extend access to American Midland Naturalist.

2 Life History and Ecology of the Freshwater Caridean Shrimp, Palaemonetes paludosus (Gibbes) J. THOMAS BECK' and BRUCE C. COWELL Department of Biology, University of South Florida, Tampa ABSTRACT: The life history and ecology of the freshwater caridean shrimp, Palaemonetes paludosus (Gibbes), was determined from monthly collections for 1 year in the Hillsborough River near Tampa, Florida. Numerical abundance increased from May (95.3/m2) to August (662.6/M2) and then decreased to 121.6/M2 by April of the following year. Biomass showed three distinct peaks, the largest occurring in November (49.2 g/m2). Females outnumbered males in all months except January and May. Ovigerous females ranging from mm long occurred from early February to mid-october at water temperatures of C; percentage of ovigerous females among mature females was highest (56%) in April. Fecundity ranged from 8-85 eggs and increased with length of the female according to the relationship: Log Y = X. Mean brood size and mean size of ovigerous females decreased from the beginning of breeding to June. Mean brood size was lowest in the last month of breeding. The incubation period in the laboratory was days at C, Growth to maturity (20 mm) took 2-3 months when water temperatures exceeded 26 C and 4-5 months when temperatures were lower. Postspawning mortality occurred from April to October. Longevity was confined to 1 year. Food consisted primarily of algae, vascular plants, detritus and aquatic insects, in decreasing order of importance. INTRODUCTION The grass shrimp, Palaemonetes paludosus (Gibbes), is common in fresh waters E of the Allegheny Mountains, from New Jersey to Florida. It also occurs in Mississippi, Louisiana, Texas and Oklahoma, probably introduced in the latter three states (Holthuis, 1952). In 1958 the species. (supplied by the Florida Game and Fresh Water Fish Commission) was introduced into the lower Colorado River by the California Department of Fish and Game and now is established in various locations (Hayden and Ringo, 1963; St. Amant and Hulquist, 1969; St. Amant and Day, 1972). Palaemonetes paludosus is predominantly a freshwater species but has been reported in brackish (Tabb and Manning, 1961; McGuire, 1961; Rouse, 1969) and salt waters (St. Amant and Hulquist, 1969). Dobkin and Manning (1964) observed survival at salinity of 300/oo (parts per 1000) in the laboratory. Although Dobkin (1963) described the larval development of Palaemonetes paludosus, there are no complete life history studies of the species. Numerous investigations have been published on P. kadiakensis Rathbun, the other epigean freshwater Palaemonetes in the United States [Meehean, 1936 (as "P. paludosa," see Holthuis, 1952; 1 Present address: Department of Biological Science, Florida State University, Tallahassee

3 1976 BECK AND COWELL: ECOLOGY OF SHRIMP 53 Broad and Hubschman, 1963); Gebhart, 1936; White, 1949; Broad and Born, 1963; Nielsen and Reynolds, 1974]. Several life history studies have been published on brackish and saltwater species: P. pugio Holthuis (Wood, 1967; Knowlton and Williams, 1970), P. vulgaris (Say) (Knowlton and Williams, 1970), and P. varians (Leach) (Gurney, 1923). This article presents information on habitat, seasonal abundance, age and growth, reproduction and feeding of Palaemonetes paludosus. These aspects of life history and ecology are compared with published data on other species of Palaemonetes. STUDY AREA The study was conducted on the lower Hillsborough River, Hillsborough Co., Fla., near State Road 582A (Secs. 2 and 11, R. 19 E., T. 28 S.). At this site the channel is 30 m wide, and the bottom is mud and sand. The sampling area along the shoreline was 45 m long and had abundant vegetation, which usually extended out 6 m from the shore to a depth of 1.5 m. Egeria densa Planch. was the dominant plant species, but Hydrilla verticillata Ro-yle, Panicum sp., Eichhornia crassipes (Mart.) Solms and Salvinia rotundifolia Willd. were observed routinely. Ceratophyllum demersum L., Pistia stratiotes L., Lemna perpusilla Torr., Nitella sp. and blooms o-f unidentified filamentous green algae occasionally were found. Flow of water through the vegetation was imperceptible during low-water periods and slight during high-water periods. The water was colored with tannins at all times. Water temperatures ranged from C, and water level fluctuated 1.1 m during the study. MATERIALS AND METHODS Field procedures.-quantitative samples of P. paludosus were collected monthly from May 1973 through April Four replicates (three in May) were taken on each sampling date with a four-sided block-off net modified from Barnett (1973). The net consisted of 1.5-mm mesh fiberglasscreen supported on four 1.4-m wooden poles. The sampler was 1.1 m deep, 2 m long and 1.0 m wide, encompassing a maximum volume of 2.2 m3 and a maximum area of 2.0 M2. The net was weighted at the bottom with 9-mm, thick-link chain sewn into a pocket in the screen material. In operation, the net was positioned in a bed of vegetation, and all plant material was removed by hand, with entangled shrimp carefully shaken off. When most of the vegetation was cleared, the shrimp were extracted with 1-mm mesh dip nets. Removal was considered complete when no shrimp were collected in 10 consecutive sweeps of the dip net. All dippings, which included various organisms, pieces of plant material and debris, were preserved in 10% formalin. In addition, smaller samples of shrimp were made randomly with a dip net 2 weeks after each quantitative collection. These

4 54 THE AMERICAN MIDLAND NATURALIST 96(1) samples were used to check on life history features and to ascertain if larval shrimp were missed with the block-off net. Water temperature and water level were recorded every 2 weeks. The temperature measurements were made cm beneath the surface with a mercury bulb thermometer, and the water level was read from a U.S.G.S. river gauge. Laboratory procedures.-the field samples were washed, and the shrimp from each rep-licate were sorted from the debris, counted and transferred to 40% isopropanol. Beginning in August 1973, a random subsampling procedure was used to reduce each replicate to approximately 300 shrimp. Each shrimp was measured (tip of the rostrum to end of the spines of the posterior telson margin) to the nearest 1.0 mm and classified according to the following sex and maturity groups: (1) Zoeae-Larval forms comprised of three stages, lengths ranging from mm (Dobkin, 1963). (2) Juveniles-No distinguishing sexual characteristics, lengths ranging from 5-11 mm. (3) Males-Distinguished from females by differences in the first and second pleopods as described by Meehean (1936) for Palaemonetes kadiakensis. (4) Immature females mm long. (No females under 20 mm long were found carrying eggs.) (5) Mature-females-Above 19 mm long. (6) Ovigerous ( = gravid) females-eggs attached to pleopods. Of 28,395 specimens collected in the course of the quantitative procedure, 16,800 were measured and classified. Measurements and classifications of the total specimens were estimated by direct proportion from the subsamples. Fecundity was determined by removing and counting eggs from the pleopods of ovigerous females. For determination of brood mortality, two stages of prehatching development were noted: (1) an early stage where eye pigment was absent, and (2) later stages where eye pigment was present. Wet weights (nearest 1.0 mg) were determined for 10 individuals (blotted dry on tissue p-aper) of each 3-mm length class ranging from mm, and a regression equation was calculated relating wet weight to length. Wet weights were then estimated for all length classes. A mixture of 200 eggs at various stages of development was weighed, and an average wet weight was calculated. By converting monthly length-frequency data into wet weight per square meter, standing crop was calculated for each sample. The stomachs of 174 shrimp collected in May, August, November and February were examined to determine the types of food eaten. An incision was made in the carapace, and the esophagus and stomach were extracted. The digestive tract was opened and contents examined under dissecting and compound microscopes. All food items were identified, and relative amounts (percentages) of each were estimated using a millimeter grid.

5 1976 BECK AND COWELL: ECOLOGY OF SHRIMP 55 RESULTS DISTRIBUTION WITHIN SAMPLING AREA Palaemonetes was always abundant in the dense beds of submerged Egeria. During high water (August and September) specimens were abundant in the semiaquatic Panicum. Many shrimp were collected among Eichhornia (water hyacinths) when prevalent in the summer. Shrimp were not common in areas devoid of vegetation. Statistical comparisons of shallow (< 0.36 m) and deep (> 0.36 m) replicates taken with the block-off net showed no statistical differences in mean sizes, life history stages or density per square meter (P > 0.05). However, high variability in the sampling area and low replicate number may be the causes for the lack of statistical differences. The only statistical difference in distribution was in the percent ovigerous females (among mature females). The May-September means fo,r shallow and deep replicates were 13.3% and 33.7%, respectively (P < 0.01). SEASONAL ABUNDANCE Numerical abundance of Palaemonetes increased from May (95.3/ m 2) to August (662.6/M2) and then decreased throughouthe remainder of the year (Fig. 1). By the following April, density (121.6/ m2) was comparable to that of the previous spring. The summer crease in- and the August peak were attributable to the presence of large numbers of zoeae and juveniles in the population. Maximum density of a single replicate was /M2 in August and the minimum was 36.0/M2 in April. Wet weight increased with length according to the length-weight relationship: Log W = Log L (r =.999). The wet weight of an average egg was 1.0 mg, and total weight of eggs counted each month was added to total body weight to obtain total biomass. In contrasto numerical abundance, biomass (wet weight) showed three distinct peaks (Fig. 1). The largest peak, 49.2 g/m2, occurred in November, and smaller peaks of 40.2 g/m2 and 37.0 g/m2 were recorded in March and August, respectively. Biomass was lowest in May at 9.5 g/m2. Mean monthly biomass was 25.9 g/m2 or 259 kg/ha (225 lbs./acre). The August peak was the result of massive recruitment of zoeae and juveniles into the population. Growth of these immature stages produced the major peak in November which was comprised mainly of adults. The smaller peak in March resulted from the predominance of large, ovigerous females in the population. REPRODUCTION Sex ratio..-the sex ratio of '24,854 specimens collected between May 1973 and April 1974 was one female to 0.78 male (P < 0.05). Females were more abundant in all months of the year except January and May. This was especially evident in the summer (May to October) when the ratio increased from 1: 1.03 to 1: Chi-square tests for

6 56 THE AMERICAN MIDLAND NATURALIST 96(1) equality of ratios indicated sex ratios in May and June were not significantly different from a 1: 1 ratio; differences in all other months were significant (P < 0.05). Breeding.-The breeding season of P. paludosus extended from early February to mid-october at water temperatures of C (Fig. 2). Ovigerous females ranging from mm long were collected throughout this interval, but the breeding peak occurred in early spring as the percentage of ovigerous females, (among mature females) increased rapidly in late winter to a peak of 56% in April. Smaller percentages of ovigerous females (20-40%) were rec,orded from May T NUMBER 70 WET WEIGHT I I'~~~~~~~C -' r - l ' l ' z 500M J J 40J Z400 ;\ I ~~~~~~~~~10 M J J A S ON DJ FM A 1973 MONTH 1974 Fig. 1.-Seasonal abundance of P. paludosus in the lower Hillsborough River, May 1973-April Vertical lines represent standard errors

7 1976 BECK AND COWELL: ECOLOGY OF SHRIMP 57 through August and a marked decrease occurred in September (12%) and October (< 1%). Fecundity.-The size of undisturbed (not damaged or hatching) broods ranged from 8-85 eggs and increased with length of the female. This relationship is represented by the equation: Log Y = X (r =.984). Mean brood size and mean size of ovigerous females decreased from February to June (Fig. 2). There were no significant differences in brood size from June through August. Mean brood size was lowest in September (the last month in which many ovigerous females were collected), although mean size of the ovigerous females was equal to that of previous months. Peak egg production (number of eggs per s,quare meter) occurred in March but did not coincide with the April peak in percentage of ovigerous females because of population density differences PERCENT GRAVID E' ----BROOD SIZE ~5O 40- ~~~~~40 ~ ~ ~ ~ ~ ~ 4 z ', r 0 > ~~~~~~~~0 < 20 \ 304. c O L30 Z 0310 NI/00 z 3- o 2 N ~~~~28.0 M J J A S O N D J F M A MONTH Fig. 2.-Percent ovigerous (gravid) females and mean brood size of P. paludosus in the lower Hillsborough River, May 1973-April Vertical lines represent standard errors, and numbers adjacent to mean brood size give mean length (in mm) of ovigerous females 12

8 58 THE AMERICAN MIDLAND NATURALIST 96(1) Many females carrying eggs were also observed to have ripe ovaries, suggesting that at least two broods per female are possible. Observations of first hatchings were made in the laboratory, but no attempts were made to observe the deposition of a second brood. Lengthfrequency distributions suggest that females hatched in early spring reproduce in late summer as small adults mm long and again in late winter as large individuals mm long (Fig. 3). Incubation.-There was no evidence of brood mortality during incubation. Average brood size remained constant as, development progressed from the prehatching condition without eye pigment (average size = 35.9 eggs) to more mature prehatching stages with eye pigment present (average size = 35.3 eggs). Eye pigment was first observed 5 days after the eggs were laid. The incubation period in the laboratory ranged from days at C; however, the incubation period in the river during late winter and early spring (18-24 C) may have been as long as 2 months since the first eggs were deposited in early February and zoeae were not collected until early April. Composition at Maturity.-Even though ovigerous females were present in the population from February to October, zoeae occurred only from Ap,ril through July (Fig. 3). The absence of zoeae after July was not an artifact of the quantitative sampling procedure as random samples with a dip net at 2-week intervals also showed no zoeae. Moreover, the percentage of juveniles decreased markedly in August and September indicating lack of recruitment of zoeae. Juveniles were most abundant in June and July, and immature females peaked in August. The proportion of males and mature females decreased from May through July and increased from August to November as the proportion of juveniles decreased. AGE, GROWTH AND MORTALITY Age and growth were determined from length-frequency histograms of the monthly collections (Fig. 3). Two year-classes, young-of-theyear and overwintering adults, were evident from April through September but were easily separated by visual inspection of the histograms. Growth to maturity (20 mm) took 2-3 months when water temperatures exceeded 26 C and 4-5 months when temperatures were lower. In the laboratory, shrimp reached 18 mm 2.5 months after hatching (mean temperature = 25.0 C). In the field, females attained a maximum size of 44 mm while the largest male was 47 mm long. However, females greatly outnumbered males in the larger size classes, and males comprised only 6.7% of the shrimp larger than 30 mm. Our estimates of growth based on mean sizes were biased low because of continuous recruitment of young during the spring and summer, but the data still showed rapid growth. Mean size of youngof-the-year increased from 4.9 mm in May to 24.4 mm in November (3.'25 mm/month). From November to February the population mean did not increase significantly, but the mninimum and maximum lengths increased from 9 to 14 mm and 37 to 43 mm, respectively, indicating

9 1976 BECK AND COWELL: ECOLOGY OF SHRIMP 59 that slow growth occurred throughout the winter. In early spring (February- April) mean size of the population increased from 24.9 to 27.6 mm. Mortality was inferred from monthly changes in length-frequency distribution. Postspawning mortality occurred from April to October as the number of overwintering shrimp decreased markedly during this interval. By October there were no individuals in the population greater than 31 mm in length. These data indicate that longevity is confined to 1 year. ZOEAE AND FEMALES FEGRAVID JUVENILES N MALES Gl FEMALES FEMALES 15 r NOVEMBER N 10 0 DECEMBER JUNE ~~~~~~~N-= _ JULY JANUARY a-- l 1 ~~~N =2640, N w 5i 10 AUGUST120 2> " N = AUGUST10 54 OCPTOMBER [LN= i P 19 N TOTAL LENGTH IAPRILM N TOTAL LENGTH IN MM Fig. 3.-Length-frequency histograms of P. paludosus collected in the lower Hillsborough River, May 1973-April Percentages of sex and maturity groups are indicated for all groups comprising more than 0.3% of the total Population

10 60 THE AMERICAN MIDLAND NATURALIST 96(1) FEEDING Food of grass shrimp consisted primarily of algae, vascular plants, detritus and aquatic insects (Table 1). Algae was the major food item, comprising 47% of the total food ingested and occurring in 83% of the stomachs. Insects contributed least to the diet, comprising 15.2% of the food ingested and occurring in only 36.2% of the stomachs; the soft parts of insects are rapidly digested and may not be recognizable. They may constitute a greater percentage of the diet than indicated. There was much seasonal variation in stomach contents. Between May and August insects and detritus decreased while algae and vascular plants increased in percent composition and percent occurrence. Food ingested was similar in August and November. Insects and detritus again increased in importance to February 1974, while vascular plants and algae (to a lesser extent) decreased in importance. Palaemonetes paludosus fed heavily on algae epiphytic on the vascular plants. Diatoms (Fragilaria, Navicula, Stephanodiscus, Gomphonema, Synedra and Cymbella) constituted a majority of the algae and often comprised all of the stomach contents. Green algae included Cosmarium, Closterium, Scenedesmus and unidentified filamentous species. Shrimp also were observed grazing over the surface of aquatic weeds in laboratory aquaria, not only feeding on the epiphytes but also on parts of the plant. Pieces of stems and leaves of :Iydrilland Egeria were often found in stomachs. Insects found in stomachs included Baetidae nymphs (Ephemeroptera) and dipteran larvae of the families Chironomidae, Heleidae, Chaoboridae and Culicidae. A terrestrial homopteran (aphid) and lepidopteran each occurred once in stomachs. Insects were not present in stomachs of the < 20 mm size class in August and September. DiscusSION The purpose of this discussion is to compare aspects of the life history of Palaemonet'es paludosus with those of other freshwater and marine species of Palaemonetes. Similarities and differences in abundance, breeding season and fecundity are presented; a more detailed treatment is given by Beck (1974). In the lower Hillsborough River Palaemonetes paludosus is extremely abundant and appears to be codominant with fish in the submersed aquatic vegetation. At the same site, Barnett (1973) found million fish/hand a maximum standing crop of kg/ha. In this study shrimp ranged from million individuals/ha with a maximum standing crop of 492 kg/ha. Nielsen and Reynolds (1974) found that Palaemonetes kadiakensis in Missouri ponds exhibited summer densities ranging from million shrimp/ha. Welsh (1973) found a high density of 1.5 million individuals/ha for P. pugio in a northern salt marsh, indicating that marine populations of Palaemonetes may be as dense as freshwater populations. The length of the breeding season of Palaemonetes varies with

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12 62 THE AMERICAN MIDLAND NATURALIST 96(1) latitude and is longer in southern locations. This is especially evident in peninsular Florida. We collected ovigerous females in the Tampa Bay area from February through October, but Dobkin (1963) collected ovigerous females throughouthe year in Miami. Other southeastern populations of Palaemonetes show breeding seasons similar to that of P. patudosus in central Florida. Ovigerous females of P. kadiakensis were found in southern Louisiana from February to late October (White, 1949). Wood (1967) collected ovigerous females of P. pugio in Texas from March to October, and Knowlton and Williams (1970) reported ovigerous females of P. pugio and P. vulgaris from April to mid-october in North Carolina. Ovigerous females of P. intermedius Holthuis were present as early as February in Texas (Hedgepeth, 1950) and from May to September in the Carolinas and Virginia (Knowlton and Williams, 1970). In more northern areas breeding does not begin until late spring or early summer. In Missouri Palaemonetes,kadiakensis reproduction occurred in early summer (Nielsen and Reynolds, 1974), while Broad and Born (1963) recorded spawning of this species from late May through August in Ohio. Welsh (1973) observed that P. pugio in Rhode Island reproduced in May, June and July, and Jenner (1955) stated that reproductive activity of P. pugio and P. vulgaris in Massachusettstopped in late August or early September. Only large females of Palaemonetes breed early in the season. They are gradually replaced by smaller females as the breeding season progresses. This trend has been reported for P. paludosus (present paper), P. kadiakensis (Meehean, 1936), P. pugio (Wood, 1967; Knowlton and Williams, 1970) and P. vulgaris (Knowlton and Williams, 1970). The size range of ovigerous females of other species of Palaemonetes was similar to the mm range of P. paludosus. P. kadiakensis was from '23-49 mm (Meehean, 1936); P. vulgaris and P. intermedius, mm (Williams, 1965); P. pugio, mm (Williams, 1965) in the Carolinas and mm (Wood, 1967) in Texas; and P. argenticus Nobili, mm (Holthuis, 1952). The number of eggs carried by the females of Palaemonetes paludosus from central Florida (8-85) is considerably less than the found for P. kadiakensis (Meehean, 1936). Moreover, the greater size of ovigerous females of the latter species does not fully account for the greater fecundity. For example, when the maximum length of gravid females of P. kadiakensis (49 mm) is inserted into the equation relating number of eggs with total body length calculated for P. paludosus in this article, the estimated maximum fecundity would be only 116 eggs. Fecundity of P. paludosus in Miami, Florida, ranged from eggs (Dobkin, 1963), and Sollaud (1923) found a similar range of eggs for the European freshwater species, P. antennarius (Edwards). Marine and brackish water Palaemonetes tend to have smaller and more numerous eggs per female (Sollaud, 1923; Holthuis, 1952). A 22-mm gravid female P. intermedius (pers. observ.), collected in mid-

13 1976 BECK AND COWELL: ECOLOGY OF SHRIMP 63 November in St. Petersburg, Florida, carried 129 eggs. This compares with a maximum of 24 eggs carried by the same size females of P. paludosus. Wood (1967) found a maximum mean fecundity of 372 eggs per female and a minimum of 198 eggs per female for P. pugio, while in our study mean monthly fecundity ranged from a maximum of 50 to a minimum of 23 eggs per female. Wood's, equation, Log Y = X, relating number of eggs with total body length in mm for P. pugio, indicates that 20-mm females of P. pugio are 6.2 times more fecund than the same size females of P. paludosus and that 40-mm females are 10.6 times more fecund. The smaller fecundity of the freshwater species may be an adaptation to compensate for greater mortality of free-swimming larval stages in the freshwater habitat. The production of fewer but larger eggs enables the larvae to hatch at an advanced stage with a corresponding reduction in the total number of free-swimming larval stages. Freshwater Palaemonetes typically have an abbreviated larval development although P. kadiakensis (Broad and Hubschman, 1963) and P. argenticus (Men'u- Marque, 1973) are exceptions. Our data suggest that Palaemonetes paludosus is an iteroparous organismn, producing at least two broods of young per female. White (1949) and Broad and Hubschman (1963) observed females of P. kadiakensis having two broods in the laboratory. Knowlton and Williams (1970) mentioned that eggs are redeposited within 1-2 days after hatching of a previous brood in P. pugio and P. vulgaris, indicating several broods in females. Gurney (1923), on the contrary, stated that second broods in females of P. varians are the exception. The lack of zoeae in our collections from August-September cannot be explained easily since ovigerous females were present during these months. In other species (Palaemonetes pugio and P. vulgaris), zoeae have been collected throughout the breeding season, up to late November (Knowlton and Williams, 1970). A few zoeae of P. paludosus must have been present after July to produce the few juveniles found in September-December, but apparently were too sparse to be collected. Sampling error cannot be cited, as large numbers of juveniles were not found after August, indicating that zoeae were scarce. Evidently, some environmental factor(s) either decreased the percentage of eggs hatching or decreased survival of zoeae once hatched. A 1-year life cycle has been reported for Palaemonetes paludosus (present article), P. kadiakensis (Meehean, 1936), P. pugio (Wood, 1967) in Texas and P. pugio (Welsh, 1973) in Rhode Island. Acknowledgments.-We gratefully acknowledge the field assistance of D. N. David, J. L. Elmore, C. H. Resico, Jr. and S. N. Young. Drs. Jerry H. Hubschman, James B. Reynolds and Joseph L. Simon reviewed the manuscript. LITERATURE CITED BARNETT, B. S A technique for fish population sampling in dense submersed vegetation. Progr. Fish-Cult., 35:

14 64 THE AMERICAN MIDLAND NATURALIST 96(1) BECK, J. T Some aspects of the life history and ecology of the freshwater caridean shrimp, Palaemonetes paludosus. M. A. Thesis, Univ. South Florida, Tampa. 45 p. BROAD, A. C. AND J. W. BORN The biology of a freshwater shrimp, Palaemonetes kadiakensis, in an artificial empoundment in Ohio. Am. Zool., 3:523. (Abstr.). AND J. H. HUBSCHMAN The larval development of Palaemonetes kadiakensis M. J. Rathbun in the laboratory. Trans. Am. Microsc. Soc., :82: DOBKIN, S The larval development of Palaemonetes paludosus (Gibbes, 1850) (Decapoda, Palaemonidae), reared in the laboratory. Crustaceana, 6: AND R. B. MANNING Osmoregulation in two species of Palaemonetes (Crustacea: Decapoda) from Florida. Bull. Mar. Sci. Gulf Caribb., 14: GEBHART, J. W Studies on Palaemonetes exilipes Stimpson. M. A. Thesis, Ohio State University, Columbus. 31 p. GURNEY, R Some notes on Leander longirostris M. Edwards and other British prawns. Proc. Zool. Soc. Lond., 19233: HAYDEN, R. P. AND R. D. RINGO Introduction of Palaemonetes paludosus, a freshwater shrimp, into the lower Colorado River. Calif. Fish Game, 49: HEDGPETH, J. W Notes on the marine invertebrate fauna of salt flat areas in Aransas National Wildlife Refuge, Texas. Publ. Inst. Mar. Sci., 1: HOLTHUIS, L. B A general revision of the Palaemonidae (Crustacea Decapoda Natantia) of the Americas. II. The subfamily Palaemoninae. Allan Hancock Found. Publ. Occas. Pap., 12: JENNER, C. E A field character for distinguishing Palaemonetes vulgaris from Palaemonetes pugio. Biol. Bull., 1,09: KNOWLTON, R. E. AND A. B. WILLIAMS The life history of Palaemonetes vulgaris (Say) and P. pugio Holthuis in coastal North Carolina. J. Elisha Mitchell Sci. Soc., 86:185. McGUIRE, E. J The influence of habitat NaCl concentrations on the distribution of two species of Palaemonetes. Proc. La. Acad. Sci., 24: MEEHEAN, 0. L Notes on the freshwater shrimp, Palaemonetes paludosa (Gibbes). Trans. Am. Microsc. Soc., 55: MEN(u-MARQUE, S. A Desarrollo larval de Palaemonetes argenticus (Nobili, 1901) en el laboratorio (Crustacea, Caridea, Palaemonidae). Physis, 32: NIELSEN, L. A. AND J. B. REYNOLDS Life history of a freshwater shrimp, Palaemonetes kadiakensis, and its potential use as fish forage. 22nd annual meeting Midwest Benthological Society, Cincinnati, Ohio. 5-6 (Abstr.). RousE, W. L Littoral crustacea from southwest Florida. Q. J. Fla. Acad. Sci., 32: ST. AMANT, J. A. AND R. G. HULQUIST Palaemonetes paludosus collected in the Rio Hardy and Colorado River, Baja California. Calif. Fish Game, 55: 252. AND J. S. DAY Range extension of Palaemonetes paludosus in California. Ibid., 58:

15 1976 BECK AND COWELL: ECOLOGY OF SHRIM P 65 SOLLAUD, E Le developpement larvaire des "Palaemoninae." I. Partie descriptive. La condensation progressive de l'ontogenese. Bull. Biol. Fr. Beig., 57: TABB, D. AND R. B. MANNING A checklist of the flora and fauna of northern Florida Bay and adjacent brackish waters of the Florida mainland collected during the period July, 1957 through September, Bull. Mar. Sci. Gulf Caribb., 11: WELSH, B. L The grass shrimp, Palaemonetes pugio, as a major component of a salt marsh ecosystem. Ph.D. Thesis, Univ. Rhode Island, Kingston. 97 p. University Microfilms, Ann Arbor, Mich. (Diss. Abstr., 34B: 2764). WHITE, F. A Preliminary notes on the breeding season of Palaemonetes kadiakensis Rathbun in the Baton Rouge area. Proc. La. Acad. Sci., 12: WILLIAMS, A. B Marine decapod crustaceans of the Carolinas. U. S. Fish Wildl. Serv. Fish. Bull.,,65: WOOD, C. E Physioecology of the grass shrimp, Palaemonetes pugio, in the Galveston Bay estuarine system. Contrib. Mar. Sci., 12: SUBMITTED 19 NOVEMBER 1974 ACCEPTED 17 FEBRUARY 1975