Northeast Gulf Science Volume 4 Article 11 Number 1 Number 1

9-1980 Some Factors Influencing the Distribution of the H.K. Lehman Florida State University

P.V. Hamilton University of West Florida

DOI: 10.18785/negs.0401.11 Follow this and additional works at: https://aquila.usm.edu/goms

Recommended Citation Lehman, H. and P. Hamilton. 1980. Some Factors Influencing the Distribution of the Snail Neritina reclivata. Northeast Gulf Science 4 (1). Retrieved from https://aquila.usm.edu/goms/vol4/iss1/11

This Article is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Gulf of Mexico Science by an authorized editor of The Aquila Digital Community. For more information, please contact [email protected]. Lehman and Hamilton: Some Factors Influencing the Distribution of the Snail Neritina r

Short papers and notes 67

Mex., No. 3, pp. 57-120, pis. 15-20. SOME FACTORS INFLUENCING Powers, L. W. 1978. A Catalogue and Bib­ THE DISTRIBUTION OF THE SNAIL liography to the Crabs (Brachyura) of Nerltlna recllvata the Gulf of Mexico. Contributions in Marine Science, supplement to vol. 20. The gastropod Fam:ly con­ Rathbun, M. J. 1925. The spider crabs of tains over 200 living species, most of America. Bull. U. S. natn. mus. 129: which inhabit intertidal zones in tropical 1-613. and temperate climates. The olive nerite, Rouse, W. L. 1970. Littoral Crustacea Neritina reclivata Say, is irregularly dis­ from southwest Florida. Q. J. Fla. Acad. tributed along coastal regions of the Gulf Sci. 32: 127-152. of Mexico and the Caribbean Sea from 10 Soto, L. A. 1972. Decapod shelf-fauna of to 30 degrees N latitude. Its distribution the northeastern Gulf of Mexico, Distri­ ends in the north at Jacksonville, Florida bution and zoogeography. M.S. Thesis. on the Atlantic Ocean and in the south at Florida State University, Tallahassee, Trinidad (Russell, 1941 ). Most records of Florida. 128 pp., 47 text-figs. N. reclivata are from coastal regions of the Wass, M. L. 1955. The decapod crusta­ Gulf of Mexico, but this may be due to the ceans of Alligator Harbor and adjacent paucity of faunal surveys elsewhere in its inshore areas of northwestern Florida. range. Q. J. Fla. Acad. Sci. 18: 129-176. Despite the common occurrence of N. Williams, A. B. 1965. Marine decapod reclivata, it remains virtually unstudied. crustaceans of the Carolinas. Fish Bull. Russell (1941) reported that N. reclivata 65: 1-298. inhabits brackish and freshwater, and is _____ , J. K. Shaw and T. S. Hop­ absent from many small islands in the kins. 1977. Stilbomastax, a new genus Antilles that do not support permanent of spider crab (Majidae Tychinae) from freshwater rivers. According to this the West Indies Region, with notes on author, N. rec/ivata is found on solid sub­ American relative. Proc. Bioi. Soc. strates in the water, but not on mud. N. Wash. 90(4): 884-893. reclivata crawls using monotaxic retro­ grade waves, a type of locomotion often Gary D. Goeke and J. Kevin Shaw, Barry found in species living on solid substrate A. Vittor & Associates, 8100 Cottage Hill (Gainey, 1976). Pilsbry (1931) noted the Road, Mobile, AL 36609. snail's presence on reeds and other aqua­ tic plants near drainage canals and sug­ gested that algae may comprise the food of the snail. We have collected N. reclivata from hard substrates (e.g., plants, stumps, rocks) at locations between 5 km up the Escambia River and the western tip of the Gulf Breeze peninsula, Santa Rosa County, Florida. These locations corre­ spond to a salinity range of 1 to 19 ppt (U.S. Environmental Protection Agency, 1975). Because our preliminary observa­ tions suggested an affinity of Neritina for solid substrates, we investigated this Published by The Aquila Digital Community, 1980 1 Gulf of Mexico Science, Vol. 4 [1980], No. 1, Art. 11

68 Northeast Gulf Science Vol. 4, No. 1 September 1980

relationship to determine its ecological and decomposing organic material. Both basis. the bottom detritus and the Vallisneria detritus were concentrated and homo­ MATERIALS AND METHODS genized before use. Sand was collected from the top 5 em of the upper intertidal Grass Bed Population zone, dried and passed through a 250-pm Neritina reclivata were found on the sieve before use. plants Ruppia maritima, Spartina alterni­ Food consumption was measured by flora and Vallisneria americana, with the two methods. First, the amount of a submerged seagrass Ruppia being the potential food material remaining on a primary natural substrate. A test surface after being browsed upon by homogeneous area covered by Ruppia was compared to a control surface was studied in detail to determine if a lacking snails. This method permitted correlation existed between snail and determining the amount of material re­ seagrass density. A square having 4 m moved by the snails. Second, the amount sides was delineated in water 0.75 to 1.5 m of feces produced by snails after brows­ deep. At 1 m intervals throughout the ing on a test surface possessing the sample area, a core (182 cm2 diameter, 10 potential food material was compared to em deep) of grass and substrate was re­ the amount produced by snails browsing moved and sifted with a 1 mm2 sieve. For on a control surface lacking this material. each of these 25 cores, the dry weight of This method permitted determining if the the entire plants was measured after snails were actually ingesting the materi­ exposure to 100° C for 24 hours, and the al. Both methods were accomplished shell lengths of all snails were measured. simultaneously by including test surfaces containing the potential food and snails, Food Analysis containing food only, and containing An experiment was conducted in the snails only, in the same aquaria. laboratory to determine whether epiphytic The food analysis experiments were algae, bottom detritus, Vallisneria prepared by placing 151iters of 5-!lm filter­ detritus, and sand were ingested by Neri­ ed seawater (20°C, 12 ppt) into a 75.51iter tina reclivata. These materials were con­ aquarium. The aquarium was aerated and sidered to be the primary potential foods placed in a dark box fitted with a fluo­ either attached to or settling on surfaces rescent light operating on a 14L:10D inhabited by the snail. regime. Bottoms of 10-cm diameter petri The epiphytic unicellular algae were dishes served as test surfaces. Dishes collected by scraping leaves of living requiring a potential food material were Vallisneria americana in ambient sea­ placed on the bottom of the aquarium and water. Algae were concentrated by allow­ a standard amount of the material was ing the suspension to settle in a 1 liter suspended in the aquarium and allowed flask for 24 hours. Bottom detritus was to settle evenly. The standard amounts scraped from the surface of the substrate were 150 ml of epiphytic algae, 50 ml of and consisted of macrophytic plant cells, bottom detritus, 150 ml of Vallisneria organic material in various stages of de­ detritus, and 2 gm of sand. Once the composition, unicellular algae and sand material settled, dishes to be tested with­ grains. Vallisneria detritus floated on the out a potential food were added to the surface of the intertidal zone; it consisted aquarium. One snail was placed on each of Val/isneria plant cells, unicellular algae appropriate dish. Nitex screen covers https://aquila.usm.edu/goms/vol4/iss1/11 2 DOI: 10.18785/negs.0401.11 Lehman and Hamilton: Some Factors Influencing the Distribution of the Snail Neritina r

Short papers and notes 69

were placed on all dishes to confine each Epiphyte density was measured by snail's movements to its own dish. After 48 carefully scraping the leaves of a seagrass hours, snails were removed and placed in sample and rinsing the epiphytes into 20 individual net bags in 100-ml test tubes to ml of 1-JJm filtered seawater. After the collect their feces. The petri dishes were solution of seawater and epiphytes was carefully removed by hand and any food thoroughly mixed, the epiphyte concen­ remaining on them was collected by tration was estimated by counting three rinsing and filtering. The residue was separate aliquots using a hemocytometer. dried for 24 hours and weighed. The Each week for five weeks, we measured snails in the test tubes were allowed to the epiphyte concentration in one jar pass feces for 48 hours before the feces containing snails and in one jar lacking were collected, dried and weighed. snails. For each week, Student's t-test was Weights were measured with a Mettler used to determine if snails significantly H20 balance to the nearest 10 JJg. reduced epiphyte populations by com­ Sixteen replicates were performed for paring the three concentration estimates each of the four potential foods. Student's obtained for each of the two jars. t-test was used to compare means for the food removal data because variances RESULTS were not significantly different in all four cases. The less powerful Mann-Whitney Grass Bed Population U-test was used to analyze the feces pro­ The data from the 25 core samples are duction data because variances were sig­ summarized in Figure 1. The density of nificantly different in three of four cases. The total organic carbon content of each potential food was determined by the ~ combustion method described by Byers z Vegetation To examine the effects of N. rec/ivata on

epiphytes attached to the seagrass, Rup­ .5 1.0 1.5 2.0 pia maritima, ten 1.9-liter glass jars were DAY WEIGHT OF AUPPIA (gms} supplied with 300 ml of sand-mud sub­ Figure 1. Relationship between the amount of strate, 1300 ml of 1-JJm filtered seawater Ruppia maritima and the number of snails present in 25 core samples (y = 4.21x-.24). (19-23°C, 7-11 ppt) and equal amounts of seagrass having attached epiphytes. Equal amounts of seagrass were obtained snails was positively correlated to the by counting the number of leaves and amount of vegetation present in the area nodes and by measuring plant length. (r = 0.785, P <0.01). For this study site, 1 Ten adult snails of about equal length gm dry weight of Ruppia supported 3.97 were placed in each of five of the culture snails. In the 25 cores, a total of 66 snails jars; the remaining five jars lacked snails. were collected, with a mean shell length An overhead fluorescent light operated of 5.1 mm (s.d. = 1.7). on a 14L:10D regime. Light levels were 150 and 400 ft-c in tests A and B, respec­ Food Analysis tively. Because of the observed positive cor-

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70 Northeast Gulf Science Vol. 4, No. 1 September 1980

relation between snail and Ruppia did produce significantly more feces density, a study was conducted to deter­ (P<0.05). Figure 4 shows that epiphytes mine if the basis for the relationship was nutritional. Consumption of a food was A B measured by examining both the amount a; 'E 1 .§. 2 of food removed from a test surface and El N.S. Cfl P<.05 c UJ the amount of feces produced in order to 0 u UJ 0 u. insure that the food's absence from the LL LL .5 LL 1 0 0 test surface resulted from ingestion by the t- t- :I: 1 :I: snail. (!) (!) iii Figure 2 shows that snails significantly iii :: :: SNAIL FOOD SNfll SNAIL SN+Ail ONLY ONLY FOOD FOOD FOOD

A B Figure 4. Same as for Figure 2 except for epiphytes 'E Ci as the potential food. -"? 2.0 E. F 2.0 c F N.S. w 0 "'(.) 0 w were significantly reduced (P<0.005) LL u. u. u. N.S. from the test surfaces by snails, and also 0 0 IIi 1.0 1.0 f.I t- t- :1: :1: that snails feeding on epiphytes pro- (!) (!) iii iii :: :: duced significantly more feces (P<0.05) ,.,. than unfed snails. Figure 5 shows that no FOOD SNAIL SNAIL SNAIL ONLY ONLY ~~~~~ FOOD FOOD

Figure 2. (A) Mean and standard deviation for the amount of Vallisneria detritus present on petri dishes A B Ci after 48 hours. Sixteen dishes had only this potential 'E P<.005 N.S. -"? .2 E. 2 food present, 16 had this food and one snail present, c w 0 "'(.) and 16 had only the single snail present on the 0 w u. u. surface. (8) Mean and standard deviation for the u. u. 1 amount of feces produced by the same snails used in 0 .1 0 1- 1- :1: :1: part A. during the 48 hours immediately following (!) (!) iii iii removal from their respective petri dishes. :: :: FOOD SNAIL SNAIL SNAIL SNAIL ONLY ONLY reduced (P <0.005) the amount of Vallis­ fOOD fOOD FOOD neria detritus on the test surface but did Figure 5. Same as for Figure 2 except for sand as the not produce significantly more feces than potential food. unfed snails. Figure 3 shows that snails significant differences existed in either of the two measures when sand was sup­ A B plied as the potential food. Va/lisneria Ci detritus had the most organic content by 'E .2 E. -"? P<.005 P<.05 weight, 69.4%; epiphytic algae had 36.8%, c w 4 0 "'(..) 0 w bottom detritus had 5.8% and sand had u. "- 3 u.. .1 "- 0 0 1.0%. 1- I~ :!: J: (!) Cl 1 1 iii iii :: :: Effects of Nerltlna on Submerged fOOD SNAIL SNAIL SNAIL SNAil ONLY ONLY fOOD FOOD FOOD Vegetation Figure 3. Same as for Figure 2 except for bottom In each culture jar containing both detritus as the potential food. snails and Ruppia, the concentration of algal epiphytes was significantly less than did not remove a significant amount of (P<0.025 or better) that in the correspond­ bottom detritus from the test surface but ing jar containing only Ruppia (Figure 6). https://aquila.usm.edu/goms/vol4/iss1/11 4 DOI: 10.18785/negs.0401.11 Lehman and Hamilton: Some Factors Influencing the Distribution of the Snail Neritina r

Short papers and notes 71

A plant and snail density could be that more ~ 16 plant surface area supports more of a potential food such as epiphytes. j 12 "'w 0 Food analysis studies (Figures 2 to 5) ~ 8 >- showed that N. reclivata ingested :I: 0.. epiphytic algae and did not ingest sand. 0: 4 w I I I It was unclear from these data if N. 2 3 4 5 rec/ivata ingested bottom detritus and TIME (WEEKS) Val/isneria detritus. N. reclivata could be expected to consume epiphytic algae because it is a naturally occurring food B 12 28 ~ source attached to the plants and has a :j 20 high organic carbon content. The fact "'w 0 that sand was present in bottom detritus w 12 ~ but not Vallisneria detritus may have been ~ 4 responsible for the differences in removal w of these two materials from the test sur­ TIME (WEEKS) faces. The fact that the low-organic Figure 6. Concentrations of algal epiphyte cells content sand was not removed from the present on Ruppia over a 5 week period, with and test surfaces validates this procedure for without Neritina present in the culture jars. Tests A measuring food consumption by Neritina. and B were conducted in 150 and 400 ft-c of light, respectively. The dashed lines indicate the esti­ The fact that no significant differences mated concentrations of epiphytes present in all jars existed between the pairs of variances for at the beginning of the tests. Solid bars indicate the food removal data suggests that all epiphytes in jars containing Ruppia and snails while striped bars indicate epiphytes in jars containing snails tested with a given food removed Ruppia only. that food at an approximately equal rate. The significant differences that existed The results at both light levels clearly between pairs of variances for the feces indicate that Neritina significantly re­ production data (for all foods except duced the number of epiphytes attached sand) may reflect variation in the rate of to the Ruppia. Throughout each test, movement of food through the gut. Ruppia leaves were carefully examined The food analysis study indicates that for damage by the snails. No damage was N. reclivata selectively ingest food. Be­ observed. cause radula structure is related to the type of food ingested by molluscs, the DISCUSSION spacing and shape of the radular teeth may influence the size of particles in­ Because Ruppia maritima density was gested by N. rec/ivata. Thus the basis for positively correlated with snail density the preferred selectivity of epiphytic algae (Figure 1 ), the surface area of Ruppia was may have been its smaller particle size as considered to be the critical factor influ­ compared to the other three potential encing snail density. The hypothesis that food materials tested. seag rass simply comprises space for snai I Epiphytic algae were determined to be attachment is essentially untestable the major natural food source for N. because of the difficulty of excluding reclivata. In the culture jar experiments potential food materials from a surface. (Figure 6), snails significantly reduced The basis for the relationship between the epiphytes attached to Ruppia but did

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72 Northeast Gulf Science Vol. 4, No. 1 September 1980

not damage the Ruppia itself. In these termining organic carbon in marine experiments, the reduction of epiphytes sediments, with suggestions for a could have resulted from snails detaching standard method. Hydrobiologia 58: them from the plants with the foot. 43-48. However, because the food analysis tests Gainey, L.F., 1976. Locomotion in the showed that N. reclivata ingested epi­ : Functional morphology phytes, we conclude that the reduction of of the foot in Neritina reclivata and Thais epiphytes on the Ruppia in the jars con­ rustica. Malacologia 15: 411-431. taining snails resulted from the snails Pilsbry, H.A., 1931. A new race of Neritina actually ingesting the epiphytes. reclivata Say. Nautilus 45: 67-68. Russell, H.D., 1941. The recent mollusks of the Family Neritidae of the Western ACKNOWLEDGMENTS Atlantic. Bull. Mus. Comp. Zool. 88(4): 347-403. We thank M.E. Tagatz and P.A. Winter U.S. Environmental Protection Agency, for suggestions and R.J. Merlano for field 1975. Environmental and Recovery assistance. Portions of this work were Studies of Escambia Bay and the Pen­ supported by NSF-URP Grant SM176- sacola Bay System, Florida. EPA 904/ 83291 to PAW and by Environmental Pro­ 9-76-016. tection Agency Contract CF70811A, by a University Research Committee award and by E.P.A. Grant R806121 to PVH. H.K. Lehman. Department of Biological Sciences, Florida State University, Talla­ LITERATURE CITED hassee, FL 32306. P.V. Hamilton. Department of Biology, Byers, S.C., E.L. Mills and P.L. Stewart, University of West Florida, Pensacola, 1978. A comparison of methods of de- FL 32504.

ERRATA, Vol. 3, No. 2:

P. 57-58 in the key to species of Leptocaris, the indicated couplets should read as fol­ lows.

couplet 1. . .. Exp. P2 and P3 with 3 setae couplet 2. . .. L. armatus Lang couplet 7. . .. L. pori Lang couplet 9. . .. L. doughertyi Lang couplet 13. . .. L. minutus T. Scott

P. 104. Senior author is Martin F. Gomon https://aquila.usm.edu/goms/vol4/iss1/11 6 DOI: 10.18785/negs.0401.11