MARINE ECOLOGY PROGRESS SERIES Published November 2 Mar Ecol Prog Ser

Defenses of Caribbean against predatory reef fish. 11. Spicules, tissue toughness, and nutritional quality

Brian Chanas, Joseph R. Pawlik*

Biological Sciences and Center for Marine Science Research. University of North Carolina at Wilmington, Wilmington, North Carolina 28403-3297, USA

ABSTRACT: Laboratory and field feeding experiments were conducted to assess the palatability to predatory reef fish of prepared foods containing natural concentrations of glass spicules from 8 specles of Caribbean reef sponges. with high concentrations of spicules in their tissues, and with variable spicule morphologies, were chosen for the experiments. The presence of spicules did not alter food palatability relative to controls for any of the sponges tested. Analyses of ash content, tensile strength, protein, carbohydrate, and lipid content, and total energy content were conducted on tissue samples from 71 species of Caribbean from reef, mangrove, and grassbed habitats, and compared to previously reported data on the chemical defenses of the same species. There was no evi- dence to support the hypothesis that sponge species with palatable extracts have higher concentrations of inorganic structural elements, as measured by the mean ash content of their tissues. In addition, the tissues of palatable sponges were not different from those of chemically deterrent species with regard to mean tensile strength, protein content, carbohydrate content, and total energy content, but the tis- sues of chemically defended species did have a higher mean lipid content than those of palatable spe- cies. Sponges that lack chemical antipredatory defenses do not appear to compensate with structural or nutritional defenses, but may instead direct energy otherwise used for the production and storage of secondary metabolites to increased growth and reproduction.

KEYWORDS: Sponge . Defense . Caribbean . Coral reef . Predation . Spicules . Nutritional value . Toughness

INTRODUCTION toughness (as in some holothunans) that may exceed the abilities of most predators to bite or tear prey; and (4)re- Tropical reef ecosystems are characterized by high duced tissue food value that renders prey largely undi- levels of herbivory and predation (Huston 1985, Hay gestible, including the perfusion of tissue with water 1991), yet these environments are dominated by fleshy, (many cnidarians), calcium carbonate (red and green sessile, benthic invertebrates and plants. The defensive algae), cellulose (tunicates) or refractory collagen options available to marine organisms can include one or (sponges). In the preceding contribution (Pawlik et al. several of the following: (1) chemical defenses (demon- 1995, this issue), we investigated the first of these strate- strated for several sponges, corals, tunicates, etc.); (2) gies, chemical defense, as elaborated by 71 species of structural defenses, including shells (most gastropods), Caribbean demosponges. We discovered that 69% of spines, pincers (many echinoderms, bryozoans), or these species yielded organic extracts that deterred the skeletal elements such as an endoskeleton (hard corals), feeding of a predatory reef fish, but many very common sclerites (soft corals), or spicules (sponges); (3) tissue sponges produced palatable extracts. In this paper, we survey the same species of sponges with regard to the 'Addressee for correspondence. other 3 defensive strategies: structural elements, tissue E-mail: [email protected] toughness, and nutritional quality.

O Inter-Research 1995 Resale of full article not permitted 196 Mar Ecol Prog Ser 127: 195-211, 1995

Structural defenses of terrestrial and marine plants Considering the foregoing, one could make the fol- ('quantitative' defenses as defined by Feeny 1976) lowing predictions when examining the relationships have been the subject of noteworthy research; these between structural elements, tissue toughness, food defenses include resins and lignins of terrestrial plants value, and chemical defenses in a suite of Caribbean (Rosenthal & Janzen 1979, Coley 1983) and calcified demosponges: species with highly deterrent crude inclusions of marine algae (Littler et al. 1983, Paul organic extracts (potent chemical defenses) are more 1992, Hay et al. 1994). For sessile marine invertebrates, likely to have tissues (1) with fewer inorganic struc- spicules and sclerites are known to play an important tural elements, (2) that are less tough, and (3) with role in colony support (Koehl 1982, Lewis & VonWallis higher food value, than species with palatable crude 1991), but their defensive function has been debated. organic extracts. To address these hypotheses, we For example, Harvell et al. (1988) demonstrated that assembled data on spicule content (as ash mass), tis- the addition of sclerites from the coenenchyme tissues sue toughness (as tensile strength), and nutritional of the gorgonian Pseudopterogorgia acerosa to food quality (as protein, carbohydrate, lipid, and energy strips reduced their consumption by reef fish in field content) for 71 species of Caribbean demosponges assays, but Wylie & Paul (1989) reported that butterfly- and compared these to the data on the chemical fish preferred to feed on species of the soft coral Sinu- defenses of the same species (Pawlik et al. 1995). In laria that had the greatest concentrations of large, addition, we tested the capacity of the siliceous sharp sclerites. spicules of 8 species to deter predation by offering Demosponges show considerable diversity of struc- prepared foods containing natural concentrations of tural elements; most have siliceous spicules (which can spicules to predatory reef fish in aquarium and field vary considerably in size and shape, depending on the assays. species) and proteinaceous spongin fibers (which are similarly variable), but many have only the latter (e.g. Verongida, ) and some have nei- MATERIALS AND METHODS ther (e.g. some Homosclerophorida) (Bergquist 1978). Spicules may offer an effective structural defense Sponge collection and identification. This study was against generalist predators, as they do for some gor- conducted over the course of 5 research expeditions: gonian corals (Harvell et al. 1988, VanAlstyne & Paul 2 on board the RV 'Columbus Iselin' to the Bahamas 1992), but it appears that they are not effective against Islands in July 1992 and August 1993, 1 on board the some sponge specialists (Randall & Hartman 1968, RV 'Seward Johnson' in October 1994, and 2 at the Meylan 1988). Proteinaceous spongin fibers may be National Undersea Research Program facility in Key indigestible for some generalist predators, and if the Largo, Florida, USA, in December 1992 and again in fraction of indigestible material (spicules + spongin) is May 1994. Portions of sponges were collected by too high, predators may not eat the sponge tissue, as gently tearing, or when necessary, by cutting tissue has been found for some herbivores feeding on woody with a sharp knife. Sponges were collected from reef, plants (Mattson et al. 1988) and calcified seaweeds mangrove, and seagrass bed habitats. For each spe- (Paul & VanAlstyne 1988, Hay et al. 1994). Recent cies, replicate collections were taken from distant sites studies of the interaction of chemical defenses and to avoid collecting asexually produced clones. Tissue food nutritional quality by Duffy & Paul (1992) and was immediately frozen and stored at 20°C until used Pennings et al. (1994) revealed that prepared foods in subsequent biochemical and tensile strength analy- having a high protein content and also containing algal ses. Sponges were identified on the basis of spicule or sponge metabolites were readily eaten by reef and tissue preparations (DeLaubenfels 1936, Wieden- predators, but low protein foods containing the same mayer 1977, Zea 1987, Kelly-Borges & Pornponi 1992, compounds deterred predation. Therefore, if the nutri- R. W. M. VanSoest unpubl.). tional value of tissue is sufficiently low, it may offer a Laboratory assays. Aquanum assays were per- selective advantage to an organism (1) by decreasing formed as described in Pawlik et al. (1995) on board tissue palatability, (2) by increasing the effectiveness the RV 'Columbus Iselin' using tissue from 5 species of chemical defenses, and, if the nutritional value is of highly spiculose sponges, representing a range of decreased through the addition of structural elements, spicule types. The species assayed were: Cribro- (3) by increasing tissue toughness and resilience to chalina vasculum, neptuni. Mycale laevis, physical harm. It stands to reason that any defensive Neofibulana nolitangere, and Xestospongia muta. A mechanism will have a metabolic cost, so that the duplicate assay was performed on different specimens greater elaboration of any combination of chemical of the last 3 species, collected from different sites. A and structural defenses will be counterbalanced by 10 m1 volume of sponge ectosome tissue (within 1 cm reductions in growth and fecundity. of sponge surface) was measured by displacement Chanas & Pawlik: Defenses of sponges. 11. Spicules 197

into a graduated 50 m1 plastic centrifuge tube filled was 60 ml; approximately 5 m1 of volume was lost as with 40 m1 of water. The water was discarded and the water vapor. The gel was sliced into 1.0 X 0.5 X tube filled with chlorine bleach (sodium hypochlorite, 0.5 cm strips with a scalpel, each strip having a string 5.25%).After the solution stopped bubbling (1 to 5 h), embedded in its center For each experiment, 20 the supernatant was carefully decanted, and fresh spicule treated and 20 control strips were prepared. bleach added. This process was repeated until the To distinguish treated from control strips, the cotton a.ddition of fresh bleach resulted in no further bub- string attached to each strip was marked with a small bling (usually 3 treatments), and a pellet of splcules colored ink spot. was left on the bottom of the tube. After the final Field assays were based on those of Hay (1984). One treatment, the bleach was decanted and replaced treated and one control strip each were tied to a 50 cm with distilled water. The distilled water was decanted length of 3-strand nylon rope at a distance of -4 and and replaced for a total of 3 rinses. After the last rinse, 12 cm from one end of the rope (the order was haphaz- the water was replaced with a 1.0 M solution of ard). Twenty ropes were deployed on the reef for each sodium thiosulfate to neutralize any residual bleach. experiment, with the end of each rope opposite the After 10 to 15 min, the spicule pellet was rinsed food strips unwound and clamped onto a piece of coral 3 times in distilled water, and then transferred to a or rock. Identifications of fish sampling food strips glass scintillation vial. were made by consulting Randall (1983) and Humann A mixture of 0.3 g alginic acid and 0.5 g of freeze- (1989). Within 1 h, the ropes were retrieved and the dried, powdered squid mantle in distilled water was percentage decrease in the strip length recorded to the added to each vial containing the spicule pellet from nearest 5%. The Wilcoxon paired-sample test (1- 10 m1 of sponge tissue to yield a final volume of 10 ml. tailed; Zar 1984) was employed to analyze the results The mixture was gently stirred to homogenously dis- after excluding pairs for which both control and tribute the spicules in the alginic acid matrix while treated strips had been either completely eaten, or not avoiding breakage of spicules. The mixture was then eaten at all. loaded into a 10 m1 syringe, the syringe tip was sub- Measuring ash mass. Frozen tissue samples from merged in a 0.25 M solution of calcium chloride, and each of 3 or more individuals from each of 71 species the contents of the syringe emptied to form a long, of Caribbean sponges were weighed (wet mass) and spaghetti-like strand. After a few minutes, the hard- their volume determined by displacement of distilled ened strand was removed, rinsed in seawater, and water. Samples were freeze-dried for 12 h, weighed chopped into 4 mm long pellets with a razor blade. (dry mass), and extracted twice: first in 1:l dichloro- Control pellets were made the same way, but without methane:methanol for 24 h, then in methanol for 1 h. addition of spicules. Control and treated pellets were The 2 extracts were combined, evaporated on a presented to groups of 3 bluehead wrasses Thalassoma warming tray at 60°C and weighed (extract mass). bifasciatum (1 blue-head phase, 2 yellow phase) held The extract and extracted tissue were recombined in each of 10 separate, opaque-sided compartments in and ashed at 45OoC in a muffle furnace for 12 h, then laboratory aquaria, as described in Pawlik et al. (1995). weighed (ash mass). This combustion temperature Excess pellets not used in feeding assays were treated has commonly been used to ash organic material but with bleach as before to yield spicules that were then retain water that is bound in mineralized skeletons examined for breakage. (Paine 1964, Harvell & Fenical 1989, Bjorndal 1990). Field assays. Experiments were performed as Ash content was compared with data on the deter- described in Pawlik & Fenical (1992) on shallow rency of crude organic extracts from the same (< 10 m) reefs in the Bahamas. A spicule pellet from sponge species (Pawlik et al. 1995) to determine 60 m1 of sponge tissue was prepared as before (see whether a relationship exists between the content of 'Laboratory assays') from samples of Ayelas clath- inorganic structural elements and chemical defense. rodes, Chondrilla nucula, Ectyoplasia ferox, Neofibu- Further, the ash mass data were divided into laria nolitangere and Xestospongia muta. For each 2 groups, data from sponges with palatable crude species, the spicule pellet was gently homogenized extracts, and data from sponges with deterrent crude into a pre-mixed matrix of 1.5 g of carrageenan (Type extracts (Pawlik et al. 1995), and significant differ- I, Sigma) and 3.0 g of freeze-dried, powdered squid ences in the means of the 2 groups determined with mantle, and brought to a final volume of 65 m1 with a t-test (Zar 1984). distilled water. The mixture was heated to boiling in Measuring tensile strength. Frozen tissue samples of a n~icrowaveoven (about 1 min on full power), then each of 3 individuals from each sponge species were poured into plastic molds crossed by lengths of cotton allowed to thaw to -25°C. For each sample, 3 thin, rec- string that protruded from the ends of the molds. tangular strips of tissue were cut and the cross- After the matrix cooled, the total volume of the gel sectional area estimated by measuring the width and Mar Ecol Prog Ser 127: 195-211, 1995

thickness to the nearest 1.0 mm. Each strip was content by combustion in a Parr oxygen bomb calo- gnpped lengthwise at both ends with spring-steel rimeter (as in Dayton et al. 1974). Samples of assay paper clamps equipped with thin corrugated alu- foods were subjected to the same analyses. Because minium strips to prevent tissue slippage. The clamp at potential predators consume tissue on the basis of vol- one end of the strip was attached to a support, while a ume, rather than mass, all values for protein, carbohy- tripour beaker was suspended from the clamp at the drate, and lipid (as mg) and energy content (as kJ) other end of the strip. Distilled water was slowly added were expressed on a per volume basis calculated from to the beaker until the tissue faded along the measured the ratio of mean dry mass:volume for each sponge cross-sectional area between the clamps. Trials in specles (see 'Measuring ash mass'). This standardiza- which failure occurred at the clamp edge, or obliquely tion is particularly important because sponges vary to the cross-sectional area, were not recorded. Tensile widely in their density, because of differences both in strength was calculated as follotvs: spicule mass and in the amount of water present in the tissues. All 4 values relating to nutritional quality were compared with data on the deterrency of crude organic where o, is the nominal stress at failure (N m-'), A is extracts from the same sponge species (Pawlik et al. the cross-sectional area (m2),and 1995) to determine whether relationships exist between these nutritional values and chemical de- fense. Further, data on nutritional quality were each where Fis the force (N),m is the combined mass of the divided into 2 groups, data from sponges with palat- water, beaker, and clamp (kg), and g is gravitational able crude extracts, and data from sponges with deter- acceleration, 9.8 m S-'. rent crude extracts (Pawlik et al. 1995), and significant The mean tensile strength of 3 tissue strips was com- differences in the means of the 2 groups determined puted for each sample, and a mean of the 3 replicate with a t-test (Zar 1984). sample means was taken for each sponge species. Some species had tissue that was too weak to test using thls method, while others were too strong (the clamps RESULTS would slip before the tissue would fail). For 19 species, the tensile strength of freshly collected tissue samples Deterrency of spicules was measured using the same techniques, and these values were comparable to those of thawed tissue from Five species of reef sponges were chosen for the same species; therefore, only the data from analy- aquarium assays of their spicules at concentrations that ses of thawed tissue are reported herein. Tensile occur naturally In sponge surface tissues (Flg 1). All strength was compared with data on the deterrency of 5 species have a high density of spicules in their tis- crude organlc extracts from the same sponge species sues, with a range of spicule sizes and morphologies (Pawlik et al. 1995) to determine whether a relation- (see Figs. 1 8 2). readily ate ship exists between tensile strength and chemical spicule-laden food pellets in every case (Fig. 1). Fish defense. Further, tensile strength data were divided swallowed spicule-treated pellets without any immedi- into 2 groups, those from sponges with palatable crude ate or long term ill effects (i.e, no flaring of gills or extracts, and those from sponges with deterrent crude regurgitation, as seen with food pellets treated with extracts (Pawlik et al. 1995), and significant differ- mildly unpalatable organic extracts, and no negative ences in the means of the 2 groups determined with a effects after several weeks of subsequent captivity). t-test (Zar 1984). Spicules were reclaimed from unused food pellets by Measuring nutritional quality. The techniques of treating them with bleach (see 'Materials and meth- McCLintock (1987) were adapted to measure the nutri- ods') and compared with spicules that had not been tional value of sponge tissue. Frozen tissue samples of incorporated into food, and there were no obvious at least 3 individuals from each sponge species were increases in the amount of spicule breakage due to separately freeze-dried and ground to a fine powder in food preparation. a high-speed mill (CRC micro-mill). Subsamples of Field assays of the spicules of 5 sponge species at powder were weighed and subjected to the following natural concentrations also revealed no inhibition of analyses based on well-established protocols: (1) feeding by a natural assemblage of reef fish (Fig 2). NaOH-soluble protein content (Bradford 1976) using There was a significant difference in feeding on food bovine serum albumen as a standard, (2) TCA-soluble strips perfused with the spicules of Chondrilla nucula carbohydrate content (Dubois et al. 1956) using glyco- (Fig. 2B), but more bites had been taken of treated gen as a standard, (3) llpid content using a gravimetric food strips than controls (Wilcoxon signed rank test, technique (Freeman et al. 1957), and (4) total energy p = 0.04, l-tailed test). A wide variety of fish fed on Chanas & Pawlik: Defenses of sponges 11. Spicules

Fig. 1 Aquarium assay. Consumption by Thalassoma bifasciatum of food pellets (mean +SE) containing sponge spicules at natural concentrations. Geodlaneptuni - 1 Fish consumed all 10 control pellets in \ --Z- .c?- all cases. The number of replicate assays follows each species name. Mycale laevis -2 Drawings of representative spicule , types are indicated for the first 3 spe- /eofibularin nolitangere-2 cles (adapted from Zea 19871, while spicules of the last 2 species are E - Xestospongiamuta -2 shown in Fig. 2. All the spicules are , drawn to the same scale (bar on nght), except for the 2 in the left-most part of U012345678910 the figure from Geodianeptuni MEAN PELLETSEATEN treated and control food strips, particularly wrasses sponge: for most species, the ash- residue was com- Thalassoma and Halichoeres spp., snappers Ocyurus posed mostly of glass spicules (e.g. Placospongia chrysurus, parrotfish Scarus and Sparisoma spp., rnelobesioides, Geodia neptuni, Xestospongia muta), grunts Haemlilon spp., tilefish Malancanthus plu- but in others it was primarily carbonate sand (e.g. mieri, porgy Calamus spp. and angelfish Pomacan- Dysidea janiae) or inorganic salts from the seawater thus arcuatus. held by the tissue of some species (e.g. all Aplysina and Ircjnia spp.). The highest ash mass values were among highly spiculose species in the tetractin- Ash mass compared with extract palatability omorph families Placospongiidae, Spirastellidae, and . For the purposes of comparisons with The ash mass of tissue was determined for all 71 other studies in which all ash and nutritional values Caribbean sponge species (Fig. 3). The mean concen- are expressed on the basis of dry mass, mean values tration (+ SD) of ash was 78.4 + 84.7 mg ml-l The of extract mass and dry mass per volume are listed in composition of the ash varied depending on the Table 1

A clathrodes B Chondrilla nucula C Ectyoplasiaferox N = 10 (18); P = 0.09 N = 13 (20);P = 0.04 N = 12 (20);P = 0.38 120 120 , 110 7

TREATED CONTROL TREATED CONTROL TREATED CONTROL

Fig 2. Field assay. Consumption by reef fishes of paired control food strips D E Xestospongiamuta and stnps containing spicules at the N = 14 (20);P = 0.48 N = 14 (20);P = 0.58 120 , 120 , , . same concentrations as found In sponge tissues. 1 SD above the mean is indicated. N = no. of paired treated and control strips used in statistical analysis (no. of pairs retrieved of 20 deployed). Probability calculated using the Wil- coxon paired-sample test. Drawings of representative spicule types are indi- cated for each species (adapted from Zea 1987), and are drawn to the same scale (given in B) TREATED CONTROL TETRACTINOMORPHA : HOMOSCLEROMORPHA CERACTINOMORPHA CHORlSTlDA HOMOSCLEROPHORIDA HAPLOSCLERIDA Geodlldee Hallclonidae Plaklnldee Erylus lormosus -3 m Hellclona hogetihl -3 Geodle glbberosa -3 Plekortls engulosplculalus Callysponglidae Geodle neplunl -3 Plakorlls hallchondroldes -4 Cellyspongle lallax -2 SPIROPHORIDA Pl~kortl~lll~ -3 Cellyspongle pllcllera -5 Tetlllldee Cellyspongle veglnells -3 CERACTINOMORPHA Clnechyre ellocleda -3 Nlphalldae HADROMERIDA HALICHONDRIDA Amphlmedon compresse -7 Tethyiidae Hallchondrlldae Amphhdon ertne -3 Crlbrochallne vasculum -3 Telhye ectlnle -3 Hellchondrla melanodocle -3 Splrastrellldae Nlphales dlgltalls -3 Anlhoslgmelle verlens -3 Myrmekloderma slyx -3 Nlpheles erecle -3 Olplaslrella megeslellate - 3 Slphonodlclyon coralliphagum S~heclosnonole. - olhella -3 1- +76 Mvcalldae Petrosildae Xeslospongle mule 17 Spheclospongle vesparlum -4 - Mycele leevls -3 Oceanaplldee Splmswlla cocclnee -2 -3 Placosoonalldsm Mycele laxisslme calyx pod01ype -3 -r- - --- Plecorpongle melobesloldes -3 DICNOCERATIDA Spongiidae Chondroslldae Blemne lubulala -2 Hlppospongle lachne -3 Chonddlla nucula -4 Neollbulerle nolltengere -5 -3 Chondmsle colleclrlx -3 Spongle obllqua -3 Desrnacldonldae 1- Thorectidee Chondrosle renllormls lrclnie lellx -3 AXlNELLlDA Holopsamme helwlgl -3 Irclnle slroblllne -3 Axlnellldae lolrochote blrotulela 3 Smenospongle euree -3 Pseudexlnelle lunaecherte 3 Dysldeldee -3 Ptlloceulls splculllare Dysldea elherle -3 Pllloceulls walpersl4 Dysldee jenlae -3 Telchaxlnelle morchellum -3 Phorbasldae VERONGIDA Ulose ruefzler1.3 Phorbes ameranthus -3 C Aplyslnldae Raspelllldae Myxillldee Aplyslna archer1 3 Eclyoplesle lerox 4 Llssodendoryx lsodlcfyells Aplyslna caulllormls -3 Agelasldae Aplyslna IIsIularis -3 Ageles clelhrodes -5 Llssodendoryx slgmala -2 Aplyslna lulve -3 Ageles conllem -3 Clethrlldae AplysIn8 Iacunosa 3 Ageles dlsper -3 Pendaros acanthlfollum -3 VemnguIa glganlee 3 Ageles lnequells -3 Verongule dglda -3 Rhephldophlus junlperlnus Ageles sceplrum -3 l Aplyslnellldae Ageles wledenmayerl -3 Rhephldophlus venosus .2 I Pseudocerallne crasse -3 0 100 200 300 0 100 200 300 0 100 200 300 ASH, mg ml-' ASH, mg ml" ASH, mg ml "

Fig. 3. Ash mass of the tissues of Caribbean sponges. Species are taxonomically grouped by subclass, order, and family based on Kelly-Borges & Pomponi (1992).The num- ber oI replicate samples is indicated after each species name Clianas & Pawlik: Defenses of sponges. 11. Spicules 20 1

Table 1. Mean extract mass (mg ml-l) and dry mass (mg ml-l) of the tissue of 71 species of Caribbean demosponges

I Species n Extract Dry mass Species n Extract Dry mass

Agelas cla throdes felix 142 Agelas con~fera Irclnia strobilina 150 Agelas dispar Llssodendoryx isodictyal~s 126 Agelas lnequalis Ljssodendoryx sigmata 68 Agelas sceptrum Mycale laevis 132 Agelas wiedenn~ayeri Mycale laxissima 156 Amphimedon conipressa Myrmekioderma styx 166 Amphimedon erina Neofibularia nolitangere 190 Anthosigmella varians Niphates digitalis 95 Aplysina archeri Niphates erecta 126 Aplysina ca uliformis Pandaros acanthifolium 163 Aplysina fistularis Phorbas amaranthus 120 Aplysina fulva Placospongia melobesioides 787 Aplysina lacunosa Plakortis angulospiculatus 118 Biemna tubulata Plakortis halichondro~des 214 Callyspongia fallax Plakortis lita 140 Callyspongia plicifera Pseudaxinella lunaecharta 161 Callyspongia vaginalis Pseudoceratina crassa 256 Calyx podotypa Ptiloca ulis spiculifera 160 Chondrilla nucula Ptiloca ulis walpersi 159 Chondrosia collectriv Rhaphidophlus juniperinus 178 Chondrosia reniformis Rhaphidophlus venosus 200 C~nachyraalloclada Siphonodictyon corall~phagum 133 Smenospongia aurea Cribrochalina vasculum 171 Diplastrella megastellata Spirastrella coccinea 256 Dysidea etheda Spongia obliqua 160 Dysidea janiae Spheciospongia othella 317 Ectyoplasia ferox Spheciospongia vesparium 334 Erylus formosus Tedania ignis 85 Geodia gibberosa Teichaxinella morchellum 158 Geodia neptuni Tethya actinia 267 Haliclona hogarthi Ulosa ruetzleri 204 Halichondria melanodocia Verongula gigantea 185 Hippospongia lachne Verongula rigida 135 Holopsamma helwigi Xestospongia muta 171 Iotrochota birotulata

There was little relationship between ash mass and measurement. Tensile strength varied widely across chemical deterrency of sponge extracts [deterrency taxa, with a mean value (+ SD) of 8.8 * 15.0 N m-2 x 10'. data from Pawlik et al. (1995); r2 = 0.092; Fig. 4A]. Sponges with the highest tensile strength included Although the slope of the correlation was signifi- and Mycale laxissima, both of which cantly different from zero (p = 0.012), the low coeffi- were too strong to measure, and Chondrosia reniformis, cient of determination (r2)indicates that sponges that Diplastrella megastellata and Teichaxinella morchellum, lack chemically deterrent organic extracts do not nec- which gave some of the highest tensile strength values. essarily have a higher concentration of structural ele- Sponges in the genera Ptilocaulis and Agelas also had ments in their tissues. The weakness of the relation- tough tissue ship was confirmed by comparing the mean tissue There was no relationship between mean tissue ten- ash mass of sponges that yielded unpalatable vs sile strength and palatability of tissue organic extracts palatable crude organic extracts (Fig. 5A, p = 0.16, for the 58 species for which tensile strength was deter- t-test). mined (r2 = 0.007, p = 0.606, Fig. 4B). Surprisingly, many of the toughest sponges also yielded the most de- terrent extracts (Pawlik et al. 1995), including all of the Tensile strength compared with extract palatability species referred to in the preceeding paragraph, with the exception of Chondrosia reniformis. A direct com- The tensile strength of 58 of ?l species of sponges was parison of the mean tissue tensile strength of sponges measured (Fig. 6),with the remaining species having tis- with palatable and unpalatable organic extracts also sue that was either too strong or too weak for an accurate revealed no difference (Fig. 5B,p = 0.62, t-test). 202 Mar Ecol Prog Ser 127: 195-211, 1995

Fig. 4. Correlation of the deter- rency of organic extracts with (A) ash content (n = 71) and (B) 012345678910 01 2345678910 tensile strength (n = 51) of the MEAN PELLETS REJECTED MEAN PELLETS REJECTED tissues of Caribbean sponges

Nutritional quality compared with extract Table 2. Comparison of nutritional quality of prepared foods used in feeding assays with those of sponge tissue. Values for palatability prepared foods represent means of triplicate analyses, values for sponge tissue are means of means from Figs. 7 to 10 for The nutritional quality expressed as protein content, 71 species carbohydrate content, lipid content, and energy con- tent of sponge tissue for 71 species of Caribbean demo- Protein Carbohdrate Lipid Energy sponges is shown in Figs. 7 to 10, respectively. Mean (mg rnl-') (mg ml-') content (kJ ml-l) protein, carbohydrate, and lipid contents (+ SD) of (mg ml-') t t t sponge tissue were 20.7 11.6, 3.5 2.2, and 11.4 Aquarium assay food pellets 8.1 mg ml-l, respectively (Table 2). There was little 13.2 0.5 3.6 1.1 relationship between protein, carbohydrate or lipid Field assay food strips contents and the palatability of organic extracts of 8.9 10.6 3.1 1.1 sponge tissue (rZ = 0.006, 0.011, and 0.138, respec- Sponge tissue mean * SD, n = 71) 20 7 2 11.6 3.5 * 2 2 11.4 * 8.1 2.0 * 0.9 tively; Fig. 11A, B, C). The slopes of the correlations were not significant for protein or carbohydrate con- tent (p = 0.402 and 0.313, respectively), but the slope was significant for lipid content (p < 0.001). The mean (rZ = 0.058; p = 0.025; Fig. 11D).When sponges that energy content (+ SD) of sponge tissue was 2.0 t yielded unpalatable versus palatable crude organic 0.9 kJ ml-l, and there was also little relationship extracts were compared with regard to nutritional between energy content and the deterency of tissue quality, there were no differences in mean protein, car-

Fig. 5. Comparison of mean (+ SE) ash content (A) and tensile strength (B) of the tis- sues of sponges that yielded palatable and unpalatable crude organic extracts. The number of specles used in each comparison is indicated at the base of each bar. There were no significant differ- ences in the mean values for either cornpanson (p > 0.05, TENSILE STRENGTH t-test) TETRACTINOMORPHA HOMOSCLEROMORPHA CERACTINOMORPHA CHORlSTlOA HOMOSCLEROPHORlDA HAPLOSCLERIDA Geodiidae HallclonMaa Plaklnldae Erylus Ionnosus -3 H8lklona hogarlhl TW G&& glbberosa -3 Plakorlls engulospiculafus -1 Callysponglldae Gwdla neptunl -3 Plakortls ha1IchondroIdes-3 ) Callyspongla fallax -1 SPIROPHORIDA Plakortls 1118 - 1 CBIlyspongla pllcllsrs -3 B Talllldae Cal!yspongle baglnalls -3 Clnachym alloclada -3 CERACTINOMORPHA Nlphatldaa HADROMERIDA HALICHONDRIDA Amphimedon compress8 -3 Telhylldae Hallchondrlldae Amphlmsdon erina -3 Crlbrochallru vssculum -3 Tethye actlnle -3 Hellchondrla melenodocla -3 C Splraslrallldae Nlph.18~dlgl18IIs -3 AnthoslgmeNe varlens -3 Myrmekloderms styr -3 I Nlphafer ern18 -3 Dlplastrelle megastellate 3 Slphonodictyon ~~alllphegum- TW - Petrosildae Spheciospongla othella -3 Xesfospongla mufa -3 I Spheclospongle vesparium -3 Mycale laevls TW Oceanaplldae SplnstmIIa cocclnea Mycale laxlsslma Calyx podotypa -3 Placosponglldae TS DICTYOCERATIDA Plemspongla melobesloldes Biernnldae Sponglldae Chondroslldae Blemne tubulate -2 Hlppospongla lachne -3 D ChondrNls nucule -3 Neollbulerla nolltangereJ l Spongla obliqua -3 I Chondrosla collectrix -3 Desmacidonldae Thoreclldae Chondrosla renMormls -3 Holopsamma helwlgl-3 B Irclnle lellx -3 I AXlNELLlDA lrclnla stroblllna - TS Axlnellldae lotrochom blrofulefe -3 Smenospongle aurae -3 m PseudsxlnelU, lunaecharte -3 Tedanlldae Dysldeldee Ptlloceulls splculllera -3 Tedenla lgnls -3 Dysldea etharla - TW Pt/locaulls welpersl -3 Dysldea janlee TW Telchaxlnelle morchellum -3 Phorbssldee - 37.2+6.5 VERONGIDA Ulose ruelzlerl - TW Phorbas amaranthus TW Aplyslnldaa Raspallildae Myxillldae Aplyslne amherl-3 Ecfyoplasla lerox - TW Aplyslna ceulllormls -3 - Lissodendoryx lsodlcfyells -2 Agelesldae Aplysina llstularls -3 Ageles Clafhrodes -3 Ussodendoryx sigmata -2 Aplyslne lulve -3 Agelas conllera -3 Clathrlldae Aplyslne lacunosa -3 Agelas dlspar -3 Pandaros acanfhllollum -3 - Verongule glganfea -3 D Agelas Inequalls -3 Verongula rlglda -3 E Agelas sceptrum -3 Rhaphldophlus /un$erinus 3 - Aplyslnellldaa Rhaphldophlus venosus TW Agelas wledenmayerl -3 Pseudocemtlne cmssa -3 d-

0 10 20 30 0 10 20 30 0 10 20 30 TENSILE STRENGTH , N m -'X 10' TENSILE STRENGTH , N m'' X 105 TENSILE STRENGTH , N m " X 10'

Fig. 6. Tensile strength of the tissues of Caribbean sponges. The number of replicate samples is indicated after each species name. TS: too strong to measure, TW: too weak to measure TETRACTINOMORPHA l CERACTINOMORPHA CHORlSTlDA HOMOSCLEROPHORIDA HAPLOSCLERIDA Gaodlldae Hallclonldae Plaklnldae Erylus lormosus -3 - Helklona hoganhl-4 Geodla glbbarosa -3 Plekorfls angulosplculefus Callysponglldae Geodh nepfunl3 Plakorfls hellchondroldes -3 Celfyspongle lallax -l SPIROPHORIDA Plakorfls llfe -3 ce~fysponglapllclfera -4 Tellllldae Celfppngla vsglnalls -5 Clnachyra ellocleda -3 CERACTINOMORPHA Nlphelldae HADROMERIDA HALICHONDRIDA Amphlmedon comprews -3 Tethylldae Hallchondrlldae Amphlmedon erbra -4 Tefhya acflnla -3 Crfbmchallne vaSCUlUm -3 Hallchondrla melenodocla -3 Splraslrellldae Niphefes dlglfalls -3 Anfhoslgmalla varfens -3 Myrmeklodarme sfyx -3 Nlphefes erecla -3 Dlplasrrella megesfellafa - 3 - POECILOSCLERIDA Slphonodlcfyon coralllphagum -3 Spheclospongla ofhella -3 -- Mycalldae Petroslldae Xesfospngla mule -7 Spheclospongla vesparlum -3 - Mycale laevls -3 Oceanaplldae Splrastrella cocclnaa-2 Placosponglldae Mycele laxlsslma -3 Calyx podofypn -3 Plecospongla melobesloldes -3 - Blemnldae DICTYOCERATIOA Sponglldae Chondroslldae Bkrmna fubulefa -2 Hlppospongle lachne -3 Chondrllla nucula -4 Neollbularla nolllangere .3 Spongla obllqua -3 Chondrosla collectrlx 3 Desmacldonldae Chondrosla renllormls 3 Thoreclldee 0 lrclnle lellx -3 AXlNELLlDA Holopsamma hahvlgl -3 lrchla sfroblllna -3 Axlnellldae lofrochofa blrofulate -3 Smenospongla aurea -3 Pseudaxlnella luneechana -3 Tedanlldae Dysideldae Pflloceulls splculllera -3 Dysldea alherla -4 Pflloceulls walparsl-3 Tedanle lgnls -3 Dysldea lenlae -3 Telchaxlnella morchellum -3 Phorbasldae Ulosa ~etzlarl -3 VERONGIDA Phorbas amaranthus -5 Aplyslnldae Raspalllldee t Aplyslna archer1 3 Myrlllldee Ecfyoplesla lerox -5 Llssodendoryx lsodlcfyalls Aplyslna caulIIormIs -4 Agelasldae Aplyslna 11sful.rrs -3 Ageles clafhrodes -4 Llssodendoryx slgmafa -2 Aplyslna fulva -3 Agelas conllera -3 Clethrlldee Aplyslna Iacunos. 3 Ageles dlspar 3 Panderos ecanfhllollum -3 Verongufa glganfea 3 Agelas lnequalls -3 Verongula rlglda 3 Rhaphldophlus /unlperlnus -4 Ageles scepfrum 3 Aplyslnellldae Ageles wlsdsnmayerl -3 Rhephldophlus venosus -4 Pseud~~~raflnacraesa 0102030405060 L0 10 M 30 40 50 60 0 10 20 30 40 M 60 PROTEIN, mg ml" PROTEIN , mg ml-' PROTEIN , mg ml-'

Fig. 7 Protein content of the tissues )ICaribbean sponges. The number of replicate samples is indicated after each species name TETRACTINOMORPHA HOMOSCLEROMORPHA CERACTINOMORPHA CHORlSTlDA HOMOSCLEROPHORIDA HAPLOSCLERIDA Geodlldae Hallclonldae Erylus formosus -3 Plaklnldae Hallclone hogarthl -3 Geodle glbberosa -3 Plakortls angulospiculatus - Callysponglldae Geodla neptunl-3 Plakortls hallchondroldes -3 Cellyspongla fellax -1 SPIROPHORIDA - Cellyspongla pllclfera -3 Plakorlls llta -3 Tetlllldae Callyspongie vaglnalis -4 CERACTINOMORPHA Clnachyre elloclada -3 Nlphatldaa HADROMERIDA HALICHONDRIDA Amphlmedon compressa -3 Telhylldae Hallchondrlldae Amphlmedon erlne -3 Tethya acllnla -3 Crlbrochallne vasculum -3 Hellchondrle melanodocie -3 Splraslrellldae Niphares dlgllells -3 Anthoslgmelle varlans -3 Myrmekloderma styx -3 Nlphales erecta -3 Dlplestrella megastellata - 3 m POECILOSCLERIDA Slphonodlclyon corelllphagum Spheclospongla olhelle -3 Mycalldae Petroslldae Xestospongla muta -3 Spheclospongla vesparlum -3 -- Mycele laevls -3 Splraslrelle cocclnea -2 Oceanaplidae Placosponglldae Mycale laxlsslma -3 Celyx podotypa -3 Placospongla melobesloldes -3 Blernnldae DICTYOCERATIDA Chondroslldae Blemne tubulate -2 Sponglldee Chondrllla nucula -3 Hlppospongle lachne 3 Neoflb~larlenolllangere -3 Chondrosle collectrlx -3 Spongia obllque -3 Chondrosla renlformls -3 Desmacldonldae Thorectldae AXlNELLlDA Holopsamma helwlgl-3 lrcinla fellx -3 Axlnellldae lrcinla slroblllna -3 lotrochote blroluleta -3 Smenospongla aurea -3 Pseudaxlnelle lunaecharla -3 + Tedanlldae PTllocaulls splcullfera -3 D Dysldeldae Dysidee etherla -3 PNloceulls walpersl -3 Tedanla lgnls -3 Dysldea janlee -3 Talchaxlnelle morchellum -3 7- Phorbasldae Ulosa ruehlerl-3 VERONGIDA Phorbas amaranthus -3 Raspalllldae Aplyslnldae Ectyoplasla ferox -3 Myxlllldae Aplyslna archer1 3 Llssodendoryx lsodlctyalls Aplyslne caullformls -3 Agelasldae Aplyslna f/stular/s -3 Ageles clalhrodes -3 Llssodendoryx slgmata -2 Aplysina fulve -3 Ageles conlfera -3 Clathrlldae Aplyslne lacunose -3 Agelas dlspar -3 Verongula glganlea -3 Ageles lnequells -3 Pendaros ecanlhllollum -3 Verongula rlglda -3 Rhaphldophlus juniperinus Agebs sceptrum -3 Aplyslnellldae Agelas wledenmayerl-3 Rhaphldophlus venosus -3 Pseudocerallna crassa -3 I'''I''~I'~~,'~~/..I,.I,...,. 0 2 4 6 8 l01214 0 2 4 6 B101214 0 2 4 6 8 l01214 CARBOHYDRATE, mg rnl " CARBOHYDRATE, rng m1 -' CARBOHYDRATE, rng rnl"

Flg 8 Carbohydrate content of the tlssues of Car~bbeansponges The number of replicate samples IS lndlcated after each specles name TETRACTINOMORPHA HOMOSCLEROMORPHA CERACTINOMORPHA CHORlSTiDA HOMOSCLEROPHORIDA HAPLOSCLERIDA Geodildae Hallclonldae Plaklnidae Etylus lormosus -3 Hallclona hogarihl -4 Geodle glbberose -3 Plakorils angulosplculatus - 1 Callysponglldae Geodle neplunl-3 - Plekortls hellchondmldes -3 CeIIyspongIa fallex -1 SPIROPHORIDA - Callyspongln pllclla~-4 Plekortls llte -3 Tetlllldee Callyspongla veglnelk -5 CERACTINOMORPHA Clnechyre elloclede -3 Nlphatldae HADROMERIDA HALICHONDRIDA Amphlmedon comprese -3 Telhylldae Hallchondrildae Amphlmedon erlne -4 Jelhye acllnla -3 Crlbrochallna vesculum -3 Hallchondrle melenodocle -3 - Splraslrellldae Nlphales dlgllalls 3 -3 Myrmekloderme slyx -3 - Nlphetes erecla -3 Anlh~Slgm~ll~verlans Dlples~rellamegaste~iata - 3 - POECILOSCLERIDA Slphonodlclyon corelllphagum Spheclospon~leothella -3 Mycalldae Pelroslldae Xestospongle mule d Spheclospongle vesperlum 9 -m Mycale laevls -3 I. Oceanaplldae Splreslrelle cocclnea -2 Mycale lexlsslme -3 Placosponglldae - calyx podorype -3 Placospongle melobesloldes -3 Blernnldae DICTYOCERATIDA Spongildae Chondroslldae - Bbmne lubu$le -2 Hlppospongle lechne -3 Chondrllllle nucula -4 Neollbularla nolllengere -3 Spongle obllqua -3 Chondrosle collectrlx -3 Desmacldonldae Thorectldee Chondrosle renllormls -3 - Irclnla lellx -3 AXINELLIDA H0lop~e1nm8hehvlgl-3 D Irclnle slrobUlna -3 Axlnellldae lolrochole bl~lul8la-3 Smenospongla nuns -3 Pseudexlnella luneecheria -3 m Tedanlldae Dysldeldse Pllloceulls SplculMers -3 Tedanla lgnls -3 D Dysldea elherla -4 Pfnoceulls walpenl -3 m DysIdea janlm -3 Jelchexlnelle morchellum -3 Phorbasldae VERONGIDA Ul0Sd ~0lzlerl-3 Phorbas amaranthus -5 Aplyslnidae Raspallildee Myxlllldae Aplyslna ercherl-3 Ec~pleslalerox -5 Llssodendoryx Isodlclyslls -3 Aplyslna caulllormls -3 Agslasldee ApIysIne Ilslularls -3 Ageles clerhrodes -4 Llssodendoryx slgmala -2 I ApIyslna lulva -3 Ageles conllera -3 Clalhrlldaa Aplyslne lacunoss J Ageles dlsper -3 Penderos acan~h~fo~~um-3 Vemngula glgenlee J Ageles lnequells -3 Vemngula rlglde -3 Rhaphldophlus /unlperlnus -4 Ageles sceplrum -3 Aplyslnellldm Agelas wladenmeyerl -3 Rhephldophlus venosus -4 v Pseudocerellna crassa -3 1"'I""1"''I' " l'll'l'.'ll''''l.'' 0 10 20 30 0 10 20 30 ) 0 10 20 30 LIPID, rng ml" LIPID, rng ml" LIPID, rng ml"

Fig. 9. Lipid content of the tissues of Caribbean sponges. The number of replicate samples is indicated after each species name TETRACTINOMORPHA HOMOSCLEROMORPHA CERACTINOMORPHA CHORISTIDA HOMOSCLEROPHORIDA HAPLOSCLERIDA Geodlldae Hallclonldae Plakinldae Erylus lormosus -3 Hellclona hogerfhl -3 Plakorfls angulospiculafus Geodla glbberose -3 Callysponglldae Geodle nepfunl -3 Plakorfk hallchondroldes -3 Callyspongia fallax -1 SPIROPHORIDA Plakorlls Ill8 -3 Cellyspongla pllclfera -3 Cellyspongle v~glnalls-3 Tetlllldae CERACTINOMORPHA Clnechyre elloclede -3 Nlphatldae HADROMERIDA HALICHONDRIDA Amphlmedon compressa -3 Tethylldee Hallchondrlldae Amphlmedon erlna -3 Crlbrochallna vasculum -3 Tethya acflnle -3 HBlichondrle melenodocle -3 Niphetes dlglfells -3 Splraslrellldee Myrmkloderme sfyx -3 Anthoslgmeile varlans -3 Nlphefes erecte -3 Slphonodlcfyon corelllphegum Dlplestrells megasfallala - 3 POECILOSCLERIDA Petroslldae Spheclospongla orhella -3 Mycalldae Xestospongle mute 4 Spheclospongia vesparlum - ~ycelelaevls -3 Oceanaplldm Splraslrella cocclnaa -2 Mycale lexlsslma -3 calyx podofypa -3 Placosponglldae DICTYOCERATIDA Placospongle melobesloldes Blemnldae Blemna fubulela -2 Sponglldae Chondroslldae Hlppospongle lachna -3 Chondrllle nucule -3 Neoflbularla nollfangen, -3 Spongle obllqua -3 Chondrosle collecfrlx -3 Desmacldonldae Thorectldae Chondrosle renllormls -3 Holopsemma helwlgl -3 lrclnle fellx -3 AXlNELLlDA lrclnld stroblllne -3 Axinellldae lofrochofa blrotulefe -3 Smenospongle euree -3 Pseudaxlnelle luneecharle -3 Tedanlldae Dysideldae PfIIoceulls spicullfera -3 Tedanle lgnls -3 Dysldea etherle -3 Pflloceulls walprsl3 Dysidee jenlee -3 Telchaximlla morchellum -3 Phorbasldae VERONGIDA Uiose ruerzlerl -3 Phorbas emarenthus -3 Aplyslnldae Raspalllldee Myxlllldae Apfyslna archer1 -3 Ecfyoplasla lerox -3 Llssodendoryx lsodlcfyells 3 Apfyslna ceullformls -3 Agelasldae Aplyslna llstularls -3 Agebs clafhrodes -4 Llssodendoryx slgmete -2 Aplysine fulva -3 Ageles conllera -3 Clathrlldae Aplysine lecunose -3 Agelas dlspar -3 Panderos ecenfhlfolium -3 Vemngule gigenfee 3 Ageles Inequalis -3 Verongule rlglde -3 Rhaphldophlus lunlperlnus -3 Ageles sceptrum J Aplyslnellldae Agelas wledenmayeri -3 Rhaphldophlus venosus -3 0123456 Pseudocereflne crassa -3 0123456 L ENERGY CONTENT, kJ ml.' ENERGY CONTENT, kJ ml"

Fig. 10. Energy content of the tissues of Caribbean sponges. The number of replicate samples is indicated after each specles name 208 Mar Ecol Prog Ser 127: 195-211, 1995

bohydrate, or energy content (Fig. 12A, B, p > 0.05, arrangement of spicules in the prepared foods was t-test), but there was a significantly higher lipid con- haphazard, with points directed at all angles, from per- tent in the t~ssuesof chem~callydeterrent sponges pendicular to parallel to the surface. If arrangement (Fig. 12A, p = 0.003, t-test). was important to the defensive function of spicules, it might be expected that some intermediate level of deterrency would be observed when spicules were DISCUSSION improperly arranged in an assay food, but foods per- fused with spicules from each species were readily Do spicules deter sponge predators? consumed in each case. Moreover, we have subse- quently assayed pieces of the skeletons of A. clath- Although opaline spicules have long been thought to rodes and X. muta in which cellular material was play a role in defending demosponges from predators removed by treatment with mild bleach solutions, leav- (e.g. Hartman 1981), the results of this study suggest ing the spongin and spicule tracts intact, and these that they do not. Prepared foods containing volumetri- were similarly non-deterrent (Chanas 1995). At the cally equivalent concentrations of spicules did not same time, spicule morphologydid not appear to have deter feeding by fish in aquarium or field assays, any effect on palatability, because none of the spicule despite the fact that we chose species that have tissues types were deterrent, including oxeas (X. muta), acan- that are particularly rich in spicules. Some of the spe- thostyles (A. clathrodes), and spherasters (Chondrilla cies assayed have spicule tracts that run parallel to the nucula, Geodia neptuni) (Figs. 1 & 2). sponge surface so that the points are not directed out- To corroborate the lack of deterrency in field and ward (e.g. Neofibularia nolitangere, Xestospongia laboratory assays of sponge spicules, there was no muta), while others have a perpendicular arrangement relationship between the concentration of inorganic (, Ectyoplasia ferox; Zea 1987). The structural elements and the elaboration of chemical

012345678910 012345678910 MEAN PELLETS REJECTED MEAN PELLETS REJECTED

Flg. 11. Correlation of the deterrency of organic extracts with (A)protein, (B)carbohydrate, (C) lipid and (D)energy content of the tissues of 71 species of Canbbean sponges Chanas & Pawlik: Defenses of sponges. 11. Spicules

I PALATABLE I 20 - UNPALATABLE Fig. 12. Comparison of mean (+ SE) P=0003 protein, carbohydrate and lipid con- '- 15- tent (A) and energy content (B)of E the tissues of sponges that y~eld palatable and unpalatable crude Plo; organic extracts. The mean values of 20 palatable and 51 unpalatable 5 - sponges were compared in each case. There were no significant dif- ferences in the mean values for any 0 - comparison except for lipid content PROTEIN CARBOHYDRATE LlPlD ENERGY CONTENT

defenses. Ash content was used as a measure of struc- but that high-quality foods containing the same com- tural elements, whether as siliceous spicules (most spe- pounds at the same concentrations may be eaten. To cies) or incorporated sand grains (e.g. species in the address this concern, we analyzed the nutritional genera Dysidea, Hippospongia,and Spongia).Inverse quality of control assay foods used in this and the pre- relationships between the concentrations of structural vious study (Pawlik et al. 1995)and compared the val- and chemical defenses have been demonstrated for ues of protein, carbohydrate, lipid, and energy con- some marine algae (Hay et al. 1988) and octocorals tent to the mean values for sponge tissue determined (e.g. Harvell & Fenical 1989, see next paragraph), but in this study (Table 2). Aquarium assay food used in were not evident in the present study. this study compared favorably with sponge tissue in Previous investigations have found that calcitic scle- protein content, which is the nutritional component rites from the coenenchyme of alcyonacean and gorg- most likely to influence the effectiveness of a chemi- onacean corals deter the feeding of both generalist and cal defense (Duffy & Paul 1992).Therefore, it seems specialist predators (Gerhart et al. 1988, Harvell et al. unlikely that the results of feeding experiments in this 1988,VanAlstyne & Paul 1992, VanAlstyne et al. 1992, or the previous study (Pawlik et al. 1995) were influ- 1994).In light of these past studies, the results of the enced by the nutritional quality of the aquarium assay present investigation are surprising, given that soft food, but instead by the addition of spicules or organic coral sclerites are similar in size, morphology, and extracts. abundance to the spicules in the tissues of many spe- cies of sponges. One important difference may be in the composition of the structural elements: siliceous Do chemically undefended sponges have tissues that spicules are largely inert, while sclerites of calcium are tougher or less nutritious? carbonate may dissolve and alter the pH of an acidic gut. In this regard, the calcitic sclerites of octocorals The results of this study indicate that there is little may be acting more as an inorganic chemical defense difference in tissue toughness and nutritional quality than a structural defense, as has been suggested for between sponges that have palatable organic tissue calcified algal defenses against herbivores (Hay et al. extracts and those that have deterrent extracts. The 1994). Siliceous spicules pass through the guts of only significant difference was that deterrent sponges sponge-eating marine reptiles (Meylan 1988), fish had a higher mean concentration of lipid than palat- (Randall & Hartman 1968),and invertebrates (Biren- able species (Fig. 12A),but this did not translate into a heide et al. 1993)without obvious long-term ill effects, difference in the mean energy content of the tissues of and the same was noted for the wrasses used as assay the 2 groups. Assessments of food quality generally fish in the present investigation. use protein content as a key indicator (Duffy & Paul The relationship between the nutritional quality of 1992, Pennings et al. 1994);in the case of coral reef an assay food and the deterrent capacity of structural environments, nitrogen is generally considered to be elements or secondary metabolites is another impor- the limiting nutrient (Grigg et al. 1984),yet there was tant consideration. Recent work by Duffy & Paul no difference in the mean protein content of chemi- (1992)and Pennings et al. (1994)has demonstrated cally defended and undefended sponges. that low-quality assay foods containing secondary It is possible that one major source of protein found metabolites may be rejected by potential predators, in sponges may be unavailable to some generalist con- Mar Ecol Prog Ser 127: 195-211, 1995

sumers because it requires long periods of digestion. Florida, for their cooperation. We are grateful to the govern- The spongin skeleton of many demosponges, if suffi- ment of the Bahamas for permission to perform research in ciently condensed and cross-linked, is difficult to their territorial waters. The authors thank Emmett Duffy and 3 anonymous reviewers for their helpful comments on an ear- digest (Bjorndal1990, Meylan 1991). Hawksbill turtles, lier version of this paper. for example, are unable to fully digest the skeletons of some fibrous sponges (Meylan 1985, 1991). Sponge- eating fish, such as angelfish (Randall & Hartman LITERATURE CITED 1968), may have longer gut retention times, allowing Bergquist PR (1978) Sponges. Univ of California Press, Los spongin digestion, while other predatory fish, such as Angeles wrasses, may eliminate their gut contents before spon- Birenheide R, Amemiya S, Motokawa T (1993) Penetration gin fibers are digested. We have examined the gut and storage of sponge spicules in tissues and coelom of contents of several species of angelfish and found that spongivorous echinoids. Mar Biol 115:677-683 Bjorndal K (1990) Digestibility of the sponge ChondriUa samples from the foregut have clearly identifiable nucula in the green turtle, Chelonia mydas. Bull mar SCI spongin fragments, while hindgut samples do not. This 47567-570 situation may be analogous to that found among ter- Bradford MM (1976) A rapid and sensitive method for the restrial herbivores that digest cellulose (with the aid of quatification of microgram quantities of protein utlzing the principle of protein-dye binding. Analyt Biochem 72: microorganisms) by decreasing the rate of food pas- 248-254 sage through the gut (as in cows) or by passing food Chanas B (1995) Physical and chemical defenses of three through the gut repeatedly (as in rabbits). Caribbean sponges. MSc dissertation, Univ of North Car- If sponges that are chemically undefended do not olina, Wilrnington use structural or nutritional defenses as an alternative, Coley PD (1983)Herbivory and defensive characteristics of tree species in a lowland tropical forest. Ecol Monogr 53:209-233 how do they survive (and thrive, e.g. Callyspongia va- Dayton PK, Robilliard GA, Paine RT, Dayton LB (1974) Bio- ginalis and Niphates erecta) on Caribbean coral reefs? logical accommodation in the benthic community at One possibility is that chemically undefended sponges McMurdo Sound, Antarctica. Ecol Monogr 44:105128 grow faster than unpalatable species, perhaps because DeLaubenfels MW (1936) A discussion of the sponge fauna of the Dry Tortugas in particular, and the West Indies in gen- energy used for the production of secondary metabo- eral, with material for a revision of the families and orders lites is instead used for growth. Unlike most other of the Ponfera. Papers Tortugas Lab 30. Carnegie Inst invertebrates, sponges can survive and regenerate Wash Pub1467 after considerable tissue damage, to the point that Dubois M, Gilles KA, Hamilton JK, Rebers PA. Smith F (1956) some reef species appear to rely on storm-induced Colorimetric method for determination of sugars and related substances. Analyt Chem 28:350-356 fragmentation for reproduction (Wulff 1991).Palatable Duffy JE, Paul VJ (1992) Prey nutritional quality and the sponges may sustain non-fatal grazing by sponge-eat- effectiveness of chemical defenses against tropical reef ing fish and counter with faster growth. In the same fishes. Oecologia 90:333-339 vein, palatable sponges may allocate the energy other- Feeny P (1976)Plant apparency and chemical defense Recent Adv Phytochem 10:l-40 wise used to synthesize secondary metabolites to pro- Freeman N. Lindgren FT, Ng YS, Nichol AV (1957) Serum duce more offspring, and thereby experience higher lipid analysis by chromatography and infrared spec- rates of recruitment to offset the effects of spongivory. trophotometry. J biol Chem 277:449-464 Gerhart DJ, Rittschof D, Mayo SW (1988) Chemical ecology and the search for marine antifoulants. J chem Ecol 14: Acknowledgements Funding for this research was provided 1905-1917 by grants from the NOAA/National Undersea Research Pro- Grigg RW, Polovina JJ, Atkinson MJ (1984) Model of a coral gram (UNCW9414 to J.R.P.), from the UNCW Graduate reef ecosystem. 111. Resource I~mitation,community regu- School Summer Fellowship Program (to B.C.), and from the lation, fisheries yield and resource management. Coral National Science Foundation (OCE-9158065 and OCE- Reefs 3:23-27 9314145 to 3.R.P): the last of these inciuded support for the Hartman \MD (1981) Form and distribution 01 silica in use of the research vessels 'Columbus Iselin' and 'Seward sponges. In: Simpson TL, Volcani BE (eds) Silicon and Johnson' Although the second author takes full responsibility siliceous structures in biological systems. Springer-Verlag, for any taxonomic errors, we wish to thank Shirley Pomponl, New York, p 451-493 Mlchelle Kelly-Borges, and Cristina Diaz for their expert help Harvell CD, Fen~calW (1989) Chemlcal and structural de- with sponge idenhflcatlons. Several UNCW undergraduate fenses of Caribbean gorgonians (Pseudopterogorgia spp.): students provided valuable assistance, particularly Vince intracolony localization of defense. L~rnnolOceanogr 34: Bowman and Victoria Towne. Craig Dahlgren, Rob Toonen. 382-389 Greg McFall, Alicia Henrikson, David Swearingen, and Matt Hamell CD, Fenical W, Green CH (1988) Chemical and struc- Dunlap helped with sponge collections. Assistance with bio- tural defenses of Caribbean gorgonians (Pseudopterogor- chemical analyses were provided by James McClintock, gia spp.). I Development of an in situfeeding assay Mar Thomas Shafer, and David Padgett. B111 K~erprovided helpful Ecol Prog Ser 49:287-294 advice on biomechanics. We thank the captain and crew of Hay ME (1984) Patterns of f~shand urchin grazlng on the 'Columbus Iseh', the 'Seward Johnson', and the staff of Caribbean coral reefs: are previous results typlcal? Ecol- the NOAA/National Undersea Research Center at Key Largo, ogy 65:446-454 Chanas & Pawlik: Defenses of sponges 11. Spicules 21 1

Hay ME (1991) Fish-seaweed interactions on coral reefs: Comstock Publishing, lthaca, NY, p 124-150 effects of herbivorous fish and adaptations of their prey. Paul VJ. VanAlstyne KL (1988) Chemical defense and In: Sale PF (ed)The ecology of fishes on coral reefs. Acad- chemical variation in the Halimeda. Coral Reefs 6: emic Press, San Diego, p 96-1 19 263-269 Hay ME, Kappel QE, Fenical W (1994) Synergisms in plant Pawlik JR, Chanas B, Toonen RJ, Fenical W (1995) Defenses defenses against herbivores: interactions of chemistry, cal- of Caribbean sponges against predatory reef fish. I. ciflcat~on,and plant quality. Ecology 75:1714-1726 Chemical deterrency. Mar Ecol Prog Ser 127 183-194 Hay ME, Paul VJ, Lewis SM, Gustafson K,Tucker J, Trindell Pawlik JR, Fen~calW (1992) Chemical defense of Pterogorgia R (1988) Can tropical seaweeds reduce herbivory by anceps, a Caribbean gorgonian coral. Mar Ecol Prog Ser growing at night? Die1 patterns of growth, nitrogen con- 87:183-188 tent, herbivory, and chemical versus morphological Pennings SC, Pablo SR, Paul VJ, Duffy JE (1994) Effects of defenses. Oecologia 75233-245 sponge secondary metabolites in different diets on feed- Humann P (1989) Reef fish identification. New World Publica- ing by three groups of consumers. J exp mar Biol Ecol tions, Inc. Jacksonville, FL 180:137-149 Huston MA (1985) Patterns of species diversity on coral reefs. Randall JE (1983) Caribbean reef fishes. 2nd edn, revised. A Rev Ecol Syst 16:149-177 TFH Publications, Neptune City, NJ Kelly-Borges M, Pomponi S (1992) The simple fool's guide to Randall JE, Hartman WD (1968) Sponge feeding fishes of the sponge . Harbor Branch Oceanographic Institu- West-Indies. Mar Biol 1:216-225 tion, Ft Plerce, FL Rosenthal GA, Janzen DH (eds) (1979) Herbivores. Their Koehl MAR (1982) Mechanical design of spicule-reinforced interaction w~thsecondary plant metabolites. Academic connective tissue: stiffness. J exp Biol 983239-263 Press, New York Lewis JC, VonWallis E (1991) The function of surface sclerites VanAlstyne KL, Paul VJ (1992) Chemical and structural in gorgonians (Coelenterata, Octocorallia) Biol Bull 181: defenses in the sea fan Gorgonia ventalina: effects against 275-288 generalist and specialist predators. Coral Reefs 11: Littler MM, Taylor PR, Littler DS (1983)Algal resistance to her- 155-159 bivory on a Caribbean barrier reef. Coral Reefs 2:111-118 VanAlstyne KL. Wylie CR. Paul VJ (1994) Antipredator Mattson WJ, Levieux J, Bernard-Dagan C (eds) (1988) Mech- defenses in tropical Pacific soft corals (Coelenterata: Alcy- anisms of woody plant defenses against insects. Springer- onacea) 11. The relative importance of chemical and struc- Verlag, New York tural defenses in three species of Sinularia. J exp mar Biol McClintock JB (1987) Investigation of the relationship ECO~178:17-34 between invertebrate predation and biochemical compo- VanAlstyne KL, Wylie CR, Paul VJ. Meyer K (1992) sition, energy content, spicule armament and toxicity of Antipredator defenses in tropical Pacific soft corals (Coe- benthlc sponges at McMurdo Sound, Antarctica. Mar Biol lenterata: ) I.Sclerites as defenses agalnst gen- 94:479-487 eralist carnivorous fishes. Biol Bull 182:231-240 Meylan A (1985) The role of sponge collagens in the diet of Wiedenmayer F (1977)Shallow-water sponges of the western the hawksbill turtle (Eretmocl~elysirnbricata). In: Bairati Bahamas. Experentia Suppl 28. Birkhauser Verlag, Stutt- A, Garrone R (eds) Biology of invertebrate and lower ver- gart tebrate collagens. Plenum Press, New York, p 191-196 Wulff J (1991) Asexual fragmentation, genotype success, and Meylan A (1988) Spongivory in hawksbill turtles: a diet of population dynamics of erect branching sponges. J exp glass. Science 239:393-395 mar Biol Ecol 149:227-247 Meylan A (1991) Nutritional characteristics of sponges in the Wylie CR, Paul VJ (1989) Chemical defenses in three species diet of the hawksbill turtle, Eretmochelys imbricata. In: of Sinularia (Coelenterata, Alcyonacea): effects against Riitzler K (ed)New perspectives in sponge biology. Srnith- generalist predators and the butterflyfish Chaetodon uni- sonian Inst Press. Washington, DC, p 472-477 maculatus Bloch. J exp mar Biol Ecol 129:141-160 Paine RT (1964) Ash and calorie determinations of sponge Zar JH (1984) Biostatistical analysis, 2nd edn. Prentice-Hall, and opisthobranch tissues. Ecology 45:384-387 Englewood Cliffs Paul VJ (1992) Seaweed chemical defenses on coral reefs. In: Zea S (1987) Esponjas del Caribe Colombiano. Ed~torialCata- Paul V (ed) Ecological roles of marine natural products. logo Cientifico, Santa Marta, Colombia

Thisarticle was submitted to the editor Manuscr~ptfirst received: February 10, 1995 Revised version accepted: May 22, 1995