Journal of Sea Research 66 (2011) 215–221

Contents lists available at ScienceDirect

Journal of Sea Research

j ourna l homepage: www.e lsev ie r.com/ locate /seares

Intra-plant differences in seaweed nutritional quality and chemical defenses:Importance for the feeding behavior of the intertidal amphipodOrchestoidea tuberculata

Cristian Duarte ⁎, Karin Acuña, Jorge M. Navarro, Iván GómezInstituto de Ciencias Marinas y Limnológicas, Universidad Austral de Chile, P. O. Box 567, Valdivia, Chile

⁎ Corresponding author.E-mail address: cduarte@uach.cl (C. Duarte).

1385-1101/$ – see front matter © 2011 Elsevier B.V. Aldoi:10.1016/j.seares.2011.07.007

a b s t r a c t

a r t i c l e i n f o

Article history:Received 29 July 2010Received in revised form 7 July 2011Accepted 20 July 2011Available online 31 July 2011

Keywords:Feeding behaviorOrchestoidea tuberculataAbsorption efficiencySandy beachesPerformance

As a result of their morphological complexity, large macroalgae show intra-thallus variations in theirnutritional composition and secondary metabolite content, which influences the trophic ecology ofherbivorous invertebrates, and ultimately their fitness. In this study, we evaluated for the first time thevariability in nutritional quality (protein content, carbohydrates, lipids, and total organic matter), secondarymetabolites (phlorotannins), and structure (shape and toughness) between blades and stipes of themacroalgae Durvillaea Antarctica. Specifically, we looked at their effect on feeding preference, rate ofconsumption, absorption efficiency, and growth rate of the amphipod Orchestoidea tuberculata, one of themost abundant organisms on Chilean sandy beaches. Proteins, carbohydrates, total organic matter andphlorotannin contents were significantly higher in blades than in stipes. Preference experiments revealed thatthe amphipods preferred blades when fresh pieces of blades and stipes were offered at the same time. Similarresults were found when artificial food (in which structures of both parts of the alga were standardized) wasoffered, suggesting that shape and toughness of the two different parts of the alga did not influence preferencepatterns of O. tuberculata. Absorption efficiency of O. tuberculata was higher on blades compared to stipes.When the amphipods were kept with each of the algal parts separately (i.e. no choice), they consumed asignificantly higher amount of stipe, which suggests that O. tuberculata used food quantity to compensate forthe lower nutritional quality of stipes. The higher nutritional values of blades compared to stipes appears toexplain observed preference patterns by O. tuberculata. Phlorotannin content did not appear to inhibit bladeconsumption, suggesting that the nutritional quality of the food could be more important than chemicaldefense in determining food choice in O. tuberculata. Growth did not differ between the amphipodsmaintained with either blades or stipes (i.e. no choice), which is consistent with the hypothesis ofcompensatory feeding. To conclude, O. tuberculata can actively select specific parts of an alga and this selectionappears to be based on nutritional quality. The capacity for using different feeding strategies allowO. tuberculata, in some cases, to successfully exploit food types with different nutritional qualities.

l rights reserved.

© 2011 Elsevier B.V. All rights reserved.

1. Introduction

Marine algal characteristics such as nutritional quality, chemicaldefenses and morphology (Duffy and Hay, 1990; Poore and Steinberg,1999; Taylor and Brown, 2006) can influence the feeding choices ofinvertebrate algal consumers and, in turn, these food choices affect theirsurvival, growth and reproduction (e.g. Barile et al., 2004; Cruz-RiveraandHay, 2000a, 2001; Pennings et al., 1993). Becausemacroalgaehave alow nutritional content and a high proportion of non-digestiblestructural material (e.g. Gulati and DeMott, 1997, Mattson, 1980;Sterner and Hessen, 1994), herbivores have developed a range ofbehavioral and physiological strategies to meet their nutritional

requirements, such as preferential consumption of macroalgae withhigher nutritional value (e.g. Barile et al., 2004; Pennings et al., 1993), anincrease in the consumption rate of nutritionally poorer food items(compensatory feeding) (Cruz-Rivera and Hay, 2001), or an increase inabsorption efficiency (Simpson and Simpson, 1990).

Studies on the feeding ecology of macroalgal consumers havefocused mostly on evaluating the factors that promote or inhibit theconsumption of different species of macroalgae (e.g. Cruz-Rivera andHay, 2001; Duarte et al., 2010; Goecker and Kall, 2003; Jormalainen etal., 2001a; Lastra et al., 2008; Lyons and Scheibling, 2007). Howeverincreasing evidence indicates that within-alga variation of traits canalso be important to food choices and fitness of consumers. By virtueof their morphological complexity, many algae exhibit significantintra-thallus differences in their nutrient content (e.g. Cronin and Hay,1996; Westermeier and Gómez, 1996), secondary metabolite content(which may inhibit consumption by some herbivores) (e.g. Pansch et

216 C. Duarte et al. / Journal of Sea Research 66 (2011) 215–221

al., 2008; Steinberg, 1988; Targett and Arnold, 1998; Van Alstyne andPaul, 1990) and structure (shape and toughness) (Cronin and Hay,1996; Fairhead et al., 2005; Tuomi et al., 1989; Van Alstyne et al.,1999). Thus, herbivores can exploit these differences by selectivelyfeeding on different parts of algal tissues (Cronin and Hay, 1996;Fairhead et al., 2005; Jormalainen et al., 2001b; Pansch et al., 2008;Pavia et al., 2002; Taylor et al., 2002; Toth and Pavia, 2002; VanAlstyne et al., 2001). For example, Taylor et al. (2002) reported thattougher tissues at the base of the stipes of the brown alga Sargassumfilipendula C. Agardh, 1824, were less palatable to the amphipodAmphitoe longimana Smith compared to the top of the stipes andblades. In other studies, the same amphipod significantly preferyounger tissues of the macroalga Dictyota ciliolata Kûtzing, apparentlyin response to the higher content of chemical defenses in the oldertissues (Cronin and Hay, 1996).

On many sandy beaches, algal deposits represent the main foodresource for upper shore consumers (Colombini et al., 2000; Dugan etal., 2003). Despite the demonstrated importance of these trophicsubsidies to the food webs of several coastal ecosystems (seeBustamante et al., 1995; Bustamante and Branch, 1996; Rodríguez,2003) relatively little attention has been paid tomacrofaunal utilizationofmacrophyteson sandy beaches. The fewstudies on algal consumptionby sandy beach macrofauna have focused only in evaluating feedingpreference on different macroalgae species (see Adin and Riera, 2003;Lastra et al., 2008; Pennings et al., 2000) while preferences of theseorganisms for differentmacroalgal parts or tissue types has largely beenignored. In addition, unlike published studies for other environments,the factors that influence feedingbehavior (e.g. nutrient content) and itsconsequences on growth rate and fitness of sandy beach macrofauna,have received far less attention (but see Duarte et al., 2010).

Thepurposeof this studywas to evaluate the feedingpreferences andperformance (growth) of the intertidal talitrid amphipod Orchestoideatuberculata (Nicolet) on stipes and blades of the brown alga Durvillaeaantarctica (Chamisso) Hariot. O. tuberculata is the dominant algalconsumer in terms of abundance and biomass in the upper intertidalzone of sandy beaches in southern-central Chile (Jaramillo et al., 2000,2006; Jaramillo and McLachlan, 1993), and D. antarctica is its preferredfood resource (Duarte et al., 2008, Duarte et al., 2010). D. antarcticaallocates N90% of its biomass to blades, where it concentratesreproductive and major metabolic functions (Cheshire and Hallam,1988; Westermeier et al., 1994). This alga therefore represents a highlyvariable food source for its consumers. In order to determine ifnutritional status and concentration of chemical deterrents along thethallus influence the feedingbehavior ofO. tuberculata, we evaluated thedifferences in concentrations of proteins, lipids, carbohydrates, totalorganic matter, and phlorotannins (a type of phenolic compound foundin brown algae) between blades and stipes. Moreover, we also assesseddifferences in the shape and toughness of these structures. Morespecifically, we sought to answer the following questions: i) does theamphipod O. tuberculata prefer feeding on blades or stipes? ii) doesnutrient content, thallus structure, and phlorotannin content influencethe feeding preferences and consumption rates of this amphipod?iii) does compensatory feeding occur when amphipods are offered withlowquality food? iv) howdoes the absorption efficiency ofO. tuberculatafeeding on different parts of the alga differ? v) does the amphipodexhibit a differential growth pattern when fed separately with eitherblades or stipes (i.e. no choice?). We discuss the results in relation todifferent feeding strategies shown by herbivorous invertebratessupplied with foods of different palatability.

2. Materials and methods

2.1. Sampling of experimental animals

We collected adult individuals of O. tuberculata by hand from theintertidal zone of the sandy beach at Calfuco, on the Valdivian coast,

South-Central Chile (ca. 39° S) during the fall 2008. The amphipodswere kept in moist sand for transport to the laboratory, where theywere transferred to plastic boxes with perforated lids (for airexchange) and a layer of damp sand. All individuals were maintainedwithout food for 48 h prior to the start of the experimental trials inorder to avoid the influence of past diet on feeding behavior (e.g.Pennings et al., 1993) and to eliminate the possibility that prior gutcontents could influence the estimation of the absorption efficiencyfor each macroalgal part.

2.2. Analysis of food preference

2.2.1. Fresh algaeWe collected D. antarctica individuals from the shallow and rocky

intertidal zone next to the sandy beach at Calfuco and transported themto the laboratory where they were immediately used in the preferenceexperiment. To determine food preferences of O. tuberculata, wesimultaneously offered pieces of a similar size (approximately 4 g onaverage) and volume of blades and stipes. Experimental animals wereplaced in 10 cm diameter petri dishes with perforated lids (to allow airexchange). These dishes were then placed in a plastic box,40×30×20 cm with a 5 cm deep layer of moist sand, to maintain aconstant and appropriate humidity. The experiment ran for 24 h in atemperature-controlled environmental chamber at 20 °Cwith a naturallight/dark cycle.

We used five replicates (i.e. five petri dishes), each containing fiveexperimental animals and pieces of blades and stipes. In addition,each replicate was associated with a control dish that contained onlyalgae, which we used to estimate weight changes in the absence ofamphipod feeding (Roa, 1992). Before starting the experiments, algalpieces were gently blotted and weighed on an analytical balance(precision ±0.0001 g). At the end of the experimental run we blottedand reweighed the pieces of experimental and control algae todetermine mass changes during the experiment. To determine thechange in mass, we subtracted the final weight of the experimentalalgae from the initial weight. Finally, from the change in mass of eachexperimental alga, we subtracted the change in mass of itscorresponding control replicate to eliminate variation in mass thatwas not related to consumption (see Roa, 1992; Silva et al., 2004):

Einitial–Efinalð Þ– Cinitial–Cfinalð Þ = consumption

2.2.2. Artificial foodIn order to evaluate the possible influence of the characteristics of

algal structure (i.e. shape and toughness) on palatability to amphipods,separate agar pelletswith algal tissuewere prepared for each part of thealga, following the methodology of Hay et al. (1994). Fresh pieces fromboth parts of the algawere oven-dried at 40 °C to a constant weight andthen ground up with a pestle and mortar into a fine, homogeneouspowder. The ground tissue was mixed with agar to produce pelletswith an algal concentration of 0.15 g per gram of food. This mix wasimmediately poured in a plastic cuvette and subdivided intoreceptacles measuring 15×15×15 mm. Once the pellets solidified,pieces averaging 1 g from each part of the alga were simultaneouslyoffered to the amphipods following the same protocol describedearlier for fresh algae.

2.3. Food consumption rate

Given that some herbivores can increase their consumption rate tocompensate for the low quality of available food (Cruz-Rivera andHay, 2001), we evaluated the consumption rate of O. tuberculataseparately (i.e. a no choice experiment) for each part of the alga. Asdescribed above, five replicates and associated controls were used foreach experimental treatment. The experiments were maintained for

217C. Duarte et al. / Journal of Sea Research 66 (2011) 215–221

24 h under the same conditions as the food preference experiments.The rate of food consumption was calculated as the loss of freshmaterial from the alga offered to the amphipods, following the samemethodology outlined for the food preference experiments.

2.4. Absorption efficiency

Absorption efficiency was measured with the method described byConover (1966),which is based on the relationship between organic andinorganic matter values of ingested food and fecalmaterial. This methodassumes that the absorption process affects only the organic portion ofthe food. Absorption efficiencywas calculated as: AE=[(F′−E′)/(1−E′)F′]∗100, where: AE=Absorption efficiency expressed as percentage,F′=Proportion of organic matter in the food and E′=Proportion oforganic matter in the feces.

To obtain fecal pellets, groups of 5 amphipods were maintained inpetri dishes with fragments of blades or stipes. Each of the treatments(i.e. blades or stipes) was replicated five times. The experimentalplates were maintained under the same conditions described forconsumption experiment. We collected the produced feces every 12 hand froze them until analysis; at the same time each piece of alga wasremoved and replaced with fresh fragments. The experiments run for4 days. To determine percent organic matter, feces were dried at 60 °Cfor 2 days, incinerated in a muffle furnace at 500 °C for 4 h, and thenreweighed. The same methodology was used to determine thepercent organic matter in the different algal treatments (fivereplicates for each portion).

2.5. Growth rate

To evaluate the effect of different parts of D. antarctica on thegrowth rate of O. tuberculata, one individual (approximately 200–300 mg) was placed with either a piece of blade or stipe in a dish(identical to those used in the previous experiment). The twotreatments (i.e. each part of the alga) were replicated 12 times each.The algal fragments weighing approximately 2 to 4 g were replaceddaily with fresh pieces. Based on previous growth studies on thisspecies (Duarte et al., 2010) and other talitrid amphipods (Lastraet al., 2008), that detected changes in growth over a 7-day span,experiments run 7 days. At the beginning and end of the experiments,we gently dried and weighed each amphipod on an analytical balanceto the nearest 0.0001 g. Amphipod growth was calculated as thedifference between final and initial weight.

2.6. Food analysis

To determine the differences in quality between the different partsof the alga, we measured the concentration of proteins, lipids,carbohydrates, total organic matter (methodology described above)and phenolic compounds (hereafter referred to as phlorotannins, VanAlstyne, 1995) in triplicate (from three independent algal tissuesamples), using dry (40 °C) and finely groundmaterial. It is importantto note that phlorotannin estimates can be affected by oven-dryingthe tissues. Because of logistical problems, we could not freeze-drythese plants. However, we compared estimates of phlorotannins usingboth methods and obtained concentration values within the samerange; i.e. both methods produced similar results.

To quantify protein content of each part of the alga, we used thebicinchoninic acid method (BCA) from Pierce (BCA Protein Assay Kit)using bovine albumin serum as a standard. Samples were mixed withSDS (0.5%), sonicated for 1.5 min and centrifuged at 5500 rpm for35 min. The supernatant was incubated with BCA at 45 °C for 30 min.Protein concentration was determined colorimetrically by estimatingthe absorbance at 562 nm.

To determine lipid content, we used the gravimetric proceduredeveloped by Bligh and Dyer (1959)modified from Folch et al. (1957).

Lipids were extracted with chloroform-methanol from previouslyweighed tissues (50 mg dry weight) and centrifuged at 3500 rpm for15 min. The lower phase, corresponding to lipids, was extracted,placed in glass containers, dried at 50 °C for 5 h andweighed. We thencalculated total lipid content of the specimens as the difference inweight between the total sample and the lipid fraction.

We determined total carbohydrate for weighed samples (10 mg),using the phenol-sulphuric acid method of Dubois et al. (1956), afterextraction by boiling in 5% trichloroacetic acid (TCA) containing 0.1%silver sulfate (Barnes and Heath, 1966). Carbohydrate was estimatedfrom absorbance at 490 nm, using glucose as a standard.

To determine the total content of phlorotannins, we used thetechnique from Folin–Ciocalteau (modified by Nurmi et al., 1996)with phloroglucinol as a standard. We use the term phlorotanninsbecause brown algae are not known to contain other polyphenols(Targett and Arnold, 1998).

2.7. Data analysis

We evaluated food preference experiments with fresh andartificial food using a paired t-test (Zar, 1999). Consumption rate,absorption efficiency and growth of O. tuberculata were comparedusing one-way ANOVA (Zar, 1999). We evaluated differences innutritional characteristics and phlorotannin content in the differentparts of alga using one-way ANOVA. The assumptions of normalityand homocedasticity were evaluated with Kolmogorov–Smirnov andBartlett tests, respectively. All statistical analyses were performedusing Statgraphics 2.0.

3. Results

3.1. Food analysis

Proteins, carbohydrates and total organic matter content in theblades were 1.6, 3.2 and 1.2 times higher respectively than in thestipes (one-way ANOVA, proteins: F1, 4=33.02, pb0.05; carbohy-drates: F1, 4=5316. 26, pb0.05; organic matter: F1, 8=47.13, pb0.05)(Fig. 1a, c, d). Nonetheless, lipid content did not differ significantlybetween thallus parts (one-way ANOVA, F1, 4=2.53, pN0.05, Fig. 1b).Blades contained higher concentrations of phlorotannins (one-wayANOVA, F1, 4=11.19, pb0.05, Fig. 1e) which was 1.4 times higherthan in stipes.

3.2. Food experiments

When fresh pieces from both parts of the alga were offeredsimultaneously, O. tuberculata consumption of blades was approxi-mately 11 times greater than that of stipes (paired t-test, t4=6.30,pb0.05, Fig. 2a). Similar results were found with reconstituted, agar-based food where consumption of blades was 6.8 times that of stipes(paired t-test, t4=20.53, pb0.05, Fig. 2b). Consumption rate of stipeswas 1.2 times higher than that for blades (one-way ANOVA, F1, 8=7.08,pb0.05, Fig. 2c) for amphipods maintained with a single food type (i.e.no choice).

The absorption efficiency of O. tuberculata with blades was 1.2times higher than with stipes (one-way ANOVA, F1, 8=30.03, pb0.05,Fig. 3). The average growth rate of O. tuberculata did not differsignificantly between food type (one-way ANOVA, F1, 22=0.95,pN0.05, Fig. 4).

4. Discussion

This study evaluates for the first time patterns of feedingpreference, ingestion rate, food absorption and growth for an algalconsumer on sandy beaches feeding on different parts of an alga, andhow these patterns relate to the morphological and chemical

Fig. 1. Content of proteins (a), lipids (b), carbohydrates (c), total organic matter (d) and phlorotannins (e) in stipe and blade of D. antarctica. The bars correspond to mean % dryweight (+1 sd) and P values are from ANOVA test comparing stipes and blades.

218 C. Duarte et al. / Journal of Sea Research 66 (2011) 215–221

characteristics of each part of the alga. O. tuberculata showedpreferences by different parts of D. antarctica, with blades preferredover stipes (Fig. 2a). In other consumers, preferences for differenttissues within individual alga have been linked to differences instructure (shape and toughness), nutritional quality, and theconcentration of chemical defenses in tissues (Cronin and Hay,1996; Jormalainen et al., 2001b; Pansch et al., 2008; Pavia et al.,1999; Taylor et al., 2002).

Algal morphology and toughness have been shown to influencefeeding preference of grazers (Pansch et al., 2008; Pennings et al.,1998; Pennings and Paul, 1992). For example, Pansch et al. (2008),suggested that toughness was the most important factor in explainingwhy the amphipod Parhyalella penai Pérez-Schultheiss and Crespo2008 preferred vegetative blades over reproductive blades of thebrown alga Macrocystis integrifolia Bory 1826. We found no evidenceto suggest that the feeding preference of O. tuberculata for blades wasinfluenced by structure, because when morphology and toughness ofboth parts of the algawere standardized in agar-based food, amphipodsstill preferred blades (Fig. 2b). Similar results were recently reported byDuarte et al. (2010)who found that preference patterns ofO. tuberculataamong three species of macroalgae were not influenced by theirstructure.

Because nitrogen concentration is usually considered the limitingnutrient for consumers of plants and algae (Galán Jiménez et al. 1996;Mattson, 1980; Sterner and Hessen, 1994), plant protein content isregarded as a good measure of the nutritional quality. Following thisgeneral assumption, those algae or parts of an algawith higher protein

content should be more valuable for amphipods (e.g. Barile et al.,2004; Cruz-Rivera and Hay, 2003). Our results supported thisexplanation given that O. tuberculata fed preferentially on blades inboth experiments (i.e. with fresh tissue and with agar-based food),the part of the alga with the highest protein concentrations (Fig. 1a).Moreover, blades also contained higher concentrations of solublecarbohydrates (Fig. 1c), suggesting that these nutrients could alsoplay an important role in feeding preferences of herbivorousconsumers, as recently proposed by Jormalainen et al. (2001a). Thehigher nutrient content (proteins and carbohydrates) and totalorganic matter for blades, as well as the higher absorption efficiencydisplayed by O. tuberculata when feeding on this part of the alga,suggest that blades could be a better food resource (see below)compared to the stipes of the macroalga D. antartica, perhapsexplaining why this species feeds preferentially on blades.

Phlorotannins are chemical defenses that inhibit consumption ordiminish the absorption efficiency of some herbivores (Boettcher andTargett, 1993; Hay, 1996; Jormalainen et al., 2005; Pavia and Toth,2000; Steinberg and Van Altena, 1992). Within-plant differences inthe concentration of these chemical defenses (e.g. Van Alstyne et al.,1999) have been proposed as key determinant of feeding preferencein herbivorous invertebrates (Cronin and Hay, 1996; Fairhead et al.,2005; Macaya et al., 2005; Pavia et al., 2002; Taylor et al., 2002, VanAlstyne et al., 1999). For example, Pavia et al. (2002) determined thatphlorotannins significantly influenced feeding preference of thegastropod Littorina obtusata (L.) on different parts of the brown algaAscophyllum nodosum (L.), inhibiting consumption of tissues with

Fig. 2. Feeding preference of O. tuberculata between stipe and blade of D. antarctica basedon fresh alga (a), or artificial food (b) and consumption rate on each part of the alga testedindividually (no choice) (c). The bars correspond to means (+1 sd) and P values are frompaired t-test (a and b) and ANOVA test (c) comparing stipe and blade.

Fig. 4. Growth rate of O. tuberculata on stipe and blade of D. antarctica. The barscorrespond to means (+1 sd) and P value is from ANOVA test comparing stipe andblade.

219C. Duarte et al. / Journal of Sea Research 66 (2011) 215–221

higher concentrations of chemical defenses. In contrast, Jormalainenet al. (2005) found that phlorotannins did not deter feeding by theisopod Idotea baltica (Pallas), but reduced its assimilation efficiency.Our study suggests that phlorotannins did not negatively affect foodpreference or absorption efficiency, given that blades, the preferred foodfor O. tuberculata and on which this amphipod reached its highestabsorption efficiency, exhibited higher concentrations of chemicaldefenses (Fig. 1e). This inconsistency could mean that O. tuberculatahas evolved the ability of utilizing foods containing phlorotannins, asreported for other algal consumers (Jormalainen et al., 2005; Macaya

Fig. 3. Absorption efficiency (%) of O. tuberculata on stipe and blade of D. antarctica. Thebars correspond to means (+1 sd) and P value is from ANOVA test comparing stipe andblade.

and Thiel, 2008; Rothäusler et al., 2005; Van Alstyne et al., 2001) orbecause phlorotannin concentration in both algal treatments were verylow (about 1% by dry mass) and therefore ineffective as an anti-herbivore compound. However, the phlorotannins content in our studywas not independent of food quality; therefore, these conclusionsshould be viewed with caution.

O. tuberculata feed on detached D. antarctica stranded on thebeach, which can either be fresh or in decomposing; thus, theirchemical status (e.g. chemical defenses and nutritional quality) maydiffer from attached individuals and therefore their palatability toherbivores may also differ (Rothäusler et al., 2005). For example,Rothäusler and Thiel (2006) reported that detached Lessonianigrescens (Bory) became more palatable to the amphipod Parhyalellaruffoi (Lazo-Wasem and Gable) 12 days after detachment, as a resultof the loss of chemical defenses. Therefore, future studies on temporalchanges in chemical characteristics and palatability of strandedmacroalgae are necessary to better understand herbivore feedingpatterns and the consequences for their growth and fitness.

Evaluation of food quality is fundamental to understandingthe relationship between preference and performance of grazers(Cruz-Rivera andHay, 2000b; Hay, 1996; Jormalainen et al., 2001a). Apositive relationship between preference and performance impliesthat the preferred food has higher quality for the grazer. However,the capacity of some species to increase the consumption orabsorption efficiency of less nutritious food (i.e. nutritional compen-sation, e.g. Cruz-Rivera andHay, 2000b; Simpson and Simpson, 1990)can significantly alter this relationship (Cruz-Rivera and Hay, 2001;Stachowicz and Hay, 1996). The performance consequences ofconsuming a single food type were not related to feeding preference,because O. tuberculata significantly preferred blades over stipes.However, the growth rate of the amphipods did not differ significantlybetween the two different food items (Fig. 4). The results of this studysuggest that the increase in feeding rate (and not absorption efficiencyincrease) by O. tuberculata allowed it to maintain growth on stipes, thealgal part with the lower nutritional value (Fig. 1). Previous studiesinferred that the increase in consumption rate is a physiologicaladaptation to compensate for low food quality (e.g. Cruz-Rivera andHay, 2000a; Cruz-Rivera andHay, 2001; Stachowicz andHay, 1996) andproposed as a strategy for several algal consumers (e.g. Poore andSteinberg, 1999). For example, Cruz-Rivera and Hay (2001) observedthat the amphipod Amphitoe longimana could successfully maintain itsfitness on algae differing in nutritional quality by adjusting its feedingrate. Although increasing ingestion rate appears to be advantageous forO. tuberculata, allowing it to compensate for nutritionally inferior fooditems when more palatable algal parts are unavailable, this behavior isnot always used.Duarte et al. (2010), usingmacroalgaewith contrastingnutritional content, found that O. tuberculata did not respond to lowquality food by increasing its feeding rate. The factors responsible for

220 C. Duarte et al. / Journal of Sea Research 66 (2011) 215–221

these different responses are unclear, but may include physical andphysiological constraints (see Cruz-Rivera and Hay, 2001 for details).

5. Conclusions

This study indicates that O. tuberculata can actively select betweendifferent parts of an alga and this choice appears to be based onnutritional quality. The concentration of secondary metabolites(phlorotannins) does not apparently affect feeding preference orabsorption efficiency. The ability to use different feeding strategiesallows O. tuberculata, under some circumstances, to successfullyexploit food types with contrasting nutritional quality. Future studiesmust evaluate the relationship between feeding behavior and fitnessin order to better understand and predict the feeding ecology of theseorganisms.

Acknowledgments

The technical assistance of Marcela Oróstegui during phlorotanninsanalyses is fully appreciated. This study was supported by CONICYT-CHILE (Proyecto FONDECYT no.3085 005 to C.D. and 1060503 to I.G.).

References

Adin, R., Riera, P.R., 2003. Preferential food source utilization among strandedmacroalgae by Talitrus saltator (Amphipod, Talitridae): a stable isotopes study inthe northern coast of Brittany (France). Estuar. Coast. Shelf S. 56, 91–98.

Barile, P.J., Lapointe, B.E., Capo, T.R., 2004. Dietary nitrogen availability in macroalgaeenhances growth of the sea hare Aplysia californica (Opisthobranchia: Anaspidea).J. Exp. Mar. Biol. Ecol. 303, 65–78.

Barnes, H., Heath, J., 1966. The extraction of glycogen from marine invertebrate tissues.Helgoland. Wiss. Meer. 13, 115–117.

Bligh, E.G., Dyer, W.J., 1959. A rapid method of total lipid extraction and purification.Can. J. Biochem. Physiol. 37, 911–917.

Boettcher, A.A., Targett, N.M., 1993. Role of poliphenolic molecular size in reduction ofassimilation efficiency in Xiphister mucosus. Ecology 74, 891–903.

Bustamante, R.H., Branch, G.M., 1996. The dependence of intertidal consumers on kelp-derived organic matter on the west coast South Africa. J. Exp. Mar. Biol. Ecol. 196,1–28.

Bustamante, R.H., Branch, G.M., Eeekhout, S., 1995. Maintenance of an exceptionalgrazer biomass on South African intertidal shores: trophic subsidy by subtidalkelps. Ecology 76, 2314–2329.

Cheshire, A.C., Hallam, N.D., 1988. Morphology of the southern bull-kelp (Durvillaeapotatorum, Durvilleales, Phaeophyta) from King Island (Bass Strait, Australia). Bot.Mar. 31, 139–148.

Colombini, I., Aloia, A., Fallaci, M., Pezzoli, G., Chelazzi, L., 2000. Temporal and spatial useof stranded wrack by the macrofauna of a tropical sandy beach. Mar. Biol. 136,531–541.

Conover, R.J., 1966. Assimilation of organic matter by zooplankton. Limnol. Oceanogr.11, 338–345.

Cronin, G., Hay, M.E., 1996.Within-plant variation in seaweed palatability and chemicaldefenses: optimal defense theory versus the growth-differentiation balancehypothesis. Oecologia 105, 361–368.

Cruz-Rivera, E., Hay, M.E., 2000a. Can quantity replace quality? Food choice,compensatory feeding, and fitness of marine mesograzers. Ecology 81, 201–219.

Cruz-Rivera, E., Hay, M.E., 2000b. The effects of diet mixing on consumer fitness:macroalgae, epiphytes, and animal matter as food for marine amphipods. Oecologia123, 252–264.

Cruz-Rivera, E., Hay, M.E., 2001. Macroalgal traits and the feeding and fitness of anherbivorous amphipod: the roles of selectivity, mixing, and compensation. Mar.Ecol. Prog. Ser. 218, 249–266.

Cruz-Rivera, E., Hay, M.E., 2003. Prey nutritional quality interacts with chemicaldefenses to affect consumer feeding and fitness. Ecol. Monogr. 73, 483–506.

Duarte, C., Jaramillo, E., Contreras, H., 2008. Macroalgas varadas sobre la superficie deuna playa arenosa del sur de Chile: preferencias alimentarias y de hábitat dejuveniles y adultos de Orchestoidea tuberculata (Nicolet), (Amphipoda, Talitridae).Rev. Chil. Hist. Nat. 80, 69–81.

Duarte, C., Navarro, J.M., Acuña, K., Gómez, I., 2010. Preferences of the sandhopperOrchestoidea tuberculata: the importance of algal traits. Hydrobiologia 651,291–303.

Dubois, M., Gilles, K.A., Hamilton, J.K., Rebers, P.A., Smith, F., 1956. Colorimetric methodfor determination of sugars and related substances. Anal. Chem. 29, 350–356.

Duffy, J.E., Hay, M.E., 1990. Seaweed adaptation to herbivory. BioScience 40, 368–375.Dugan, J.E., Hubbard, D.M., McCrary, M.D., Pierson, M.O., 2003. The response of

macrofauna communities and shorebirds to macrophyte wrack subsides onexposed sandy beaches of southern California. Estuar. Coast. Shelf S 58s, 25–40.

Fairhead, V.A., Amsler, Ch.D., McClintock, J.B., Baker, B.J., 2005. Within-thallus variationin chemical and physical defences in two species of ecologically dominant brownmacroalgae from the Antarctic Peninsula. J. Exp. Mar. Biol. Ecol. 332, 1–12.

Folch, J., Lees, M., Sloane-Stanley, G.H., 1957. A simple method for the isolation andpurification of total lipids from animal tissues. J. Biol. Chem. 193, 265–275.

Galán Jiménez, E., Hauxwell, J., Heckscher, E., Rietsma, C., Valiela, I., 1996. Selection ofNitrogen-Enriched Macrolagae (Cladophora vagabunda and Gracilaria tikvahiae) bythe Erbivorous Amphipod Microdeutopus gryllotalpa. Biol. Bull. 191, 323–324.

Goecker, M.E., Kall, S.E., 2003. Grazing preferences of marine isopods and amphipods onthree prominent algal species of the Baltic Sea. J. Sea Res. 50, 309–314.

Gulati, R.D., DeMott, W.R., 1997. The role of food quality for zooplankton: remarks onthe state-of-the-art, perspectives and priorities. Freshw. Biol. 38, 753–768.

Hay, M.E., 1996. Marine chemical ecology: what is known and what is next? J. Exp. Mar.Biol. Ecol. 200, 103–134.

Hay, M.E., Kappel, Q.E., Fenical, W., 1994. Synergisms in plant defenses againstherbivores: interactions of chemistry, calcification, and plant quality. Ecology 75,1714–1726.

Jaramillo, E., Mclachlan, A., 1993. Community and population responses of themacrofauna to physical factors over a range of exposed sandy beaches in south-central Chile. Estuar. Coast. Shelf S. 37, 615–624.

Jaramillo, E., Duarte, C., Contreras, H., 2000. Sandy beach macrofauna from the coast ofAncud, Isla de Chiloé, southern Chile. Rev. Chil. Hist. Nat. 73, 771–786.

Jaramillo, E., De La Huz, R., Duarte, C., Contreras, H., 2006. Algal wrack deposits andmacroinfaunal arthropods on sandy beaches of the Chilean coast. Rev. Chil. Hist.Nat. 79, 337–351.

Jormalainen, V., Honkanen, T., Heikkila, N., 2001a. Feeding preferences and perfor-mance of a marine isopod on seaweed hosts: costs of habitat specialization. Mar.Ecol. Prog. Ser. 220, 219–230.

Jormalainen, V., Honkanen, T., Hemmi, A., Mäkinen, A., Vesakoski, O., 2001b. Why doesherbivore sex matter? Sexual differences in utilization of Fucus vesiculosus by theisopod Idotea baltica. Oikos 93, 77–86.

Jormalainen, V., Honkanen, T., Vesakoski, O., Koivikko, R., 2005. Polar extract of thebrown alga Fucus vesiculosus (L.) reduce assimilation efficiency but do not deter theherbivorous isopods Idotea baltica (Pallas). J. Exp. Mar. Biol. Ecol. 317, 143–157.

Lastra, M., Page, H.M., Dugan, J.E., Hubbard, D.M., Rodil, F., 2008. Processing ofallochthonous macrophyte subsidies by sandy beach consumer: estimates offeeding rates and impacts on food resources. Mar. Biol. 154, 163–174.

Lyons, D.A., Scheibling, R.E., 2007. Effect of dietary history and algal traits of feeding rateand food preference in the green sea urchin Strongylocentrotus droebachiensis.J. Exp. Mar. Biol. Ecol. 349, 194–204.

Macaya, E.C., Thiel, M., 2008. In situ tests on inducible defenses in Dictyota kunthii andMacrocystis integrifolia (Phaeophyceae) from the Chilean coast. J. Exp. Mar. Biol.Ecol. 354, 28–38.

Macaya, E., Rothäusler, E., Thiel, M., Molis, M., Wahl, M., 2005. Induction of defenses andwithin-alga variation of palatability in two brown algae from the northern-central coastof Chile: effect of mesograzers and UV radiation. J. Exp. Mar. Biol. Ecol. 325, 214–227.

Mattson, W.J., 1980. Herbivory in relation to plant nitrogen content. Annu. Rev. Ecol.Syst. 11, 119–161.

Nurmi, K., Ossipov, V., Huakioja, E., Pihlaja, K., 1996. Variation of total phenolic contentand individual low-molecular-weight phenolics in foliage of mountain birch trees(Betula pubescens ssp. tortuosa). J. Chem. Ecol. 22, 2023–2040.

Pansch, C., Gómez, I., Rothäusler, E., Veliz, K., Thiel, M., 2008. Species-specific defensestrategies of vegetative versus reproductive blades of the Pacific kelp Lessonianigrescens and Macrosystis integrifolia. Mar. Biol. 155, 51–62.

Pavia, H., Carr, H., Åberg, P., 1999. Habitat and feeding preferences of crustaceanmesoherbivores inhabiting the brown seaweed Ascophyllum nodosum (L.) Le Jol.and its epiphytic macroalgae. J. Exp. Mar. Biol. Ecol. 236, 15–32.

Pavia, H., Toth, G., 2000. Inducible chemical resistance to herbivory in the brownseaweed Ascophilum nodosum. Ecology 81, 3212–3225.

Pavia, H., Toth, G.B., Åberg, P., 2002. Optimal defense theory: elasticity analysis as a toolto predict intraplant variation in defenses. Ecology 83, 891–897.

Pennings, S.C., Paul, V.J., 1992. Effect of plant toughness, calcification, and chemistry onherbivory by Dolabella auricularia. Ecology 73, 1606–1619.

Pennings, S.C., Masatomo, T.N., Paul, V.J., 1993. Selectivity and growth of the generalistherbivore Dolabella auricularia feeding upon complementary resources. Ecology 74,879–890.

Pennings, S., Carefoot, T., Siska, E., Chase, M., Page, T., 1998. Feeding preferences of ageneralist salt-marsh crab: relative importance of multiple plant traits. Ecology 79,1968–1979.

Pennings, S., Carefoot, T., Zimmer, M., Danko, J.P., Ziegler, A., 2000. Feeding preferencesof supralittoral isopods and amphipods. Can. J. Zool. 78, 1918–1929.

Poore, A.G.B., Steinberg, P.D., 1999. Preference-performance relationships and effects ofhost plant choice in an herbivorous marine amphipod. Ecol. Monogr. 69, 443–464.

Roa, R., 1992. Design and analysis andmultiple-choice feeding-preference experiments.Oecologia 89, 509–515.

Rodríguez, S.R., 2003. Consumption of drift kelp by intertidal populations of the seaurchin Tetrapygus niger on the central Chilean coast: possible consequences atdifferent ecological levels. Mar. Ecol. Prog. Ser. 251, 141–151.

Rothäusler, E., Macaya, E.C., Molis, M., Wahl, M., Thiel, M., 2005. Laboratory experimentsexamining inducible defense show variable responses of temperate brown and redmacroalgae. Rev. Chil. Hist. Nat. 78, 603–614.

Rothäusler, E., Thiel, M., 2006. Effect of detachment on the palatability of two kelpspecies. J. Appl. Phycol. 18, 423–435.

Silva, J., Larraín, A., Bay-Schmith, E., Roa, R., 2004. Feeding regime experiments toenhance gamete production in the carnivorous sea urchin Arbacia spatuligera.Aquaculture 321, 279–291.

Simpson, S.J., Simpson, C.L., 1990. The mechanisms of nutritional compensation byphytophagous insects. In: Bernays, E.A. (Ed.), Insect-plant interactions, vol. 2. CRCPress, Boca Raton, pp. 111–160.

221C. Duarte et al. / Journal of Sea Research 66 (2011) 215–221

Stachowicz, J.J., Hay, M.E., 1996. Facultative mutualism between an herbivorous craband a coralline alga: advantages of eating noxious seaweeds. Oecologia 105,377–387.

Steinberg, P.D., 1988. The effects of quantitative and qualitative variation in phenoliccompounds on feeding in three species of marine invertebrate herbivores. J. Exp.Mar. Biol. Ecol. 120, 221–237.

Steinberg, P.D., Van Altena, I.A., 1992. Tolerance of marine invertebrate herbivores tobrown algal phlorotannins in temperate Australasia. Ecol. Monogr. 62, 189–222.

Sterner, R.W., Hessen, D.O., 1994. Algal nutrient limitation and the nutrition of aquaticherbivores. Annu. Rev. Ecol. Syst. 25, 1–29.

Targett, N.M., Arnold, T.M., 1998. Predicting the effects of brown algal phlorotannins onmarine herbivores in tropical and temperate oceans. J. Phycol. 34, 195–205.

Taylor, R.B., Sotka, E., Hay, M.E., 2002. Tissue-specific induction of herbivore resistance:seaweed response to amphipod grazing. Oecologia 132, 68–76.

Taylor, R., Brown, P., 2006. Herbivory in gammarid amphipod Aora typica: relationshipsbetween consumption rates, performance and abundance across ten seaweedspecies. Mar. Biol. 149, 455–463.

Toth, G.B., Pavia, H., 2002. Intraplant habitat and feeding preference of two gastropodherbivores inhabiting the kelp Laminaria hyperborea. J. Mar. Biol. Assoc. U. K. 82,243–247.

Tuomi, J., Ilvessalo, H., Niemelä, P., Sirén, S., Jormalainen, V., 1989. Within-plantvariation in phenolic content and toughness of the brown alga Fucus vesiculosus L.Bot. Mar. 32, 505–509.

Van Alstyne, K.L., 1995. Comparison of three methods for quantifying brown algalpolyphenolic compounds. J. Chem. Ecol. 21, 45–58.

Van Alstyne, K.L., Paul, V.J., 1990. The biogeography of polyphenolic compounds inmarine macroalgae: temperate brown algal defenses deter feeding by tropicalherbivorous fishes. Oecologia 84, 158–163.

VanAlstyne, K.L., Ehlig, J.M.,Whitman, S.L., 1999. Feedingpreferences for juvenile and adultalgae depend on algal stage and herbivore species. Mar. Ecol. Prog. Ser. 180, 179–185.

Van Alstyne, K.L., Whitman, S.L., Ehlig, J.M., 2001. Differences in herbivore preferences,phlorotannin production, and nutritional quality between juvenile and adulttissues from marine brown algae. Mar. Biol. 139, 201–210.

Westermeier, R., Müller, D.G., Gómez, I., Rivera, P.J., Wenzel, H., 1994. Populationbiology of Durvillaea antarctica and Lessonia nigrescens (Phaeophyta) on the rockyshores of southern Chile. Mar. Ecol. Prog. Ser. 110, 187–194.

Westermeier, R., Gómez, I., 1996. Biomass, energy contents and major organiccompounds in the brown alga Lessonia nigrescens (Laminariales, Phaeophyceae)from Mehuin, south Chile. Bot. Mar. 39, 553–559.

Zar, J.H., 1999. Biostatistical Analysis, Fourth ed. Prentice Hall, Upper Saddle River.