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1
DIGENEAN (PLATYHELMENTHES: TREMATODA)INFRACOMMUNITY STRUCTURE IN THE SURGEONFISH,
ZEBRASOMA SCOPAS AT VARIOUS CORAL REEF HABITATS
JEREMY CRAM AND JONATHAN REUM
Abstract. Endoparasite communities are strongly influenced by the habitat of the host. Thirty fishwere caught from the crest slope, barrier reef, fringe reef and inner bay habitats found on MooreaIsland, French Polynesia. The abundance, prevalence and intensity of four digenean taxa werescored for each location. Only Neohexangitrema, Preptetos and Cleptodiscus were found inabundance; Gyliauchenid were scarce. We found highly distinct assemblages of parasites at eachlocation, which were typically dominated by one taxon. A significant positive host size to parasiteload relationship was found for Neohexangitrema in the Barrier reef environment; conversely, anegative relationship was observed for Preptetos. Significant differences in parasite intensity wereobserved between sexes for Neohexangitrema and Cleptodiscus. Using canonical scoring and aclassification matrix, the dissimilarities of infracommunity structure is highlighted. Possiblebiological and physical mechanisms are discussed to explain the observed variation in parasiteassemblages among the different habitats.
IntroductionThe coral reef environment is characterized by heterogeneity in geomorphology and
correspondingly in species assemblages. This diversity in habitats recapitulates heterogeneityin parasite compositions (Rigby et al. 1999, Lo 2000, Lo et al. 2001). The effect of parasiteinfection on coral reef fish hosts has received scarce attention (Rigby et al. 1999). Adlard &Lest (1994) showed that parasitized Chromis nitida experienced reduced growth, fecundity,and survivorship (see Lo 1999). Individuals with large parasite burdens were increasinglylethargic, and in turn more susceptible to predation. Further insight into the formation andregulation of infracommunity structure may elucidate the role of parasites in the regulation ofcoral reef fish populations.
The prevalence (number of infected hosts/number of observed hosts) and intensity(number of one parasite species/number of hosts infected) of digenean (Platyhelmenthes:Trematoda) parasites is tightly coupled to the successful infection of the intermediate hosts,which is typically a single species for each stage (Lutz 1985). Although there are several wellstudied examples of digenean life cycles (see Lutz 1985 and citations therein), theoverwhelming number of possible intermediate hosts and the difficult task of identifying thedevelopmental stages of digeneans to the species level, make detection of the exactintermediate host pathway challenging (Lutz 1985; Lo 1998). Despite these apparent gaps inlife history knowledge, some generalities concerning the life cycle are known. The digeneanlife cycle incorporates two intermediates. The first intermediate host is a benthic mollusc andthe second is a planktonic copepod. Ingestion of the copepod by the definitive host, usually avertebrate , finalizes the life cycle. Following from this, the distribution of the intermediatehosts and the ecology associated with different habitats regulates abundance of the adultparasite.
Moorea Island, French Ploynesia is denoted by a large, discontinuous encircling coralreef complex characterized by different sectors with distinct biological and hydrographicfeatures. On the crest slope, the shoreward movement of oceanic waters associated with waveaction results in continuous renewal of the water column and plankton abundance is high.
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Water from the crest slope region then flows over the reef crest and through the coral patchmatrix that comprises the barrier reef; water velocity in this region is markedly slower thanon the crest slope and the density of planktivores is comparatively higher. From the shallowbarrier reef sector, shoreward moving waters entering the lagoon are redirected and funnelledback to the ocean through a pass. Transient waters from the barrier reef sector in the lagoonalchannel buffer the fringing reef. This water has diminished levels of plankton due toabundant planktivores on the crest slope and barrier reef. The bays on Moorea Island areinfluenced by freshwater inputs at the base of the bay, resulting in high turbidity. Surfacecurrents along the sides of the bay flow southerly, paralleling the shoreline. Additionally,retention time of bay water is comparatively longer than the other locations. Terrestrial freshwater inputs drain agricultural fields, homesteads, and grazing lands, which contribute runoffladen with sediments, nutrients and refuse. Reduced effects from freshwater outflow occurseaward.
The influence of habitat on endoparasite abundances has been previously studied byLo et al. (1998), who surveyed the abundance of digeneans in damselfish occurring in twodistinct coral reef habitats. Results from this study demonstrated a clear, differentialrelationship between habitat and parasite abundances. The scope of this study, however, wasrestricted to only two habitats, failing to profile the full range of habitats associated with the
Figure 1. Map of Opunohu Bay, Moorea Island, French Polynesia. Sample sites are highlighted by bold circles: CS, Crest slope; BR, Barrier Reef; FR, fringing reef; IB, Inner Bay.
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Figure 1. Map of Opunohu Bay, Moorea Island, French Polynesia. Sample sites are highlighted by bold circles: CS, Crest slope; BR, Barrier Reef; FR, fringing reef; IB, Inner Bay.
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greater coral reef complex. Moreover, only two species of helmenths were scored, thusrestricting inferences on infracommunity structure (endoparasitic assemblages).
The ubiquitous distribution of the surgeon fish, Zebrasoma scopas, (Acanthuridae)along the coastline of Moorea Island provides a unique opportunity to surveyinfracommunities in relationship to habitat. Furthermore, in a survey of parasites associatedwith coral reef fish, Rigby et al. (1998) identified this species as a prominent candidate foradditional investigations into infracommunity dynamics. The shear abundance of Z. scopasand the diversity of macroparasitic digeneans living in the gastrointestinal track allowuncomplicated scoring of internal parasites.
In the current study, the parasite loads of Z.scopas was assessed in four distincthabitats: the outside of the reef crest, the coral patch habitat of the barrier reef, the fringingreef and the coastal habitat along the inner bay. The aim of this study was to (1) describe theabundance (number of parasites of one species/total number of hosts examined), prevalenceand intensity of digenean in Zebrasomas scopas at four distinct habitats (2) assess host sizeand sex relationships to parasite loads and (3) explore possible factors causing variations inparasite compositions at each habitat. Four genuses of digenean parasites were scored in thisstudy: Neohexangitrema sp. (F. Angioictydae), Gyliauchenid sp. (F. Gyliauchenidae),Cleptodiscus sp. (F. Paramphistomidae) and Preptetos sp. (F. Lepocreadiidae). We anticipateparasite levels to be highest outside the reef crest, and sequentially lower at the coral patchmatrix of the barrier reef, the fringe reef and the inner regions of Oponahu Bay.
Methods and Materials
Study SitesFour sites were selected throughout the Oponohu Bay region on Moorea Island,
French Polynesia (17°30’ S 149°50’W) for sampling (Figure 1). Specific habitat types anddistinct hydrographic conditions characterized each location. At the most seaward site locatedin waters north of the reef crest (herein termed ‘crest slope’), the shoreward movement ofoceanic waters associated with wave action results in continuous renewal of the watercolumn. Waters passing from the crest slope site flow over the reef crest and into the barrierreef sector of the coral reef which in comprised of a dense matrix of coral patches. Theportion of the barrier reef used in our study (herein termed ‘barrier reef’) was near thetransition zone between coral patches and the sandy lagoon. The fringe reef site (hereintermed ‘fringe reef’) was situated roughly at a convergence zone between oceanic watersintruding shoreward from the bay and draining lagoonal waters from the east. The inner baysites (herein termed ‘inner bay’) were located near the base of the bay. One site was locatedon the eastern coast of the bay and second on the western. These sites were both influencedby freshwater inputs at the base of the bay, resulting in high turbidity and fluctuations insalinity. Coral cover was sparse and boulders and gravel dominated the substrata.
Parasite CollectionThirty Zebrasomas scopas were captured using spears between November 15 and
November 26, 2002 from each site. Hosts from the crest slope were collected from depths of5 to 20m using SCUBA. From the other three sites, hosts were collected in depths of 1 to 4musing snorkel apparatuses. Inner Bay hosts were collected and pooled from two differentlocations due to low population densities. Hosts were kept alive in aquaria until dissection,which typically occurred within four hours of capture.
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The standard and total length of each host was measured and sex was determined.Parasites were sorted from gut contents using a saline rinse method (Lo 1998b). All digestivecontents of the gastrointestinal organs were removed and homogenised in a jar filled with 700mL of saline solution (1:3 saltwater to freshwater) by brisk shaking. Particles in the mixturealong with the parasites were then allowed to sink out of solution. Buoyant material waspoured off with the top _ of the solution. Sediments were then re-rinsed if necessary toremove more debris and further concentrate the parasites. Sediments retrieved from the finalrinsing were sorted for parasites. Using microscopy, the following parasites were scored:Neohexangitrema sp., Preptetos sp., Cleptodiscus sp., and Gyliauchenid sp. Parasites wereidentified using diagrams and species descriptions found in Lo et al. (2001) (Figure 2).
From these data, parasite abundance (number of parasites of one species/total numberof hosts examined), prevalence (number of infected hosts/number of observed hosts) andintensity (number of one parasite species/number of hosts infected) were calculated forsubsequent statistical analyses.
Statistical analysesAll statistical analyses were preformed using the Systat 9.0 software package.
Differences in parasite abundance by species and location were assessed using multivariateANOVA. Mean differences in parasite abundance by sex were determined using two-tailed t-test. Intensity values between sexes by location were compared using two-way ANOVA.Linear regression and ANOVA were used to identify the relationship between host size andparasite abundance. Discriminate analysis of parasite abundance and location was used todetermine site differences in abundance. A classification matrix was constructed usingsomething nifty; the resulting values were divided by the total number of hosts observed forthe respective site to calculate relative assignment probabilities. Canonical scoring was usedto group locations based on infracommunity structure. For comparison of Neohexangitrmaintensity in monospecific and co-occurrence conditions, intensities were log transformed andassessed using one-way ANOVA. We considered all P-values < 5% to be significant
Figure 2. (A) Cleptodis sp. Large ventral sucking disk (B) Gyliauchenid sp. Posterior dorsal process (C) Neohexangitrema sp. Dorso-ventrally flattened with pronounced lateral gonad structures (D) Preptetos sp. Pear-shaped body form. Vertical line equals 1 mm. (Courtesy of Cedrik Lo)
A B C D
Figure 2. (A) Cleptodis sp. Large ventral sucking disk (B) Gyliauchenid sp. Posterior dorsal process (C) Neohexangitrema sp. Dorso-ventrally flattened with pronounced lateral gonad structures (D) Preptetos sp. Pear-shaped body form. Vertical line equals 1 mm. (Courtesy of Cedrik Lo)
A B C DA B C D
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Results
Abundance, Prevalence and IntensitiesWe found parasite abundance levels varied among location and taxa (Figure 3). The
prevalence and intensity of Preptetos, Gyliauchenid, Cleptodiscus and Neohexangitremawere calculated for each location (Figure 4, 5). In general, the inner bay had the lowest levelsof prevalence across all parasite taxa. The dominant parasite was Preptetos (0.48), followedby Cleptodiscus (0.17) and Gyliauchenid (0.03); no Neohexangitrema were found. At thefringe reef all four digeneans were represented. Cliptodiscus had the highest prevalence(0.57), Preptetos was intermediate (0.27) and Gyliauchenid and Neohexangitrema both hadthe lowest prevalence (0.03). The barrier reef was characterised by the high prevalence ofNeohexangitrema (0.87), followed by Preptetos (0.17) and Cleptodiscus (0.13). Thedominant parasite at the crest slope was Cleptodiscus (0.83) then Neohexangitrema (0.13),Preptetos (0.10) and Gyliauchenid (0.03). Intensity levels tracked prevalence patterns at theinner bay, barrier reef and crest slope. At the fringe reef, however, Neohexangitrema had thehighest intensity followed by Cleptodiscus, contrasting sharply to prevalence ranking. Intotal, Gyliauchenid was found in only two fish and was omitted from statistical analyses.Multivariate analysis of parasite abundance in relationship to location took into account thethree most abundant digeneans. Cleptodiscus, Neohexangitrema and Preptetos were all foundto have radically and highly significant different abundance levels based on location (Wilk’sLambda=0.31, F=19.54, P<0.001).
Between sexes, parasite intensity was found to vary substantially, but only at certainlocations and for specific parasite taxa. Pronounced differences in intensity between malesand females were found at the barrier reef and fringe reef locations for Neohexangitrema andCleptodiscus respectively (Figure 5). Males at the barrier reef had significantly higherintensities of Neohexangitrema compared to females (Two tailed t-test, T=-2.96, P=0.006).Intensity levels of Cleptodiscus were found to differ significantly between sexes whenfactored with location (two-way ANOVA, F=4.34, P=0.016), however, the sex associatedwith higher intensity was not independent of location. Males at the fringe reef had lowerintensities of Cleptodiscus compared to females. Conversely, at the crest slope malesexpressed higher intensity. There was no apparent relationship between sex and intensity forPreptetos.
Parasite Intensity and Host SizeBoth Neohexangitrema and Preptetos showed significant, yet opposing trends in
abundance as a function of increasing host size (Figure 8). Loads of Neohexangitrema werefound to increase linearly with standard length, specifically at the barrier reef whereNeohexangitrema abundance was highest (One-way ANOVA, F=2.69, P<0.001) (Figure 8a).The reverse relationship was true for Preptetos. Data from the two locations where Preptetoswas most abundant, the fringe reef and inner bay, were pooled for comparison of parasiteloads to host size. A significant negative linear relationship was found (One-way ANOVA,F=6.22, P=0.016) (Figure 8b). No significant relationship was found between host size andabundance levels of Cleptodiscus.
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Figure 3. Abundance (number of parasites of one species/total number of hosts examined) of parasites by taxa (± s.e).
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Figure 3. Abundance (number of parasites of one species/total number of hosts examined) of parasites by taxa (± s.e).
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Habitat and Infracommunity StructureParasite community structure was found to vary substantially among the four different
habitats characterizing each location. The contrasting parasite assemblages found at eachlocation may possibly act as a marker for habitat association for individual Z. scopas. Aclassification matrix was calculated based solely on the occurrence and intensity ofNeohexangitrema, Preptetos and Cleptodiscus at each location. The resulting matrix ofvalues reflect probabilities of assigning origins of fish taken from the locations listed in theleft hand column of Table 1. Although correct assignment of the origin was approximately 50% for each location, at least one of the possible origins was completely excluded, narrowingthe number of possible origins to either two or three. Locations that have zero probability of
0.170.03 0
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Figure 4. Prevalence (number of infected hosts/number of observed hosts) by species.
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Figure 4. Prevalence (number of infected hosts/number of observed hosts) by species.
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Figure 5. Parasite intensity (number of one parasite species/ number of ho sts infected) by taxa(± s.e).
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Figure 5. Parasite intensity (number of one parasite species/ number of ho sts infected) by taxa(± s.e).
assignment indicate a high degree of dissimilarity regarding parasite composition, while locationsof increasing misidentification probabilities are closer in parasite composition.
Canonical scoring was used to directly assess the similarity of parasite communitiesamong locations (Figure 9a). Parasite composition at the fringe reef was intermediate to theother three locations; the highest degree of overlap was observed between the fringe reef andthe remaining locations. This degree of relatedness diminished the distinction of the
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Figure 6. Prevalence of four parasite taxa between sex at three different locations. Individuals samples from the Inner Bay were juvenile and sex cou ld not be determined.
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Figure 6. Prevalence of four parasite taxa between sex at three different locations. Individuals samples from the Inner Bay were juvenile and sex cou ld not be determined.
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remaining three locations and a second canonical score plot was calculated neglecting thefringe reef location, accentuating the dissimilar parasite assemblages (Figure 9b).
Monogeneric parasite intensities were calculated for each species at all sites andcompared to intensities in instances of co-occurrences. Of the 120 fish sampled in this study,only 21 had combination of parasite genera co-occurring. The limited number of interactionsmakes inferences on interspecific interactions difficult. Only intensities of Neohexangitremaand Neohexangitrema in the presence of Cleptodiscus or Preptetos at the barrier reef locationwere comparable. The remaining combinations among the different locations were too low innumber to analyse. Neoheaxgitrema intensity was was found significantly lower when in thepresence of Cleptodiscus (Two-way ANOVA, P=0.016). In the presence of Preptetos nosignificant difference was found.
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Figure 7. Mean abundance of parasites among infested individuals between sexes.
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Figure 7. Mean abundance of parasites among infested individuals between sexes.
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Discussion
Infracommunities at the four different locations examined in this study were markedlydistinct from one another (Figure 9, Table 1). The emergence of a single, dominant parasitespecies at each location and the infrequency of co-occurrences suggest that habitat-specificselecting factors result in differential survivorship of parasite species and subsequentinfection of the definitive host. Predation and the natural distribution of the intermediatehosts, in addition to the feeding behavior of Z. scopas may be responsible for the observedpatterns in parasite community structure. These two factors are treated separately below.
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Habitat Influences: Ecology and Hydrography
Although the dominant parasite taxon was different at each location (Figure 3), thehighest parasite abundances were found at the barrier reef and crest slope locations followedby the fringe reef and inner bay, respectively. The variations observed in infracommunitystructures among these sites suggest heterogeneity in the abundance and distributions of the
Figure 8.(A) The number of Neohexangitrema found in each fish plotted against standard length for the barrier reef. (B) The number of Preptetos from the inner bay and fringe reef plotted against standard length; a significant linear relationsh ip was found when data from the inner bay and fringe reef were pooled.
Abundance of Neohexangitrema vs. Host Standard Length at the Barrier Reef
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Figure 8.(A) The number of Neohexangitrema found in each fish plotted against standard length for the barrier reef. (B) The number of Preptetos from the inner bay and fringe reef plotted against standard length; a significant linear relationsh ip was found when data from the inner bay and fringe reef were pooled.
Abundance of Neohexangitrema vs. Host Standard Length at the Barrier Reef
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(B)
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Table 1. Classification Matrix. Values indicate probability of assigning location of origin; bold values are correct assignments.
Inner BayCrest Slope
Fringe Reef
Barrier Reef
Inner Bay 0.47 0.03 0.5 0Crest Slope 0 0.53 0.47 0Fringe Reef 0.2 0.25 0.55 0Barrier Reef 0.04 0 0.4 0.56
Act
ual O
rigi
n
Predicted Origin
Table 1. Classification Matrix. Values indicate probability of assigning location of origin; bold values are correct assignments.
Inner BayCrest Slope
Fringe Reef
Barrier Reef
Inner Bay 0.47 0.03 0.5 0Crest Slope 0 0.53 0.47 0Fringe Reef 0.2 0.25 0.55 0Barrier Reef 0.04 0 0.4 0.56
Act
ual O
rigi
n
Predicted Origin
Inner BayCrest Slope
Fringe Reef
Barrier Reef
Inner Bay 0.47 0.03 0.5 0Crest Slope 0 0.53 0.47 0Fringe Reef 0.2 0.25 0.55 0Barrier Reef 0.04 0 0.4 0.56
Act
ual O
rigi
n
Predicted Origin
intermediate copepod hosts. The herbivorous Z.scopas acquires digeneans by grazing algalturfs that are coincidentally grazed upon by infected copepod intermediate hosts. Theinadvertent ingestion of copepods completes the life cycle of the digenean and the adult stagedevelops in the definitive host, Z. scopas. In a review by Lo (1998b), zooplankton abundancewas described as highest in the crest slop and barrier reef environments and lowest at thefringe reef. Inner bay zooplankton abundance has not been well described, but is likely at atransitional level between the crest slope and fringe reef due to mixing from these twosources. The apparent gradient in zooplankton abundance is attributed to plaktivorous feedingthroughout the barrier reef sector. Waters laden with high levels of plankton, includingcopepods, flow over the reef crest and through the barrier reef coral patch matrix. A highdensity of planktivorous fauna in this region has a significant impact on the quantity ofzooplankton exiting the barrier reef sector into the lagoonal channel. Waters reaching thefringe reef have drastically reduced levels of zooplankton. Consequently, the distribution ofparasites dependent on plankter intermediates will be effected.
The inner bay had the lowest abundance and intensities for all taxa scored. Thisseemingly conflicts with the transitional nature of the inner bay waters. In a study by Lefevre(1985) zooplankton abundance was surveyed around Oponohu Bay and the northern coast ofMoorea Island. Copepods were determined to be most abundant in the inner bay and crestslope environments, and least abundant at the barrier reef and fringe reef sites. The highabundance of copepods in the inner bay would suggest correspondingly high parasite levelsbut this was not the case. Little overlap of copepod distribution and the feeding ranges of Z.scopas may be responsible for low abundance levels. The deep submarine ravine running thelength of Oponohu Bay provides a preferred deep-water habitat for the copepods, leading tolower densities in shallow waters (Lefevre 1985). High turbidity in the inner bay restrictsalgal growth to near surface waters as opposed to the crest slope, where high visibility allowsdeep algal growth. Zebrasomas scopas ranges most likely track the distribution of turf algae;subsequently, Z. scopas is segregated from the copepod intermediates in the inner bay.
Parasite Intensity Differentials Between SexesDifferences between sexes in parasite intensity were observed at the barrier reef for
Neohexgangitrema (Figure 6). This may have stemmed from separate feeding behaviorsbetween males and females. Lo et al. (1998a) determined that consumption was positivelyrelated to parasite levels. In a study reviewed by Lutz (1985) phospholipid levels were
13
monitored in Z. scopas and was able to infer ingestion rates. Males and females showeddifferent feeding patterns throughout the year due to mating cycles. This disparity betweensexes in Neohexangitrema counts may be accounted for by the different volumes algaeingested, and correspondingly, copepods ingested.
The intensity of Cleptodiscus was also found to vary between sexes, however, the sexwith higher intensity changed with location (Figure 6). At the crest slope males expressedhigher intensity and at the fringe reef the converse was true. Different feeding strategiesbetween the sexes may change based on the dominate food types. The exact mechanismdriving this pattern remains elusive, like the snow leopard.
Host size vs. Parasite LoadAnalysis of host size and parasite intensity revealed two significant relationships.
Neohexangitrema on the barrier reef had a strong positive correlation with length, however,this finding should be interpreted cautiously. A sexual dimorphism was found in Z. scopas(Figure 10). Males showed higher intensity of Neohexangitrema at the barrier location thanfemales (Two-tailed t-test, T=-3.677, P<0.001), but it is unclear as to whether this is causedby differential consumption rates of males and females or purely by size. Maximum size for
10
11
12
13
14
female male
Figure 10. Mean standard length between sexes. Males were significantlylarger than females, indicating a sexual dimorphism.
Stan
dard
Len
gth
(cm
)
N = 35
N = 51
10
11
12
13
14
female male
Figure 10. Mean standard length between sexes. Males were significantlylarger than females, indicating a sexual dimorphism.
Stan
dard
Len
gth
(cm
)
N = 35
N = 51
14
FA
CT
OR
(1)
FACTOR(2)
Barrier Reef
Fringe Reef
Crest Slope
Inner Bay
LOCATION
FACTOR(1)
FA
CT
OR
(2)
Barrier ReefCrest SlopeInner Bay
LOCATION
Figure 9. Canonical score plots. (A) Delineation of the four habitats based on parasite compositions (B) Delineation of three locations: Inner Bay, Barr ier Reef, and Crest Slope based on parasite community structure. The intermediate parasite assembl ages found at the Fringe Reef diminished the distinction among the remaining locations and was omitted in analysis.
(A)
(B)
FA
CT
OR
(1)
FACTOR(2)
Barrier Reef
Fringe Reef
Crest Slope
Inner Bay
LOCATION
Barrier Reef
Fringe Reef
Crest Slope
Inner Bay
LOCATION
FACTOR(1)
FA
CT
OR
(2)
Barrier ReefCrest SlopeInner Bay
LOCATION
Barrier ReefCrest SlopeInner Bay
LOCATION
Figure 9. Canonical score plots. (A) Delineation of the four habitats based on parasite compositions (B) Delineation of three locations: Inner Bay, Barr ier Reef, and Crest Slope based on parasite community structure. The intermediate parasite assembl ages found at the Fringe Reef diminished the distinction among the remaining locations and was omitted in analysis.
(A)
(B)
femalesat the barrier reef was approximately 15 cm, while male individuals were captured up to 20
15
cm in length. The dual effect of sex dependent consumption rates and host size differencesare most likely exacerbating parasite intensity in males relative to females.
A negative relationship between Preptetos abundance and length conflicts withconventional views on host size and parasite interactions (Lo et al. 1998a) (Figure 8).Acquisition of Preptetos may occur early in life during the pelagic larval stage. The relativelyshort life span of digeneans of 9 to 31 months (Lo et al. 1998) means that after larvalrecruitment to the reef, infection by Preptetos would terminate and intensities would decline.
Infracommunity structureThe vast majority of hosts were infected by only one digenean taxon. Instances of co-
occurrences were low in number, hampering statistical analysis. Only 17% of hosts examinedhad more than one parasite taxa. There was only one case in which mean intensity could becompared between heterogeneric and monogeneric conditions. Neohexangitrema was foundto be lower in intensity when co-occuring with Cleptodiscus. This may be due to interspecificcompetition, but low numbers of both parasites makes assessment of the interaction difficult.Information on the succession of parasites in coral reef fish is limited. Movement betweenhabitats and changes in diet most likely drive the supplanting of parasites, more so thancompetitive exclusion.
This study has attempted to characterize the digenean composition of Zebrasomasscopas in four habitats. Our data show that the heterogeneity of the coral reef complex isreflected in infracommunities. The four locations examined in this study showed dramaticdissimilarities in abundance, prevalence and intensity. The distinctiveness of these parasiteassemblages, if further refined, may be a practical means of identifying the habitat fromwhich a fish was taken. In addition to raw prevalence and intensity values, differencesbetween sexes were found, however, disparities between the sexes were parasite- and site-specific. This pattern is most likely related to varying diets.
High loads of macroparasites can regulate host populations (Lo, pers. comm.). Insightinto the mechanisms that structure infracommunities has meaningful implications forunderstanding coral reef fish population dynamics. Additional knowledge of life historiesspecific to each parasite species may possibly clarify the patterns observed in thisinvestigation. We hope that the data presented here might provoke further examination ofhabitat effects on parasite compositions.
Acknowledgements
We would like to thank Cedrik Lo and Ernesto (the Italian guy that was at the station for afew weeks and new a lot about parasites and stuff) for their technical guidance and debriefingon parasitology. We would also like to thank Giacomo and Pete, the gifted instructors of thiscourse, for their enthusiasm towards this project and their constructive comments. Theteaching assistants, Dawn, Mark and Jonna, were cool, and by cool I mean totally sweeeeet.Our classmates, well, we liked them along with all the staff and researchers at CRIOBE. Theyfostered an emotional environment that facilitated the evolution and completion of this study.Jeremy would like to thank his mom for loving him, even though he has a lot of problems(Jon, pers. observation). Dear Family (Jon’s), Thank you!
We made this.
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References
Cribb T. H., Pichelin S., Dufour V., Bray R. A., Chauvet C., Faliex E., Galizen R., Lo M. C., Lo-Yat A.,Morand S., Rigby M. C., Sasal P., 2000. Parasites of recruiting coral reef fish larvae in New Calidonia.International Journal for Parasitology 30: 1445-1451
Lefevre, M. (1985) Spatial variablility of zooplanktonic populations in the lagoons of a high island. Proceedingsof the Figth International Coral Reef Symposium, Tahit 6: 39-45
Lo C. M., Morgan J. A. T., Galzin R., Cribb T. H., 2001. Identicle digeneans in coral reef fishes from FrenchPolynesia and the Great Barrier Reef (Australia) demonstrated by morphology and molecules.International Journal for Parasitology 31: 1573- 1578
Lo C. M, Morand S., Galzin R. (1998a) Parasite diversity/host age and size relationships in three coral-ref fishesfrom French Polynesia. Intern. J. of Parasitology. 28: 1695-1708
Lo C. M, Morand S., Galzin R. (1998b) The parasitism of coral reef fish. Reflection of habitat? Animal Biology322: 281-287
Lutz, P. E. (1985) Invertebrate Zoology. Menlo Park, CA. Addison-Wesley Publishing Company
Rigby M. C., Lo C. M., Cribb T. H., Euzet L., Faliex E., Galzin R., Holmes J. C., Morand S., 1999. Checklist ofthe parasites of coral reef fishes from French Polynesia, with considerations on their potential role inthese fish communities. Cybium 23(3): 273-284
