Ruthenica, 2020, vol. 30, No. 4: 195-202. © Ruthenica, 2020 Published online October 1, 2020. http: ruthenica.net

Trophic interactions between gall-forming molluscs Stilifer spp. (, ) and their hosts (Echinodermata)

E.S. MEKHOVA1, P.Yu. DGEBUADZE 2 A.N. Severtsov Institute of Ecology and Evolution of Russian Academy of Sciences, 33, Leninsky prospekt, Moscow, 119071, RUSSIA. E-mail: [email protected], [email protected] (corresponding author)

ABSTRACT. The trophic relationships between two of symbiotic gall-forming molluscs from the Stilifer (family Eulimidae) and two of their hosts-asteroid species, and Culcita noveaguineae, were investigated using the stable isotope analysis of carbon and nitrogen. The aim of present study was to identify the most preferable host tissue in the symbionts’ diet. We analyzed δ15N and δ13C values in tube-feet, gonads and digestive glands of the hosts- and in muscles of the molluscs. Both symbiont species did not differ to each other both in δ15N and δ13C values. The average δ15N and δ13C values of Stilifer variabilis were significantly different from the digestive glands and gonads of their host Culcita novaeguineae and did not show differences from the tube-feet of starfishes. A similar pattern was found in the symbiotic association of Stilifer utinomi and Linckia laevigata. The tube-feet of analyzed starfishes had significantly higher average δ15N and δ13C values than the digestive glands and gonads. Obtained isotopic signatures indicate that symbionts do not feed on the host’s tissues, but take nutrients from their digestive system. It seems that the proboscis of Stilifer spp. absorbs the nutrients from the digestive system of the host- thereby not disturbing significantly the host’s immune system.

Трофические взаимодействия между галлооб- выявлена в симбиотической ассоциации между мол- разующими моллюсками рода Stilifer (Gast- люсками Stilifer utinomi и морскими звездами ropoda, Eulimidae) и их хозяевами (Echi- Linckia laevigata. Амбулакральные ножки исследу- nodermata) емых морских звезд имели достоверно более высо- кие средние значения δ15N и δ13C, чем пищевари-

1 2 тельные железы и гонады. Полученные результаты Е.С. МЕХОВА , П.Ю. ДГЕБУАДЗЕ позволяют говорить, симбионты питаются не тканя- Институт проблем экологии и эволюции им А.Н. Север- ми хозяина, а компонентами пищи хозяина. Вероят- цова РАН, Ленинский пр-т 33. Москва,. 119071, но, что хобот представителей рода Stilifer всасывает РОССИЯ. E-mail: [email protected], питательные вещества из пищеварительной систе- [email protected] (автор-корреспондент) мы морской звезды-хозяина, тем самым не сильно раздражая иммунную систему хозяина. РЕЗЮМЕ. В данной работе рассмотрены трофичес- кие отношения между двумя видами симбиотичес- ких галлообразующих моллюсков из рода Stilifer (се- мейство Eulimidae) и их хозяевами – морскими звез- Introduction дами, Linckia laevigata и Culcita novaeguineae, с использованием метода анализа стабильных изото- Trophic relations between parasites and their пов углерода и азота. Целью настоящего исследова- hosts are very diverse. In trophic aspect they range ния было определение наиболее предпочтительной from kleptoparasitism, when the symbionts do not ткани хозяина в пищевом рационе моллюсков-сим- feed on their host’s tissues, to extremely narrow 15 13 бионтов. Проанализированы значения δ N и δ C в cases of , when the parasites feed on амбулакральных ножках, гонадах и пищеваритель- specific host’s tissue. Identifying these relation- ных железах хозяев-морских звезд, а также в мышцах ships is crucial for understanding the functioning of моллюсков. Оба вида симбионтов не отличались друг от друга, как по азоту, так и по углероду. Средние the symbiotic community and ecosystem as a whole значения δ15N и δ13С в тканях моллюсков Stilifer [Lafferty et al., 2008]. For a long time, parasites variabilis достоверно отличались от значений пище- were ignored in the trophic webs studies. Parasites варительных желез и гонад их хозяина Culcita play an important role in benthic communities, but novaeguineae и не отличались от амбулакральных cryptic nature of parasitic relationships requires ножек морских звезд. Аналогичная картина была labor intensive methods to study them. 196 E.S. Mekhova, P.Yu. Dgebuadze

FIG. 1. Schematic map of sampling sites. РИС. 1. Карта-схема расположения точек отбора проб.

Gastropods from the family Eulimidae are spe- al., 1988]. The representatives of the genus Stilifer cialized parasites of , although the level have an elongated proboscis that can be introduced of specialization varies from strictly species-specif- deep into the body or rays of the starfishes. Since ic to species with a wide range of hosts [Warén, these eulimids form galls in body wall of their hosts, 1983]. Some details of the symbiont-host relation- the movement of their proboscis is seriously limited ships are known for a small number of species [e.g. as it passes through the host’s tissues, including Crossland et al., 1991, 1993; Dgebuadze, Kantor, their body wall. Most eulimids have no radula and 2015; Queiroz et al., 2017]. There are a few papers feed on liquid or semi-dissolved food, which makes with the description of eulimids snout morphology, it impossible to analyze the composition of the food where the sources of their diet are suggested. For lump [Lützen, 1972]. example, the proboscis of Crinophtheiros comatuli- Stable isotope analysis (SIA) of carbon and cola (Graff, 1875) reaches the coelomic canal of nitrogen has been successfully used to study the the arm of its host, feather star, and the symbiont trophic relationships for decades [Fry, 2006]. This absorbs the coelomic fluid [Bacci, 1948]. Melanel- method can help to overcome some difficulties and la alba (da Costa, 1778), a temporary ectoparasite understand trophic dynamics between the symbi- of holothurians, drills the wall of the host with its onts and their hosts. The isotopes values differ proboscis that secretes a substance which is proba- between organisms due to their diets because of bly used to quickly relax the host’s tissues [Cabioch small selective retention of the heaviest isotope and et al., 1978]. Feeding on the host’s body fluids was excretion of the lighter one. Typically, with each also shown for Ophieulima minima (Dall, 1927) trophic transfer between a consumer and its diet, and Peasistilifer edulis Hoskin, Warén, 1983, and δ15N values increase by approximately 3-5‰ [De- was well studied for crystallina (Gould, 1846) Niro, Epstein, 1981; Minigawa, Wada, 1984]. On [Warén, Sibuet, 1981; Hoskin, Warén, 1983; Egloff the other hand, an has δ13C values close to et al., 1988]. Since the females of the latter ec- that of its diet with, however, a slight enrichment of toparasitic species are tightly attached to the bodies 1‰ [DeNiro, Epstein, 1978; Tieszen et al., 1983; of their hosts, they lost some anterior parts of the Hobson, Clark, 1992]. body. Their digestive system is substantially re- SIA nowadays allows us to study trophic rela- duced, and the salivary glands are enlarged, so tionships in different ecosystems, and find some these molluscs can only assimilate food that does peculiarities, especially in parasitic communities not require complex digestion. The degree of pene- [Deudero et al., 2002; Dubois et al., 2009]. For tration of Th. crystallina proboscis into its host example, some authors proposed that the isotope allows suggesting that its main sources of food are signatures of intestinal parasites (helminths) coin- the hemal and perihemal systems of the host, as cide or are close to the signatures of their hosts well as the surrounding fluids and tissues [Egloff et [Neilson et al., 2005; Navarro et al., 2014; Lafferty Trophic interactions between Stilifer spp. and their hosts 197

FIG. 2. Gall-forming eulimids and their hosts: A, C. Stilifer utinomi in the ray of a starfish Linckia laevigata; B, D. Stilifer variabilis in the gall on a starfish Culcita novaeguineae. РИС. 2. Галлообразующие эулимиды и их хозяева: A, C. Stilifer utinomi в луче морской звезды Linckia laevigata; B, D. Stilifer variabilis в галле в теле морской звезды Culcita novaeguineae. et al., 2008]. For digenean trematodes from marine to 10 meters in the Nha Trang Bay (South China molluscs no fractionation or low 15N trophic en- Sea, central Vietnam) in 2015. Sampling sites are richments due to parasite metabolism were detected indicated in Fig. 1. All samples were fixed with 80% [Dubois et al., 2009]. Parmentier and Das [2004] ethanol. This method of preservation is acceptable used the SIA to study the relationships between the since the task of this study is to compare the tissues Carapidae fishes and their hosts and showed differ- of symbionts and their hosts [Kaehler, Pakhomov, ences in feeding behavior (commensal and parasi- 2001; Carabel et al., 2009]. Some authors noted tic) of these symbionts. So, this method seems that the relative trends in fixed samples should be appropriate for symbiotic communities, where it is unaffected and thereby they can be used for inter- difficult to determine the source of symbionts’ diet comparison in some ecological analyses [Canuel et due to their small sizes, and the food does not al., 1995; Gladyshev, 2009]. contain any solid elements. Two obligate parasitic species of gall-forming The aim of this study is to reveal trophic interac- eulimids from the genus Stilifer associated with tions between the gall-forming eulimids and their starfishes were studied (Fig. 2); S. utinomi Habe, hosts – echinoderms. We suppose that these symbio- 1951 inhabits blue starfishes Linckia laevigata (Lin- tic gastropods feed on their host and can choose the naeus, 1758) and S. variabilis O. Boettger, 1893 most preferable tissue. forms galls in the cushion starfish Culcita no- vaeguineae Müller et Troschel, 1842. Totally five Materials and methods specimens of S. variabilis from five host speci- mens and seven of S. utinomi from three host Sample processing. The material for the study specimens were collected. All molluscs were col- was collected by SCUBA divers from a depth of 3 lected with their hosts. Foot muscles were taken 198 E.S. Mekhova, P.Yu. Dgebuadze from the molluscs for the analysis [Fedosov et al., the tube-feet of C. novaeguineae, 9.8±0.9‰, p>0.05; 2014; McKinney et al., 1999]. Different starfishes’ as were the average δ13C values (-14.7±0.9‰, tissues (tube-feet, digestive gland and gonads) were p>0.05). dissected and fixed separately. Each tissue was The mean δ15N value of S. utinomi muscles was selected and analyzed in five samples. significantly different from the digestive glands and Isotopic analysis. Prior to the analysis, all sam- gonads of their host L. laevigata: 9.2±0.4‰, ples were dried for 5-7 days at 50°C, grounded into 7.4±0.2‰ and 8.1±0.3‰, respectively, p<0.01. Si- powder using a mortar and pestle and packed in tin milarly, the mean δ13C value of S. utinomi, -14.1± foil (200-500 micrograms each). The SIA was car- 0.6‰, was higher than that of the digestive glands ried out using Thermo Delta V Plus isotope mass and gonad of L. laevigata, -18.5±0.7‰ and -17.4± spectrometer and Thermo Flash 1112 element ana- 0.8‰, respectively. These differences were statisti- lyzer (Thermo Scientific, USA) at the Joint Usage cally significant, p<0.01. The mean δ15N value of S. Center “Instrumental Methods in Ecology” at the utinomi muscles was not significantly different from A.N. Severtsov Institute of Ecology and Evolution that of the tube-feet of L. laevigata, 9.1±0.9‰, of RAS. p>0.05; as were the mean δ13C values (-15.5±0.2‰, The ratio of stable isotopes (13C/12C and 15N/14N) p>0.05).The tube-feet of C. novaeguineae had sig- is presented in per mill units (δ, ‰) of deviation nificantly higher mean δ15N value than the gonads from international standards (VPDB for δ13C and and digestive glands of this species, 9.8±0.9‰, 15 atmospheric N2 for δ N). The analytical error in 7.9±0.4‰ and 7.6±0.5‰, respectively, p<0.01. The determining the isotope composition (SD in the same differences were found for mean δ13C: the laboratory standard analysis, n = 6-8) did not ex- tube-feet of C. novaeguineae had significantly higher ceed 0.2‰. To represent the results, mean values mean δ13C value than the gonads and digestive of δ13C and δ15N ± 1 standard deviation are report- glands of this species: -14.8±0.9‰, -17.0±1.3‰ ed. The δ13C values have been corrected for lipid and -18.3±1.5‰, respectively, p<0.01. The tube- concentration using equation proposed by Post et feet of L. laevigata had significantly higher mean al. [2007] for samples with mass C/N ratio higher δ15N value than the digestive glands of this species, than 4. 9.0±0.3‰ and 7.4±0.2‰, respectively, p<0.01. The Statistical analysis. Kolmogorov-Smirnov one- average δ13C of tube-feet of L. laevigata was sample test was used to test the normality of the significantly higher than that of the digestive data. One-way ANOVA followed by post hoc multi- glands: -15.5±0.8‰ and -18.5±0.7‰, respectively, ple comparison tests (Tukey HSD post hoc test) p<0.01. Between the tube-feet of both echinoderm were used to compare the data on the different species the differences were insignificant in both hosts tissues and symbionts. All statistical analyses the δ15N values, p>0.05, and the δ13C values, p>0.05. were performed with STATISTICA 9.0 (StatSoft, Inc., Tulsa, OK, USA). Discussion Results As expected, the starfishes’ tissues differ in heavy nitrogen isotope enrichment within a species. Using one-way ANOVA, we found significant The nitrogen variances in the different tissues were differences between and symbionts tis- shown for some organisms and sometimes such sues both in δ13C (F (3, 33) = 17.629, p<0.05) and differences can reach up to 4‰ (as for δ13C – up to in δ15N (F (7, 33) = 18.141, p<0.05). 2‰) [Deudero et al., 2002]. Parmentier and Das S. utinomi and S. variabilis muscles had similar have previously shown such differences of δ15N for mean δ15N values, 9.2±0.4‰, Tukey HSD test with C. novaeguineae tissues [Parmentier, Das, 2004]. d.f. = 33, p>0.05 (Fig. 3) The average δ13C value of Indeed, it is known that nitrogen trophic enrich- S. utinomi, -14.1±0.2‰, tended to be lower, than ment is the result of transamination and the loss of that of S. variabilis, -14.5±0.5‰, but the differen- “light” 14N excretory products [Macko et al., 1986]. ce was statistically insignificant, p>0.05. The mean In addition, gonads have more fatty tissue and are δ15N value of S. variabilis muscles is significantly low in carbon heavy isotopes saturation [DeNiro, different from the digestive glands and gonads of Epstein, 1978; McConnaughey, McRoy, 1979; Post their host C. novaeguineae: 9.2±0.4‰, 7.6±0.5‰ et al., 2007]. The tube-feet are therefore the most and 7.9±0.4‰, respectively, p<0.01. Similarly, the indicative of a starfish’s diet in comparison to other mean δ13C value of S. variabilis, -14.5±1.1‰, was analyzed organs. higher than that of the digestive glands and gonads The lack of significant differences in both δ13C of C. novaeguineae, -18.3±1.5‰ and -17.0±1.3‰, and δ15N values indicates the similarity of feeding respectively. These differences were statistically preferences between both species of starfishes in significant, p<0.01. The mean δ15N value of S. va- our study. The cushion starfish C. novaeguineae riabilis was not significantly different from that of primarily prefers corals, but also feeds on algae and Trophic interactions between Stilifer spp. and their hosts 199

FIG. 3. The average δ13C and δ15N values and standard deviations of the muscle tissues of the gall-forming species Stilifer variabilis and Silifer utinomi and organs of their hosts Culcita novaeguineae and Linckia laevigata collected in 2015 in the Nha Trang Bay, Vietnam. РИС. 3. Средние значения δ13C и δ15N и стандартные отклонения в мышечных тканях галлообразующих видов Stilifer variabilis и Silifer utinomi, а также органах их хозяев Culcita novaeguineae и Linckia laevigata, собранные в 2015 году в заливе Нячанг, Вьетнам.

coral rubble [Bell, 2008]. Another analyzed species complicating matters, different parasite species on L. laevigata mainly feeds on coralline algae and the same host or the same parasite species on detritus [Coleman, 2007; Laxton, 1974]. So, our different hosts can differ in their isotope enrich- result may demonstrate on the seasons or local ment [Deudero et al., 2002]. This difference in conditions of the bay. δ15N between predators and parasites likely stems The ratio of 15N/14N can indicate an organism’s from the fact that parasites are relatively selective in trophic position, but this may not work well for which parts of the host they consume. For in- parasites. Although predators are always 15N-en- stance, some parasites may feed on the intestinal riched in comparison to their prey, parasites are contents rather than on the host tissue; others se- sometimes 15N-depleted when compared with their lectively absorb particular biochemical compounds hosts, as a whole [Pinnegar et al., 2001]. Other such as amino acids, live in and feed on different parasites have a similar enrichment comparing to host tissues, or have altered metabolism that varies their hosts, whereas a few parasites are more en- with life stage [Pinnegar et al., 2001; Deudero et riched than expected for a direct consumer al., 2002]. For these reasons, a topological assess- [O’Grady, Dearing, 2006]. The level of enrichment ment seems to be the best approach for determining can even vary between parasite taxa within the the trophic differences between parasites and their hosts. For example, intestinal nematodes parasitiz- hosts [Lafferty et al., 2008]. ing rabbits are δ15N-enriched whereas intestinal ces- The obtained data indicates that molluscs tissues todes in the same host species are δ15N-depleted are more enriched in heavy nitrogen isotope rela- [Boag et al., 1998; Neilson et al., 2005]. Further tively to the digestive glands and gonads of their 200 E.S. Mekhova, P.Yu. Dgebuadze hosts. However, the difference between them was it was concluded, based on the structure of the less than 3.4‰, that was also previously shown for digestive system, that the powerful development of other ectoparasites. For example, Pinneagar and the pharynx’s radial muscles, as well as the reduc- co-authors [2001] noted that the blood eating iso- tion of the stomach, involves feeding only on gut pod Anilocra physodes (Linnaeus, 1758) and larvae contents of the host [Ivanov, 1952]. In addition, of the copepod Lernaeocera branchialis (Linnaeus, Queiroz et al. [2017] studied the lifecycle of gall- 1767) did not differ significantly in δ15N with re- forming eulimid Sabinella troglodytes (Thiele, 1925) spect to their hosts: bogue Boops boops (Linnaeus, from sea urchins and additionally observed the feed- 1758) and flounder Platichthys flesus (Linnaeus, ing mechanisms. They described the feeding pro- 1758). Our data partially correlates with the data on cess of symbionts on their hosts’ spines using an other symbionts of echinoderms: for some carapid acrembolic proboscis to erode and suck the calcar- species [Carapus boraborensis (Kaup, 1856) and eous matrix to access the scarce spine tissue. It Encheliophis homei (Richardson, 1846)] the 15N- seems amazing why these molluscs do not pene- enrichment was shown compared to different tis- trate the test of sea urchins but make galls and feed sues (digestive tract, gonads, digestive glands and on their spines. The morphology and the lifestyle of tube-feet of starfishes) of their hosts holothurians representatives from the genus Stilifer suggest that and starfishes. These symbionts use their host as a the mollusc is closely connected with one starfish shelter and leave it to feed in the environment all its life. Probably, the symbiont proboscis is [Parmentier, Das, 2004]. As with nitrogen isotopes, seriously limited in its movements as it passes symbiotic gastropods tissues were consistently en- through the host’s tissues, including the host’s body riched in 13C in respect to digestive gland and go- wall [Lützen, 1972]. Hence, such eulimids cannot nads of their hosts (Fig. 3). This disagrees with the change the source of food. enrichment pattern “δ13C < 1‰ conventionally as- Thus, in our study of gall-forming eulimids diet, sumed between consumers and their diets. Mean- we conclude that the most feasible food source for while, the δ13C values of symbionts tissues and their Stilifer spp. is “a stealing” of nutrients from the hosts are almost the same and it demonstrates the celomic cavity of the starfishes, without irritating absence of differences between host tube-feet and the host’s immune system. Since we do not know symbionts muscles. All obtained results for both the peculiarities of the symbionts’ metabolism, our δ13C and δ15N allow us to conclude that these gall- results should be considered preliminary. Further forming molluscs feed on what the starfish itself studies are needed to confirm these assumptions, consume and then accumulate in its tube-feet. In including the investigations of the molluscs’ mor- that case, symbionts obtain the necessary nutrients phology. of the host from the coelomic cavity without pene- trating specific organs and thus causing no fatal Conclusions damage to their hosts. SIA is a useful tool to characterize the trophic But, last year Thieltges and co-authors made an status in symbiotic associations but should be inter- extensive comparative analysis of different host- preted with caution. Our results confirm the para- parasite systems using SIA and showed that the sitic feeding of gall-forming eulimids, and the most traditional isotope framework does not apply well to likely source is the coelomic fluid. It is proved by parasitic trophic relations. They concluded, that morphological data, but physiological features of “the average discrimination factors observed in pred- parasites should be further considered, for example ator–prey and herbivore–plant trophic interactions selective assimilation by parasites of certain com- (Δ 15N of 3.4‰ and Δ 13C of 1.0‰) do not hold true pounds from the food. as a general indicator for trophic relationships be- tween parasites and their hosts” [Thieltges et al., Acknowledgements 2019: 1335]. Authors suggested that one of the reasons of this situation may be the different meta- We thank Dr. A.V. Tiunov, Dr. Prof. Michail I. Gladyshev bolic pathways of parasites, especially endobionts. and Dr. A.K. Zalota for helpful discussions during the sample The morphological features suggest that gall- analysis and manuscript preparation, our colleagues from the forming molluscs feed on the host tissues. For Laboratory of Morphology and Ecology of Marine example, it was described that the representatives Invertebrates of A.N. Severtsov Institute of Ecology and of the genus Stilifer have an elongated proboscis Evolution (SIEE RAS), the Coastal Branch of the Russian- Vietnamese Tropical Center and Joint Usage Centre that is introduced deeply into the body or rays of the “Instrumental Methods in Ecology” (SIEE RAS) for their starfish [Lützen, 1972]. However, most research- collaboration during the field sampling and in the laboratory. ers did not analyze the method of feeding and the The work was suported by the grant from the Russian type of absorbed food. In one study of gall-forming Science Foundation (grant number 16-14-10118-П; PI Y. species Paramegadenus arrhynchus (Ivanov, 1937), Kantor). Trophic interactions between Stilifer spp. and their hosts 201

References , an ectoparasitic gastropod. The Veliger, 30(4): 342–346. Bacci G. 1948. Melanella comatulicola (Graff), un Fedosov A., Tiunov A., Kiyashko S., Kantor Yu. 2014. Gasteropodo parassita della Antedon mediterra- Trophic diversification in the evolution of predato- nea (Lam.). Italian Journal of Zoology, 15(1–3): ry marine gastropods of the family Terebridae as 89–98. inferred from stable isotope data. Marine Ecology Bell J. 2008. Feeding preferences of the cushion star Progress Series, 497: 143–156. Culcita novaeguineae in the presence of the crown Fry B. 2006. Stable isotope ecology. New York, Spring- of thorns starfish Acanthaster planci. UC Berke- er, 308 p. ley: UCB Moorea Class: Biology and Geomor- Gladyshev M.I. 2009. Stable isotope analyses in aqua- phology of Tropical Islands. Student Research Pa- tic ecology (a review). Journal of Siberian Federal pers, https://escholarship.org/uc/item/97r5p1r3 University. Biology, 2(4): 381–402. Boag B., Neilson R., Robinson D., Scrimgeour C.M., Hobson K.A., Clark R.G., 1992. Assessing avian diets Handley L.L. 1998. Wild rabbit host and some para- using stable isotope II: factors influencing diet– sites show trophic-level relationships for δ13C and tissue fractionation. Condor, 94: 189–197. δ15N: A first report. Isotopes in environmental and Hoskin G.P., Warén A. 1983. Peasistilifer edulis, a new health studies, 33: 81–85. eulimid prosobranch, parasitic on an Indo-Pacific Cabioch L., Grainger J.N., Keegan B.F., Konnecker G. holothurian. Nautilus, 97: 23–26. 1978. Balcis alba (Da Costa). A temporary ectopar- Ivanov A.V. 1952. The structure of the ectoparasic gas- asite on Neopentadactyla mixta Ostergren. In: tropods of Stiliferidae as a result of their lifestyle. McHusky D.S., Berry A.J. (Eds) Proceedings of the Trudy Leningradskogo Obschestva Estestvoispy- 12th European Marine Biology Symposium. Perga- tateley, 71(4): 86–140 [In Russian]. mon Press, Oxford: 237–241. Kaehler S., Pakhomov E.A. 2001. Effects of storage and Canuel E.A., Cloern J.E., Ringelberg D.B., Guckert J.B., preservation on the δ13C and δ15N signatures of Rau G.H. 1995. Molecular and isotopic tracers used selected marine organisms. Marine Ecology to examine sources of organic matter and its incor- Progress Series, 219: 299–304. poration into the food webs of San Francisco Bay. Lafferty K., Allesina S., Arim M., Briggs C.J., De Leo G., Limnology and Oceanography, 40: 67–81. Dobson A.P., Dunne J.A., Johnson P.T.J., Kuris A.M., Carabel S., Verisimo P., Freire J. 2009. Effects of preser- Marcogliese D.J., Martinez N.D., Memmott J., Mar- vatives on stable isotope analyses of four marine quet P.A., McLaughlin J.P., Mordecai E.A., Pascual species. Estuarine, Coastal and Shelf Science, 82: M., Poulin R., Thieltges D.W. 2008. Parasites in 348–350. food webs: the ultimate missing links. Ecology Let- Coleman N. 2007. Sea stars: Echinoderms of the Asia- ters, 11: 533–546. Indo-Pacific. Springwood. Neville Coleman’s Un- Laxton J. H. 1974. A preliminary study of the biology derwater Geographic Pty Ltd., 136 p. and ecology of the blue starfish Linckia laevigata Crossland M.R., Alford R.A., Collins J.D. 1991. Popula- (L.) on the Australian Great Barrier Reef and an tion dynamics of an ectoparasitic gastropod, Hy- interpretation of its role in the coral reef ecosystem. permastus sp. (Eulimidae), on the sand dollar, Arach- Biological Journal of the Linnean Society, 6: 47–64. noides placenta (Echinoidea). Australian Journal Lützen J. 1972. Studies on parasitic gastropods from of Marine and Freshwater Research, 42: 69–76. echinoderms II. Det Kongelige Danske Videnskab- Crossland M.R., Collins J.D., Alford R.A. 1993. Host ernes Selskab Biologiske Skrifter, 19(6): 1–20. selection and distribution of Hypermastus placen- Macko S.A., Estep M.F., Engel M.H., Hare P.E. 1986. tae (Eulimidae), an ectoparasitis gastropod on the Kinetic fractionation of stable nitrogen isotopes sand dollar Arachnoides placenta (Echinoidea). during amino acid transamination. Geochimica et Australian Journal of Marine and Freshwater Re- Cosmochimica Acta, 50: 2143–2146. search, 44: 835–844. McConnaughey T., McRoy C.P. 1979. Food-web struc- DeNiro M.J., Epstein S. 1978. Influence of diet on the ture and the fractionation of carbon isotopes in the distribution of carbon isotopes in . Geo- Bering Sea. Marine Biology, 53: 257–262. chimica et Cosmochimica Acta, 42: 495–506. McKinney R.A., Lake J.L., Allen M., Ryba S. 1999. DeNiro M.J., Epstein S. 1981. Influence of diet on the Spatial ability in mussels used to assess base level distribution of nitrogen isotopes in animals. Geo- nitrogen isotope ratio in freshwater ecosystems. chimica et Cosmochimica Acta, 45: 343–351. Hydrobiologia, 412: 17–24. Deudero S., Pinnegar J.K., Polunin N.V.C. 2002. Insights Minigawa M., Wada E. 1984. Stepwise enrichment of into fish host–parasite trophic relationships re- δ15N along food chains: further evidence and the vealed by stable isotope analysis. Diseases of relation between δ15N and animal age. Geochimica Aquatic Organisms, 52: 77–86. et Cosmochimica Acta, 48: 1135–1140. Dgebuadze P.Yu., Kantor Yu.I. 2015. The preference of Navarro J., Albo-Puigserver M., Coll M., Saez R., Forero symbiotic Annulobalcis gastropods (Eulimidae) for M.G., Kutcha R. 2014. Isotopic discrimination of a their crinoid hosts. Symbiosis, 68(1): 109–114. stable isotopes of nitrogen (for δ15N) and carbon Dubois S.Y., Savoye N., Sauriau P.-G., Billy I., Martinez (δ13C) in a host-specific holocephalan tapeworm. P., de Montaudouin X. 2009. Digenean trematodes– Journal of Helminthology, 88(3): 371–375. marine mollusc relationships: a stable isotope study. Neilson R., Boag B., Hartley G. 2005. Temporal host– Diseases of Aquatic Organisms, 84: 65–77. parasite relationships of the wild rabbit, Oryctola- Egloff D.A., Smouse D.T. Jr., Pembroke J.E. 1988. Pene- gus cuniculus (L.) as revealed by stable isotope tration of the radial hemal and perihemal systems of analyses. Parasitology, 131: 279–285. Linckia laevigata (Asteroidea) by the proboscis of O’Grady S.P., Dearing M.D. 2006. Isotopic insight into 202 E.S. Mekhova, P.Yu. Dgebuadze

host–endosymbiont relationships in liolaemid liz- tribuloides (Echinodermata: Echinoidea). Journal ards. Oecologia, 150: 355–361. of Conchology, 42(5): 371–377. Parmentier E., Das K. 2004. Commensal vs. parasitic Thieltges D.W., Goedknegt M.A., O’Dwyer K., Senior relationship between Carapini fish and their hosts: A.M., Kamiya T. 2019. Parasites and stable iso- some further insight through δ13C and δ15N meas- topes: a comparative analysis of isotopic discrimi- urements. Journal of Experimental Marine Biolo- nation in parasitic trophic interactions. Oikos, 128: gy and Ecology 310: 47–58. 1329–1339 Pinnegar J.K., Campbell N., Polunin N.V.C. 2001. Unu- Tieszen L.L., Boutton T.W., Tesdahl K.G., Slade N.A. sual stable isotopic fractionation patterns observed 1983. Fractionation and turn-over of stable carbon for fish host–parasite trophic relationships. Jour- isotopes in animal tissues: implication for δ13C anal- nal of Fish Biology, 59: 494–503. ysis of diet. Oecologia, 57: 32– 37. Post D.M., Layman C.A., Arrington D. A., Takimoto G., Warén A. 1983. A generic revision of the family Eulimi- Quattrochi J., Montaña C.G. 2007. Getting to the fat dae (Gastropoda, Prosobranchia). Journal of Mol- of the matter: models, methods and assumptions for luscan Studies, 49 (Supplement 13): 1–96. dealing with lipids in stable isotope analyses. Oeco- Warén A., Sibuet M. 1981. Ophieulima (, logia, 152: 179–189. doi:10.1007/s00442-006-0630-x Prosobranchia), a new genus of ophiuroid para- Queiroz V., Neves E., Sales L., Johnsson R. 2017. The sites. Sarsia, 66: 103–107. gall-former Sabinella troglodytes (Caenogastropo-  da: Eulimidae) and its association with Eucidaris