scholarly journals Stable Isotope Dynamics of Herbivorous Reef Fishes and Their Ectoparasites

Diversity ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 429
Author(s):  
William G. Jenkins ◽  
Amanda W. J. Demopoulos ◽  
Matthew D. Nicholson ◽  
Paul C. Sikkel
Keyword(s):  
Coral Reef ◽  
Stable Isotope ◽  
Host Species ◽  
Isotope Analysis ◽  
Fish Tissue ◽  
Reef Fishes ◽  
Species Discrimination ◽  
Interspecific Differences ◽  
Discrimination Factors ◽  
Trophic Linkages

Acanthurids (surgeonfishes) are an abundant and diverse group of herbivorous fishes on coral reefs. While their contribution to trophic linkages and dynamics in coral reef systems has received considerable attention, the role of linkages involving their parasites has not. As both consumers of fish tissue and prey to microcarnivores, external parasites may play a significant role in trophic transfer between primary consumers (and hence their predominantly algae-based diet) and the broader coral reef community. Stable isotope analysis is a common tool for studying trophic linkages which can be used for studies involving parasites. We examined the stable isotope ecology (13C and 15N) of copepod (Caligus atromaculatus) and monogenean (Neobenedenia sp.) ectoparasites collected from two species of Caribbean acanthurids (Acanthurus coeruleus and Acanthurus bahianus). There were significant intraspecific differences in isotope discrimination factors between parasites collected from the two different host species as well as interspecific differences between parasites collected from the same host species. Discrimination factors for 15N were consistently positive but varied in magnitude depending on host and parasite species and were slightly lower than what would be expected for consumers. The 13C discrimination factors for both monogeneans and copepods collected from A. coeruleus were consistently positive but were negative for copepods collected from A. bahianus. These findings emphasize the complexity of the stable isotope trophic interactions occurring between parasites and their hosts, highlighting the value of these types of host-parasite isotopic studies.

scholarly journals Screening of Ciguatoxins in the Philippines by Animal Assay: Symptoms, Levels, and Distribution in Fish Tissue

2021 ◽  
pp. 87-95
Author(s):  
Bryan Tanyag ◽  
Karl Bryan Perelonia ◽  
Flordeliza Cambia ◽  
Ulysses Montojo
Keyword(s):  
Coral Reef ◽  
Fish Tissue ◽  
Reef Fishes ◽  
The Philippines ◽  
Coral Reef Fishes ◽  
Human Consumption ◽  
Mouse Bioassay ◽  
Major Protein ◽  
Commercially Important ◽  
Fish Viscera

The Philippines is an archipelagic country that belongs to the biologically diverse Pacific Coral Triangle, rich in marine resources, including corals, reef fishes, and algae. This explains the continuous sustenance of the Filipinos on fish as a major protein source. Despite their contribution to human consumption, some commercially important coral reef fishes are a threat to food safety, compromising public health. Currently, ciguatera fish poisoning (CFP) has been focused on by scientists since it is the most frequently reported seafood-toxin illness in the world acquired from contaminated coral reef fishes. The present study investigates the contamination of reef fishes in the West Philippine and Sulu Seas using animal assay. Ciguatoxins (CTX) are present in commercially important reef fishes such as barracuda (Sphyraena barracuda), parrotfish (Scarus quoyi), rabbitfish (Siganus guttatus), grouper (Plectropomus leopardus), moray eel (Gymnothorax melanospilos), and snapper (Lutjanus campechanus). Scarus quoyi had the highest toxicity of 0.65 ± 0.55 ppb and 0.48 ± 0.36 ppb found in flesh and viscera, respectively. Although higher toxicities were observed from fish viscera, toxicities between fish parts did not vary greatly (p > 0.05). Positive samples exceeded the 0.01 ppb guideline established by the US Food and Drug Administration and the Philippines’ regulatory limit set by the Bureau of Fisheries and Aquatic Resources. Symptoms of mice showing the presence of Pacific CTX-1 were noted. Since mouse bioassay was used in screening reef fishes that pose non-specificity and insensitivity problems, the researchers suggest that analytical methods must be used in characterizing and quantifying these types of toxins. Establishing the methodologies in detecting CTX would greatly help monitor and manage CFP in commercially identified reef fishes in the country.

Food source determines stable isotope discrimination factors ΔN and ΔC in tadpoles

2020 ◽  
Vol 41 (4) ◽  
pp. 501-507
Author(s):  
Julian Glos ◽  
Katharina Ruthsatz ◽  
Dominik Schröder ◽  
Jana C. Riemann
Keyword(s):  
Stable Isotope ◽  
Food Source ◽  
Trophic Ecology ◽  
Rana Temporaria ◽  
Isotope Ratios ◽  
Bufo Bufo ◽  
Discrimination Factor ◽  
Fractionation Factor ◽  
Interspecific Differences ◽  
Discrimination Factors

Abstract Analyses of stable isotope ratios are widely applied in studies on a large variety of aspects in trophic ecology. Most studies rely on a precise estimation of the relevant discrimination factor Δ (also called the fractionation factor), that reflects the fractionation or differences in isotope ratios of a certain element (mainly nitrogen N and carbon C) between an animal’s diet and its tissue and is used to identify one step in the food web. We experimentally determined ΔN and ΔC of two species of widespread amphibians in Europe, Rana temporaria and Bufo bufo, and tested for the effect of food source (cyanobacteria Spirulina vs. zooplanktonic Daphnia) on Δ and for interspecific differences. Our study shows high variation in Δ in relation to the food source, but low interspecific differences. Tadpoles that were fed with Spirulina did have considerably lower ΔN than tadpoles fed with Daphnia in both species, and lower ΔC only in R. temporaria. The range of Δ obtained here can be a useful baseline for future trophic studies on tadpoles of Rana and Bufo. The strong diet-dependency of Δ, however, argues strongly against the use of a fixed discrimination factor in future isotope studies.

Identifying carbon sources and trophic position of coral reef fishes using diet and stable isotope (δ15N and δ13C) analyses in two contrasted bays in Moorea, French Polynesia

Coral Reefs ◽  
2013 ◽  
Vol 32 (4) ◽  
pp. 1091-1102 ◽  
Author(s):  
Y. Letourneur ◽  
T. Lison de Loma ◽  
P. Richard ◽  
M. L. Harmelin-Vivien ◽  
P. Cresson ◽  
...  
Keyword(s):  
Coral Reef ◽  
Stable Isotope ◽  
Trophic Position ◽  
Carbon Sources ◽  
Reef Fishes ◽  
French Polynesia ◽  
Coral Reef Fishes ◽  
Δ15n And Δ13c

scholarly journals Isotopic discrimination in helminths infecting coral reef fishes depends on parasite group, habitat within host, and host stable isotope value

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Philip M. Riekenberg ◽  
Marine J. Briand ◽  
Thibaud Moléana ◽  
Pierre Sasal ◽  
Marcel T. J. van der Meer ◽  
...  
Keyword(s):  
Stable Isotopes ◽  
Coral Reef ◽  
Stable Isotope ◽  
Reef Fish ◽  
Coral Reef Fish ◽  
Trophic Ecology ◽  
Negative Relationship ◽  
Reef Fishes ◽  
Trophic Relationships ◽  
Host Parasite

AbstractStable isotopes of carbon and nitrogen characterize trophic relationships in predator–prey relationships, with clear differences between consumer and diet (discrimination factor Δ13C and Δ15N). However, parasite–host isotopic relationships remain unclear, with Δ13C and Δ15N remaining incompletely characterized, especially for helminths. In this study, we used stable isotopes to determine discrimination factors for 13 parasite–host pairings of helminths in coral reef fish. Differences in Δ15N values grouped according to parasite groups and habitat within the host with positive Δ15N values observed for trematodes and nematodes from the digestive tract and variable Δ15N values observed for cestodes and nematodes from the general cavity. Furthermore, Δ13C values showed more complex patterns with no effect of parasite group or habitat within host. A negative relationship was observed between Δ15N and host δ15N values among different host-parasite pairings as well as within 7 out of the 13 pairings, indicating that host metabolic processing affects host-parasite discrimination values. In contrast, no relationships were observed for Δ13C values. Our results indicate that parasite group, habitat within host, and host stable isotope value drive Δ15N of helminths in coral reef fish while their effect on Δ13C is more idiosyncratic. These results call for use of taxon- or species-specific and scaled framework for bulk stable isotopes in the trophic ecology of parasites.

scholarly journals Effects of preservation methods of muscle tissue from upper-trophic level reef fishes on stable isotope values (δ13C and δ15N)

2014 ◽  
Author(s):  
Christopher D. Stallings ◽  
James A. Neslon ◽  
Katherine L. Rozar ◽  
Charles S. Adams ◽  
Kara R. Wall ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Mass Balance ◽  
Muscle Tissue ◽  
Stable Isotope Analysis ◽  
Trophic Level ◽  
Isotopic Ratio ◽  
Isotope Analysis ◽  
Reef Fishes ◽  
Δ13c And Δ15n ◽  
Preservation Methods

Research that uses stable isotope analysis often involves a delay between sample collection in the field and laboratory processing, therefore requiring preservation to prevent or reduce tissue degradation and associated isotopic compositions. Although there is a growing literature describing the effects of various preservation techniques, the results are often contextual, unpredictable and vary among taxa, suggesting the need to treat each species individually. We conducted a controlled experiment to test the effects of four preservation methods of muscle tissue from four species of upper trophic-level reef fish collected from the eastern Gulf of Mexico (Red Grouper Epinephelus morio, Gag Mycteroperca microlepis, Scamp Mycteroperca phenax, and Red Snapper Lutjanus campechanus). We used a paired design to measure the effects on isotopic values for carbon and nitrogen after storage using ice, 95% ethanol, and sodium chloride (table salt), against that in a liquid nitrogen control. Mean offsets for both δ13C and δ15N values from controls were lowest for samples preserved on ice, intermediate for those preserved with salt, and highest with ethanol. Within species, both salt and ethanol significantly enriched the δ15N values in nearly all comparisons. Ethanol also had strong effects on the δ13C values in all three groupers. Conversely, for samples preserved on ice, we did not detect a significant offset in either isotopic ratio for any of the focal species. Previous studies have addressed preservation-induced offsets in isotope values using a mass balance correction that accounts for changes in the isotope value to that in the C/N ratio. We tested the application of standard mass balance corrections for isotope values that were significantly affected by the preservation methods and found generally poor agreement between corrected and control values. The poor performance by the correction may have been due to preferential loss of lighter isotopes and corresponding low levels of mass loss with a substantial change in the isotope value of the sample. Regardless of mechanism, it was evident that accounting for offsets caused by different preservation methods was not possible using the standard correction. Caution is warranted when interpreting the results from specimens stored in either ethanol or salt, especially when using those from multiple preservation techniques. We suggest the use of ice as the preferred preservation technique for muscle tissue when conducting stable isotope analysis as it is widely available, inexpensive, easy to transport and did not impart a significant offset in measured isotopic values. Our results provide additional evidence that preservation effects on stable isotope analysis can be highly contextual, thus requiring their effects to be measured and understood for each species and isotopic ratio of interest before addressing research questions.

scholarly journals The impact of metabolism on stable isotope dynamics: a theoretical framework

2010 ◽  
Vol 365 (1557) ◽  
pp. 3455-3468 ◽  
Author(s):  
Laure Pecquerie ◽  
Roger M. Nisbet ◽  
Ronan Fablet ◽  
Anne Lorrain ◽  
Sebastiaan A. L. M. Kooijman
Keyword(s):  
Stable Isotope ◽  
Life Histories ◽  
Isotope Analysis ◽  
Individual State ◽  
Dynamic Energy Budget ◽  
Discrimination Factors ◽  
Reliable Interpretation ◽  
The Impact ◽  
Selection Of ◽  
Isotopic Incorporation

Stable isotope analysis is a powerful tool used for reconstructing individual life histories, identifying food-web structures and tracking flow of elemental matter through ecosystems. The mechanisms determining isotopic incorporation rates and discrimination factors are, however, poorly understood which hinders a reliable interpretation of field data when no experimental data are available. Here, we extend dynamic energy budget (DEB) theory with a limited set of new assumptions and rules in order to study the impact of metabolism on stable isotope dynamics in a mechanistic way. We calculate fluxes of stable isotopes within an organism by following fluxes of molecules involved in a limited number of macrochemical reactions: assimilation, growth but also structure turnover that is here explicitly treated. Two mechanisms are involved in the discrimination of isotopes: (i) selection of molecules occurs at the partitioning of assimilation, growth and turnover into anabolic and catabolic sub-fluxes and (ii) reshuffling of atoms occurs during transformations. Such a framework allows for isotopic routing which is known as a key, but poorly studied, mechanism. As DEB theory specifies the impact of environmental conditions and individual state on molecule fluxes, we discuss how scenario analysis within this framework could help reveal common mechanisms across taxa.

scholarly journals Stable isotope turnover rates and fractionation in captive California yellowtail (Seriola dorsalis): insights for application to field studies

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Daniel J. Madigan ◽  
Owyn E. Snodgrass ◽  
John R. Hyde ◽  
Heidi Dewar
Keyword(s):  
Stable Isotope ◽  
Isotope Analysis ◽  
Field Studies ◽  
Individual Variability ◽  
Turnover Rates ◽  
Tissue Discrimination ◽  
Aquaculture Feed ◽  
Discrimination Factors ◽  
Seriola Dorsalis

AbstractStable isotope analysis (SIA) measurements from long-term captivity studies provide required parameters for interpretation of consumer SIA data. We raised young-of-the-year (14–19 cm) California yellowtail (Seriola dorsalis) on a low δ15N and δ13C diet (pellet aquaculture feed) for 525 days, then switched to a high δ15N and δ13C diet (mackerel and squid) for 753 days. Yellowtail muscle was sequentially sampled from each individual after the diet switch (0 to 753 days) and analyzed for δ15N and δ13C, allowing for calculation of diet-tissue discrimination factors (DTDFs) from two isotopically different diets (low δ15N and δ13C: pellets; high δ15N and δ13C: fish/squid) and turnover rates of 15N and 13C. DTDFs were diet dependent: Δ15N = 5.1‰, Δ13C = 3.6‰ for pellets and Δ15N = 2.6‰, Δ13C = 1.3‰ for fish/squid. Half-life estimates from 15N and 13C turnover rates for pooled yellowtail were 181 days and 341 days, respectively, but varied considerably by individual (15N: 99–239 d; 13C: 158–899 d). Quantifying DTDFs supports isotopic approaches to field data that assume isotopic steady-state conditions (e.g., mixing models for diet reconstruction). Characterizing and quantifying turnover rates allow for estimates of diet/habitat shifts and “isotopic clock” approaches, and observed inter-individual variability suggests the need for large datasets in field studies. We provide diet-dependent DTDFs and growth effects on turnover rates, and associated error around these parameters, for application to field-collected SIA data from other large teleosts.

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