Food quality affects secondary consumers even at low quantities: an experimental test with larval European lobster

The issues of food quality and food quantity are crucial for trophic interactions. Although most research has focussed on the primary producer-herbivore link, recent studies have shown that quality effects at the bottom of the food web propagate to higher trophic levels. Negative effects of poor food quality have almost exclusively been demonstrated at higher food quantities. Whether these negative effects have the same impact at low food availability in situations where the majority if not all of the resources are channelled into routine metabolism, is under debate. In this study a tri-trophic food chain was designed, consisting of the algae Rhodomonas salina, the copepod Acartia tonsa and freshly hatched larvae of the European lobster Homarus gammarus. The lobster larvae were presented with food of two different qualities (C:P ratios) and four different quantities to investigate the combined effects of food quality and quantity. Our results show that the quality of food has an impact on the condition of lobster larvae even at very low food quantities. Food with a lower C:P content resulted in higher condition of the lobster larvae regardless of the quantity of food. These interacting effects of food quality and food quantity can have far reaching consequences for ecosystem productivity.     

Intraspecific selectivity,compensatory feeding and flexible homeostasis in the phagotrophic flagellate <Emphasis Type="Italic">Oxyrrhis marina</Emphasis>: three ways to handle food quality fluctuations

The phagotrophic flagellate Oxyrrhis marina shows a strong stoichiometric plasticity when fed differently grown Rhodomonas salina. We tested whether differently pre-conditioned O. marina displayed selective feeding behaviour from a mixture of nitrogen and phosphorus depleted R. salina. We observed selective feeding of O. marina, always selecting phosphorus rich R. salina independent of the pre-conditioning of the protists. In a second experiment, O. marina was again pre-conditioned either with nitrogen- or phosphorus-depleted R. salina and was refed with either of the differently limited R. salina in single food treatments (not in a mixture). The phagotrophic flagellate displayed compensatory feeding which means that O. marina feed more on the food source which they were not given before. Due to its stoichiometric plasticity, O. marina might handle bad quality food by following the stoichiometry of its prey and additionally by active selective feeding towards P-rich algae to enhance growth. Post-ingestion selection might as well be an important feature which means that ingested elements in excess are quickly excreted and scarce elements are ingested through accelerated food uptake.     

Food intake and absorption are affected by dietary lipid level and lipid source in seabream (Sparus aurata L.) larvae

Marine larval nutrition studies have classically focused on essential fatty acid (EFA) requirements and very little is known regarding the effect of total lipid level or lipid source on food ingestion and absorption, which are important factors determining growth. In the present work two experiments analysed food intake and nutrient absorption in seabream larvae in response to two dietary lipid levels (17-18% and 25-28%). The first experiment tested Artemia enriched on two levels of a fish oil emulsion (higher and lower—HF and LF, respectively), while in the second experiment larvae were co-fed Artemia enriched on one of two levels of a soybean oil emulsion and a microdiet (MD) containing one of two levels of soybean oil as the main lipid source (higher and lower—HS and LS, respectively). Food intake and nutrient absorption were determined by performing radioactive trials using Artemia radiolabelled with [1-¹⁴C] oleic acid in the first experiment (at 26 and 33 days after hatching—DAH) and MD labelled with [1-¹⁴C] oleic acid or glycerol tri[1-¹⁴C] oleate (31 and 32 DAH) in the second experiment. The dietary treatments did not induce significant differences in larval dry weight in the first experiment, while food intake was significantly higher and nutrient absorption significantly lower in larvae fed the HF diet, compared to the LF treatment. In the second experiment, a significantly higher dry weight was achieved by larvae fed on the LS diet, which was also significantly more ingested and absorbed. The fish oil experiment supports the hypothesis that a higher food intake may cause a decrease in nutrient absorption efficiency, possibly through a faster gut transit, but in the soybean oil experiment total absorption appears to have simply reflected food intake. The results show that dietary lipid level significantly affects larval food intake and absorption efficiency but the effect was dependent on lipid source, suggesting that dietary fatty acid (FA) composition might be a more determinant factor than total lipid level. Food intake was apparently not regulated to meet a requirement for EFA. Lipid source or FA composition may regulate food intake through pre- or post-absorptive mechanisms, such as through effects on palatability, digestibility and stimulation of neuroendocrine pathways.     

Optimization of photosynthesis,growth, and biochemical composition of the microalga <Emphasis Type="Italic">Rhodomonas salina</Emphasis>—an established diet for live feed copepods in aquaculture

The cryptophyte Rhodomonas salina is widely used as feed for copepod cultures. However, culturing conditions to obtain high-quality algae have not yet been efficiently optimized. Therefore, we aimed to develop a cultivation protocol for R. salina to optimize its nutritional value and provide technical recommendations for later large-scale production in algal photobioreactors. We studied photosynthesis, growth, pigments, fatty acid (FA) and free amino acid (FAA) composition of R. salina cultured at different irradiances (10–300 μmol photons m^?2 s^?1) and nutrient availability (deficiency and excess). The optimal range of irradiance for photosynthesis and growth was 60–100 μmol photons m^?2 s^?1. The content of chlorophylls a and c decreased with increasing irradiance while phycoerythrin peaked at irradiances of 40–100 μmol photons m^?2 s^?1. The total FA content was maximal at optimal irradiances for growth, especially under nutrient deficiency. However, highly unsaturated fatty acids, desired components for copepods, were higher under nutrient excess. The total FAA content was highest at limiting irradiances (10–40 μmol photons m^?2 s^?1) but a better composition with a higher fraction of essential amino acids was obtained at saturated irradiances (60–140 μmol photons m^?2 s^?1). These results demonstrate that quality and quantity of FA and FAA of R. salina can be optimized by manipulating the irradiance and nutrient conditions. We suggest that R. salina should be cultivated in a range of irradiance 60–100 μmol photons m^?2 s^?1 and nutrient excess to obtain algae with high production and a balanced biochemical composition as feed for copepods.     

Does the nutrient stoichiometry of primary producers affect the secondary consumer Pleurobrachia pileus?

We investigated whether phosphorus limitations of primary producers propagate upwards through the food web, not only to the primary consumer level but also onto the secondary consumers’ level. A tri-trophic food chain was used to assess the effects of phosphorus-limited phytoplankton (the cryptophyte Rhodomonas salina) on herbivorous zooplankters (the copepod Acartia tonsa) and finally on zooplanktivores (the ctenophore Pleurobrachia pileus). The algae were cultured in phosphorus-replete and phosphorus-limited media before being fed to two groups of copepods. The copepods in turn were fed to the top predator, P. pileus, in a mixture resulting in a phosphorus-gradient, ranging from copepods having received only phosphorus-replete algae to copepods reared solely on phosphorus-limited algae. The C:P ratio of the algae varied significantly between the two treatments, resulting in higher C:P ratios for those copepods feeding on phosphorus-limited algae, albeit with a significance of 0.07. The differences in the feeding environment of the copepods could be followed to Pleurobrachia pileus. Contrary to our expectations, we found that phosphorus-limited copepods represented a higher quality food source for P. pileus, as shown by the better condition (expressed as nucleic acid content) of the ctenophore. This could possibly be explained by the rather high C:P ratios of ctenophores, their resulting low phosphorus demand and relative insensitivity to P deficiency. This might potentially be an additional explanation for the observed increasing abundances of gelatinous zooplankton in our increasingly phosphorus-limited coastal seas.     

Performance of Five Food Regimes on Anopheles gambiae Senso Stricto Larval Rearing to Adult Emergence in Insectary

Background

Rearing of Anopheles gambiae s.s mosquitoes in insectary with quality cheap food sources is of paramount importance for better and healthy colony. This study evaluated larval survival and the development rate of aquatic stages of An.gambiae s.s under five food regimes; tetramin fish food (a standard insectary larval food), maize pollen, Cerelac, green filamentous algae and dry powdered filamentous algae.

Methods

Food materials were obtained from different sources, cerelac was made locally, fresh filamentous algae was taken from water bodies, dry filamentous algae was ground to powder after it was dried under shade, and maize pollen was collected from the flowering maize. Each food source type was used to feed three densities of mosquito larvae 20, 60, and 100 in six replicates each. Larval age structure was monitored daily until pupation and subsequently adult emergence. Tetramin was used and taken as a standard food source for An. gambiae s.s. larvae feeding in Insectary.

Results

Larval survivorship using maize pollen and Tetramin fish food was statistically insignificant (P = 0.564). However when compared to other food regime survivorship was significantly different with Tetramin fish food performing better than cerelac (P<0.001), dry algae (P<0.001) and fresh algae (P<0.001). The pupation rates and sex ratio of emerging adults had significant differences among the food regimes.

Conclusion

The findings of this study have shown that maize pollen had closely similar nutritional value for larval survivorship to tetramin fish food, a standard larvae food in insectary. Further studies are required to assess the effect of food sources on various life traits of the emerged adults.     

Effect of dietary polyunsaturated fatty acids on reproductive output and larval growth of bivalves

The pre-spawning condition of adult bivalves is influenced by quantity and quality of available food. For bivalves, the essential polyunsaturated fatty acids (PUFAs) eicosapentaenoic acid (EPA) 20:5(n-3) and docosahexaenoic acid (DHA) 22:6(n-3) are presumed to determine the nutritional value of algae. Macoma balthica kept on a broodstock diet supplemented with PUFAs spawned a larger number of eggs (average 22220) per female and larger sized eggs (106.7 μm) compared to adults kept on a diet without PUFA supplementation (962.5 eggs with average size 99.8 μm).Larvae of M. balthica from the same parental pool however did not profit from a diet where a part was replaced with PUFA spheres. Instead, larvae reared on Isochrysis sp. showed lower mortality and higher growth rates than larvae fed on the same algae supplemented with lipid spheres. Crassostrea gigas larvae showed no clear response to a PUFA supplemented diet.     

Biotesting of water quality in Peter the Great Bay with the use of the microalga Dunaliella salina and embryos and larvae of the sea urchin Scaphechinus mirabilis

Comparative biotesting was performed using embryos and larvae of the sea urchin Scaphechinus mirabilis and the microalga Dunaliella salina. These two species were taken as test organisms for estimating water quality in areas of various anthropogenic loads. Seawater from Nakhodka and Vostok bays, as well as from the southwestern part of Peter the Great Bay (Sea of Japan) near the Tumen River mouth, was tested. Water from Vostok and Nakhodka bays had a harmful effect on embryonic and larval development of the sea urchin. The algal culture kept in the water of Vostok Bay was depressed throughout the experiment, while development of the alga in the water from Nakhodka Bay hardly differed from the control but was unstable. Water from the southwestern part of Peter the Great Bay did not have any significant harmful effect on both test organisms. Embryos and larvae of the sea urchin S. mirabilis were several orders more sensitive to salinity changes and content of toxic agents; they responded more readily to changes in water quality than D. salina cells. Correspondingly, embryos and larvae of the sea urchin S. mirabilis were found to be a preferable test organism for assessment of pollution in various marine environments.     

Optimization of environmental parameters for <Emphasis Type="Italic">Nannochloropsis salina</Emphasis> growth and lipid content using the response surface method and invading organisms

Algae biofuel has the potential to replace fossil fuels. However, cultivation and productivity of target algae need improvement, while controlling undesired organisms that can lower the efficiency of production systems. A central composite design and response surface model were utilized to predict cultivation optima of marine microalga, Nannochloropsis salina, under a suite of environmental parameters. The effects of salinity, pH, and temperature and their interactions were studied on maximum sustainable yield (MSY, a measure for biomass productivity), lipid content of N. salina, and invading organisms. Five different levels of each environmental predictor variable were tested. The environmental factors were kept within ranges that had previously been determined to allow positive N. salina growth (14.5–45.5 PSU; pH 6.3–9.7; 11–29 °C). The models created for this experiment showed that N. salina’s MSY and lipid content are not strongly affected over the broad range of salinity and temperature values. Calculated optima levels were 28 PSU/20 °C for MSY and 14.5 PSU/20 °C for lipid accumulation, but neither value significantly influenced the model. However, pH was the most important factor to influence algae productivity, and pH optimum was estimated around 8. Both MSY and lipid content were strongly reduced when pH deviated from the optimum. Occurrence of invading organisms seemed stochastic, and none of the environmental factors studied significantly influenced abundance. In conclusion, pH should be kept around 8 for maximum productivity of N. salina. Temperature and salinity should be kept around 20 °C and 28 PSU; however, moderate variations are not too much of a concern and might enhance lipid content of N. salina.     

The significance of diet in the growth and development of larvae of the blue crab,Callinectes sapidus rathbun,under laboratory conditions

The following protistan diets were tested on blue crab larvae: the algae Isochrisis galbana Parke, Monochrisis lutheri Droop, Dunaliella sp., and an unknown mixture; and the ciliated protozoans Euplotes vannus Muller and Parauronema virginianum(2/1) Thompson. None of these diets resulted in development past the first zoea stage, although some apparently were ingested and delayed mortality as compared to unfed controls.The rotifer Brachionus plicatilis Müller sustained good survival through early zoea development; however, rotifer-fed larvae did not metamorphose to the megalopa. Larvae of the polychaete Hydroides dianthus (Verrill) sustained crab larvae throughout zoea development, resulting in 17% survival to metamorphosis. The percentage mortality per stage was significantly lower in polychaete-fed larvae when compared with rotifer-fed larvae during zoea stages III, VI, and VII. Mean intermolt duration varied between diet treatments during the first three stages, but showed no differences during later zoea development. In tests on groups of late stage sibling larvae, Artemia salina L. nauplii gave development to metamorphosis, whereas rotifers did not.All the diets so far tested on blue crab larvae are classified according to their ability to sustain development. It is demonstrated that the two diets which allow completed development, Hydroides dianthus larvae and Artemia salina nauplii, contain 2–3 times as much lipid per dry weight as do rotifers. A metabolic requirement for lipid late in development may be indicated. Invertebrate larvae derived from yolky telolecithal and centrolecithal eggs may be an important dietary component for brachyuran larvae.     

Nucleic acid indices of egg production in the tropical copepod Acartia sinjiensis

Two experiments were conducted to evaluate the effects of food and temperature on the nucleic acid content and egg production (and their relationship) of the tropical copepod Acartia sinjiensis. Experiment 1 evaluated the effect of food quality (as different algae species) on the relationship between nucleic acid content and egg production. In Experiment 2, the main and interaction effects of food type, food concentration and temperature on the total, Carbon and Nitrogen specific egg production and nucleic acid indices were evaluated in a factorial experimental design. Food quality, concentration and temperature significantly affected the nucleic acid content, egg production rate and the nucleic acid-egg production relationship of A. sinjiensis. RNA indices were correlated with egg production in females fed Pavlova salina, Tetraselmis chuii and Chaetoceros muelleri, but not in females fed Isochrysis aff. galbana. The slopes of the linear regressions of RNA indices as predictors of egg production were similar in females fed different algae species, suggesting that the slope of these relationships might be independent of food quality. The DNA content of females was significantly affected by food and temperature, suggesting that it is not a good index of cell number in this species. Nevertheless, the RNA:DNA ratio was as good a predictor of egg production as total RNA content. Egg production showed a weakly positive correlation with temperature. On the other hand, total, C- and N-specific nucleic acid indices had a strong negative correlation with temperature. In addition, temperature had a non linear effect on the slopes of the regression lines of RNA content and RNA:DNA ratio as predictors of egg production—slopes were similar at 25 °C and 30 °C, but significantly lower at 20 °C. Furthermore, the predictability of egg production was improved when the interaction term of nucleic acid indices with temperature was used instead of the nucleic acid indices alone in linear regression models. Our results suggest food quality has a limited influence on the nucleic acid-egg production relationship, and that temperature should be accounted for in models using nucleic acid indices as predictors of egg production in A. sinjiensis.     

Interspecific and nutrient-dependent variations in stable isotope fractionation: experimental studies simulating pelagic multitrophic systems

Stable isotope signatures of primary producers display high inter- and intraspecific variation. This is assigned to species-specific differences in isotope fractionation and variable abiotic conditions, e.g., temperature, and nutrient and light availability. As consumers reflect the isotopic signature of their food source, such variations have direct impacts on the ecological interpretation of stable isotope data. To elucidate the variability of isotope fractionation at the primary producer level and the transfer of the signal through food webs, we used a standardised marine tri-trophic system in which the primary producers were manipulated while the two consumer levels were kept constant. These manipulations were (1) different algal species grown under identical conditions to address interspecific variability and (2) a single algal species cultivated under different nutrient regimes to address nutrient-dependent variability. Our experiments resulted in strong interspecific variation between different algal species (Thalassiosira weissflogii, Dunaliella salina, and Rhodomonas salina) and nutrient-dependent shifts in stable isotope signatures in response to nutrient limitation of R. salina. The trophic enrichment in ¹⁵N and ¹³C of primary and secondary consumers (nauplii of Acartia tonsa and larval herring) showed strong deviations from the postulated degree of 1.0‰ enrichment in δ¹³C and 3.4‰ enrichment in δ¹⁵N. Surprisingly, nauplii of A. tonsa tended to keep “isotopic homeostasis” in terms of δ¹⁵N, a pattern not described in the literature so far. Our results suggest that the diets’ nutritional composition and food quality as well as the stoichiometric needs of consumers significantly affect the degree of trophic enrichment and that these mechanisms must be considered in ecological studies, especially when lower trophic levels, where variability is highest, are concerned.     

Feeding and growth kinetics of the planktotrophic larvae of the spionid polychaete Polydora ciliata (Johnston)

We studied the effect of food concentration on the feeding and growth rates of different larval developmental stages of the spionid polychaete Polydora ciliata. We estimated larval feeding rates as a function of food abundance by incubation experiments with two different preys, presented separately, the cryptophyte Rhodomonas salina (ESD = 9.7 µm) and the diatom T.weissflogii (ESD = 12.9 µm). Additionally, we determined larval growth rates and gross growth efficiencies (GGE) as a function of R. salina concentration.P.ciliata larvae exhibited a type II functional response. Clearance rates decreased continuously with increasing food concentration, and ingestion rates increased up to a food saturation concentration above which ingestion remained fairly constant. The food concentration at which feeding became saturated varied depending on the food type, from ca. 2 µg C mL^− 1 when feeding on T. weissflogii to ca. 5 µg C mL^− 1 when feeding on R. salina. The maximum carbon specific ingestion rates were very similar for both prey types and decreased with increasing larval size/age, from 0.67 d^− 1 for early larvae to 0.45 d^− 1 for late stage larvae. Growth rates as a function of food concentration (R. salina) followed a saturation curve; the maximum specific growth rate decreased slightly during larval development from 0.22 to 0.17 d^− 1. Maximum growth rates were reached at food concentrations ranging from 2.5 to 1.4 µg C mL^− 1 depending on larval size. The GGE, estimated as the slope of the regression equations relating specific growth rates versus specific ingestion rates, were 0.29 and 0.16 for early and intermediate larvae, respectively. The GGE, calculated specifically for each food level, decreased as the food concentration increased, from 0.53 to 0.33 for early larvae and from 0.27 to 0.20 for intermediate larval stages.From an ecological perspective, we suggest that there is a trade-off between larval feeding/growth kinetics and larval dispersal. Natural selection may favor that some meroplanktonic larvae, such as P.ciliata, present low filtration efficiency and low growth rates despite inhabiting environments with high food availability. This larval performance allows a planktonic development sufficiently long to ensure efficient larval dispersion.     

The ontogenetic stoichiometric bottleneck stabilizes herbivore–autotroph dynamics

In the ecological stoichiometry theory of population dynamics, ontogenetic changes in nutrient demand have been ignored. Here, I studied a stage-structured Daphnia–algae herbivore–autotroph model, in which the juveniles of the herbivore had a higher nutrient (phosphorous) demand for maturation than the adults for reproduction. The model predicted that while an increase in the juvenile nutrient demand (i.e., ontogenetic stoichiometric bottleneck) affects stage-specific performances in complex ways through nutrient dynamics and resource quality, in general it has stabilizing effects on the population dynamics.     

Schinus terebinthifolius Leaf Extract Causes Midgut Damage,Interfering with Survival and Development of Aedes aegypti Larvae

In this study, a leaf extract from Schinus terebinthifolius was evaluated for effects on survival, development, and midgut of A. aegypti fourth instar larvae (L4), as well as for toxic effect on Artemia salina. Leaf extract was obtained using 0.15 M NaCl and evaluated for phytochemical composition and lectin activity. Early L4 larvae were incubated with the extract (0.3–1.35%, w/v) for 8 days, in presence or absence of food. Polymeric proanthocyanidins, hydrolysable tannins, heterosid and aglycone flavonoids, cinnamic acid derivatives, traces of steroids, and lectin activity were detected in the extract, which killed the larvae at an LC₅₀ of 0.62% (unfed larvae) and 1.03% (fed larvae). Further, the larvae incubated with the extract reacted by eliminating the gut content. No larvae reached the pupal stage in treatments at concentrations between 0.5% and 1.35%, while in the control (fed larvae), 61.7% of individuals emerged as adults. The extract (1.0%) promoted intense disorganization of larval midgut epithelium, including deformation and hypertrophy of cells, disruption of microvilli, and vacuolization of cytoplasms, affecting digestive, enteroendocrine, regenerative, and proliferating cells. In addition, cells with fragmented DNA were observed. Separation of extract components by solid phase extraction revealed that cinnamic acid derivatives and flavonoids are involved in larvicidal effect of the extract, being the first most efficient in a short time after larvae treatment. The lectin present in the extract was isolated, but did not show deleterious effects on larvae. The extract and cinnamic acid derivatives were toxic to A. salina nauplii, while the flavonoids showed low toxicity. S. terebinthifolius leaf extract caused damage to the midgut of A. aegypti larvae, interfering with survival and development. The larvicidal effect of the extract can be attributed to cinnamic acid derivatives and flavonoids. The data obtained using A. salina indicates that caution should be used when employing this extract as a larvicidal agent.     

The biochemical composition of the larvae of two strains of Artemia salina (L.) reared on two different algal foods

A sequential carbohydrate, protein, and lipid method of analysis has been used to determine the biochemical composition of freshly hatched and 48-h old larvae of two strains of the brine shrimp Artemia salina (L.). During a 48-h starvation period the percentage of carbohydrates and lipids of freshly hatched larvae decreases whereas the ash content increases by 40–100%. When fed with dried Scenedesmus or dried Spirulina for 2 days after hatching the protein level of the larvae increases significantly and the relative increase in ash content is lower than in the case of starvation.Amino acid analyses of the algal food and the unfed and fed larvae did not show any change except for the absence (below detection) of methionine in the starved nauplii.The fatty acid pattern of 48-h old Artemia larvae is different from that of freshly hatched nauplii both in unfed and fed larvae; in the latter case it seems to be determined to a large extent by the fatty acid composition of the food.     

Minor food sources can play a major role in secondary production in detritus‐based ecosystems

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Use of dried algae as a food source for zooplankton growth and nutrient release experiments

Zooplankton growth and nutrient recycling are key processes in the operation of pelagic food webs. Most studies investigating these processes rely on complex methods and often require extensive laboratory facilities. Here we introduce a technique for preserving algae by rapid drying for later use in laboratory- or field-based growth and nutrient recycling experiments. Chemostat-grown Scenedesmus acutus was rapidly dried for later experiments evaluating its nutritional composition, suitability for animal growth and potential for use in nutrient release experiments. Reconstituted dried algae had slightly lower nitrogen (N), Phosphorus (P) and protein content (% dry weight) than fresh algae, but lipid content did not differ and elemental ratios were in the range considered to indicate favorable food quality. These elemental and biochemical differences did not appear functionally important, as Daphnia magna grew identically on fresh and dried food. Freeze-dried S.acutus did not work as an alternative to oven drying as it resulted in 100% mortality. NH4 and PO4 concentrations did not change over 24 h when dried algae were resuspended in normal media or boiled lake water. However, concentrations of PO4 decreased over 24 h, suggesting chemical adsorption of PO4 to the dried algae and reinforcing the need for animal-free controls in nutrient release experiments using this approach. N and P release rates for D.magna and natural zooplankton communities were estimated using dried algae, and values were comparable to published ones. Thus, dried algae may be a useful, simple technique for studying food quality and nutrient release in environments where maintaining active algal cultures may not be practical and a constant supply of consistent quality food is needed.      

Some aspects of the feeding and behavior of larvae of the Barents Sea capelin Mallotus villosus villosus (Salmoniformes, Osmeridae) in experimental conditions

The results of experimental investigations on the feeding and behavior of larvae of the Barents Sea capelin Mallotus villosus villosus during their transition to exogenous feeding are presented. Data concerning the passage duration of nauplii of Artemia salina along the intestine, feeding intensity, the portion of feeding larvae, swimming speed, sinking speed of non-feeding individuals, distances of responses and escape, as well as certain features of the passage of food through the intestines are given.     

Gardening by the psychomyiid caddisfly Tinodes waeneri: evidence from stable isotopes

Sedentary species face a trade-off between the benefits of exploiting food close to their homes and the cost of defending it. In aquatic systems, it has been suggested that some sedentary grazers can increase the range of circumstances under which they are at an advantage over mobile grazers by enhancing food resources within their feeding territories through ‘gardening’. We examined this for the retreat-building sedentary larvae of the caddis Tinodes waeneri, which are often dominant in the littoral of lakes. We hypothesised that T. waeneri gardens by fertilising its retreat (a fixed ‘gallery’ on which algae and other microorganisms grow), and that gardening would be more important in lower productivity lakes. We tested this by analysing the carbon and nitrogen stable isotope ratios of larvae, their galleries and the general background epilithon, collected from rocks in the littoral zones of six lakes spread across a natural nutrient gradient. We found evidence of nutrient recycling within the Tinodes gallery community in all lakes. Galleries were ¹⁵N-depleted compared to the epilithon, suggesting that algae on galleries preferentially assimilated ¹⁴N from larval excretions that were themselves ¹⁵N-depleted relative to the larval food source. Mixing model results indicate that galleries formed an important larval carbon and nitrogen source, with mean gallery dietary contributions of over 40% in at least one sample period in all lakes studied. Gallery contributions were greater between April and October than in January and, contrary to our initial hypothesis, greater in the more productive lakes of those surveyed. Nevertheless, T. waeneri galleries do act as a fertilised garden. ‘Gardening’ appears to be widespread in this species, and may affect productivity and patterns of nitrogen retention within the stony littoral of lakes.