Korobushkin D.I., Gongalsky K.B. Intra-body Variations of Stable Isotope Ratios (δ13С and δ15N) of Mediterranean Soil Invertebrate Species // Arid ecosystems. 2022. V.28. № 2 (91). P. 71-77. | PDF
In recent decades, the analyses of stable isotopes have been widely used to study trophic relationships in soil ecosystems. The isotopic signature of heterotrophic organisms reflects the isotopic composition of their food. To discover trophic position of soil invertebrates in detrital food webs, stable isotopes of carbon (δ13С) and nitrogen (δ15N) are mainly used. However, the correct use of this technique is often obstructed by the individual (within the organism) variability of the isotopic composition of carbon and nitrogen between tissues and organs of many soil invertebrate taxa. The aim of this study was to compare the individual variability of the isotopic composition of various tissues and organs of the mass Mediterranean species of woodlice (Isopoda, Armadillidae, Armadillo officinalis and Armadillidiidae, Armadillidium vulgare) and centipedes (Chilopoda, Scolopendromorpha, Scolopendra cingulata).
Soil invertebrates were collected within Utrish State Nature Reserve (Krasnodar krai). For isotopic analysis, the following tissues/organs were used: exoskeleton, muscles, Gastrointestinal wall, fatbody (only in scolopendra), reproductive system, legs, whole homogenized organism. The isotopic composition of δ13С and δ15N was estimated using a set of equipment consisting of an elemental analyzer and an isotope mass spectrometer.
Differences of carbon isotopic composition between woodlice tissues reached 5-6‰ due to the inclusion of inorganic carbonates in the exoskeleton. No significant difference in the isotopic composition was found between the tissues of the scolopendras. For a correct assessment of the trophic position of large woodlice species using isotope analysis, it is most preferable to use muscle tissue. The use of legs is possible only after a preliminary assessment of the carbonate content in the integumentary tissues of the species. It is necessary to exclude the homogenization of specimens of large isopods, as well as the inclusion of exoskeleton fragments and food debris into the analyzed sample. To estimate the isotopic position of scolopendra, muscles, homogenized samples of the whole animal, as well as individual parts of the body and organs, with the exception of the stomach contents, can be used. The results obtained are applicable to optimize soil-zoological studies using isotopic analysis of invertebrate tissues.
Keywords: soil macrofauna, isopodes, centipedes, stable isotopes, Utrish nature reserve, detrital food webs.
Financing. The study of the isotopic composition of invertebrates was carried out with the financial support of the RGNF grant No. 19-74-104, year 2019-2022: «The role of marine organic matter subsidy in the formation of the functional and taxonomic structure of terrestrial detritus food webs».
Acknowledgements. The authors are grateful to O.N. Bykhalova for her help in organizing work on the territory of the Utrish Nature Reserve.