Vol. 60, 2021
(update: 2021.03.18; 07.02)
Tissue-specific Isotopic
Incorporation Turnover Rates and Trophic Discrimination Factors in the
Freshwater Shrimp Macrobrachium
borellii (Crustacea: Decapoda: Palaemonidae)
María
Florencia Viozzi1,* , Carlos
Martínez del Rio2, and Verónica Williner1,3
doi:10.6620/ZS.2021.60-32
1Laboratorio
de Macrocrustáceos, Instituto Nacional de Limnología, Consejo Nacional
de Investigaciones Científicas y Técnicas, Argentina.
E-mail:
fviozzi@inali.unl.edu.ar (Viozzi)
2Department of
Zoology and Physiology, University of Wyoming, Laramie, Wyoming 82071,
USA. E-mail: CmDelRio@uwyo.edu (Martínez del Rio)
3Universidad Nacional del Litoral, Santa Fe,
Argentina. E-mail: vwilliner@inali.unl.edu.ar (Williner)
Received 8 April 2020 / Accepted 15
March 2021
Communicated by Benny K.K. Chan
The
interpretation of isotopic data in ecology requires knowledge about two
factors: turnover rate and the trophic discrimination factor, which
have not been well described in freshwater shrimps. We performed a
142-day diet shift experiment on 174 individuals of the omnivorous
shrimp Macrobrachium borellii,
measured their growth, and temporally serially sampled muscle and
hepatopancreas tissue to quantify carbon and nitrogen incorporation
rates and isotope discrimination factors. Shrimps were fed with
artificial diets (δ13C = -26.1‰, δ15N= 2.1‰) for 45 days in attempt to
standardize the shrimps’ initial δ13C and δ15N values for subsequent
experiments. Shrimps were then feed with another artificial diet (δ13C=
-16.1‰, δ15N= 15.8‰) and the change in δ13C and δ15N was observed for a
period of 97 days. The trophic discrimination factor (∆) for δ13C was
significantly higher in hepatopancreas (0.7 ± 0.36‰) than in muscle
(-0.1 ± 0.83‰); however, the opposite was the case for δ15N (1.7 ±
0.43‰ and 3.6 ± 0.42‰, respectively). In the hepatopancreas the mean
residence time (τ) of 13C was 26.3 ± 4.3 days compared to a residence
time of 16.6 ± 5.51 days for δ15N, whereas the τ in muscle was 75.8 ±
25 days for δ13C and 40 ± 25 days for δ15N. The rate of incorporation
of carbon into muscle was higher than that predicted by allometric
equations relating isotopic incorporation rate to body mass that was
developed previously for invertebrates. Our results support ranges of
traditional trophic discrimination factor values observed in muscles
samples of different taxa (Δ15N around 3‒3.5‰ and Δ13C around 0‒1‰),
but our work provides evidence that these traditionally used values may
vary in other tissues, as we found that in the hepatopancreas Δ15N is
around 1.7‰.
Key words: Stable isotopes, Carbon, Nitrogen,
Muscle, Hepatopancreas.
Citation:
Viozzi MF, Martínez del Rio C, Williner V. 2021. Tissue-specific
isotopic incorporation turnover rates and trophic discrimination
factors in the freshwater shrimp Macrobrachium
borellii (Crustacea: Decapoda: Palaemonidae). Zool Stud 60:32. doi:10.6620/ZS.2021.60-32.

Supplementary
Materials: Supplementary material
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