Effects of formaldehyde preservation time on the length-weight relationship of the ubiquitous neotropical cladoceran Ceriodaphnia silvestrii

Rafael Lacerda Macêdo,Christina Wyss Castelo Branco,Odete Rocha,Lorena Pinheiro-Silva,Betina Kozlowsky-Suzuki,Adriana Lamanna Puga,Gabriel Klippel

doi:10.1590/s2179-975x3321

Abstract

Abstract: Aim In this study, the effect of preservation time on total body length and dry weight of adult specimens of the neotropical cladoceran Ceriodaphnia silvestrii preserved with 4% formalin solution were examined. Methods The relationship between these variables was examined under increasing gradual time effects (i.e. 7, 30, and 60 days) after preservation using linear models and analysis of variance. Results Total body length did not statistically differ between fresh and preserved cladocerans at any preservation time, whereas dry weight was drastically reduced with increasing preservation time, with 15, 47 and 57% weight losses. Length-weight relationships were significantly and positively related in all treatments, though higher values of slope were found for fresh and 7 days samples. Conclusions We highlight that, for Ceriodaphnia silvestrii, the use of the formalin solution as a preservation fixative is not adequate when the major interest is biomass estimation. Also, we recommend that dry weight estimations from preserved samples should be done as soon as possible. Finally, considering the preservation losses and intra-specific composition of organisms, the application of correction factors is advised since preserved samples are important in the evaluation of long-term changes of biological communities.

Highlights

Biological and ecological studies often require biometrical measurements, biomass calculations or estimates as tools to evaluate community structure
Aim: In this study, the effect of preservation time on total body length and dry weight of adult specimens of the neotropical cladoceran Ceriodaphnia silvestrii preserved with 4% formalin solution were examined
We evaluated the effect of 4% formalin solution buffered with sodium tetraborate on body length and dry weight of the widely spread neotropical cladoceran Ceriodaphnia silvestrii Daday 1902 (Daday, 1902) sampled in a tropical reservoir

Summary

Introduction

Biological and ecological studies often require biometrical measurements, biomass calculations or estimates as tools to evaluate community structure. Size per se influences functional and ecological traits of organisms and their role in ecosystem processes (Brown et al, 2004; Woodward et al, 2005). As a result, studying the influence of body size on trophic efficiency has become a prominent focus in ecology and applied biology, emphasizing the need for accurate and efficient individual and population measurements (LaBarbera, 1989; Wetzel et al, 2005; Costa-Paiva et al, 2007; Souza & Barros, 2017). An immediate sorting of sampled material, as well as any subsequent processing, are almost impossible under field conditions and samples need to be preserved immediately after collection. Qualitative and quantitative measurements are mostly determined from preserved organisms

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