Inconsistency in the analysis of morphological deformities in chironomidae (Insecta: Diptera) larvae

Abstract

The incidence of morphological deformities of chironomid larvae as an indicator of sediment toxicity has been studied for decades. However, standards for deformity analysis are lacking. The authors evaluated whether 25 experts diagnosed larval deformities in a similar manner. Based on high-quality digital images, the experts rated 211 menta of Chironomus spp. larvae as normal or deformed. The larvae were from a site with polluted sediments or from a reference site. The authors revealed this to a random half of the experts, and the rest conducted the assessment blind. The authors quantified the interrater agreement by kappa coefficient, tested whether open and blind assessments differed in deformity incidence and in differentiation between the sites, and identified those deformity types rated most consistently or inconsistently. The total deformity incidence varied greatly, from 10.9% to 66.4% among experts. Kappa coefficient across rater pairs averaged 0.52, indicating insufficient agreement. The deformity types rated most consistently were those missing teeth or with extra teeth. The open and blind assessments did not differ, but differentiation between sites was clearest for raters who counted primarily absolute deformities such as missing and extra teeth and excluded apparent mechanical aberrations or deviations in tooth size or symmetry. The highly differing criteria in deformity assignment have likely led to inconsistent results in midge larval deformity studies and indicate an urgent need for standardization of the analysis.

Use of Larval Morphological Deformities in Chironomus plumosus (Chironomidae: Diptera) as an Indicator of Freshwater Environmental Contamination (Lake Trasimeno, Italy)

“…In this regard, some studies based on ecotoxicological laboratory experiments queried the relationship between chironomid deformities and toxicity assessment in freshwater ecosystems [24,49,[72][73][74][75][76]. However, the high variability of those experimental results can be influenced by different variables, such as: (i) the endpoint used (mentum, mandibles, pectin epipharyngis); (ii) the deformity types considered; (iii) the larval instars used in the experiment; (iv) the type of cultures used which often cause a high incidence of deformities in the control test; (v) the exposure time of the larvae to the contaminants; and (vi) the type of contaminant mixture used in the test.…”

Biological responses of midge (Chironomus riparius) and lamprey (Lampetra fluviatilis) larvae in ecotoxicity assessment of PCDD/F-, PCB- and Hg-contaminated river sediments

“…Chironomid mentum deformity incidence (DI) did not differ among the sediments, and was in all exposures within the range suggested to represent a background incidence of 2.8 % to less than 8.0 % (Dickman et al 1992;Vermeulen 1995;Salmelin et al 2015) found in minimally disturbed sites in the field. DI seemed not to be related to the chironomid growth, which was reduced in 1A, 2B and 4B sediments, but not in 3A sediment, where the DI was the highest.…”

“…Only mentum deformities were considered. Missing or additional teeth, and Köhn gaps were counted as deformities, and to avoid a preconception bias, deformity analysis was conducted blind (Salmelin et al 2015).…”

A kétszárnyúakhoz (Diptera) kötődő ökoszisztéma-szolgáltatások

“…gyakran használják a szennyeződések és a víz alacsony oxigéntartalmának indikátorául (Lenat 1993, Michailova et al 2015. A környezeti stressz vizsgálatára jól használhatóak a vízben élő légylárvák fejtokjának morfológiai elváltozásai (Warwick 1991, Salmelin et al 2015. Bár az az általános vélekedés, hogy a legtöbb vízi Diptera toleráns a környezeti hatásokkal szemben, de bizonyos csoportok, például a Blephariceridae, Thaumaleidae családok fajai rendkívül érzékenyek a környezeti zavarásokra (Lenat 1993, Searher & Wagner 2002.…”