Chironomid species

In practice, the extent to which a freshwater system has been stressed by pollutants can be determined through an examination of the presence or absence of specific chironomid species with known pollution tolerances. Finer scale analyses of relative abundances can also provide clues to the presence of specific stressors. For instance, high abundance of a chironomid species such as Dicrotendipes nervosus frequently indicates the presence of abundant decomposable organic matter, whereas species such as Cricotopus bicinctus are found more commonly in systems with high levels of inorganic contaminants (7). Since even closely related species can have distinct pollution tolerances, the need for proper identifications is particularly important and useful (d). 

Macroinvertebrates such as chironomid larvae have been used as integral parts of freshwater monitoring systems by the Ohio EPA since 1973 (7). The principal chironomid-based measurement of macroinvertebrate integrity is the Invertebrate Community Index (ICI) 8). The ICI considers the status of a total of 150 different chironomid species commonly found in North American streams and was developed in a fashion similar to that used for the more broadly based Index of Biotic Integrity (IBl) (P). These standardized systems have avoided many of the complications encountered with more subjective approaches (i). 

Improvements in the ability to resolve and distinguish chironomid species has the potential to clarify the taxonomic status of many specimens of this diverse group that are currently unknown. With more reliable and complete identifications, a detailed survey of species composition and range could be... 

Figure /. Morphological structures are slightly varied between chironomid species (Simpson and Bode 1980). 1(A) The labial plate of Polypedilum illinoense 1(B) The labial plate of Polypedilum convictum.

Figure 2. PCR amplification of the internal transcribed spacer regions of five Chironomid species. Using primers specific to the 18S and 28S regions of rDNA, five different Chironomid species yield amplification products of characteristic lengths. Lane A - Glyptotendipes lobiferous, Lane B -Cardiocladiiis obscurus, Lane C - Chironomus riparius, Lane D - Dicrotendipes fumidus, Lane E - Cricotopus bicinctus, and Lane SM -100 bp size marker.

Figure 5. Alignment of sequence data of rDNA from chironomid species. Sequence data is aligned showing similarities and differences. (5A) Alignment of C. tentans (Chironomus tentans), D. fumidus (Dicrotendipes fumidus,), and C, bicinctus (Cricotopus hicinctus) from the 18S subunit of rDNA. (5B) Alignment ofpartial /8S, ITS-], 5.8S, ITS-2, and 2 8S subunits of rDNA from 14 chironomid species C. tentans (Chironomus tentans) Genbank accession X992I2, D.fumidus (Dicrotendipes fumidus,) Genbank accession, ...

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