First Gut Content Analysis of 4th Instar Midge Larvae (Diptera: Chronomidae) In Large-Scale Weirs Using a DNA Meta-Barcoding Approach

Abstract

Chironomidae larvae play an important role in the food chain of river ecosystems in Korea, where it is dominant. However, detailed information on the diet of Chironomidae larvae are still lacking. The purpose of this study was to identify the gut contents of 4th instar larvae of a Chironomidae inhabiting four large-scale weirs (Sejong Weir, Juksan Weir, Gangjeong-Goryeong Weir, and Dalseong Weir) using a DNA meta-barcoding approach. We found that dominant Operational Taxonomic Unit (OUT) was assigned to Paractinolaimus sp. (Nematoda), and the sub-dominant OTU was assigned to Dicrotendipes fumidus (Chironomidae). The most common OTUs among the individuals included phytoplankton, such as Tetrahymena sp., D. armatus, Pseudopediastrum sp., Tetradesmus dimorphus, Biddulphia tridens, and Desmodesmus spp. We calculated the selectivity index (E’) and provided scientific evidence that Chironomidae larvae have a significant preference (E’ > 0.5) for Desmodesmus armatus, E. minima, and T. dimorphus, while it does not show preference for other species found in its gut. Differences in physico-chemical factors, such as water quality, nutrients, Chl-a, and carbon concentrations, resulting from anthropogenic impacts (i.e., construction of large-scale weirs) as well as the particle size of prey organisms (small-sized single cell) and effects of chemicals (chemokinesis) could affect the feeding behavior of Chironomidae larvae.

Profiling Analysis of Filter Feeder Polypedilum (Chironomidae) Gut Contents Using eDNA Metabarcoding Following Contrasting Habitat Types—Weir and Stream

“…According to the functional OTUs identified, the relative frequency of the diet profile was determined. The diversity of the food resource in the habitats and the diet of midges relied mostly on the phytoplankton corresponding to algae, relating the observations of Jo et al (2020) [ 29 ]. According to the predominant groups and relative genus coverage to the assigned OTUs, we could categorize the algal groups into Chlorophyta (green algae), Diatomea (microalgae), and Ochrophyta (golden algae—Chrysophyceae).…”

“…The gut samples were dissected from the 4th instar Polypedilum sp. larvae of each sample site followed by a sample processing procedure after the complete volatilization of ethanol (Jo et al, 2020 [ 29 ]). Genomic DNA was extracted using DNeasy Blood & Tissue Kit (Qiagen, Düsseldorf, Germany) as per the manufacturer’s protocol.…”

“…Meta-analysis of gut composition has been discussed in crustaceans, copepods, and other aquatic animals [ 25 , 26 , 27 , 28 ], while only a few works have been reported on the chironomid diet. The initial works of Jo et al (2020) [ 29 ] on eDNA sampled 18S rRNA metagenomic sequencing indicated the food content of chironomids with different phytoplankton at the species level. This study represents the first eDNA-based diet composition information among generalist Polypedilum midges.…”

Eutrophication and the Ecological Health Risk

“…Jo et al [ 22 ] used a DNA meta-barcoding approach to identify the gut contents and analyze the feeding behavior of fourth-instar larvae of a chironomid ( Dicrotendipes fumidus ) that inhabits large-scale weirs. Their results indicate that the most common operational taxonomic unit (OTU) among individuals included phytoplankton, such as Tetrahymena sp., Pseudopediastrum sp., Tetradesmus dimorphus , Biddulphia tridens , Desmodesmus armatus , and other Desmodesmus spp.…”

“…Herein, I summarize the contributed papers in the context of eutrophication and related risks to the health of ecological systems to paint an overall picture of this Special Issue ( Table 1 ). Three studies focused on “eutrophication” [ 17 , 18 , 19 ], four on “ecological health risk” [ 20 , 21 , 22 , 23 ], and a further three papers on “ecosystem health and services” [ 24 , 25 , 26 ] have been included in this issue. A more detailed summary of all articles is offered in the following section.…”