Chironomus Species Dna Barcording in Monitoring the Pollution Levels of the Nyanza Gulf in Lake Victoria, Kenya

Abstract

Chironomidae is a group of diptera insects, commonly known as “non-biting midges'' in the adult stage and “bloodworms” in the larval stage, represent a group of insects that thrive in various aquatic environment worldwide. Despite the plethora of information on Chironomidae in many parts of the world, there is a paucity of data regarding this indicator species in the polluted Kenyan Nyanza Gulf of Lake Victoria and molecular identification has not been explored. This study aimed to characterize Chironomidae species based on the mitochondrial DNA barcoding of the cytochrome oxidase subunit 1(COI) gene. Aquatic insects were collected from inshore and offshore in the Nyanza gulf, with a focus on pollution gradient. Chironomus larvae were subjected to analysis to discern divergence or convergence among conspecifics or intraspecific based on pollution gradients. The COI gene was amplified, sequenced using species-specific primers and compared to Gene Bank entries. Genetic analysis was done using MEGA version 11. Phylogenetic analyses employed Neighbor-joining and maximum parsimony algorithms with 1000 bootstrap replicates. The results revealed two known species, Chironomus transvaalensis from heavily polluted Kisumu station, and Chironomus pseudothummi from moderately polluted Kendu bay and Homabay stations, within the same biogeophysical environment. Additionally, a unique Chironomus species was identified on Ndere Island, an offshore station, presumed to be a clean site with restricted human activities. Sequences comparisons with global data indicated proximity but highlighted evolutionary significance and uniqueness. The study postulates that pollution serves as a selective pressure, driving the evolution of Chironomidae species in this particular region.