Chironomidae of a Floodplain Pond in Córdoba, Argentina

Abstract

Small freshwater ponds occur on the floodplain of the río Segundo as it flows toward the large, saline lake Laguna Mar Chiquita in the notably flat landscape of eastern Córdoba. Preliminary sampling suggested that chironomids were abundant in the ponds. One of them, Laguna Sandroni, was sampled on eight dates from August to June to determine the kinds, distribution, and abundance of chironomids in it. Its area was 4.3 ha, and most of its basin was less than one meter deep and without macrophytes. Some years it dried up completely, as evidenced by fence posts in its basin. Four 15x15-cm Ekman samples were taken at each of three stations ranging in depth from 15 to 97 cm. Samples were sieved through a 250 m sieve. Larvae were sorted while live, and many were reared. Eleven genera were collected; these were, in order of frequency of occurrence (dates and stations): Coelotanypus, Chironomini genus A, Chironomus, Polypedilum, Tanytarsus, Procladius, Tanypus, Cryptochironomus, Cryptotendipes, Dicrotendipes, and Djalmabatista. Coelotanypus was the most consistently abundant, with more than 1000/m2 on 11 occasions (maximum 3707/m2). Chironomini genus A, Chironomus, and Tanypus were the only other genera to exceed 1000/m2. Chironomus and Tanypus were abundant only in October, but at that time Chironomus had a maximum abundance of 6949/m2, more than any other genus. The four most abundant taxa were evidently univoltine. The next three taxa, Polypedilum, Procladius, and Tanytarsus, may have been bivoltine or may have had more than one species in the pond. Identification to species was not attempted.