New record of Laonome sp. (Annelida, Sabellidae) in inland Waters of Pampa Ecorregion

Abstract

The genus Laonome Malmgren, 1866 (Annelida: Sedentaria) belongs to the Sabellidae family. A new species, Laonome xeprovala, was described in 2018 based on specimens found in 2009 at different sites in Europe and unknown until then. In Argentina, it was recorded for the first time in 2019 in the Paraná River System and tributaries, from Santa Fe to the middle-lower stretch, molecular studies determined that it was the same species found in Europe. In this study, specimens of this genus were recorded in November 2022 at the locality of General Lavalle, at three sites of Canal 2 (an artificial canal flowing into the estuarine area of the Río de la Plata), being to date the southernmost record. The samples where these specimens were found were collected from the benthos and associated vegetation using an Ekman dredge and a D-net. The organisms found were identified and quantified. The “polychaete” specimens were assigned to the genus level by morphological characters using bibliography and by comparison with specimens obtained from other sites in the Río de La Plata Basin by other researchers. The identification will be confirmed by molecular analysis. The density was determined, showing values between 4 and 66 ind/m2. In relation to the macroinvertebrates, an important percentage of crustaceans were observed at the two sites closest to the mouth (relative density values between 40 and 70%), consistent with more brackish waters, while insects predominated at the remaining site (values greater than 50%).