New findings of shallow water caprellids (Crustacea, Amphipoda, Caprellidae) from Uruguay with an illustrated key to species

There is a lack of studies focusing on caprellid amphipods along the coasts of Uruguay. So far, only three species, Caprella bathytatos, C. equilibra, and C. penantis, have been recorded from Uruguay. Sampling was carried out for one year (from April 2022 to March 2023) along the Uruguayan coast between latitudes 34°02'43.4"S and 34°55'05.7"S at rocky outcrops in the localities of Piriápolis, Punta Ballena, La Barra, La Paloma, La Pedrera, and Punta del Diablo.

At each sampling point, scraping was performed in intertidal and shallow waters up to a depth of 10 m by snorkeling and SCUBA. All substrata, consisting mainly of algae and bryozoans, were collected within a 50 × 50 cm grid. Additionally, in Punta del Diablo, buoyant material stranded on the beach was also collected.

This work represents the first record of the species C. andreae, C. dilatata, C. scaura, and Paracaprella aff. pusilla for Uruguay, increasing the number of known species in the country to seven. Herein, an illustrated key to the seven species known to occur in Uruguay is presented. The low caprellid diversity in Uruguay could be related to the highly variable abiotic characteristics of the Uruguayan coast, mainly due to the freshwater input from the Río de la Plata, and to other biotic factors such as the low diversity of macroalgae.

The taxonomical impediment (lack of taxonomists and scarce sampling in the area) could also cause an underestimation of species richness. Therefore, additional sampling efforts, especially in deeper waters and sediment habitats, are still necessary to properly characterize this amphipod group in Uruguay.