Hidden Marine Diversity in Intertidal Sediments: First Record of a Juvenile Halechiniscidae (Tardigrada) from Southern Peru

Marine meiofaunal communities represent a significant yet understudied component of marine biodiversity, particularly along the southeastern Pacific coast. This study reports the first documented record of a juvenile marine tardigrade assigned to the family Halechiniscidae from intertidal sediments at La Francesa Beach, Quilca, Arequipa, Peru. Sediment samples were collected during low tide and processed using standard meiofauna extraction and separation techniques. Recovered microinvertebrates were examined using optical and phase-contrast microscopy and documented photographically. Taxonomic assignment was based on diagnostic morphological characters described in specialized taxonomic literature. The specimen exhibited two claws per limb, a characteristic associated with juvenile stages of some Halechiniscidae representatives. In addition, the presence of cephalic appendages and the absence of body armor supported its assignment to the family Halechiniscidae, although species-level identification was not possible because only a juvenile specimen was recovered. Additional sampling efforts are currently being conducted at the same locality to obtain adult specimens for a more robust taxonomic assessment. This record provides baseline information for future studies on the diversity and distribution of marine tardigrades along the southeastern Pacific coast. These findings highlight the hidden diversity of intertidal meiofaunal communities and emphasize the importance of continued taxonomic surveys integrating both morphological and molecular approaches to improve our understanding of Peru's marine biodiversity.