Sea cucumbers (holothuroids) play a major role in coastal environments; their detritivore conduct favors oxygen penetration in the sediments and the disposal of pathogens on the sea floor. This study ...determined holothuroid diversity in the rocky intertidal zone of Matanchen Bay, Mexico. Sampling campaigns were carried out in January, March, May, and July 2018. Linear transects (10 m length and 1 m width) perpendicular to the coastline in rocky areas (0-3 m depth) were established, where the density (ind m.sup.-2) and proportion (%) of sea cucumbers were estimated. Organisms were photographed, examined live, and preserved in 70% alcohol for subsequent identification utilizing ossicle characterization. Our results show the presence of four sea cucumber species: Holothuria (Halodeima) inornata Semper, 1868, Holothuria (Selenkothuria) lubrica Selenka, 1867, Holothuria (Selenkothuria) portovallartensis Caso, 1954, and Holothuria (Mertensiothuria) viridiaurantia Borrero-Perez & Vanegas-Gonzalez, 2019. The average density per species was 0.208, 0.108, 0.017, and 0.025 ind m.sup.-2, respectively; each species' proportion was 58.1, 30.2, 4.7, and 7.0%, respectively. Due to the above values, we found that the number and spatial distribution of sea cucumber species vary in Matanchen Bay.
