Distribution record of the spiny crab Acanthonyx lunulatus (Risso, 1816) and the bristle crab Pilumnopeus vauquelini (Audouin, 1826) in the rocky bottom habitat of Mersin (Akkum)

The present investigates the distribution of Acanthonyx lunulatus and Pilumnopeus vauquelini in rocky bottom habitats in the Akkum region of Mersin (the Mediterranean coast of Turkey).During the ecological survey, the female spiny crab species (A.lunulatus) and the male bristle crab (P.vauquelini) were collected during dives along the Erdemli-Akkum coast in July and August 2024.Samples were obtained from the rocky area at a depth of approximately 3 m.The identification of two species of crab was based on distinctive morphological features.The shell lengths and widths of the two crab specimens were measured meticulously using digital callipers.The details of both specimens were then recorded at the Mersin University Museum of Marine Life, and catalogue numbers were allocated for both species.Both crab species play essential roles in benthic ecosystems. A. lunulatus inhabits rocky areas usually covered with algae, while P. vauquelini prefers microhabitats such as under rocks and crevices.A. lunulatus has ecosystem engineering roles such as increasing microhabitat diversity and providing shelter, while P. vauquelini contributes to the sustainability of seafloor ecosystems by consuming organic matter and mixing sediments.This study provides an essential basis for assessing the long-term effects of human impact and invasive crab species on Mediterranean ecosystems.Also, it presents important information for the development of regional biodiversity management and conservation strategies.Besides, long-term monitoring studies are needed to understand better the impact of environmental factors on the distribution of these species.