Multiple Rhizochepalan Infestation in the Crucifix Crab, Charybdis Feriata in Sabah, Malaysia: A Case Report

The crucifix crab, Charybdis feriata, is a commercially valuable species distributed across the Indo-Pacific and known for its distinctive white carapace. It thrives in various habitats and can grow up to 1kg. However, it is vulnerable to parasitic infections, particularly rhizocephalan barnacles, which cause sterilization, stunted growth, and behavioral changes. This report documents the first case of rhizocephalan infection in Charybdis feriata from Sabah, Malaysia. Of two male crabs sampled, one showed abnormal characteristics linked to sacculinid barnacle infection, including a widened abdominal flap and two yellowish parasitic externae. Such infections are known to alter male crabs by inducing female-like features and castration, with rare cases of double externae suggesting possible multiple infestations based solely on morphological observations. It should be noted that interpretations regarding multiple infestations in this study are derived exclusively from external morphological characteristics, as molecular confirmation was not performed. Limited molecular identification prevented further analysis, but this case highlights the need for continued research and surveys in Sabah to better understand the ecological and economic impact of these parasites on local crab populations and fisheries.