Morphology and Morphometry Analysis of Toxic Brachyurans from Nglolang Beach, Gunungkidul

Abstract

Toxic crabs from the families Xanthidae and Eriphiidae pose health risks due to variable toxicity influenced by diet, habitat, and environmental conditions. Xanthidae species are known to contain neurotoxins such as tetrodotoxin (TTX) and saxitoxin (STX), which can cause paralysis and poisoning in humans, whereas Eriphiidae crabs generally exhibit lower but more consistent toxin levels. Although toxic crab species have been reported across the Indo-Pacific, applied morphometric studies at local coastal scales remains limited. Thus, this research aims to characterize morphometric features of toxic Xanthidae and Eriphiidae crabs at Nglolang Beach to support species identification and risk awareness. This study was conducted at Nglolang Beach, Gunungkidul, using purposive sampling method in the intertidal zone with concurrent measurement of water temperature and salinity. Collected specimens were anesthetized, photographed, morphologically identified, and preserved in a 70% alcohol-glycerin solution at a 9:1 ratio. This study aims to characterize morphometric features of toxic Xanthidae and Eriphiidae crabs at Nglolang Beach to support species identification and risk awareness. Four toxic species were identified: Eriphia scabricula, Atergatis floridus, Etisus laevimanus, and Platypodia granulosa. These species display measured morphometric parameters, including chela dimensions and carapace surface texture, which are associated with intertidal survival. Environmental factors, particularly temperature and salinity, were observed to influence crab activity. By providing region-specific morphometric data for known toxic taxa, this study supports coastal biodiversity documentation, public safety, and sustainable tourism. Notably, crab toxins may persist after cooking, posing a continued risk if consumed.