Étrille Nageuse

Overview

The Achelous hastatus is a marine swimming crab belonging to the family Portunidae. It is widely distributed across the Mediterranean Sea and the eastern Atlantic, ranging from Morocco down to Angola.

Appearance

This crab features a broadly hexagonal, flattened carapace that typically displays a brownish-yellow to brick-red coloration. Its most distinctive morphological features include a frontal margin divided into four lobes and nine anterolateral teeth on each side, with the ninth tooth being notably elongated and sharp. The species possesses robust chelipeds with slender fingers and specialized, flattened fifth pereiopods that function as natatory paddles, allowing it to swim effectively.

Distribution & habitat

Achelous hastatus is commonly found in shallow marine environments, including sandy patches, muddy bottoms, and areas with mixed sand and rock substrates. While it can be found from the intertidal zone down to 60 meters, it is most frequently observed at depths shallower than 20 meters. Juveniles are often encountered in very shallow water along sandy beaches.

Biology & behavior

Primarily nocturnal, this crab remains buried in the substrate during the day and emerges at night to forage. It is an active swimmer and an opportunistic feeder, often scavenging on organic remains, including vertebrate matter. Observations have documented individuals engaging in group scavenging behavior, potentially to exploit available food sources in their nearshore habitats.