The spermatozoon of Solea senegalensis (Kaup, 1858) consists of an acrosome-less ovoid head, a short midpiece containing several irregular mitochondria embedded in the cytoplamic mass, and a long tail with two lateral fins and a conventional 9 + 2 axoneme. The centrioles are housed in a deep nuclear fossa and are both orientated in the same longitudinal axis of the spermatozoon. The overall structure of this spermatozoon conforms to the sperm type considered to be plesiomorphic in the neopterigians (type I sperm). The likely apomorphic (coaxial) orientation of the centrioles defines the spermatozoal morphology of the Soleidae investigated thus far and separates them from the other known pleuronectiform spermatozoa.