The brown shrimp, Penaeus aztecus
, is a species of grooved, burrowing shrimp, common in Florida waters. Antennae are significantly longer than body length. Its carapace has a medial carina on the anterior surface that is bordered on either side by a broad, somewhat rounded groove. The prominent rostrum is slightly upturned with 5-10 sharp teeth on the upper edge. The integument is thin and translucent in appearance. Chromatophores give the animal a brown to olive-green appearance, though both red and green specimens of this species have been reported. The first 3 pairs of walking legs are chelate. Uropods are rounded and generally colored reddish-brown in the distal portions. The telson bears a sharp tip and a deep medial groove anteriorally. This species exhibits sexual dimorphism, with females growing larger than males. Generally, males attain only 3/5 of female weight, and 5/6 of female length. Females are further distinguished by the presence of a closed thelycum located on the ventral sternum of the thorax, while males are identified by the presence of the pentasma.