Pericelis orbicularia

Pericelis orbicularia (Schmarda, 1859) Fig. 4 Material examined. Yucatan coast, Mexico • 1; Punta Piedra, Sisal; 21.2°N, 90.1°W; 1 m; 30 Apr. 2018; A. Hernández leg.; CRPPY -0087 • 1; Dzilam; 21.5°N, 88.9°W; 9.3 m; 8 May 2018; A. Hernández leg.; CRPPY -0091 • 1; 12 slides; Dzilam; 21.5°N, 88.9°W; 13 m; 10 May 2018; A. Hernández leg.; CRPPY -0097. Distribution. Pericelis orbicularia is known from the south coast of Jamaica (Schmarda 1859); Port Aransas, Texas, USA (Hyman 1955); and Key Biscayne (Florida, USA; Marcus and Marcus 1968). This is the first record for the coast of Yucatan (Mexico). Description. Body oval-shaped, 2 cm in length and 1 cm in width, with small pseudotentacles, less than 1 mm. Dorsal surface exhibits an orange to light brown reticulated pattern on a regular creamy beige background (Fig. 4 A, D, E). The pigmentation corresponds to the colouration described by Hyman (1955) for specimens of Port Aransas, Texas. According to Hyman, Pericelis orbicularia presents “ a reddish-brown network on a paler ground ”. Cerebral eyes are arranged in two elongated clusters. Tentacular and marginal eyes scattered along the margin. A swelling in the body’s midline is caused by the highly folded pharynx and the copulatory organ (Fig. 4 A, B, E). Pericelis orbicularia was observed to secrete an abundant and viscous mucus. Reproductive system. The male and female copulatory apparatus are located just posterior to the pharynx and before the prominent sucker, 0.5 mm distance between them. Live specimens exhibit distinct female and male gonopores, but in our fixed specimens, the gonopores appear as a concavity, giving the impression of a single gonopore (Fig. 4 C, D). The male copulatory apparatus shows an anteroposterior orientation, including a highly muscular seminal vesicle and an ejaculatory duct lined with glandular epithelium.