First record of two sabelline fan-worms in the tunic of the exotic sea squirt Cnemidocarpa amphora (Kott, 1992) (Stolidobranchia, Styelidae) from the Mediterranean Sea off Alexandria, Egypt

Abstract

The sea squirt Cnemidocarpa amphora was collected from Ras El-Tin beach in the Mediterranean Sea off Alexandria, Egypt. This study identifies two small sabelline fan-worms, Parasabella minuta and Parasabella leucaspis, inhabiting the tunic of the sea squirt. The identification was made on live and fixed worms using stereoscopic and scanning electron microscopes based on body size, radiolar crown, ciliation in the radioles, lenticular, pygidial and peristomial eyes, thorax and abdomen, morphology of lips, noto- and neuropodia, uncini, setae, secondary denticles, manubrium and the peristomial collar. P. minuta measures up to 5.5 mm in length and up to 1 mm in width, bearing lenticular radiolar eyes. Dorsal lips are triangular and the ventral lips are curved. Thoracic neuropodia are provided with uncini aviculares and three rows of secondary denticles. The manubrium is well-developed and slightly short. Abdominal neuropodia are provided with 2–6 elongated setae and the abdominal ones are provided with uncini aviculares covered by 3–4 rows of secondary denticles. P. leucaspis measures 5–41 mm long and up to 5 mm wide, with radiolar crown measuring 1–10 mm long. Dorsal lips are triangular and are provided with radiolar appendages while the ventral lips are curved. The thorax consists of 5–9 segments. The first segment has a narrow margin and is provided with elongated setae. From the second segment, the notopodia are provided with elongated upper setae. Thoracic neuropodia are provided with uncini aviculares and five rows of secondary denticles with elongated manubrium. Abdominal neuropodia are provided with 2 rows of bristles and the abdominal notopodia are provided with uncini aviculares and 5–6 rows of secondary denticles.