Hydra vulgaris Pallas, 1766, (=Hydra attenuata) (Cnidaria; Hydrozoa) from the Los Padres Lagoon (Buenos Aires province, Argentina)

Résumé

This paper reports the presence of Hydra vulgaris Pallas, 1766, from the Los Padres Lagoon (Buenos Aires province, 37º 56’ S; 57º 45’ W), and represents the first record of this species for Argentina. The study showed that morphological characters coincide with what has been reported by other authors, such as stenoteles 10-3 µm (15.48 ± 0.44; mean ± standard deviation) long and 6-20 µm (11.75 ± 0.82) in diameter, holotrichous isorhiza 9-14 µm (11.96 ± 0.56) long and 4-7 µm (5.45 ± 0.31) in diameter, atrichous isorhiza 5-13 µm (8.00 ± 0.87) long and 3-8 µm (4.80 ± 0.38) in diameter and the desmonemes 6-12 µm (8.24 ± 0.67) long and 4-8 µm (5.70 ± 0.43) in diameter. The colour of this species is brown; the column oscillates between 1.98-9.88 × 0.31-1.82 mm and their tentacles, ranging from 6 to 9, have a relative length of ~¾ the length of the column. This species is dioecious; young buds have five or six tentacles, with discontinuous growth.