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COMMENTARY
The published literature, especially textbooks, describe the life history of Acetabularia acetabulum (= mediterranea) in its native habitat, the Mediterranean, as requiring three years until the reproductive cap with cysts is formed. Our experiments prove that, although the cell may become dormant in cold-water conditions (10 deg C), it can also complete its life history in one growing season. Such is the situation in the Mediterranean. The misconception that A. acetabulum is a short-lived perennial stems from field observations in the original 19th century literature that have not been checked either in situ or with experimental evidence.
In 1862, Woronine wrote that `Acetabular-ia mediterranea Linnaeus' (= A. acetabulum PC. Silva) is a perennial plant. He reported that in the Mediterranean Sea, its native habitat, the cells start to grow in early spring (he first observed them in February or March) and develop caps with 'spores' (cysts = gametangia) in summer. All the cells he observed in spring reached maturity within a single season. The mature caps fell off, leaving parts of the tube (= stalks) and the rhizoid. He thought that one cell would remain in the stalk and that the plant could therefore survive the loss of the cap. In February or March, besides new plants, Woronine also observed new tips growing out from old bases, giving rise to cyst-bearing plants. In an illustration (Woronin 1862, pl. 7, fig. 2), he showed that the new tip grows out of the former cell and is overlapped by the old stalk cell wall. He said his conclusions were supported by the report of a person who observed meadows of broken Acetabularia stalks in late autumn, at a time when Woronine was not able to continue observations himself.
De Bary & Strasburger (1877) also studied the life cycle of A. mediterranea (= acetabulum) and wrote a joint publication in which de Bary reported observations mainly of developing cells, and Strasburger described gametogenesis in cysts and, for the first time, reported copulation of gametes in Acetabularia. De Bary observed populations of Acetabularia cells at different developmental stages. He believed he was observing stages in a life cycle lasting several years. The youngest cells were simple, club-shaped sacs. De Bary found them in both spring and...