Beiträge zur Planktonbevölkerung der Weddellsee nach den Ergebnissen der Deutschen Antarktischen Expedition 1911–1912. Beitrag VI. Die Hydromedusen der Weddellsee

The classification of Antarctic appendicularians: the Oikopleura gaussica group

“…The different species were compared (Table I) on the basis of the characters included in the original descriptions by Lohmann (1905Lohmann ( , 1928, Lohmann & Bückmann (1926) and Tokioka (1964). All of the examined specimens have ovoid and elongate trunks, the right and left lobes of the stomach are of equal size, the oesophagus enters the postero-dorsal edge of the rounded left lobe of the stomach (Fig.…”

“…Authors & Lohmann (1905& Lohmann ( , 1928 and Lohmann & Bückmann (1926) Tokioka (1964 specimens whereas shorter in more mature specimens, thus leaving the intestinal ball exposed. The different trunk and tail measurements taken in each one of the three maturity stages defined are indicated in Table II.…”

“…These samples were obtained with a traditional open plankton net 0.50 m in diameter and 200 µm mesh, without flow meter, at the following depths: 10, 100, 200, and 500 m. The animals were fixed in 2% formaldehyde. A total of 495 well-preserved specimens were selected from the whole area to study the taxonomic characters defined by Lohmann (1905Lohmann ( , 1928 and Lohmann & Bückmann (1926).…”

“…vanhoeffeni Lohmann, 1896 have been the object of numerous and detailed studies describing the architecture of their houses (one of the most elaborated in their class), water circulation, food retention efficiency, as well as other physiological and ecological traits (Shiga 1982, Deibel & Turner 1985, Deibel 1986, 1988, Deibel & Powell 1987, Flood 1991, Urban et al 1993, Acuña et al 1996, 1999, Bochdansky et al 1998, 1999, Bochdansky & Deibel 1999a, 1999b. Conversely, for the Antarctic region only a few articles have mentioned O. gaussica Lohmann, 1905, O. valdiviae Lohmann, 1905, O. drygalskii Lohmann & Bückmann, 1926, and O. weddelli Lohmann, 1928 (Fenaux 1966, Bückmann & Kapp 1975, Galt et al 1985, Esnal 1999, and in all cases they refer to the descriptions by Lohmann (1905Lohmann ( , 1928 and Lohmann & Bückmann (1926) of material collected by the Challenger Expedition (1874) and the Deutschen Südpolar Expedition , without having examined new material. Based on the original descriptions and the study of only nine specimens, Tokioka (1964) questioned the validity of these four very similar species, and proposed considering them as variants of a single species, O. gaussica (the use of this name follows nomenclatorial rules).…”

“…Based on the original descriptions and the study of only nine specimens, Tokioka (1964) questioned the validity of these four very similar species, and proposed considering them as variants of a single species, O. gaussica (the use of this name follows nomenclatorial rules). This author postulated that some of the specific differences considered by Lohmann (1905Lohmann ( , 1928 and Lohmann & Bückmann (1926) might be either attributed to the degree of development of the individuals or to the stage of development of the house. Tokioka´s proposal was considered valid by Fenaux (1993Fenaux ( , 1998 in spite of the fact that he did not examine new material.…”