Actiniaria of the southwestern Atlantic Ocean. II. Sagartiidae and Metridiidae.

On the biogeography of the southwest Atlantic with special reference to the sea anemones (Coelenterata: Actiniaria).

In September 1993, 26 live specimens of the small, delicate sea anemone Haliplanella luciae (Verrill, 1898) were sampled from the hull of a ship docked in Hamburg Harbour. After a worldwide journey the ship had passed into the freshwater region of the river Elbe. Although the migratory potential of the species (supposed home region is Japan) is well known, its transport on ships' bottoms has never been documented. Behavioural traits enabling the anemone to settle on ships are discussed together with probable reasons why Haliplanella luciae did not establish itself in the fauna of the German Bight.

The Porcupine Abyssal Plain in the north-eastern Atlantic Ocean is subject to periodical deposition of phytodetritus and has a highly diverse benthic fauna dependent on this source of organic matter. Among the most abundant species from the northern study site of the Institute of Oceanographic Sciences Deacon Laboratory (IOSDL) at ~48°50′N 16°30′W, 4850 m, is Iosactis vagabunda gen. nov., sp. nov. (Cnidaria: Actiniaria, Iosactiidae fam. nov.), a small endomyarian sea anemone. The fact that this species is a burrower, with a smooth, unspecialized column, and a rounded aboral end provided with a central pit, makes it stand out from the other families of endomyarian anemones and prompted the establishment of the new family Iosactiidae. There is evidence that the closest relatives of the new family are the ‘deep water actiniids’ (e.g. Bolocera, Liponema, Leipsiceras), and the Andresiidae. Long-term in situ time-lapse photographs indicate a unique behaviour of this anemone in that it moves out of its hole at times, presumably exhibiting a hemisessile lifestyle in this peculiar abyssal habitat.

The new species Saccactis coliumensis is described with an emendation of genus Saccactis Lager, 1911 (family Actiniidae). The taxonomic relations of the genus are discussed giving additional information on Isoulactis chilensis Carlgren, 1959 and Isocradactis magna sensu Carlgren, 1924. The terms "verrucae", "vesicles" and "acrorhagi" are discussed and taxonomically valuated.The anemone S. coliumensis hves in eutrophicated sediments on the central Chilean shelf that is at least temporarily under the impact of deoxygenated waters from the Peru-Chile-SubsurfaceCurrent. The most conspicuous features of the new species (the ruff of dehcate, gill-hke vesicles beneath the tentacles and its thick pedal disc ectoderm with small, fragile spirocysts and ciha-hke structures) may be considered adaptive in this peculiar habitat.

Actinoscyphia saginata (Verrill, 1882; type species) and Actinoscyphia aurelia (Stephenson, 1918) are redescribed with special reference to characters of diagnostic significance in order to differentiate the two species both inhabiting the 2000 m slope region of the North Atlantic. In situ photograph of A. aurelia off the North West African coast shows it to display a novel life form type in expanding its bi‐lobed tentacular disc like a Venus‐fly‐trap and standing on the muddy sediment with a small, non‐adhesive base penetrating just below the surface of the sediment. The peculiar nematocyst equipment found in both species makes it necessary to rehabilitate the family Actinoscyphiidae Stephenson, 1920. The systematic position of the family is discussed and eventually the Actinoscyphiidae is considered as sister group (sensu Hennig) of the Hormathiidae. Because of the loss of acontia in the Actinoscyphiidae, this taxon is considered to be the more advanced one. Chondrodactis japonica Wassilieff, 1908, is found to belong to the genus Actinoscyphia.

The Arctic abyssal anemone Bathyphellia margaritacea, type species of the genus and of the family Bathyphelliidae is redescribed. Acontia in this species are highly variable both in quantity and in cnidome characteristics, implying that this genus is one of the links between acontiate and nonacontiate mesomyarian actiniarians, and has to be considered a ‘late’ mesomyarian according to the scheme proposed by Schmidt (1972b, 1974). By contrast, the new abyssal species Daontesia porcupina has normally developed acontia, a cuticle consisting of multistratified sheets and a more archaic and diverse cnidome, suggesting its systematic allocation within the ‘early’ mesomyarians. The allocation of the genus Daontesia to the family Bathyphelliidae is questionable.

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