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Zur Populationsstruktur interstitieller Typhloplanoida und Dalyellioida (Turbellaria, Neorhabdocoela): Untersuchungen an einem mittellotischen Sandstrand der Nordseeinsel Sylt
Ehlers, U. (1973). Zur Populationsstruktur interstitieller Typhloplanoida und Dalyellioida (Turbellaria, Neorhabdocoela): Untersuchungen an einem mittellotischen Sandstrand der Nordseeinsel Sylt. Mikrofauna des Meeresbodens, 19. Akademie der Wissenschaften und der Literatur: Mainz. 105 pp.
Part of: Mikrofauna des Meeresbodens. Akademie der Wissenschaften und der Literatur: Wiesbaden. ISSN 0342-3247, more
Peer reviewed article  

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    VLIZ: Non-open access 305344

Keywords
    Population structure; Dalyellioida [WoRMS]; Typhloplanoida [WoRMS]; ANE, Germany, Schleswig-Holstein, Sylt I. [Marine Regions]; Marine

Author  Top 
  • Ehlers, U.

Abstract
    On the population structures of interstitial Typhloplanoida and Dalyellioida (Turbellaria, Neorhabdocoela): investigations in a middlelotic sandy beach of the island of Sylt (North Sea). 90 species of the Typhlopianoida and Dalyellioida are found in a sandy beach of the island of Sylt. The population density is greater in wadden areas and sublittoral sands than in the beach slopes. In wadden areas the animals inhabit the oxidized sands above the sulfid-layer. Only few species prefer to live in the HaS-horizont. In the beach slope Dalyellioida are usually missing. Typhlopianoida occupy the median beach slope. Damp sands are preferred. The abundance of Typhlopianoida and Dalyellioida shows significant seasonal dynamics. The minimum occurs in March. Abundance is higher in summer. The density of population diminishes in winter. Horizontal and vertical distributions of 29 species are described. Correlations of zonation patterns and environmental factors are pointed out. Many Typhloplanides and Dalyellioides show significant seasonal vertical migrations into deeper layers of the sediment. These movements are to observe by inhibitants of wadden areas and beach slopes. Species settling in damp sands, retire in winter into the groundwater. Ciliopharyngiella intermedia withdraws about 40 cm below the subsoil-water level. Remigration begins in springtime. Many Typhlopianoida inhabiting the beach slope, show vertical movements in summer, too. Four types of life cycles are to discern: I. Univoltine cycle. Lonchoplanella axi, Adenorhynchus halticus, Ciliopharyngiella intermedia, and Listea simplex have a long development time and an univoltine life cycle. Reproduction takes place in springtime or in summer. Perhaps Brinkmanniella macrostomoides, Anthopharynx sacculipenis, and Litucivis serpens belong to this type, too. Listea simplex and Litucivis serpens live more than one year. Haloplanella longatuba, Proceropharynx litoralis, Mariplanella frisia, Messoplana falcata, and Petaliella spiracauda are moderate univoltine. Parts of the populations produce a weak second generation at the end of the year. II. Bivoltine cycle. Pratoplana galeata, Pogaina suecica, P. kinnei, Balgetia semicirculifera, and 5 species of the genus Promesostoma have two generations in the year. Promesostoma meixneri has a bivoltine cycle with a dormancy in winter. Juveniles, which date from egg-capsules laid in autumn, hatch in springtime of the following year. III. Polyvoltine cycle. Provortex psammophilus produces 3 generations in the year at natural conditions. In the laboratory, series of generations can increase. In temperated zones reproduction takes place only from March to October. IV. Species without seasonally limited reproductive activity. Only Aulopharynx aestuarius, Adenopharynx mitrabursalis, and Drepanilla limophila lay eggs in summer and winter. Reproduction does not stojj with the onset of cold weather. There are correlations between life cycles and vertical zonations. Species inhabiting deeper layers in wadden areas and the beach slope, are univoltin. Species living in the region of the subsoil-water, have a very long life span. Typhloplanoida living in superficial sediments and all the Dalyellioida produce two or more generations from spring to autumn. The inhabitants of the boundary to the deeper HjS-layers in wadden areas are able to reproduce all over the year.

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