Phylactolaemate Bryozoans Research Articles

Cephalodiscus sp. (Hemichordata: Pterobranchia): observations of functional morphology, behavior and occurrence in shallow water around Bermuda

A pterobranch hemichordate, Cephalodiscus sp., was collected from Bermuda just below the low-tide mark in July 1983 and again in October through December 1983. This is the third report of this genus in shallow water and the second for the Western Hemisphere. Specimens were observed alive in the laboratory. Colonies consist of zooids at various stages of development arranged in clusters inside a translucent, collagenous coenecium. Cilia-driven currents of the zooids are used in a method of filter-feeding similar to phylactolaemate bryozoans.

Stereoscan studies of phylactolaemate bryozoan statoblasts including a key to the statoblasts of the British and European Phylactolaemata

The stereoscan electron microscope has been used to study morphological features of the statoblasts of nine phylactolacmate species. Pores present in the walls of annulus chambers of floating statoblasts are fully described for the first time. The taxonomic significance of surface patterning is assessed, and a key to the species found in Britain and Europe is included.

Comparative studies on the statoblasts of higher phylactolaemate bryozoans.

Statoblasts of five higher phylactolaemates were compared morphologically. As a result, they were divided into two groups: Group I comprising Lophopus crystallinus, Lophopodella carteri, and Pectinatella gelatinosa, and Group II comprising Pectinatella magnifica and Cristatella mucedo. These two groups are thought to represent independent evolutionary series. In Group I and in P. magnifica, the statoblasts are curved to varying degrees after the manner of a saddle. When the dorsal and ventral valves are flattened, therefore, the contour is different between the two. In Group I, the outermost layer of a mature statoblast is hard-gelatinous and basophilic; it remains intact after the statoblast is set free. The statoblast does not float until it is dry, and the float is similar in size on both valves. In Group II, a mature statoblast is covered by a softgelatinous basophilic layer, which decays after the statoblast is released. The statoblast floats without drying, and the float is better developed on the dorsal valve than on the ventral. Moreover, in the members of Group II, large yolk granules are first formed, followed by much smaller yolk granules. When their statoblasts are treated with KOH, the shell is separated completely into two valves. These characters are common to many lower phylactolaemates. By contrast, in L. carteri and P. gelatinosa, the yolk granules are uniformly small and the capsule proper resists KOH treatment. On these points, L. crystallinus is somewhat different from these two species, suggesting its primitive nature.

The method of feeding of lophophorates (bryozoa, phoronida, Brachiopoda)

Summary The lophophorates all feed by “impingement” feeding, so named by analogy with certain types of particle separators used in industry. In gymnolaemate bryozoans the feeding current is directed at the mouth where particles impinge and are sucked into the pharynx; in phylactolaemate bryozoans the particles impinge in the trough of the lophophore and are transported to the pharynx by cilia. In phoronids and brachiopods, particles impinge on the frontal surface of the tentacles and are conveyed to the pharynx by tracts of cilia.

Clonal Variation in Pectinatella

Previous articleNext article FreeClonal Variation in PectinatellaAnnie P. Henchman, and C. B. DavenportAnnie P. Henchman Search for more articles by this author , and C. B. Davenport Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The American Naturalist Volume 47, Number 558Jun., 1913 Published for The American Society of Naturalists Article DOIhttps://doi.org/10.1086/279356 Views: 165Total views on this site Citations: 1Citations are reported from Crossref PDF download Crossref reports the following articles citing this article:Hideo Mukai, Shuzitu Oda Comparative studies on the statoblasts of higher phylactolaemate bryozoans, Journal of Morphology 165, no.22 (Aug 1980): 131–155.https://doi.org/10.1002/jmor.1051650203